ishwar project report

INDUSTRIAL TRAINING REPORT ON

CORRECTION OF MOLD YL-1 HEATER BRACKET

carried out at

SUBROS LTD.NOIDA

BYISHWAR WALIKAR

SPG 16 1314

Submitted in partial fulfillment of Post Graduate Diploma in Tool Design

2013-2014

Under the guidance of

INTERNAL GUIDE EXTERNAL GUIDE

Mr. Naresh .T.R Mr. Manoj patra

Faculty- Tool Design Senior Manager,manufacturing Department

School of PG Studies, NTTF SUBROS TOOL ENGINEERING CENTRE.

Bangalore -560058 NOIDA-201303

SCHOOL OF POSTGRADUATE STUDIESNETTUR TECHNICAL TRAINING FOUNDATION

BANGALORE-560 058


SCHOOL OF POSTGRADUATE STUDIESNettur Technical Training Foundation

CERTIFICATE

This project report is the bonafide work done by Mr. Ishwar Walikar and

submitted in partial fulfillment of the requirements for the award of

Postgraduate Diploma Degree in TOOL Design.

Title : CORRECTION OF MOLD YL-1 HEATER BRACKET

Batch : 2013-2014

Signature of the Student :

Guide(s)(Name & Signature) :

Examiner(s)(Name & Signature) :

NTTF SPG, BANGALORE


SYNOPSIS

The project is correction of mold parts that is YL-1 Heater Bracket. The step involves trial

run,inspection,finding root cause of different defects, correction done in mold as well as in

design,selecting correcting methods. For this I have been communicating with assembly

section and design department.

In initial trial it need not necessary to achieve all product design requirements. The

product designer designs the component by not seeing physically. Once it comes out as

real product significant changes may occur with reference to design. More over there are

factors like shrinkage,atmospheric pressure,temperature varies from place to place

affects the part dimension.

In this scenario based on trial-part dimension there has to be significant modifications to

be done in mold in-order to achieve functional requirement as well as design requirement.

For modifications in mold the best method has to choose. That includes VMC

machining,TIG Welding,EDMing. For each process shrinkage forecast has to be done

and should given allowances for each operation.

If systematically follow above process and provide allowances in each operation the

desired result will be given. There are certain deviation in dimension which doesn't affect

the function can be neglected. It doesn't mean all the deviations can be modified. For eg:

correction of certain portion,some material has to be removed from cavity and the same

amount has to be filled in core. In such cases material filling in core is difficult task.

Though it followed laser welding it is cost consuming and may not be possible. The

correction method should selected such such that it should be economically feasible and

time saving and value adding.

NTTF SPG, BANGALORE


ACKNOLEDGMENT

I am grateful to Subros Limited, Tool room for allowing me to undertake project

work at their premises. I express my appreciation towards Mr. N. Pujari, VP STEC, Noida,

for providing me with the technical and administrative support for carrying out the project.

I convey my deepest gratitude to my Project Guide Mr. Manoj Patra for conceiving the

path for my work. His valuable guidance during the course of the project has helped me in

learning a lot about the subject. It has been a great experience working under his

guidance in the cordial environment and to get better day-by-day.

It is a life time opportunity to get in a world-class institute where every prospect is

ready and waiting for being used by the concerned man. I must say the way education

goes here is incomparable. Learning things here is much more interesting than any

conventional system of schooling. I am thankful to NTTF Bangalore, Mr. Venugopalan our

Director training, and importantly my Principal Dr. N.Ramani from the bottom of my

heart for this chance.

Finally I extend my thanks to my friends and members of, Subros limited, & SPG,

NTTF who encouraged and helped me to take the task of this project successfully.

NTTF SPG, BANGALORE


CONTENTS

TOPICS PAGE NO.

1. TITLE PAGE ………………………………………………..01

2. CERTIFICATE ……………………………………………..02

3. SYNOPSIS ………………………………………………….03

4. ACKNOWLEDGMENT ………………...........................04

5. CHAPTER-01 5.1 COMPANY PROFILE……………………………….08

5.2 COMPANY PLANTS………………………………...09

5.3 PRODUCT RANGE…………………………………10

5.4 PRODUCTS………………………………………….11

5.5 KEY CUSTOMER……………………………………12

6. CHAPTER-02 6.1 INTRODUCTION……………………………….......24

7. CHAPTER-03 7.1 INDUSTRIAL TRAINING BRIEF

7.1.1 AIM OF THE PROJECT…………………………29

7.1.2 SCOPE…………………………………………....29

7.1.3 STEPS FOLLOWED…………………………..…29

8. CHAPTER-04 8.1 METHODOLOGY

8.1.1 ACTIVITIES / LIMITATIONS………….............31

NTTF SPG, BANGALORE


9. CHAPTER-05 9.1 PROJECT DETAILS

9.1.1 DATA COLLECTION, ANALYSIS

9.1.1.1 COMPONENT DRAWING………………………33

9.1.1.2 COMPONENT DETAIL…………………………..34

9.2 LITERATURE SURVEY9.2.1 PLASTICS…………………………………………….....37

9.2.2 CLASSIFICATION OF PLASTICS…………………….38

9.2.3 COMMON PLASTICS & ITS USES…….…………….39

9.2.4 PROPERTIES OF THERMOPLASTICS……………..44

9.2.5 INJ. MOULDING PROCESS………………………….45

9.2.6 MOULDING MACHINES……………………………...39

9.2.7 MOULDING TECHNIQUES……………………………42

9.2.8 FEED SYSTEMS………………………………………..51

9.2.9 COOLING………………………………………………..60

9.2.10 EJECTION…………………………………………….65

9.2.11 SHRINKAGE………………………………………….67

9.2.12 MATERIALS FOR MOULD………………………….70

9.3 CALCULATIONS…………………………………….……..74

9.4 MACHINE SPECIFICATION……………………………...77

9.5 VIEWS OF MOULDS………………………………….……78

9.6 COST ESTIMATION…………………………………..……80

9.7 TRAIL RUN DETAILS9.7.1 ERRORS…………………………….……………….….83

9.7.2 CORRECTIONS…………………………………….….84

9.8 MACHINING PROCESS……………………………….….87

9.9 BILL OF MATERIALS………………………………….….88NTTF SPG, BANGALORE


10. CHAPTER-06 10.1 OTHERS

10.1.1 SHIM…………………………………………………93

10.1.2 CONCLUSION………………………………………94

10.1.3 REFERENCES……………………………………..94

NTTF SPG, BANGALORE


CHAPTER-01

NTTF SPG, BANGALORE


COMPANY OVERVIEW

COMPANY PROFILE :

Subros was established in1985, as a joint venture between Suri brothers, Denso

Corporation, Japan and Suzuki Motor Corporation Japan.

The company has grown from a capacity of 15,000 AC kits in 1985 comprising of

largely an assembly operation, into the largest and only integrated manufacturing unit in

India for Auto Air Conditioning systems. The company has the capability to manufacture

Compressors , Condenser, Heat exchangers and all are connecting elements that are

required to complete Ac Loop.

The Subros has been constantly expanding it's manufacturing capabilities since it's

inception and has manufacturing capacity of 1.2 Million A.C. Kits per annum. Plans are

underway to increase the manufacturing capacity 2 million A.C. 2014-2015.

Subros has set-up its own R&D center which is recognized by department of

scientific, Industrial research, Ministry of science and Technology, Govt. of India. Subros

has also set-up it's own Tool Room to meet captive tooling requirement of company. Both

these facilities are part of company's long-term strategy towards building up in-house

competencies for new product development, product reliability and meeting other service

requirements for ensuring the product reliability during the life cycle of the products, which

are world class in technology.

Subros operates in compliance of the TS 16949, ISO 14001, OHSAS 18001

certifications and continues to focus on systems and new technology.

NTTF SPG, BANGALORE


COMPANY PLANTS:

FIG-1

NTTF SPG, BANGALORE


FIG-2

PRODUCT RANGE:Subros Manufactures air conditioning products for wide range of applications.

FIG-3

FIG-4

NTTF SPG, BANGALORE


FIG-5

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KEY CUSTOMERS :

FIG-6

MANUFACTURING INFRASTRUCTURE :Compressors :

FIG-7

NTTF SPG, BANGALORE


Heat Exchangers :

FIG-8

Hose and Tubes : FIG-9

NTTF SPG, BANGALORE


Research and development :

FIG-10

Tool Room :

FIG-11

NTTF SPG, BANGALORE


COMPANY VISION & CORE VALUES

VISION STATEMENT :Leadership(Mission, Vision, Policy & Frame Work)

Under the dynamic of Chairmen Mr. Ramesh Suri, Managing Director Ms. Shradha

Suri, CEO Mr. D. M. Reddy Subros has recognized itself since year 2002. The new vision

and operating principles were incorporated in the Logo itself. The logo itself now defines

the “Vision” of the company, the way to achieve through the “operating principles”, and the

wish to attend the global quality standards and Eco-Friendliness in all it's operations.

Vision“To Be World Class auto air conditioning & thermal engineering systems manufacture having

global competitiveness ”

Mission“To maintain the market leadership through total customer satisfaction in terms of Quality, Cost

& Speed”

NTTF SPG, BANGALORE


Core Values :A set of core values is established to align all the people in the organization in the

direction of the achieving stated goals all through the organization.

NTTF SPG, BANGALORE


Subros Functional Organization :Subros recognizes the importance of its functional organization to achieve the

world class PQCDSME.

The Structure is depicted below.

FIG-12

As a policy all company processes are linked & adhered to ISO/TS 16949 standard

to achieve all company's PQCDSME goals & objectives. The functions are classified as

1. Manufacturing Operations

2. R & D – NPD/NTG

3. Support Functions

NTTF SPG, BANGALORE


These processes treated as Support Oriented Process (SOP's) with process

centric approach & clearly identified process owner. All the support oriented processes

are tracked for their effectiveness & efficiency on demand periodicity as part of company’s

management review process. The company takes suggestion for direction from Head of

Department with clear policy & strategy objective & bottom up approach through

discussion held to have clear cut means to achieve & determine future course of actions.

The company has plant specific admin, Purchase, Logistics, maintenance & utility

functions reporting to respective manufacturing/Operational heads for administrative

control & functionally reporting to the support functional heads based at operational

headquarters at Noida. This is reflected in the organization structure of company.

The company's support function policy recognizes the various support functions as

enablers to the manufacturing business & product development process of the company.

The company recognized this as policy for effectiveness of the strategy deployment

process as a part of value stream mapping.

RESEARCH & DEVELOPMENT :Objective :

The company's ability to service the is majorly dependent on creating new products

& technologies to meet customer's requirement. This activity is focus the R & D & their

activities are follows.

1. New Product Development (NPD)- To develop products as per customer's

requirements (RF Q-Request For Quotation, RFP- Request for Proposal) in timely

manner as per customer schedule. This is done through understanding the

customer's needs & requirements & application engineering at Subros

technologies to meet such requirement.

2. New technology development (NTG) -To develop new technologies in product

and processes to meet emerging customer requirement in future and to achieve

superiority in products in relation to competitors offerings. This will involve transfer

of technologies from collaborators on in house development of new innovative

products/process as an improvement over current available technologies. This will

include new patents.

NTTF SPG, BANGALORE


PROCESS :In line with the aforesaid strategic objective , the company has the complete

capability to design , validate test and manufacture completely new air conditioning

system based on customer spaces. i.e. from conceptualization to launching the entire

NPD cycle can be successfully managed by the manufacturing unit.

The organization has a clearly defined New Product Development Process shown

below.

The organization has invested In the unique set-up where complete system design

parameters can be validated without going through long road test by simulating actual

vehicle condition by using the testing facilities shown below.

NTTF SPG, BANGALORE


Since the facility for the above design & test are located in-house, it results in

reduced product lead time. Moreover, the proto test is carried out at the extreme side.

where actual road conditions are replicated which leads to faster improvement

thereby taking our manufacturing to world class levels.

The above-created facilities are not only used by Subros design team but also by

its existing & prospective customer's to validate their products. This results in us getting

first hand information about the customer needs and requirements & helps in making Ist

time OK system or component. This leads to reducing in rework thereby reducing cost at

latter stages.

Before the Product is put in manufacturing the ease or Design Of Manufacturability is

carried out so as to determine standardization or simplification or ease of process through

Design & PFEMA.

NTTF SPG, BANGALORE


COST REDUCTION OF EXIISTING PRODUCT :We have adopted a unique & innovative ways of refusing cost of existing products.

In fact as a company, we have taken up the task to achieve a cost leadership among the

entire product segment we manufacture. To achieve this, there are various initiatives,

which the company has undertaken.

Strategic Initiative :Subros has identified cost reduction program as a major tool to be competitive and be a leader in

the market right from the days when liberalization had just started. Various initiatives were taken

to not only taken are:

1. Alternative Strategic Sourcing

2. Location

3. VA-VE

Tool Manufacturing:The Tool room has the world class manufacturing facility for to design and

development Plastic Injection molds, Die casting dies, Precision progressive stamping

dies, and Jigs and Fixtures.

It is backed by qualified and experienced team capable of fulfilling all internal

tooling requirement for PDC dies, Injection Molds, Sheet Metal Tools, Jigs and Fixtures,

and Gauges.

Vision:1. Design tools and equipments through the excellent manufacturing system to

meet development schedules with Speed, Quality, and Cost with Global

manufacturing standards.

Objectives:1. Tools and Equipment manufacturing with low cast and short lead time

2. Concurrent engineering for Tool Development

3. SMED Techniques for Tool Development

4. Yield improvement in plastic and Sheet Metal component

NTTF SPG, BANGALORE


5. Precision Plastic business development

6. Special purpose machines development

Goals/Targets:1. Mid Term

1. Yield improvement For In-House and Vender parts

2. Vender Up-gradation.

2. Long Term

1. Tool development for Denso and MSIL.

2. Engineering plastic part development (Design, development and production)

3. Special Purpose machines development

4. Skill development center

Concurrent Engineering:

NTTF SPG, BANGALORE


CHAPTER-02

NTTF SPG, BANGALORE


INTRODUCTION Overview of Automobile air-conditioners :

FIG-13

The automotive air-conditioners has mainly 3 important heat exchangers they are

CONDENSER : Automotive air-conditioning condenser is a heat exchanger with phase change on the

refrigerant side in which heat is rejected from refrigerant to ambient air, causing the

superheated refrigerant vapor to condense to a liquid. Heat rejected by the condenser is

the sum of evaporator heat load, compressor work and any heat gains in the lines. Heat is

removed in three steps within the condenser:

1. De-superheating: refrigerant vapor is cooled to the condensing saturation

temperature.

2. Condensation: saturated refrigerant vapor changes to a liquid, rejecting heat of

vaporization.

3. Subcooling: refrigerant liquid is cooled below the saturation (condensing)

temperature at the prevailing saturation pressure.

Refrigerant enters the condenser as a high pressure superheated (high) temperature

vapor. Leaves the condenser as a high pressure subcooled (medium) temperature liquid.

NTTF SPG, BANGALORE


EVAPORATOR :The function of an evaporator is to dehumidify and cool the ambient air going to the

passenger compartment through the HVAC module. It reduces the temperature of the

ambient air so that the air first becomes fully saturated. With a further reduction in its

temperature through the evaporator, it condenses the moisture from the air and thus it

reduces the moisture content of the air going to the passenger compartment.

COMPRESSOR :The purpose of the compressor is two-folds:

1. To raise the pressure of the refrigerant with the least amount of work

2. To circulate (pump) as much refrigerant as possible with the lowest amount of

compressor volume (displacement)

Car air conditioners can be termed as mini-central air conditioners simply due to

one reason.It is fitted with ducts to supply air from the evaporator to driver and passenger

compartment.

Air conditioners for automobiles are designed such that air can be directed straight

to the occupants. As such, these are built mainly for spot cooling because heat gain

through radiation is so quick in the vehicle that it will take a very long time before the

whole space is conditioned, if it was designed for indirect cooling.Heat loss during winter,

however, is not that sudden, and hence, indirect heating can be utilized.Automobile air

conditioning is sized about twice as large as room air conditioners. All for the reason of

large heat gain and loss through windows.

NTTF SPG, BANGALORE


Design Features : Automobile air conditioners consists of

1) Condenser, Evaporator, fan & a blower

2) Thermostatic expansion valve

3) Filter dryer & receiver

4) Thermostat

5) Ducts

6) Dampers

7) Compressor

8) Suction, throttle valve connected to a vacuum switch

9) Refrigerant

10)Set of Aluminum tubes & rubber hoses with clips and

11)Control system plus panel

Function of a Evaporator :To dehumidify and cool the ambient/cabin air to the passenger compartment,It reduces

the temperature of the ambient air so that the air first becomes fully saturated. With a

further reduction in its temperature through the evaporator ,it condenses the moisture

from the air and thus it reduces the moisture content of the air going to the passenger

compartment It receives low-pressure liquid and vapor mixture,becomes completely

superheated vapor at the exit.

Characteristics of a Evaporator :1. Amount of heat accepted by the evaporator from cabin air should be equal to

amount of heat rejected to the compressor by the evaporator.

2. Evaporator air side pressure drop should be optimized to reduce spitting of

condensate to the air stream.

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Evaporator Performance in vehicles :1. The evaporator frontal area is primarily selected to get the desired airflow rate and

minimize the condensate drainage problems. Smaller frontal areas results in lower

airflow rate and reduced A/C system performance.

2. Increasing the frontal area of the evaporator at constant airflow rate will decrease

the evaporator discharge temperature and hence increase the cooling performance

in the vehicle.

3. Evaporator performance and uniform temperature at the outlet of the evaporator

depend on the geometry of the core (number of passes, pass arrangement,

number of plates per pass),airflow distribution, core orientation (impacting

condensate carryover and drainage).

4. The orientation of the evaporator in the vehicle (HVAC module) has an impact on

the condensate drainage. For the plate-type evaporators, vertical tube orientation

with a single tank (since the vertical space is limited in the IP) drains the

condensate the best. The packaging constraints in the HVAC module also dictate

the evaporator construction type.

NTTF SPG, BANGALORE


CHAPTER-03

NTTF SPG, BANGALORE


PROJECT BRIEF

AIM OF THE PROJECT: Aim of this project is to correct the mold YL-1 Heater Bracket. Part comes

after initial molding won't meet full product design requirements. It has to further modify in

the mold as well as in mold design in order to fulfill the same and equip it for production

run.

SCOPE:

Part comes after initial molding won't meet full product design requirements. It has to

further modified to eliminate all mold defects in the mold as well as in mold design in

order to fulfill the same and equip it for production run.

STEPS FOLLOWED FOR PROJECT:

This project work involves:

1. Trial Run.

2. Inspection for aesthetics,defects,dimension.

3. Parameter study of machine.

4. Study of Part drawing

5. Correction for defect such as flash,short shot

6. Correction for dimensional deviation

7. Design update in CAM and VMC programme generation.

8. Machining of graphite electrode in VMC.

9. TIG Welding

10.Calculation for shrinkage

11.ED machining the mold

12. Inspect the mold.

13.Mold Closing

14.Trial run the mold

15.Dispatch for production run

NTTF SPG, BANGALORE


CHAPTER-04

NTTF SPG, BANGALORE


METHODOLOGY

ACTIVITY CHART

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FIG-14

CHAPTER-05

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COMPONENT DRAWING :

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COMPONENT DETAILS

FIG-15

COMPONENT NAME : HEATER BRACKET MATERIAL : PP TD40

SHRINKAGE : 1.03% AVERAGE WALL THICKNESS : 1.5 mm

FUNCTION : TO PROVIDE INSULATION

CRITICAL AREA : SNAP FIT AND BUTTING AREA’S OF THE COMPONENT

NTTF SPG, BANGALORE


DETAILS OF COMPONENT:

SL NO ITEMS SPECIFICATION1 DENSITY OF COMPONENT 1.4 gm/cc

2 MASS OF COMPONENTS 62.38 gms + 10% OF FEEDSYSTEM

3 INJECTION MOLDING PRESSURE 1100 kg / cc

4 PROJECTED AREA OF COMPO-NENT 16792.53 mm2

5 PROJECTED AREA OF RUNNER 206.50 mm2

6 MAXIMUM TONNAGE 60 TON

7 SHOT WEIGHT(PART WEIGHT WITH RUNNER) 217 gms

8 MAX. MOLD BASE SIZE 330 (X) X 220(Y) X 328 (Z)

9 GATE TYPE PIN POINT GATE

10 MOLD TYPE THREE PLATE MOLD

11 MOLD SHUT HEIGHT 328 mm

MATERIAL SPECIFICATION

SL NO ITEMS SPECIFICATION1 DENSITY OF COMPONENT 1.4 gm/cc

2 MOLD SHRINKAGE 0.02 mm/mm

3 MELT TEMPERATURE 175 - 250°C

4 MOLD TEMERATURE 65 - 100°C

5 INJECTION SPEED MEDIUM TO HIGH

6 TOTAL HEAT CONTENT 110 cal/gm

7 THERMAL CONDUCTIVITY OF PLAS-TIC 5.5 x 10-4 cal/sec cm

8 HEAT DISTRIBUTION TEMPERATURE 140°C

NTTF SPG, BANGALORE


RELEVANT LITERATURE SURVEY

Plastics:

FIG-16

A plastic material is any of a wide range of synthetic or semi-synthetic organic solids that

are malleable. Plastics are typically organic polymers of high molecular mass, but they of-

ten contain other substances. They are usually synthetic, most commonly derived from

petrochemicals, but many are partially natural.

Due to their relatively low cost, ease of manufacture, versatility, and imperviousness to

water, plastics are used in an enormous and expanding range of products, from paper

clips to spaceships. They have already displaced many traditional materials, such as

wood, stone, horn and bone, leather, paper, metal, glass, and ceramic, in most of their

former uses. In developed countries, about a third of plastic is used in packaging and an-

other third in buildings such as piping used in plumbing or vinyl siding. Other uses include

automobiles (up to 20% plastic), furniture, and toys. In the developing world, the ratios

may be different - for example, reportedly 42% of India's consumption is used in packag-

ing.

NTTF SPG, BANGALORE

http://en.wikipedia.org/wiki/Vinyl_siding

http://en.wikipedia.org/wiki/Plumbing

http://en.wikipedia.org/wiki/Piping

http://en.wikipedia.org/wiki/Ceramic

http://en.wikipedia.org/wiki/Glass

http://en.wikipedia.org/wiki/Metal

http://en.wikipedia.org/wiki/Paper

http://en.wikipedia.org/wiki/Leather

http://en.wikipedia.org/wiki/Bone

http://en.wikipedia.org/wiki/Horn_(anatomy)

http://en.wikipedia.org/wiki/Rock_(geology)

http://en.wikipedia.org/wiki/Wood

http://en.wikipedia.org/wiki/Petrochemical

http://en.wikipedia.org/wiki/Molecular_mass

http://en.wikipedia.org/wiki/Organic_polymer

http://en.wikipedia.org/wiki/Malleability

http://en.wikipedia.org/wiki/Organic_chemistry

http://en.wikipedia.org/wiki/Synthetic_polymers


Classification

Plastics are usually classified by their chemical structure of the polymer's backbone and

side chains. Some important groups in these classifications are the acrylics, polyesters,

silicones, polyurethanes, and halogenated plastics. Plastics can also be classified by the

chemical process used in their synthesis, such as condensation, polyaddition, and cross-

linking.

Thermoplastics and thermosetting polymers:

FIG-17

There are two types of plastics: thermoplastics and thermosetting polymers. Thermoplas-

tics are the plastics that do not undergo chemical change in their composition when

heated and can be molded again and again. Examples include polyethylene, polypropy-

lene, polystyrene and polyvinyl chloride. Common thermoplastics range from 20,000 to

500,000 amu, while thermosets are assumed to have infinite molecular weight. These

chains are made up of many repeating molecular units, known as repeat units, derived

from monomers; each polymer chain will have several thousand repeating units.

Thermosets can melt and take shape once; after they have solidified, they stay solid. In

the thermosetting process, a chemical reaction occurs that is irreversible. The vulcaniza-

tion of rubber is a thermosetting process. Before heating with sulfur, the polyisoprene is a

tacky, slightly runny material, but after vulcanization the product is rigid and non-tacky.

NTTF SPG, BANGALORE

http://en.wikipedia.org/wiki/Monomer

http://en.wikipedia.org/wiki/Atomic_mass_unit

http://en.wikipedia.org/wiki/Polyvinyl_chloride

http://en.wikipedia.org/wiki/Polystyrene

http://en.wikipedia.org/wiki/Polypropylene


http://en.wikipedia.org/wiki/Polyethylene

http://en.wikipedia.org/wiki/Thermosetting_polymer

http://en.wikipedia.org/wiki/Thermoplastic

http://en.wikipedia.org/wiki/Cross-link

http://en.wikipedia.org/wiki/Cross-link

http://en.wikipedia.org/wiki/Polyaddition

http://en.wikipedia.org/wiki/Condensation_reaction

http://en.wikipedia.org/wiki/Halocarbon

http://en.wikipedia.org/wiki/Polyurethanes

http://en.wikipedia.org/wiki/Silicones

http://en.wikipedia.org/wiki/Polyester

http://en.wikipedia.org/wiki/Acryl_group

http://en.wikipedia.org/wiki/Side_chain

http://en.wikipedia.org/wiki/Chemical_structure


Common plastics and uses

Polyester (PES) – Fibers, textiles.

FIG-18

Polyethylene terephthalate (PET) – Carbonated drinks bottles, peanut butter

jars, plastic film, microwavable packaging.

FIG-19

Polyethylene (PE) – Wide range of inexpensive uses including supermarket

bags, plastic bottles.

FIG-20

NTTF SPG, BANGALORE

http://en.wikipedia.org/wiki/Polyethylene

http://en.wikipedia.org/wiki/Polyethylene_terephthalate

http://en.wikipedia.org/wiki/Textile

http://en.wikipedia.org/wiki/Fiber

http://en.wikipedia.org/wiki/Polyester


High-density polyethylene (HDPE) – Detergent bottles, milk jugs, and molded

plastic cases.

FIG-21

Polyvinyl chloride (PVC) – Plumbing pipes and guttering, shower curtains, win-

dow frames, flooring.

FIG-22

Polyvinylidene chloride (PVDC) (Saran) – Food packaging.

FIG-23

NTTF SPG, BANGALORE

http://en.wikipedia.org/wiki/Saran_(plastic)

http://en.wikipedia.org/wiki/Polyvinylidene_chloride

http://en.wikipedia.org/wiki/Polyvinyl_chloride

http://en.wikipedia.org/wiki/High-density_polyethylene


Low-density polyethylene (LDPE) – Outdoor furniture, siding, floor tiles,

shower curtains, clamshell packaging.

FIG-24

Polypropylene (PP) – Bottle caps, drinking straws, yogurt containers, appliances,

car fenders (bumpers), plastic pressure pipe systems.

FIG-25

Polystyrene (PS) – Packaging foam/"peanuts", food containers, plastic table-

ware, disposable cups, plates, cutlery, CD and cassette boxes.

FIG-26

NTTF SPG, BANGALORE

http://en.wikipedia.org/wiki/Polystyrene

http://en.wikipedia.org/wiki/Plastic_pressure_pipe_systems


http://en.wikipedia.org/wiki/Garden_furniture

http://en.wikipedia.org/wiki/Low-density_polyethylene


Polyamides (PA) (Nylons) – Fibers, toothbrush bristles, tubing, fishing line, low

strength machine parts: under-the-hood car engine parts or gun frames.

FIG-27

Acrylonitrile butadiene styrene (ABS) – Electronic equipment cases (e.g.,

computer monitors, printers, keyboards), drainage pipe.

FIG-28

Polycarbonate (PC) – Compact discs, eyeglasses, riot shields, security windows,

traffic lights, lenses.

FIG-29

NTTF SPG, BANGALORE

http://en.wikipedia.org/wiki/Riot_shield

http://en.wikipedia.org/wiki/Eyeglasses

http://en.wikipedia.org/wiki/Compact_disc

http://en.wikipedia.org/wiki/Polycarbonate

http://en.wikipedia.org/wiki/Acrylonitrile_butadiene_styrene

http://en.wikipedia.org/wiki/Fishing_line

http://en.wikipedia.org/wiki/Nylon

http://en.wikipedia.org/wiki/Polyamides


Polyurethanes (PU) – Cushioning foams, thermal insulation foams, surface coat-

ings, printing rollers (Currently 6th or 7th most commonly used plastic material, for

instance the most commonly used plastic in cars).

FIG-30

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http://en.wikipedia.org/wiki/Polyurethanes


Properties of thermoplastics:

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1 INJECTION MOLDING PROCESSInjection molding is a versatile process that can produce parts

as small as a fraction of a gram and as large as 150 kg. During this process, molten

plastic is forced (injected) into a mold and cooled until the melt solidifies. When the part is

cooled sufficiently, the mold is opened, the part is ejected from the mold, and the mold is

closed again to repeat the cycle. Thus, injection molding permits mass-production, high

precision, and three-dimensional virtual net shape manufacturing of plastic parts. While

there are many variations on the basic process, 90 percent of injection molding occurs

with thermoplastic resins, and injection molding accounts for one-third of all resins

consumed in thermoplastic processing. Injection molding requires an injection-molding

machine, a mold, and ancillary equipment such as material-feeding and conveying

equipment, dryers, mold temperature controllers, chillers, and robotics and conveyers.

The material feeding and conveying equipment and the dryers are common to most

thermoplastic manufacturing processes, while the robotics and conveyers automate the

molding process. Basic injection-molding machines and plastics and basics of mold are

discussed in the next sections.

Injection molding is a high-rate production process, with good dimensional

control. Typical cycle time range from 5 to 60 sec, but can be several minutes for

thermosetting materials & this time is controlled using punched cards, punched tape or

computer. The dies are generally made of tool steel or beryllium-copper. Proper die

design & control of material flow in the die cavities are important factors in the quality of

the product & so are injection pressure, temperature & condition of the resin. Injection

molded parts are generally molded to final desired dimensions & no subsequent finishing

operation is required. When thermoplastic resins are molded, the sprue& runners can be

chopped & recycled. Newer & more expensive molds have heated sprues& runners,

which eliminate the need of trimming.

The success of any molding job depends heavily on the skills employed in

the design and construction of the mold. An injection mold is a precision instrumentyet

must be rugged enough to withstand hundreds of thousands of high-pressuremolding

cycles. The added expense for a well-engineered and constructed moldcan be repaid

many times over in molding efficiency, reduced down time and

scrap, and improved part quality.

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In brief the injection molding process contains roughly four important stages

before the final plastic product leaves the mould.

I InjectionInjection of melted plastic into the mould is the first stage of the process. With a piston or

a screw, the heated plastic is forced into the mould chamber. The injection is done under

high pressure, and the plastic should be distributed as evenly as possible in the mould

chamber.

IIAdditional injectionAfter injection the plastic begins to cool down. During cooling the material shrinks a bit

which is compensated for by injecting more plastic into the mould. Through additional

injection the plastic is prevented from getting back into the cylinder. The amount of time

required for added injection depends on the shape of the product.

III Cooling

The plastic product must cool down to make it keep shape after it's been detached from

the mould. In order to hurry this stage of the process the mould has a built-in cooling

system. During the cooling process the screw or piston is withdrawn and the funnel is

refilled for the next product.

IVEjection

After cooling the product is detached from the mould. Often it takes more than just

opening the mould before the plastic product falls out. Using ejectors such as ejection

sticks, ejection plates, or compressed air, the product is pushed out of the mould which is

then closed, and the process starts all over again.

FIG-31

Injection

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Additional injection

FIG-32

Cooling

FIG-33

Ejection FIG-34

Injection molding machines are generally horizontal & are rated according to

the capacity of mold & the clamping force on the dies. Although in most machines this

force generally ranges from 0.9 MN-to 2.2 MN [100 tons-250 tons], the largest machine in

operation has a capacity of 45 MN [5000 tons] & can produce parts weighing 25 kg.

However, parts typically weigh 100-600g [3-20 oz]. Because of the high cost of dies,

ranging from $20,000 to 200,000, high-volume production is required to justify the

investment.

9.2 INJECTION MOLDING MACINES

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Horizontal in-line Most commonly encountered design allows gravitational free fall of ejected

components away from mold halves on opening.

Uses: general-purpose molding.

Vertical in-line Requires less working floor space than horizontal in-line machine.

Uses: insert, loaded & over-molded components, frequently used in conjunction

with robots, etc.

Horizontal lock- vertical inject Enables injection directly into the split line of the mold & free fall ejection to occur.

Uses: enables direct feeding of components in smaller more economic bolsters.

Vertical lock-horizontal inject Enables injection directly into the split line of the mold.

Uses: frequently used for small insert loaded or multi-colored molded components.

Multi-unit configurations

Often manufactured directly to customer requirement (e.g. twin lock /inject configuration for the production of cases halves).

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FIG-35 Reciprocating-screw injection-molding machine.

FIG-36Injection unit.

Machine specificationsMolding machine manufacturers frequently specify their machine size rating

either by the lock tonnage available or the plasticizing capacity of the injection unit

(usually based upon polystyrene). In addition to choosing the intended machine

configuration, attention must be paid to the machine specification in order to enable the

intended mold design to function efficiently.

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The Reciprocating screw The reciprocating screw forms the backbone of the injection unit. In its

conventional form the screw is designed to perform the following functions

1. Feed the material

2. Melt & compress the material

3. Meter, thermally homogenize the material & pump it over the check value

against the backpressure.

4. Inject the required shot volume into the mold.

An extra function of the screw can be to de-gas the melt in case of wet or

hygroscopic feedstocks. A vented screw & barrel assembly are used in this case.

The conventional screw is divided geometrically into three zones; feed, compression &

metering.

1. Feed zone: The length of feed zone of the reciprocating screw is longer in comparison

with both the transition & metering zones. The extra length of the feed zone is provided to

cater for the shortening of screw in its fully retracted position. The typical feed depths &

screw diameter is in the following table. Screw feeding capacity is a function of the

Screw diameter

Channel depth

Channel width

Helix angle

Speed

Coulomb co-efficient of friction between polymer & screw (μs) & between polymer &

barrel (μb).

The feed zone analysis also shows that a reduction in the ratio μs/μb

results in an increase in conveying capacity. This is equivalent to using a smooth

screw & rough barrel combination. The analysis of feed zone also predicts that the

helix angle has an optimum value close to commonly used 17.5 ° (square pitch) & that

depravity from this value is found to reduce the feeding capacity. Further any increase

in screw channel depth in the feed section increases the feed capacity of the screw.

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2.Transition zone (Melting zone): This is the zone where the polymer is transformed

from the solid state to the molten state. It is true to say that in the transition zone three

functions take place simultaneously. These are melting, pumping & mixing, Majority

melting takes place in the interface between the barrel/screw & the solid bed. The

molten polymer is conveyed by the scraping action of the screw flight from the barrel

melt interface to melt pool between the solid bed & the leading edge of flight. The rate

at which the polymers melt inside the screw channel determines the screw plasticizing

capacity.

An important design parameter that controls the rate of melting in the transition zone is

its degree of taper. The higher the taper, the higher is the rate of melting & the shorter

is the length of the transition zone required to achieve complete melting. Experience

shows that an adequate length of the transition zone for a 20: 1 diameters long screw

is 4 to 5 diameters (D) for a general-purpose screw.

3. Metering zone (pumping section): The function of metering zone is to stabilize the

flow of the molten polymer from previous zone & also to build the pressure at the end

of the screw to overcome both the restrictions from the check valve & backpressure.

Most of the mixing & thermal homogeneity takes place in this by simple shear.

9.3 INJECTION MOLDS

When thermoplastics are heated in plasticizing unit & injection pressure is

applied, flow from the nozzle of the press into an injection mold. The mold has cavities

that, when filled with thermoplastics material, define the molded part. The material enters

into the cavities through passages cut into the mold, called runners. The mold also has

passages in it to circulate a coolant through strategic areas to chill the hot plastic. As it

cools, the thermoplastic material hardens. When cooled enough, the mold opens & the

part is removed by an ejector system.

Basic components are:

Mold base is a series of steel plates that contain mold components, runner system,

cooling system, & ejector system.

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Components are parts inserted into the base, either in bored holes or cut out pocket,

to shape & eject the part. They include cavities, cores, inserts, stripper bushing,

knockout sleeves, & knockout pins.

Runners are channels, cut into the mold base & components, to direct the flow of

molten thermoplastic from the press nozzle to the mold cavity.

Cooling channel are the holes drilled into the mold base & components to direct the

flow of coolant & control mold temperature.

Ejection systems remove the finished part after molding. Some common types are

pin, sleeve, stripper bushing, & blade.

Mold types: It is basically classified into two types.

1. Two-plate mold: Single day light Hot runner

Double day light Cold runner

Conventional sprue

2. Three plate mold:

Double day light Hot runner

Triple daylight Cold runner

TWO PLATE MOLD: Two-plate molds are most common design of injection mold used in the molding industry.

Mold designers choose the two-plate format because it offers many advantages in terms

of simplicity of design, user friendliness, and utilization of standard mold parts & above all,

it often represents the cheapest design option available. The main disadvantages of the

two-plate mold design are limitations in component gate positioning when conventionally

feeding, lack of available space for balanced feeding of multiple cavities & high material

waste levels (sprues& runners).

The two plate mold is the simplest of the entire mold design configurations,

being constructed from two distinct half units, the core half & the cavity half. The point of

which the two halves interface known as the split or part-line which divides on opening of

the mold for component ejection purpose. The core half of the mold is usually attached to

the moving platen of the molding machine since the mold ejection actuation system

(usually in the form of hydraulic cylinder) is commonly positioned behind the moving

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platen of the molding machine. The mold ejection system is correspondingly built into the

core half of the mold for actuation purpose. The cavity half of the mold is therefore

attached to the fixed platen of the molding machine directly in front of the machine

injection unit for material feeding of the mold. Cooling channels are positioned in both the

core & cavity components to control the mold temperature during use.

There are various methods by which core & cavity may be incorporated into their

respective halves of the mold. The two most commonly used are

1. The integral (or integer) method, which involves machining the core or cavity from

directly into the core or cavity, plates respectively.

2. The inserted bolster method in which the core & cavity is built up from individually

machined components & secured into machined pockets situated in the core &

cavity plate.

Two-Plate Mold

FIG-37

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FIG-38

THREE PLATE MOLD:The three-plate mold differs from the more common two-plate design format

in terms of utilizing more than one split or parting line. The tool construction is divided into

three distinct plate build-ups, which separate from each other on opening. One opening

provides clearance for component ejection, while the other allows for sprue ejection &

clearance. Being a tool of increased complexity the three-plate mold is therefore more

time-consuming & expensive to manufacture than two plates mold.

The three-plate mold opening sequence serves to highlight one of the

drawbacks encountered with this design of tool namely, long opening stroke requirement.

The major limiting factor concerned with employing any design of multi-day light tool has

to be the maximum opening stroke available on the intended-molding machine. For this

reason it is wise to calculate the required working daylight clearance before embarking

upon the chosen course of action- especially when dealing with deeply drawn moldings.

E.g. test tubes, or the like.

In order to gain control over the required mold opening sequence, platen position & speed of

movement has to be accurately set & controlled throughout the molding cycle & production run. In

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general, the closing of the three-plate mold is achieved by the closing action of the molding

machine platens, which progressively pick up & close the mold sections as they move forward.

Schematic of a two-cavity, three-plate mold with cutaway view Schematic of a two-cavity, three-plate mold with cutaway view showing first stage of opening showing second stage of opening. FIG-39 .

FIG-40Schematic of a two-cavity, three-plate mold with cutaway viewshowing final opening phase and

stripper plate in forward position.

Basis for selection of three-plate mold (Why choose a three-plate mold?)

The main reason for choosing the three-plate tool layout is flexibility, which the design

offers in terms of gate location. The three-plate configuration enables the inclusion of

multi-gate positions on larger moldings or the center gating of smaller components to

produce better quality moldings. The more recent emergence of runner less or hot runner

mold design has largely reduced the practically of adopting the three-plate design format

for most molding operations, with the various hot runner mold design, the three-plate

design still offers a few advantages, usually in terms of the following.

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1. Ease of material or color changing during use; the three-plate mold clears its

feed system every working cycle giving fast color changes without the prob-

lems of long-term material contamination.

2. Reliability, the relative complexity of many hot runner tool designs, especially their

heating & control systems makes them prone to electrical failure a subsequent

breakdown. Three-plate molds, having very few electronic components, tend to be

more reliable once set & running although having more mechanical moving parts,

i.e. linkages, bearings, etc., the three-plate design tends to be more prone to me-

chanical failure if not correctly serviced.

3. Cheaper initial capital outlay, mold heaters & temperature control equipment can be

very expensive, often resulting in high initial capital expenditure. For shorter pro-

duction run requirements, the additional capital outlay may not be financially viable

& the three-plate option could provide a cost-effective alternative.

4. The molding of thermally sensitive polymers, the thermal sensitivity of some poly-

mers could dictate need to process the material on a conventional design of mold

tool, i.e. not hot runner. In such cases two-plate mold designs are conventionally

employed but in instances when the component gate location demands off the

edge sitting the three-plate conventional format is worth consideration. Although

the three-plate mold design offer advantages under certain circumstances, gener-

ally the design tends to be inferior when compared to the production efficiency of

the various hot-runner designs available.

9.4 MOULDING UNDERCUTSAn internal undercut is any restriction which prevents a moulding from being

extracted from the core in the line of draw. Various methods are used for relieving internal

undercuts; the specific design adopted depends upon the shape and position of the

restriction.

Part features that prevent straight ejection at the parting line, tend to increase mold

complexity and lead to higher mold construction and maintenance costs. Whenever

feasible, redesign the part to avoid undercuts.

Minor part design changes can often eliminate problematic undercuts in the mold. For

example, adding through holes can give access to the underside of features that would

otherwise be under-cuts (see figure). Likewise, simple modifications enable the mold to

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form a hole in the sidewall with bypass steel rather than with a sideaction mechanism. For

more information on design alternatives to avoid undercuts

Undercut Alternatives:

FIG-41

Undercut features that cannot be avoided through redesign require mechanisms in the

mold to facilitate ejection. These types of mechanisms include

1. Side-action slides

2. Lifter rails

3. Jiggler pins

4. Collapsible cores and

5. Unscrewing mechanisms

9.4.1 Side-action slides

Use cam pins or hydraulic (or pneumatic) cylinders to retract portions of the mold

prior to ejection. Cam-pin-driven slides retract as the mold opens (see figure). As the mold

closes, the cam pins return the slides to their original position for the next injection cycle.

Slides driven by hydraulic or pneumatic cylinders can

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activate at any time during the molding cycle, an advantage in applications requiring the

slides to actuate prior to mold opening or closing.

` FIG-42

9.4.2 Lifter railsShallow undercuts can often be formed by spring-loaded lifters (see figure) or lifter

rails attached to the ejector system. These lifters move with the part on an angle during

mold opening or ejection until the lifter clears the undercut in the part.

FIG-43Typical spring-loaded lifter mechanism.

9.4.3 Jiggler pin:

The “jiggler” pin (see figure), has angled surfaces to guide the pin away from the

undercut during ejection, then return it to the molding position as the ejector system

retracts.

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FIG-44

Angled surfaces slide the jiggler pin to clear the undercut during ejection.

9.4.4 Collapsible cores:Features such as internal threads, dimples, slots, or grooves on the inside of holes or

caps may require collapsible cores. These complex cores are made in segments that

collapse toward the center as they retract during mold opening (see figure). Available in a

variety of standard sizes from various mold-component suppliers, these specialty cores

are typically modified to produce the desired undercut shape. The number and complexity

of individual core components limit the minimum size of collapsible cores. Collapsible

cores are rarely used for inside diameters less than 0.625 inch.

FIG-45Standard-style collapsible core pin in expanded and contracted position.9.4.5 Unscrewing mechanisms:

These are commonly used to produce internal threads. A variety of devices can

drive the rotation of the threaded cores, including rack and-pinion devices actuated by

mold opening, motors, or hydraulic cylinders; or motor-driven gear and chain

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mechanisms. The mold design should include provisions to lubricate the various moving

parts of the unscrewing mechanism.

Slides, cams, collapsible cores, and unscrewing mechanisms add to the cost

and complexity of the mold, as well as the mold maintenance cost. Investigate options

that avoid complex mold mechanisms. Clever part design can often eliminate

troublesome undercuts. Some undercuts are most economically produced as secondary

operations, particularly if they can be automated or performed within the cycle at the

press.

Choosing the correct mold: The number of factors & requirements imposed on the tool designer determines choice of mold

design & construction method. A good mold designer will obtain as much information as possible

about the following.

1. Component:Obtain the final signed- off drawing issue from the prospective cus-

tomer. Obtain commercial information regarding the component e.g. component

cost, size of required production batches, estimate of production cycle time accept-

able to the customer, mold life requirement, etc.

2. Material to be processed:Obtain information on material properties e.g. shrinkage,

cooling requirement, rheological features, thermal stability etc.

3. Machine data:obtain a machine specification manual.

9.5 FEED SYSTEM:

Feed system is a flow-way in the injection molds to connect the nozzle to each

impression. This flow-way is termed the feed system. Normally the feed system

comprises a sprue, runner & gate.

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FIG-46

Runner: The runner is a channel machined into the mold plate to connect the sprue with the

entrance (gate) to the impression (cavity). The wall of runner channel must be smooth (about 50

rms.) to obtain low-pressure drop & preventing the runner to stick to the mold surface.

Cold slug well:In runner layout cold slug well is provided opposite to the sprue to receive

the degraded material that has (over heated), chilled at the nozzle during cooling &

ejection phase. This well is equal to dia. of sprue at the parting line & is about 1-1.5 times

the diameter in depth. In some molds cold slug well acts as a retainer for the sprue with

runners on the moving half of the mold.

DESIGN CONSIDERATION OF RUNNER SYSTEM:1. Shape of cross section of the runner: The shape of runner should provide the maximum

possible from the point of pressure transfer & minimum contact on the periphery from the point

of heat transfer. The ratio of cross-sectional area to periphery will therefore, give a direct

indication of the efficiency of the runner design the higher the value greater the efficiency.

FIG-47

RUNNER CROSS-SECTIONS

Material passing through the runner during mold filling forms a frozen wall layer as

the mold steel draws heat from the melt. This layer restricts the flow channel and increases the

pressure drop through the runner. Round cross-section runners minimize contact with the mold

surface and generate the smallest percentage of frozen layer cross-sectional area. As runner designs

deviate from round, they become less efficient (see figure). Round runners require machining in

both halves of the mold increasing the potential for mismatch and flow restriction. A good

alternative, the “round-bottomed” trapezoid, requires machining in just one mold half.

Essentially a round cross section with sides tapered by five degrees for ejection, this design is

nearly as efficient as the full-round design.

The runner system often accounts for more than 40% of the pressure

required to fill the mold. Because much of this pressure drop can be attributed to runner

length, optimize the route to each gate to minimize runner length. For example, replace

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cornered paths with diagonals or reorient the cavity to shorten the runner.

TRAPEZOIDAL RUNNER PROFILE2. Size of the runner:

Factors considered while selecting the size of runners are

• Wall section & volume of the molding

• Distance between sprue& cavity

• Cooling time design

• Plastic material used

Runner thickness has a direct effect on filling pressure, cycle time, packing, and runner

volume. The optimum runner diameter depends on a variety of factors including part

volumes, part thickness, filling speed and pressure, runner length, and material viscosity.

• For sufficient packing, make runners at least as thick as the part nominal wall thickness.

• Increase runner thickness for long runners and runners subjected to high volumetric flow

rates.

• Amorphous resins typically require larger runners than semi crystalline resins.

3. Runner layout:The layout of the runner system will depend upon the following factors • No of impressions • Shape of components • Type of mold • Type of gate.

The runner length is always kept to a minimum to reduce pressure losses. Long runner

needs a greater injection pressure & the projected area of the mold is increased & higher

temperatures are needed as length & diameter of runner increased. The runner system

should be balanced to ensure all the cavities are filled at the least time & simultaneously

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as possible (by cutting the runner so that the plastic has the same distance to travel to all

impressions & is subject to similar degrees of construction & obstruction). Otherwise

increased pressure & projected area used will result in wastage of material.

Runners for multi cavity molds require special attention. Runners for family molds,

molds producing different parts of an assembly in the same shot, should be designed so

that all parts finish filling at the same time. This reduces over packing and or flash

formation in the cavities that fill first, leading to less shrinkage variation and fewer part-

quality problems. Consider computerized mold filling analysis to adjust gate locations and

or runner section lengths and diameters to achieve balanced flow to each cavity (see

figure) The same computer techniques balance flow within multi-gated parts. Molds

producing multiples of the same part should also provide balanced flow to the ends

ofeach cavity.

Family Mold

FIG-48

The runner diameter feeding the smaller part was reduced to balance filling.

Naturally balanced runnersprovide an equal flow distance from the press nozzle to the

gate on each cavity. Spoked-runnerdesigns (see figure) work well for tight clusters of

small cavities. However they become less efficient as cavity spacing increases because

of cavity number or size.

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FIG-49

The spoked runner on the right provides a cold slug well at the end of each primary runner branch.Often, it makes more sense to orient cavities in rows rather than circles.

Rows of cavities generally have branched runners consisting of a primary main feed

channel and a network of secondary or tertiary runners to feed each cavity. To be

naturally balanced, the flow path to each cavity must be of equal length and make the

same number and type of turns and splits. This generally limits cavity number to an

integer power of two — 2, 4, 8, 16, 32, etc. as shown in figure. Generally, the runner

diameter decreases after each split in response to the decreased number of cavities

sharing that runner segment. Assuming a constant flow rate feeding the mold, the flow-

front velocity in the cavity halves after each split. The molding press flow-rate

performance may limit the number of cavities that can be simultaneously molded if the

press cannot maintain an adequate flow-front velocity

FIG-50

Naturally balanced runners for cavities in two rows.

Artificially balanced runners provide balanced filling and can greatly

reduce runner volume. Artificially balanced designs usually adjust runner-segment

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diameters to compensate for differences in runner flow length. For instance, in ladder

runners, the most common artificially balanced runner design, a primary runner feeds two

rows of cavities through equal-length secondary runners. The diameters of these

secondary runners are made progressively smaller for the cavities with shortest runner

flow distance (see figure). These designs require enough secondary runner length to flow

balance using reasonable runner diameters.

As a general rule, secondary runner length should be no less than 1/5 the flow

distance from the inboard secondary/primary runner junction to the gates on the outboard

cavities.

FIG-51

The artificially balanced runner achieves flow balance by adjusting runner diameters instead of by maintaining uniform runner length.

GATE: Gate is a channel or orifice connecting the runner with the impression. It has a small

cross-sectional area when compared with the rest of the feed system. This small cross

section area is necessary so that

1. The gate freezes after the impression is filled so that injection plunger can be withdrawn

without the probability of void being created in the molding by back sucking.

2. It allows for simple de-gating & in some molds this de-gating can be automatic.

3. After de-gating only a small witness marks remains.

4. Better control of the filling of multi-impressions can be achieved.

5. Packing the impression with material in excess of that required compensating for shrinkage is minimized.

The size of gate can be considered in terms of the gate cross-sectional area & the gate

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length.

Factors influencing the optimization of gate size are

1. Flow characteristics of the material to be molded.

2. Wall section of the molding.

3. Volume of material to be injected into the impression.

4. Temperature of melt.

5. Temperature of the mold.

No theoretical size exists for the ideal gate. The gate size chosen in practice for a

particular component is normally based on past experience; otherwise, suitable

calculations are adopted for calculating gate dimensions.

POSITIONING OF GATE: 1. Gate must be placed in such a way that rapid & uniform mold filling is ensured.

In principle, the gate will be located at the thickest part of the molding preferably at a

spot where the function & appearance of molding are not important.

2. Gate must be placed in such a way that weld lines, gas traps, sink marks, & voids

should be taken into consideration, otherwise strength of component is reduced &

spoils the appearance of the molding.

3. Gate must be placed such that the air present inside mold cavity can escape easily

during plastic injection into the mold. If this requirement is not fulfilled either short

shots, or burnt spots on the molding will the results.

4. During mold filling thermoplastic, shows certain degree of molecular orientation in the

flow direction of melt which affects the properties of the molding & important factors

with respect to the location of gates & type of gate.

5. Gate must be placed in such a way that no jetting of plastic occurs in the mold cavity.

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Gate Types

Gate Uses/advantages

Edge For top, Side or bottom of part

Submarine Allows automatic de gating of part from

runner system during ejection.

Pin point Permits automatic ejection.

Disk For objects with large cutout areas;

eliminates weld line.

Center Similar to pinpoint but is larger; also gate

extension is left in molded part.

Fan useful for fragile sections & large area

objects.

Ring For cylindrical shapes

Tab A small gate area that enhances frictional

heating; useful for Acrylics, ABS &

polycarbonates.

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FIG-52

Gates: (a) sprue (b) tab (c) edge (d) fan (e) disk (f) spoke g) Ring (h) film (i) pin (j) hot probe and (k) submarine

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9.6 MOLD COOLING:In thermoplastic molding, the mold performs three basic functions: forming

molten material into the product shape, removing heat for solidification, and ejecting the

solid part. Of the three, heat removal usually takes the longest time and has the greatest

direct effect on cycle time. Despite this, mold cooling-channel design often occurs as an

afterthought in the mold-design process; after the feedsystem, mold mechanism, and

ejection system designs are already designed. Consequently, many cooling designs must

accommodate available space and machining convenience rather than the

thermodynamicneeds of the product and mold. This section discusses mold cooling, a

topic to consider early in the mold-design process.

Good mold-cooling design maintains the required mold temperature,

provides uniform cooling, and achieves short molding cycles. Optimizing mold cooling

promotes improved part quality and cost savings. Improper cooling can introduce

elevated levels of thermal and shrinkage stresses resulting from cooling- rate variations

throughout the part. Differences in cooling rate cause areas to shrink and solidify at

different rates and by different amounts. In parts made of semicrystalline resins such as

PA 6 or PBT, the cooling rate affects thedegree of crystallization and shrinkage. Variations

in shrinkage within the part can lead to warpage, distortion, and dimensional problems.

Before heat from the melt can be removed from the mold, it must first conduct

through the layers of plasticthickness to reach the mold surface. Material thermal

conductivity and part wall thickness determine the rate of heat transfer. Generally good

thermal insulators, plastics conduct heat much more slowly than typical mold materials.

Cooling time increases as a function of part thickness squared; doubling wall thickness

quadruples cooling time.

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FIG-53

Mold cooling time Time required to cool the molding in depend upon

1. The thermal properties of the polymer to the processed.

2. Thermal properties of the mold construction material used.

3. Distance from which cooling channels are placed

4. Cooling medium is used.

Above-mentioned factors have a direct influence on the cooling efficiency of

mold & the resultant quality of the molding produced. The final component production cost

is predominantly influenced by the molding cycle time of which a high proportion is

concerned with cooling of the molding.

Cooling media:The mold temperature required is dictated by the thermal requirements of

the polymer to be processed. To achieve the required mold temperature a range of

cooling (or heating) media are employed.

Commonly encountered coolants are:

Cooling Medium Thermal working range 0C

Antifreeze (e.g. water/glycol) 20-0

Inhibited chilled/heated water 0-90

Heated oil 90-200

NTTF SPG, BANGALORE


Electrically heated 150-450

(Usually in conjunction with water or oil, as above)

Using correct cooling medium is essential if the required heat removal rate

is to be achieved. Maintaining the coolant temperature may prove a costly process in

terms of the need for additional ancillary equipment of the required thermal capacity, e.g.

individual mold oil heater & water chiller units.

Conductive thermal properties of mold construction materials The thermal conductance properties of the mold materials have a direct

influence on the thermal efficiency of the mold. The mold designer can over look this point

during the material selection process. Mistakes occur when mold materials of relatively

low thermal conductivity are used in conjunction with polymers of relatively high specific

heat. Thermal conductance of mold making materials

Mold construction material Thermal conductivity (W/m K) Steel 46.0

Iron 62.7

Brass 104.5

Zinc 108.7

Beryllium copper 115.4

Aluminum alloy 120.8

Aluminum 209.0

Copper 384.6

Silver 405.5

Cooling-Channel Placement:Cooling-channel placement determines cooling efficiency and uniformity.

Positioning the channels too close to the cavity surface can cause cold spots and uneven

cooling. If they are too far away, cooling becomes more uniform but less efficient.

Place cooling-channel centerlines approximately 2.5 cooling-channel diameters

away from the moldcavitysurface.

As a general rule of thumb, use center-to-center spacing of no more than three

cooling-channel diameters

NTTF SPG, BANGALORE


FIG-54

Cooling-line spacing guidelines.

TYPES OF COOLING METHODS:1. Flat plate cooling

2. Baffle cooling

3. Spiral cooling

1. Flat plate cooling: Plane or plateau cooling relates to a cooling system in which the cooling

channels lay to each other within the same level or plane. This design of system can be employed

to cool large flat moldings of uniform cross-section, e.g. a plastic tray molding. Two distinct

feeding methods are employed, one connected in parallel the other in series.

2. Baffle cooling: By using baffles we can remove heat from deep cores. Adjust the

bubbler tube or baffle length for optimum cooling. If they are too long, flow can become

restricted. If too short, coolant flowmay stagnate at the ends of the hole.

In bubblers, coolant flows up through a tube and then cascades down the outside

of the tube. Baffles perform a similar function by splitting the channel with a blade.

Coolant flows up one side of the blade and then down the other side.

3. Spiral cooling:Spiral cooling systems are frequently employed for the cooling of centrally gated

moldings and for large cores. E.g. plates, bowls & buckets. The coolant enters the system at the

center & then circulates to the extremities of the mold to exist.

NTTF SPG, BANGALORE


FIG-55

Baffle cooling spiral cooling

Cooling-Line Configuration: Cooling lines can be arranged in series or parallel

configurations Cooling lines in parallel circuits share the coolant delivered by the mold

temperature controller. Assuming equal pressure drop per line, the coolant flow rate- per-

line approximately equals the total flow rate delivered by the temperature controller

divided by the number of parallel lines connected to it. For example, a 10 gallon-per-

minute control unit would deliver about 1.25 gallons per minute to each of eight

equalparallel cooling lines.

Slight differences in pressure drop between parallel lines can cause large

differences in coolant flow rate andpotential cooling problems. Series circuitsavoid this

problem by maintaining a uniform coolant flow rate throughout the circuit. On the other

hand, a large rise in coolant temperature in long series circuits can lead to less efficient.

FIG-56

NTTF SPG, BANGALORE


9.7 EJECTION: All the thermoplastic materials contract as they solidify which means that the

molding will shrink on to the core. This shrinkage makes the molding difficult to remove. In

normal practice, some means by which the mold cavity is polished in the direction of withdrawal

of component & additional taper (draft) is also provided to the cavity for easy removal of

components. Insufficient draft can cause deformation or damage of part. For deeper cavity more

draft is necessary than the lesser deeper cavity. Recommend draft: For small moldings 0.5 to 10for

large moldings up to 3 0.

Parts removed from mold are largely governed by article, size, shape, rigidity & flexibility

of plastics. Designed ejector system should not cause any permanent deformation or

damage to the component.

Facilities are provided in the injection-molding machine for automatic actuation of

an ejector system, & this is situated behind the moving platen. Commonly mold ejector system will

be most effective into the moving platen.

The ejector system in a mold is classified into three categories

1. Ejector grid

2. Ejector plate.

3. Method of ejection.

Ejector Grid:The ejector grid is that part of the mold which supports the mold plate &

provides a space into which ejector plate assembly can be fitted & operated. The grid

normally consist of a back plate on to which is mounted a number of a conveniently

shaped "support blocks".

Ejector Plate Assembly: It is a part of the mold to which the ejector element is attached.

It consists of an ejector plate, retaining plate & an ejector rod. The purpose of ejector

plate is to transmit the ejector force from the actuating system of the injection machine to

the molding via an ejector element.

Retaining plate is securely attached to the ejector plate by screws & its purpose is to

retain the ejector element. Heavy ejector plate assembly is guided by bush in the mold

itself or guide-ways in the injection mold machine for accurate alignment.

NTTF SPG, BANGALORE


Ejection methods (or techniques):

1. Pin ejection:It is simplest to incorporate in mold. With this technique molding is ejected

by application of a force by a circular steel rod, called ejector pin.

2. D-shaped ejector pin:It is primarily used for the ejection of thin-walled box type

molding & cross section & the pin looks like D-shape.

3. Sleeve ejection:with this method, the molding is ejected by means of a hollow ejector

pin & is termed as a sleeve. It is used in one of these circumstances.

1. For the ejection of circular moldings

2. For ejector of circular bosses on a molding of any shape.

3. To provide positive ejection around a local core pin deforming a round hole in

molding.

4. Blade ejection: The main purpose of the blade ejector is for the ejection of very

slender part such as ribs & other projections. Blade is basically a rectangular ejector pin.

The long thin blade is guided with some support to avoid the deflection of blade &

breakage.

5. Valve ejection:This system basically consists of a large diameter ejector pin & it is

used for large components where standard parting surface pins is impracticable for

efficiently use.

6. Air ejection:In this system the component is ejected by ejector pin by the application

of compressed air. The effective ejector force is dependent upon the pressure of

compressed air & the area on which it acts.

This system is particularly used for box-type components where the sidewalls act as seal

during a major part of the ejector stroke & thus preventing the escape of the compressed

air.

Advantages of air ejection:

1. No ejector assembly is required, hence this system reduces the cost of mold.

2. Air ejection system can be operated at any time during the operating stroke of the ma-

chine.

3. Distortion of component is reduced.

Disadvantage of air ejection system

NTTF SPG, BANGALORE


1. This method is only effective on certain types of component.

2. Compressed air supply must be readily available.

3. Air is a expensive service, hence it is not suitable for all cases.

7. Stripper bar ejection:This method is extension of the parting surface ejector pin

principle in which the ejector element is caused to push against the bottom edge of the

molding & is particularly suitable for thin-wall box-type moldings.

8. Stripper plate ejection:This technique is used primarily for circular, box-type moldings

while the design is used for shapes other than circular particularly for those which have

thin wall section the mold cost which results is relatively high.

9.8 SHRINKAGE:Mold shrinkage (in-mold shrinkage or molded part shrinkage are more

accurateterms), although a volume phenomenon, usually refers to the difference

betweenthe linear dimension of the mold at room temperature and that of the molded

partat room temperature within forty-eight hours following ejectionIt is change in

dimensions of component with respect to the mold cavity aftermold is cooled. With long

chain polymers in this forward moving unfolding path ofmaterial, there is a tendency for

orientation of the chain in the line of flow.

The length, breadth & width of molding must all have a shrinkage factor, but as

the breadth & width are at right angles to the length & in the same plane

together, the factor will usually be common for them regardless of their direction.

But practically we are only concerned with two factors in reality, the shrinkage

factor on the length of flow, the shrinkage factor on width or breadth of flow; or

more simply stated, shrinkage across the flow. In all cases, shrinkage with the

flow is of greater magnitude than across it.

In-mold shrinkage tends to respond to changes in molding conditions as

NTTF SPG, BANGALORE


shown below.

An increase in: Effect on shrinkage:

Injection pressure Decreases (usually)

Injection rate May be either (minor effect)

Holding pressure Decreases

Holding-pressure time Decreases until gate freeze

Melt temperature May be either

Mold temperature Increases

Clamping pressure Usually none; may decrease

Wall thickness May be either; usually increases

Melt flow rate Decreases

Ejection temperature Increases

Cooling time Decreases

Gate minimum dimension Decreases

Number of gates Decreases

Amount of filler Decreases

Kind of filler May be either

Mold-open time May be either

(operator break)

Environmental factors may have subtle effects on actual mold or melttemperature:

An increase in: Effect on shrinkage:

Room temperature Increases

Humidity Increases

Air movement May be either; usually decreases

The way in which the mold is filled influences the direction, degree, and type

ofmolecular orientation in the molding, especially near the surface. As the materialflows

into the mold, a spherical volume of material in the melt front is stretchedas it advances

into an ellipsoidal shape. The ellipsoid formed can be many timesgreater in length than in

width resulting in almost total straightening of molecularstrands and reinforcing fibers in

the flow direction. Dramatic evidence of thisshape change can be found in foamed

injection-molded parts. The silverystreaking on the surface is actually a multitude of

formerly spherical bubbles thathave elongated (stretched) as they approach the wall of

NTTF SPG, BANGALORE


the mold. An inspectionof this type of part indicates that any single streak is many times

longer than it iswide.

The flowing, stretched plastic is cooled rapidly by contact with or proximity to

themold wall; the fiber and molecular orientations are retained. While this ishappening,

fresh material flows between the frozen surface layers to create anew melt front. This

process continues until the mold is full. Relaxation andrandomization take place rapidly in

the melt if it has a low viscosity, and orientation is therefore highest when the melt

temperature is relatively low.On the other hand, high melt and mold temperatures give

more time for randomization and can reduce the tendency to warp. A compromise may

benecessary between product quality and production economics because low

melttemperatures reduce cycle times.

Determination of Shrinkage:ASTM D955-00 is the American document (related document: EuropeanStandard ISO

294-4) that specifies the standards that are to be used todetermine shrinkage of plastics.

[5] It states that the difference in size of themolded part and the mold is “shrink” and is

affected by a variety of factors.

Among the factors causing variation in the actual shrinkage are:

The size and shape of the part

The size and length of the runners, gates and machine nozzle

The wall thickness of the part

How the mold works and the effectiveness of the cooling channels in the mold

The flow patterns within the mold

The molding machine settings including holding times and pressures.

Minimum shrink will occur when a maximum amount of material is forced

into the mold cavity for the longest possible time as a result of adequately sized flow

channels, and when pressure is maintained at an adequately high level until the plastic is

thoroughly hardened. High shrinkage will occur when an inadequateamount of plastic is

forced into the mold and the pressure on the plastic ismaintained for too short an interval

of time. High viscosity materials make it moredifficult to maintain adequate mold pressure,

therefore tend to shrink more.The plastic whose shrinkage is to be determined may

require some specialpreparation before it is molded. For example, some thermoplastics

absorbmoisture, even from the air, and must be dried before they are introduced into

amolding machine.

NTTF SPG, BANGALORE


9.9 STEELS FOR INJECTION MOLD Steel selection in tooling can be as critical to the success of a plastics application as

the selection of resin is to the end use performance requirements of the molded product. Just as

resins are formulated to meet performance requirements in plastics applications, steels are alloyed

to meet specific performance requirements in use.

Some applications may require a mold steel with high hardness and wear resistance

for parting line durability, while others will require a mold steel with higher toughness for

resistance to mechanical fatigue. In general, steels delivering higher hardness and wear resistance

properties are those that tend to be more brittle, and in almost all cases, a steel with greater

toughness will deliver some reduction in resistance to steel-to-steel wear (adhesive wear) and

abrasive resistance to resins containing glass fibers or mineral fillers. A mold maker may select a

stainless steel to mold a resin that could be aggressive to most other steels. Listed in are some of

the most commonly used materials in mold building. Parting line integrity will typically be greater

with higher hardness steels (Rockwell 55 or higher), and where steel-to-steel shut-offs produce

coring. One or both steel faces should be in the hardness ranges of Rockwell 55 to Rockwell 58.

For abrasion protection from glass or mineral filled resins, it is suggested that gate inserts of A-2,

D-2 or M-2 steel be considered with an abrasive-resistant steel be inserted in the mold core

opposite the gate.

P-20 Steel While there is no “general purpose” steel for plastic molds, P-20 steel has

been regarded as the workhorse of the industry. Supplied in the pre-hardened state at Rc

30-32, it is very tough, yet fairly easily machined. It is a good steel to consider in

applications where cavity sizes exceed 12 ´ 12 ´ 12 inches (303.6 ´ 303.6 ´ 303.6 mm),

since the cost and associated risks of heat-treating blocks of this size may be prohibitive.

P-20 steel is also chosen in smaller cavity sizes to eliminate the time and expense of heat

treatment when it is anticipated that the mold will not exceed 500,000 cycles. When

constructing a mold of P-20 steel where slides, lifters or other cams or moving

components are necessary, it is suggested that these moving steel components be made

of steels with different alloying and hardness to reduce galling or high adhesive wear. A

common practice in large molds of P-20 steel is to employ slides or lifters of H-13 steel

that is heat treated to Rc 50-52 or to employ localized wearing surfaces of steels in the Rc

55 through Rc 58 ranges, or both.

NTTF SPG, BANGALORE


H-13 and S-7 Steels These steels offer an extremely high degree of toughness and mechanical

fatigue resistance with a perceived higher toughness in H-13 (Rc 50-52) but better

durability in S-7 because of higher hardness (Rc 55-57). Neither exhibits exceptional

abrasion resistance from glass or mineral resin fillers. Gate inserts of A-2, D-2 or M-2 are

commonly used in filled resin applications. It is common for H-13 to be chosen in cavities

larger than 8 ´ 8 ´ 8 inches (202.4 ´ 202.4 ´ 202.4 mm) where a higher degree of hardness

and toughness over P-20 is required. Smaller cavities and cores are commonly

constructed of S-7. S-7 can be heat treated in an air quench in small cross sections of 2

1/2 inches (63.25 mm) or less, and offers very good dimensional stability through this

process. Large cross-sections of H-13 and S-7 must typically be quenched in oil.

Commonly Used Materials in MoldBuilding

NTTF SPG, BANGALORE


NTTF SPG, BANGALORE


CALCULATIONS:ESTIMATION OF CYCLE TIME:CYCLE TIME = Fill time + solidifying time + mold opening and closing time +

ejection time

A. FILL TIMEInjection of material into the impression is equal to fill time.Fill time = 2.771 sec (from mold flow)

B. SOLIDIFYING TIMESolidifying time is proportional to the square of the wall thickness.

TS = ρ x a x t 2 8 x λ x (TMAT - TMOLD)

Where, ρ = density of plastic (gm/cc) a = Total heat of plastic (cal/gm)

t = wall thickness (cm)λ = Thermal conductivity of plastic (cal/cm sec °C)

Substituting the values in the equationTS = 1.4 x 110 x (.151) 2

8 x 5.5x 10-4 (175-80) = 8.4 = 10 sec (approx.)

C. MOULD OPENING AND CLOSING TIMEApproximately 10 seconds

D. EJECTION TIMEApproximately 10 seconds

E. PACKING TIME = 6.132 seconds (From mold flow)

CYCLE TIME = 2.771 + 10 +10 +10 +6.132 = 38.903 seconds = 40 sec

NTTF SPG, BANGALORE


MOLD MACHINE CALULATIONS:

Material = PPTD40

Density = 1.4 gm/cc= 0.014 gm/ mm3

Volume = 5526.3 + 8507.296 =14033.596 mm3

Wt. of component = Density x Volume= 0.014 x 14033.596= 196.47 gms

Wt. of feed system = 10% of wt. of component= 0.1 x 196.47 = 19.64 gms

Total shot wt. = 196.47 + 19.64= 216.11 gms= 217 gms

Projected Area of component = 16792.53 mm2

= 167.92 cm2

Projected Area of runner = 4534.50 mm2

= 45.34 cm2

Mold Type = 3 PLATE MOLD

Type of Gate = PIN POINT GATE

Mold Shut Height = 328

Mold Dimensions = 330X220

No. of Cavities = 01

Machine selection is done on the following three factors:

1. Based on Shot capacity

2. Based on Clamping tonnage

3. Based on Plasticizing capacity

NTTF SPG, BANGALORE


1. BASED ON SHOT CAPACITYWt. Of component =0.19647 Kg

=196.47 gms

Wt. Of Feed system = 10% of Wt. of component = 0.1 x 196.47

= 19.64gms

Total shot weight = 196.47 + 19.64 = 216.11 gms

2. BASED ON CLAMPING TONNAGE

CLAMPING FORCE (Fc) = PC X {(AP X No. of cavities) + Ar}Where,

PC = Cavity pressure (Kg/cm2)Ap = Projected area in cavity (cm2)Ar = Projected area in runner (cm2)PI = Injection pressure (Kg/cm2)PC = (1/3) PI for easy flow materials

= (1/2) PI for viscous materials PP is an viscous flow material.

PI for PP = 700-1400 Kg/cm2

Selecting PI as 1100 Kg/cm2

Pc = (1/2) x 1100 = 550 Kg/cm2 (Approx.)

Fc = 550 {(70.56 x 2) + 2.06}

= 550 x 145.35

= 79942.5 Kgf

= 80 tonnes (Approx.)

3. BASED ON PLASTICISING CAPACITY

Plasticizing capacity = shot weight x (3.6/t) Kg/HrWhere,

t = approximate cycle time in sec (3.6 for converting time in hrs and wt. in kg)

Plasticizing capacity = 216.11 x (3.6/40) = 19.44 Kg/Hr

According to the calculations and available machines, the following machine is selected:- J 85AD-110H.

NTTF SPG, BANGALORE


MACHINE SPECIFICATION:

INJECTION UNIT

SL NO ITEMS J85AD – 110H1 Screw/Barrel type A2 Screw diameter mm 353 Max. injection pressure Mpa (kgf/cm2) 225 (2290)4 Max. holding pressure Mpa (kgf/cm2) 205 (2090)5 Injection capacity cm3 1156 Injection capacity (PS) g 1057 Injection rate cm3/s 3378 Plasticizing rate (PS) Kg/h 929 Screw speed min-1 400

CLAMPING UNIT

SL NO ITEMS J85AD – 110H1 Clamping/opening force KN (tf) 834/83 (85/8.5)2 Maximum daylight opening mm 8103 Mold opening stroke (Max.) mm 3004 Mold height mm Min 180, Max 5105 Distance between tie bars (H x V) mm 410 x 3606 Platen size (H x V) mm 580 x 5307 Locating ring diameter mm Dai 1008 Ejector force KN (tf) 32.4 (3.3)9 Ejector stroke mm 8010 Minimum mold size (H x V) mm 240 x 210

OVERALL VIEW OF MODEL:

NTTF SPG, BANGALORE


FIG-57

FIXED HALF:

FIG-58

MOVING HALF:

NTTF SPG, BANGALORE


FIG-59INSERTS:

FIG-60

COST ESTIMATION:NTTF SPG, BANGALORE


INTRODUCTION:

Cost estimation, as the name implies is the estimation of the total cost of the product or component before it is manufactured, cost estimation helps in proper planning of resource, machining, manpower and expenses involved

Cost estimation can be done in two ways. In the first method, the tool to be manufactured is completely designed and then the cost is estimated for each component. But this is very tedious, time consuming process and involves the detailed knowledge of working hours and costs in mould making, but accuracy of estimation is high. The second method is the cost similarity method, in which the is to estimated is compared with another existing mould in the shop or in design. The cost of these moulds are generally known and can be used for the new component.

The mould cost mainly included the following: 1. Material cost

2. Machining cost

3. Heat treatment cost

4. Cost of bought out items

5. Trail cost

6. Design cost

7. Profits.

The basic procedure of estimating the cost of a mould is as follows:

First weight of material being used for different components is found out. The cost

per kilograms of different material is then listed out. With this we can find out the total raw

material cost.

Next the processes involved in the manufacturing of the each of the component are

listed and time required for machining of each component is calculated/estimated with

experience. The product of machining time wit particular process and machine hour rate

will give us total machining cost.

Heat treatment costs are added to this cost. The costs of standard elements are

added later.

Generally the design cost is taken as 05-10% of the total cost. Profits are

considered to be 15% and the trail run cost is based upon yhe moulding machine being

used.

COST ESTIMATION FOR INJECTION MOULD:

NTTF SPG, BANGALORE


A. COST OF MOULD BASE-HASCO RS.1,90,000/-

B. HOTRUNNER SYSTEM RS.,90,000/-

C. MATERIAL COST

1. NIMAX [email protected]/kg RS 1,08000/-

2. MILD-STEEL [email protected]/kg RS 72,000/-

3. OHNS [email protected]/kg RS 6,400/-

4. COPPER FOR ELECTRODE [email protected]/kg RS 6,250/-

5. GRAPHITE FOR ELECTRODE [email protected]/kg Rs 10,000/- D. MACHINING COST

1. ROUGH MACHINING [email protected]/hr Rs 12,000/-

2. FINISH MACHINING [email protected]/hr Rs 31,250/-

3. WIRE CUTTING [email protected]/hr Rs 45,000/-

4. EDM [email protected]/hrs Rs 75,000/-

5. GRINDING [email protected]/hr Rs 135,000/-

E. HEAT TREATMENT [email protected]/hr Rs 8,000/-

F. STANDARD ELEMENTS Rs 4,50,000/-

G. DIE INSERTS 6-INSERTS@2500/insert Rs 15,000/-

H. TRAIL CHARGES Rs 7,500/-

TOTAL= Rs1,261,400/-

NTTF SPG, BANGALORE

mailto:[email protected]/hr


mailto:[email protected]/hrs




mailto:[email protected]/kg






I. DESIGN CHARGES (10% OF TOTAL COST) Rs126,140/-

TOTAL= Rs.1,387,540/-

J. PROFIT@15% Rs 208,131/-

GRAND TOTAL= Rs.1,595,671/-

NTTF SPG, BANGALORE


TRIAL RUN DETAILS

1. FREE MOVEMENT OF SLIDER:

SLIDER DIMNENSIONS ARE OUT OF TOLERANCE.

2. SHORT SHOTS:

3. FLASHES:

CORE ARE NOT BUTTING, RESULTING IN FLASHES.

4. STEAKS:

5. ACHIEVED DIMENSIONS:

NTTF SPG, BANGALORE


INSPECTION FOR SLIDER MOVEMENT:

FIG-61

ERROR: SLIDER COLLAR THICKNESS WAS OUT OF TOLERANCE, RESULTING INTERFERANCE AND RESISTING FREE MOVEMENT OF SLIDER WHILE MOLD CLOSING.

MODIFICATION: SLIDER COLLAR THICKNESS WAS GROUND FOR 10MICRONS TO ENSURE DIMENSIONAL TOLERANCE AND FREE MOVEMENT WHILE MOULD CLOSING.

NTTF SPG, BANGALORE


INSPECTION FOR AUSTHETICS :

AREAS OF FLASH:

1. SCREW HOLE:

FIG-62

ERROR:HIGHLIGHTED HOLE WAS NOT MOULDED DUE TO INSUFFICENT LENTH OF CAVITY PIN.

FIG-63

MODIFICATION: INSTEAD OF MANUFACTURING A NEW PIN FOR REQUIRED LENGTH THE BOTTOM FACE OF COLLAR IS GROUND TO REQUIRED THICKNESS (0.13mm) AND SHIM OF SAME THICKNESS WAS ADDED TO MAKE-UP THE GAP.

NTTF SPG, BANGALORE


2. SIDE HOLES:

FIG-64

ERROR: HIGHLIGHTED HOLES WAS NOT MOULDED DUE TO INSUFFICENT LENTH OF CORE PIN.

FIG-65

MODIFICATION: BOTTOM FACE OF COLLAR IS GROUND TO REQUIRED THICKNESS (0.15mm) AND SHIM OF SAME THICKNESS IS ADDED TO MAKE-UP THE GAP.

NTTF SPG, BANGALORE


MACHINING PROCESS CARRIED OUT:

Surface grinding:

Surface grinding is used to produce a smooth finish on flat surfaces. It is a widely used abrasive machining process in which a spinning wheel covered in rough particles (grinding wheel) cuts chips of metallic or nonmetallic substance from a workpiece, making a face of it flat or smooth.

Machine details

FIG-66

NTTF SPG, BANGALORE


BILL OF MATERIALS:

BILL OF MATERIALTOOL NO : MOL-0X-00XXX PROJECT : XXX SHEET NO: 01DATE :15-12-2014 COMPONENT NAME : Bracket REV NO : 00

MOLD BASESL NO DESCRIPTION

QTY FINISHED SIZE

MATERIAL HRC REMARK

SHEET:NO

MOLD 1 460(X)x32(Y)x330(Z) - -

MOLD BASE1 TOP PLATE 1 460x320x35 C-45 -

2 EJECTOR PLATE 1 244X320X18 C-45 -

3 EJECTOR BACK PLATE 1 244X320X20 C-45 -

4 SPACERR-LH 1 80X320X105 C-45 -

5 SPACER-RH 1 80X320X105 C-45 -

6 CORE BACK PLATE 1 410X320X35 C-45 -

7 BOTTOM PLATE 1 460x320x35 C-45 -

8 TIE BAR 1 100X35X325 C-45 -

9 SUPPORT PILLAR 4 Ф 35X105 C-45 -

10 LOCATING RING 1 Ф 120x45 C-45 -

11 SLIDER 1 STOPPER 1 110X25X55 C-45 -

12 SLIDER 2 STOPPER 1 125X53X53 C-45 -

13 SLIDER 1 HOLDER 1 136X80X52 C-45 -

14 SLIDER 2 HOLDER 1 90X106X60 C-45 -

15 KNOCKOUT ROD 1Ф 40X43 EN-31

46-48 HRC

16 SPRUE BUSH 1 Ф 45x58 EN-31 46-48 HRC

17 EJECTOR STOPPER 1 Ф 30x39 EN-31 46-48 HRC

18 GUIDE PILLAR 1 3 Ф 42X232 EN-353 52-55 HRC

19 GUIDE PILLAR 2 1 Ф 38X232 EN-353 52-55 HRC

20 GUIDE BUSH 3 Ф52x84 EN-353 52-55 HRC

21 GUIDE BUSH 2 1 Ф 48x84 EN-353 52-55 HRC

22 EJECTOR GUIDE BUSH 4 Ф 38x30 EN-353 52-55

NTTF SPG, BANGALORE


HRC

23 EJECTOR GUIDE PILLAR 4Ф 25x135 EN-353 52-55

HRC

24 RETURN PIN 4 Ф 28X167 EN-31 46-50 HRC

25 STOP BUTTON 4 Ф 25X8 EN-31 46-48 HRC

26 REST BUTTON 4Ф 25X8 EN-31 46-48

HRC

27 TUBULAR DOWEL 4Ф 42X60 EN-31 48-50

HRC

28EJECTOR GUIDE PILLAR 4 EGPD 25 -105

-MISUMI

29EJECTOR GUIDE BUSH 4 EGBH 25 -15

-MISUMI

30 INSERTS31 CORE PLATE NEW 1 410X320X61 NIMAX -

32 CAVITY PLATE 1 410x320x65 NIMAX -

33 CAVITY INSERT-1 1 34X36X76 NIMAX -



36 CAVITY PIN 1 DIA 12X68 NIMAX -

37 CORE INSERT –1 1 61X68X120 NIMAX -

38 CORE PIN-1 1 DIA8X65 NIMAX -

39 CORE PIN-2 1 DIA12X49 NIMAX -

40 SLIDER-1 INSERT 1 116X30X35 NIMAX -

41 SLIDER-1 PIN-1 1 13X20X32 NIMAX -

42 SLIDER-1 PIN-2 1 Ф 11X22 NIMAX -



45 SLIDER-2 INSERT-1 1 15X26X56 NIMAX -

46 SLIDER-2 INSERT-2 1 19X31X82 -

47NON-STANDARD PARTS

48 SLIDER-1 HEEL BLOCK 1 42X94X51 EN31 -

49 SLIDER-1 HEEL PLATE 1 36X80X5 EN31 -

50 SLIDER-1 GUIDE RAIL-1 1 90X28X40 EN31 -


52 SLIDER-1 DOG LEG 1 50X47X117 EN31 -

53 SLIDER-1 WEAR PLATE 1 136X100X6 EN31 -

54 SLIDER-2 HEEL BLOCK 1 50X66X58 EN31 -

55 SLIDER-2 HEEL PLATE 1 60X45X5 EN31 -

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58 SLIDER-2 DOG LEG 1 36X70X191 EN31 -

59SLIDER-2 WEAR PLATE 1&2 2 120X25X6 EN31 -

60 SLIDER-2 WEAR PLATE-3 1 32X30X6 EN31 -

61SLIDER 1&2 BALL PLUNGER 4 DIA12X15 EN31 -

62 SCREW DETAILS63 LOCATING RING-TP 4 M6X35 -

64 TP-CAVITY PLATE 6 M12X70 -

65 STOP BUTTON-CP 4 M6X20 CSK -

66 BP-SPACER-RH 2 M12X60 -

67 BP-SPACER-LH 2 M12X60 -

68 BP-CORE BACK PLATE 4 M12X170 -

69 EJ-BP EJECTOR PLATE 4 M10X35 -

70 REST BUTTON-BP 4 M6X20 CSK -

71 SPRUE BUSH-CP 2 M5X20 -

72 SLIDER-1 HEEL BLOCK-TP 2 M8X75 -

73 SLIDER-2 HEEL BLOCK-TP 2 M6X75 -

74SLIDER-1 HEEL BLOCK-SLIDER-1 DOG LEG 2 M8X40 -

75SLIDER-2 HEEL BLOCK-SLIDER-2 DOG LEG 1 M10X40 -

76SLIDER-1 HEEL PLATE-SLIDER-1 HOLDER 4 M5X15 -

77SLIDER-2 HEEL PLATE-SLIDER-2 HOLDER 2 M5X15 -

78SLIDER-1 HOLDER SLIDER-1 INSERT 4 M6X40 -

79SLIDER-2 HOLDER SLIDER-2 INSERT 1 M6X30 -

80SLIDER-1 GUIDE RAIL-CORE PLATE 6 M8X60 -

81SLIDER-2 GUIDE RAIL-CORE PLATE 4 M8X60 -

82CORE BACK PLATE-CORE PLATE 4 M12X55 -

83SLIDER-1 WEAR PLATE-CORE PLATE 7 M8X15 CSK -

84SLIDER-2 WEAR PLATE-CORE PLATE 7 M8X15 CSK -

85BUTTOM PLATE-SUPPORT PILLAR 4 M10X40 -

86SLIDER-1 STOPPER-CORE PLATE 2 M8X40 -

87SLIDER-2 STOPPER- CORE PLATE 3 M8X70 -

88 EJECTOR PIN

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DETAILS89 EJECTOR PIN 4 REPAX8.0X180 PPD

90 EJECTOR PIN 4 REPAX5.0X180 PPD

91 EJECTOR PIN 10 REPAX4.0X180 PPD

92 BLADE EJECTOR 10FEP-180-P8.0-W3.0-N100 PPD

93 SPRING DETAILS94 SPRING 4 B40- 102 PITECH

95 SPRING 4 V10- 025 PITECH

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CHAPTER-06

SHIM (spacer):

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FIG-67

A shim is a thin and often tapered or wedged piece of material, used to fill small

gaps or spaces between objects.Shims are typically used in order to support, adjust for

better fit, or provide a level surface. Shims may also be used as spacers to fill gaps

between parts subject to wear.

Materials:Many materials make suitable shim stock (also often styled shimstock), or base

material, depending on the context: wood, stone, plastic, metal, or even paper (e.g., when

used under a table leg to level the table surface). High quality shim stock can be bought

commercially, for example as laminated shims, but shims are often created ad hoc from

whatever material is immediately available.

Laminated shim stock is stacked foil that can be peeled off one layer at a time to adjust

the thickness of the shim.

Applications:In automobiles, shims are commonly used to adjust the clearance or space between two

parts. For example, shims are inserted into or under bucket tappets to control valve

clearances. Clearance is adjusted by changing the thickness of the shim.

In Assembly and Weld Fixtures precision metal shims are used between two parts so that

the final production parts are created within the product drawing's specified tolerances.

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CONCLUSION:

After correction in the mold as well as in mold-design for YL-1 Heater Bracket, the tool was sent for trail run, after successful trail run the mold was dispatched for production run.

REFERENCES:

1. Product catalogue from HASCO PVT LTD.

2. A. Whelan, “Injection Moulding Materials”, Applied science publishers

3. Plastic Injection Moulding-An introduction from www.azom.com

4. Irvin I Rubin, “Injection moulding theory & practice”. A Wiley-Interscience publication, New York 1972.

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http://www.azom.com/

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