cnc lab record arun ridwan

8/7/2019 cnc lab record arun ridwan

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MOHAMED SATHAK ENGINEERING COLLEGEKILAKARAI-623 806

RAMANATHAPURAM DISTRICT

NAME: S.ARUNVINTHAN . CLASS: YEAR AERO .

REG NO:

Certified that this is a bonafide record of work done by the above

students in the ME1310 - CAD / CAM Laboratory During the ye

2011.

Signature of lab-in-charge Signature of Head of the Dept.

Submitted for the practical examination held on 25.10.2010

External Examiner Internal Examiner

AN ISO 9000:2000 CERTIFIED INSTITUTION

90708141002


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CAD/CAM

NO DATE NAME OF THE SUBJECT PAGE NO. SIGNATURE

INTRODUCTION OF CAD/CAM 3

INTRODUCTION TO CAD 5

1 22.6.10 GENEVA GEAR 8

2 22.6.10 SQUARE BOLT AND HEXAGONAL NUT 10

3 12.7.10 PISTON AND RINGS 12

4 12.7.10 BUSHED BEARING 14

5 26.7.10 WALL BRACKET 16

6 26.7.10 V-BLOCK 18

CAMINTRODUCTION CNC LATHE

MACHINE19

1 16.8.10CNC LATHE USING TURNING

OPERATION22

2 16.8.10 TAPPER TURNING OPERATION 27

3 21.8.10 TURNING & FACING OPERATION 29

4 21.8.10STEP TURNING G-81 CANNED CYCLE

UNSING COMMAND31

5 23.8.10TAPPER TURNING USING G-81

CANNED CYCLE35

6 23.8.10G-68 USING COMMON CANNED

CYCLE PROGRAM38

INTRODUCTION CNC MILLINGMACHING

43

1 30.8.10 TURNING OPERATION 51

2 13.9.10 SUB-ROUTINE(CCW) PROGRAM 53

3 13.9.10 SUB-ROUTINE(CW) PROGRAM 56

4 20.9.10 MIRRORING PROGRAM 59

5 27.9.10 DRILLING PROGRAM 62

6 4.10.10 RECTANGULAR POCKETING 64

7 9.10.10 CIRCULAR POCKETING 66


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CAD/CAM

INTRODUCTION OF CAD/CAM


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CAD/CAM is a term which means computer-aided design and

computer-aided manufacturing. It is the technology concerned with the use

of digital computers to perform certain functions in design and production.

This technology is moving in the direction of greater integration of design

and manufacturing, two activities which have traditionally been treated as

distinct and separate functions in a production firm. Ultimately, CAD/CAM

will provide the technology base for the computer-integrated factory of the

future.

COMPUTER AIDED DESIGN (CAD)

COMPUTER AIDED DESIGN (CAD) can be defined as the use of

computer systems to assist in the creation, modification, analysis, oroptimization of a design. the computer systems consists of the hardware

and software to perform the specialized design functions required by the

particular user firm. the CAD hardware typically includes the computer ,o

or more graphics display terminals, keyboards, and other peripheral

equipment. The CAD software consists of the computer programs to

implement computer graphics on the system plus application programs to

facilitate the engineering functions of the user company. Examples of theseapplication programs include stress-strain analysis of components, dynamic

response of mechanisms, heat-transfer calculations, and numerical control

part programming. The collection of application programs will vary from one

user firm to the next because their product lines, manufacturing process,

and customer markets are different. These factors give rise to difference in

CAD system requirements.

INTRODUCTION TO AUTOCAD


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INTRODUCTION:

Technical drawing is the universal language of engineering sketching asdrawing.graphics is one of the oldest forms of communication through to one another using agraphic.language is known as the drawing.a drawing is a graphical representation of an object oridea.the process of creating a drawing is called as drafting.

LATEST TOOL USING FOR ENGINEERING GRAPHICS:

In the last 25 years major growth has occurred in computer technology and the use ofcomputer to create graphics.the growth of computer graphics has followed.closely the evolution of thecomputer today computer became an indispensable and the enginerring and it is progressive industryuses some cad/cam application to develop their product from art of part .among these autocad is oneof the best software.nowadays most of the industry uses the autocad to create part drawing.

APPLICATIONS:

Architecture drawingInterior design and facility drawing

Drawing for various engineering applications

Technical instructions

Sketches for the fine axis

ADVANTAGES:

*It provides easy use and lesser consumer times

*It offers a clean and comfortable approach to draft

*it provides the drawing with high accuracy and precision.

SPECIAL FEATURES:

*Scaling ability to enlarge or decrease the size of displayed features without change in itsshape.

*Translating the capability to move parts of drawing and redrawing them in the new position ofselected scale.

*Rotating the capability of rotating features about a selected center and redrawing then at neangular.


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BASIC COMMANDS:

Line

Rectangle

Arc

Circle

Trim

Point

RESULT:

Thus the introduction about AUTOCAD is studied.


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GENEVA GEAR


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EX NO: 1

DATE: 2/06/2010

AIM:

To create a 3-D drawing of the given Geneva gear by using AUTO CAD.

COMMAND USED:

Circle

Arc

Array

Extrude

Subtract

PROCEDURE:

By using circle command the circle was drawn to required dimension

By using arc command the arc was drawn to required dimension

By using array command the required number of objects was created

By using etrude command the figure thus obtained is extrude in Z-axis

By using subtract command the under 3-D object was removed

GENEVA GEAR


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RESULT:

Thus the 3-D drawing of Geneva gear was drawn by using AUTO CAD

SQUARE BOLT & HEXAGONAL NUT


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EX NO: 2

DATE:22/06/2010

AIM:

To create a 3-D drawing of the given Square Bolt & Hexagonal nut by using AUTO CAD.

COMMAND USED:

Circle

Arc

Line

Extrude

Subtract

Polygon

PROCEDURE:

By using line command lines are drawn to required size



By using polygon command the polygon was drawn required dimension

SQUARE BOLT & HEXAGONAL NUT


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By using extrude command the figure thus obtained is extrude in Z-axis


RESULT:

Thus the 3-D drawing of Square Bolt & Hexagonal nut was drawn by using AUTO CAD

PISTON & RINGS


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EX NO: 3

DATE:12/07/2010

AIM:

To create a 3-D drawing of the given Piston & Rings by using AUTO CAD.

COMMAND USED:

Circle

Line

Extrude

Revole

PROCEDURE:


By using revole command the object was revoled in 360


By using etrude command the figure thus obtained is extrude in Z-axis

RESULT:

Thus the 3-D drawing of Piston & Rings was drawn by using AUTO CAD

PISTON & RINGS


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EX NO: 4

DATE:12/07/2010

AIM:

To create a 3-D drawing of the given Bushed Bearing by using AUTO CAD.

COMMAND USED: Circle

Arc

Line

Extrude

Subtract

Trim

PROCEDURE:




By using trim command the extra lines are removed


BUSHED BEARING


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RESULT:

Thus the 3-D drawing of Bushed Bearing was drawn by using AUTO CAD


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EX NO: 5DATE:26/07/2010

AIM:

To create a 3-D drawing of the given Wall Bracket by using AUTO CAD.

COMMAND USED:

Circle

Line

Extrude

Subtract

Revolve

Union

PROCEDURE:


WALL BRACKET


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By using revolve command obtained figure is revolved


By using union command the required 3-D object was combined

RESULT:

Thus the 3-D drawing of Wall Bracket was drawn by using AUTO CAD


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EX NO: 6


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DATE:26/07/2010

AIM:

To create a 3-D drawing of the given V-Block by using AUTO CAD.

COMMAND USED:

Circle

Line

Extrude

Subtract

Revolve

Boolean expression

PROCEDURE:




By using revolve command obtained figure is revolved


By using union command the required 3-D object was combined

V-BLOCK


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RESULT:

Thus the 3-D drawing of V-Block was drawn by using AUTO CAD

COMPUTER-AIDED MANUFACTURING

INTRODUCTION OF CAM:

Computer-aided manufacturing can be defined as the use of computer systems to plan, manage,

and control the operations of a manufacturing plant through either direct or indirect computer interfacewith the plants production resources. As indicated by the definition, the applications of computer-

aided manufacturing fall into two broad categories:

1. Computer monitoring and control. These are the direct applications in which the computer is

connected directly to the manufacturing process for the purpose of monitoring or controlling the

process.

2. Manufacturing support applications. These are the indirect applications in which the computer

is used in support of the production operations in the plant, but there is no direct interface

between the computer and the manufacturing process.

the distinction between the two categories is fundamental to an understanding of computer

aided-manufacturing. It seems appropriate to elaborate on our brief definitions of the two types.

Computer monitoring and control can be separated in to monitoring applications and control

applications. Computer process monitoring involves a direct computer interface with the

manufacturing process for the purpose of observing the process and associated equipment and

collecting data from the process. The computer is not used to control the operation directly. The

control of the process remains in the hands of human operators. Who may be guided by the

information compiled by the computer .


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Computer process control goes one step further than monitoring by not only observing the

process but also controlling it based on the observations. The distinction between monitoring and

control is displayed in figure with computer monitoring the flow of data between the process and the

computer is in one directionally, from the process to the computer. in control, the computer interface

allows only for a two-way flow of data. Signals are transmitted from the process to the computer, jus

as in the case of computer monitoring. In addition, the computer issues command signals directly tothe manufacturing process based on control algorithms contained in its software.

In addition to the applications involving a direct computer process interface for the purpose of

process monitoring and control, computer aided manufacturing also includes indirect applications in

which the computer serves a support role in the manufacturing operations of the plant .in these

applications ,the computer is not linked directly to the manufacturing process. Instead the computer is

used offline to provide plans, schedules, forecasts, instructions, and information by which the firms

production resources can be managed more effectively.

NUMERICAL CONTROL PART PROGRAMMING BY COMPUTERS:

Control programs are prepared for automated machine tools.

COMPUTER AUTOMATED PROCESS PLANNING:

The computer prepares a listing of the operation sequence required to process a particularproduct or component.

COMPUTER GENERATED WORK STANDARDS:

The computer determines the time standard for particular production equipment.

PRODUCTION SCHEDULING:

The computer determines an appropriate schedule for meeting production requirements.

MATERIAL REQUIREMENTS:

Planning the computer is used to determine when to order raw materials and purchased

components and how many should be ordered to achieve the production schedule.


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SHOP FLOOR CONTROL:

In this CAM application, data is collected from the factory to determine progress of the

various production shop orders.


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INTRODUCTION TO CNC PROGRAMING

EXTERNAL PROGRAMMING:

If the programming is to be carried out by means of an external peripheral, ISO code must be

used.

TEXT PROGRAMMING:

The maximum number of characters which can be written in a comment is 43, parenthesis

included. The comment must be written at the end of the block, that is :N4G..X..F..M..(comment).

CREATING A PROGRAM:

The, machining program must be entered in a form acceptable to the CNC.

It must include all the geometrical and technological data required for the machine-tool to perform therequired functions and movements.

A program is built up in the form of a sequence of blocks.

Each programming block consists of:

N : Block no.

G : Preparatory functions

X.Z : Coordinate values

F : Federate

S : Spindle

T : Tool No.

M : Miscellaneous functions

This order has to be maintained within each block, although each block does not necessarily contain

all of these items.

PROGRAM FORMAT:

The CNC is programmed in millimeters and the format is:

P(%)5 N4 G2 X+\-4.3 Z+\4.3 F5.5 S4 T2.2 M2

PROGRAM NUMBERING:

Every program must be numbered between 0 and 99998.


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BLOCK NUMBERING:

The block number is used to identify each of the blocks that make up a program.

The block number consists of the letter N followed by a figure between 0 and 9999. This number mustbe written at the start of each block.

THE FUNCTION CODE USED IN CNC PREPARATORY FUNCTION AREGIVEN BELOW :

G00-Positioning rapid move

G01-Linear interpolation

G02-Circular interpolation (cw)

G03-Circular interpolation (acw)

G04, G05 -Zero effect

G66-Pattern repeat

G68-Roughing canned cycle (x)

G64-Return to home position (y)

G74-Return to home position

G81-Canned turning cycle with straight selection

G82-Canned cycle with straight selection

G83-Deep bore building

G84-Turning with arc x

G85-Turning with arc y

G86-Longitudinal threading cutting cycle

G87-Grooving cycle x

G 89-Grooving circle y

G90-Programming of absolute co-ordination

G91-Incremental co-ordination

G92-Preselection of poles region

G93-Preselection of poles region


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G92-Setting of maximum valve

G94-Feed rate fmm/min (inch/min)

G95-Feed rate fmm/rev (rev)

G96-Speed rm/min (feet/min)

Miscellaneous function:

M00 Program stop

M01 Optional (planned) stop

M03 Spindle on (cw)

M02 End of program

M04 Spindle on (acw)

M05 Spindle off

M06 Tool change

M07 Top oil on

M08 Coolant on

M09 Coolant off

M10 B axis clamp

M11 B axis clamp

M12 Synchronization

M13, M15 Motion (t); Motion (-)

M19 Oriented spindle stop

M20 Tool change

M30 End of date

M47 Return program start

M49 Outside bypass

M50 Air blow on

M90 Reserved for used

M=Sequence number (1 t0 9999)

G=Preparatory function (to 99 on g-function in a block are permitted

Some system use on g codes is three digits.


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They are

x,y,z=Dimension made in each other up to 2 decimal places.

i,j,k=Arc centre offset in xyz axis (+) or (-) direction.

P,q=Word addressed codes, depending on g-function

B=Rotation axis about y axis

F=Feed rate mm/min

T=Tool function (txx to tyy) depending on no .of as in the machine.

S=Spindle speed e.g s2500

M=Miscellaneous function

H=Offset number

O=Cutter radius offset

L=No of repetitions of fixed.cycle and stop program.

RESULT:

Thus the study of computer numerical control are studied.


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EX NO: 1

DATE:16/08/2010

AIM:

To create a manual CNC path program for the given work piece.

PROGRAM:

N0010 (TURNING)

N0020 (ZMIN:0 ZMAX:70 DIA:30)

N0030 G53 X0 Z70

N0040 G53

N0050 G90 G94 G97 F40 S1200 T1.1 M03

N0060 G00 X31 Z1

N0070 G01 X29 F40

N0080 G01 X29 Z-30

N0090 G00 X31 Z1

N0100 G01 X28 F40

N0110 G01 X28 Z-30

N0120 G00 X31 Z1

N0130 G74

N0140 M05

N0150 M30

RESULT:

Thus the manual path program was created and verified.

CNC LATHE -TURNING


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EX NO: 2


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EX NO: 3


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N0210 M30

RESULT:

Thus the given program was created and tested using CNC lathe


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Thus the given program was created and tested using CNC lathe.


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EX NO: 5

DATE:23/08/2010

AIM:

To create a manual CNC path program for the given workpiece.

PROGRAM:

N0010 (turning)

N0020 (ZMIN: 0 ZMAX: 70 DIA: 30)

N0030 G53 X0 Z70

N0040 G53

N0050 G90 G94 G97 F40 S1200 T1.1 M03

N0060 G00 X31 Z1

N0070 G81 P0=K28 P1=K0 P2=K28 P3=K-50 P5=K0.5 P7=K0.2 P8=K0.2 P9=K20

N0080 G00 X29 Z1

N0090 G82 P0=K29 P1=K-2 P2=K0 P3=K-2 P5=K0.5 P7=K0.2 P8=K0.2 P9=K20

N0100 G00 X29 Z1

N0110 G81 P0=K22 P1=K0 P2=K28 P3=K-28 P5=K0.5 P7=K0.2 P8=K0.2 P9=K20

N0120 G00 X31 Z1]

N0130 G74

N0140 M05

N0150 M30

RESULT:

Thus the given program was created and tested using CNC lathe.

G-81 CANNED CYCLE


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EX NO: 6

DATE:23/08/2010

AIM:


PROGRAM:

N0010 (G68 TURNING)

N0020 (zmin:0 zmax:80 dia:30)

N0030 G53 X0 Z80

N0040 G53

N0050 G90 G94 G97 F40 S1200 T1.1 M03

N0060 G00 X31 Z1

N0070 G68 P0=K0 P1=K0 P5=K0.5 P7=K0.2 P8=K0.2 P9=K20 P13=K0080 P14=K0130

N0080 G00 X0 Z0

N0090 G02 X10 Z-5 I0 K-5

N0100 G01 X10 Z-15

N0110 G01 X20 Z-25

N0120 G01 X20 Z-35

N0130 G03 X30 Z-40 I5 K0

N0140 G00 X31 Z1

N0150 G74

N0160 M05

N0170 M30

RESULT:

Thus the given program was created and tested using CNC lathe

G-68 CANNED CYCLE


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INTRODUCTION OF CNC MACHINE

INTRODUCTION:

In the modern age of business competition, the aim of manufacturing activity is to manufacture the

parts of desired quality at the minimum possible cost resulting in profit to the organisation. Tocompete in the market, the quality of the product will have to be reliable and consiststent with

delivery of the product offered on schedule.

For consistency in quality especially in the manufacture of complex components, human

intervention has to be eliminated. This necessitates the use of special purpose or automatic machine

tools. These machine tools are highly specialized and have high rates of production. However, their

initial costs are high. Due to these factors these machines tools are suitable and economical for mass

production only. moreover, these machine tools are inflexible(that is the complete setup will have to

be changed for a new product). Due to this inflexibility also, these machine tools are not suitable for

job or small batch production. Thus, when the main requirement is: Mass production machine toolsinclude: Automatic unit machine tools and automatic transfer machine etc..

However, the mass production system of manufacturing accounts for only about 20% of the

total manufactured parts.

The remaining demand is met by jobbing and the batch production systems. More than half o

the machine tools are engaged in small lot and piece production. These include general purpose

machine tools, Hydraulic tracer controlled machine tools and programmed operation cycle machine

tools. The general purpose machine tools, even though highly flexible(can easily changed from one

product to another) ,are not suitable for mass production, because of longer setup times, machine

and tool adjustments. All this results in low rates of production and delays in the delivery schedule.

Also, they require too highly skilled operators. Because of the intervention of operators, the

consistency in quality cannot be assured. Therefore, when consistency in quality and delivery

schedule are of prime importants, these machine tools are not suitable. Similarly, hydraulic tracer

controlled machine tools, required longer set up times while changing over to new jobs as these

machines require cams,templates,stops,electrical trip dogs etc

Because of the above factors, a great need was felt for machine tools that could bridge the gap

between highly flexible, general purpose machine tools and highly specialized, but inflexible mass

production machines. Numerically controlled machine tools have taken up these role very well. These

machines are highly flexible and are economical for producing a single or a large no. of parts.

Numerical control, NC, can be defined simply as control by numbers. Electronics industries

association defines NUMERICAL CONTROL as a system in which actions are controlled by the

direct insertion of numerical data at some point. The system must automatically interpret at least

some portion of these data. In numerically controlled machine tools, the input information for

controlling the machine tool motion is provided by means of punched paper tapes, plastic

tapes( mylar), floppy disk, hard disk or magnetic tapes in a coded language. Thus, with numerical


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control, the operation and motions of a tool are controlled electronically. NC machine tools are thus

automated production machines.

The key difference in this system is that of reprogrammability. In NC, a changeover to a new

product, does not require extensive physical changes in the machine set up. Only a change in the

control program itself is required. Thus, the flexibility of general purpose machine tools can be

combined with the precision and accuracy of special-purpose machine tools. The human intervention,

as an interface translating the design information into machine tools. The human intervention, as an

interface translating the design information into machine activities, is replaced by some form of

information processing device, such as a computer.

The principles of NE were established in 1950s. However, with the availability of low-cost

programmable control,, based around the microprocessor in 1970s, this technology diffused widely.

This opened up the development of the concept of Computer Numerical Control (CNC), sophisticated

multipurpose machining centres, complete with a range of support functions such as tool change,

head change, transport and manipulation and so on- all under computer control. The next

development was the idea of Direct (or distributed) Numerical Control ( DNC), in which more than one

machine tool (alongwith associated functions) could be grouped into a manufacturing cell under the

overall control of a larger, supervisory computer. The early numerically controlled machine tools were

milling and profiling machines that provided faster and less expensive means for producing aircraft

parts. Now, NC, has been applied to other machine tools, such as lathes, drilling and boring

machines, welding and flame cutting machines, punching machines and inspection devices.

WORKING OF NC MACHINE TOOL:

To understand the working of a NC machine tool, The first two steps, component drawing and

process planning are similar in both operator and NC machine tools. In the operator controlled

machine tools, the operator controls the cutter position during machining. He also makes the

necessary adjustments and corrections to produce the desired component. However, in numerically

controlled system, the place of the operator is taken by the data processing part of the system and

the control unit. In the data processing unit, the co-ordinate information regarding the component is

recorded on a tape by means of a teleprinter. Tape is fed to the control unit which sends the position

command signals to slide-way transmission elements of the machine tool. At the same time, the

command signal is constantly compared with the actual position achieved, with the help of position.

The difference in the two signals, if any, is corrected until the desired component is produced.

The conventional NC system consists of basically two parts: Machine Tool and Machine Control Un(MCU).


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The main elements of a NC machine tool are shown in FIG.

These are :

1. The machine control unit (MCU), also known as N.C. console or director.

2. The drive units, or actuators.

3. The position feed back package.

4. Magnetic box.

5. Manual control.

The hardware also includes the associated circuits.

The functional elements involved in MCU are:

1. Data Input. The instructions for manufacturing the component are written in a Coded language

( Paper tape is the most commonly used device ) are read by a tape reader.

2. Date Processing. The instruction undergo electronic processing resulting in information in the

form of electrical signals (pulsed commands).

3. Data Output. The control unit sends command signals to the drive units of machine tool and

also to the Electrical control cabinet called Magnetic Box. Command signals sent to the driveunits of the machine tool, control the lengths of travel and the feed rates , while the command

signals sent to the magnetic box control other functions such as : spindle motor starting and

stopping, selecting spindle speeds, actuation of tool change, coolant supply etc.

It is clear from above that MCU basically consists of two elements: Data Processing Unit

(CPU) and the Control Loops Units( CLU ).

The DPU process the data ( in coded form ) read from the tape or any other source and

passes the information regarding the various controls to CLU.


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NC is used to provide the following controls:

-

All cutting speeds

- Complete path and feed rates of a cutter in relation to the workpiece or fixture

- All auxiliary functions such as turning cutting fluids off and on.

The CLU operates the drive mechanisms of the machine tool, receives feedback signals

regarding the actual position and velocity of each of the axes and signals the completion of the

operation.

The DPU reads and processes the data sequentially. When a line has completed execution as

signalled by CLU, the DPU reads and processes the next line of the programme and so on.

To check whether the required lengths of travel have been obtained, a feedback transducer is

provided. The feedback transducer sends the information of the actual position achieved to the

control unit. If there is any difference between the input command signal and the actual position

achieved, the drive unit is actuated by suitable amplifier from the error signal.

Manual control or operator control helps the operator to perform some functions manually such

as : motor start-stop, coolant supply control, axes movements, speed change, feed change etc.

CLASSIFICATION OF NC MACHINES:

NC machine tools can be classified in different ways. Based on the type of power drive

or the actuation system used, these are three common NC systems :

1. Electro-mechanical

2. Hydraulic, and

3. Pneumatic

The range of the machines performance capabilities and its application will normally dependupon the type of the power source.

Hydraulic power provides the largest power. The movement of the machine slides is more

uniform in speed. However, the drawbacks are : Higher cost, noise, hydraulic contamination from

leaking fluid and the need for additional equipment such as reservoir, intensifier, valves, etc.

Pneumatic power is least expensive, because the shop air can be tapped for this purpose.

However, the motion of the workable is not uniform.


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Electro-mechanical drives are the most precise and the most commonly used power sources .

The group of electro-mechanical, hydraulic or pneumatic equipment used to control the motion

of an NC machine is called the Servo.

Based on control system feature, NC machine are classified as :

1. Point-to-Point system

2. Straight line system

3. Contour system

These three systems are illustrated in figure.

In point-to-point system, the machining is done at specific positions. The working-piece

remains unaffected as the tool moves from one position to the next. This system is the simplest. In

figure, after drilling the hole at position A, the tool moves to the position B, along the dotted line. A

drilling machine is the best example of point-to-point system.

Straight line system, figure is an extension of point-to-point system. Here the tool moves at a

controlled feed rate in one axis direction at a time. The examples of straight line system are; stepped

turning on lathe, pocket milling etc.

In contour or continuous path system, figure , there are continuous, simultaneous and co-

ordinated motions of the tool and the workpiece along different co-ordinate axes. The various lines,

contours and curved surfaces are machined by this system.

Depending on the feedback, NC machine systems are of two types :

1. Open loop system

2. Closed loop system

As discussed above, a command signal is sent to the machine tool o carry out a certain

operation. In the open loop system, there is no feedback and no return signal to indicate whether the

tool has reached the correct position at the end of the operation, or not. Hence, there are no means of

knowing whether there is an error or not between the input command signal and the result achieved

An example of open loop system is a co-ordinate drilling machine.

Figure illustrates an open loop systems. The command signal from the MCLU is given to the

servo-motor (here a stepper motor). The motor is driven a precise angular rotation for every pulse

issued by CLU. So, the response of the motor is in incremental steps. An incremental step of 1.8 o is

common. This will result in a corresponding linear movement of the lead screw (depending upon it

lead) and hence of the machine slide.

In closed loop system, a feedback is built into the system, which automatically monitors the position

of the tool. From the feedback signal to the control unit, it is automatically controlled until it is in th

right position. Such a device is known as a position feedback transducer. Common position feed back


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devices used on modern NC machines are : shaft encoders, liner scales or Inductosyns. In the

contour or continuous path system, velocity the feed drive system

A closed loop system is more expensive than an open loop system.

A block diagram of a closed loop system is shown in fig. 16.4 (b). Since there is a continuous

monitoring of the positions, the drive is a continuous-positions device. These servomotors provide asmoother and continuously controllable movement of the work-table.

A.C servo-motors have better reliability, better performance-to-weight ratio and lower power

consumption. So, these are rapidly replacing the DC servomotor on new NC machine tools

PROGRMMING FOR NC MACHINES:

As discussed above, the complete information for producing a component on an NC machine,

is punched on a paper tape. The information punched on the paper tape includes :

1. The co-ordinate values of the entire tool path.

2. The co-ordinate values are prefixed with certain codes indicating the type of movement of

the tool (point-to-point, straight line, contour) from one co-ordinate to the next.

3. The co-ordinate values are also suffixed with certain codes indicating the various machine

functions, such as, start/stop, spindle coolant etc. The co-ordinate values are also

supplemented with other functions such as feed rates, spindle speeds, etc.

Programming to obtain the punched paper tape can either be done manually or with

The help of computer. Simple point-to-point programs can be easily developed manually, but morecomplex ones, as well as almost all contouring programs are developed with the help of computers.

Before making the part programme, the programmer first studies the part drawing and decides

upon : the proper sequence of operations, the cutting tools, the path of the cutter/tools. Speeds and

feeds at various points and the other related information, such as starting and stopping of the

machine etc.

MANUAL PROGRAMMING:

The first step is to establish the zero the reference axes on the part drawing and determine set

particular format acceptable to the machine tool-control unit combination. This sheet includes the

following information : the co-ordinate dimensions for each operations, the spindle traverse that

determines the depth of cut, the spindle speed and feed, tool change. After preparing the programme

sheet, the programmer uses it to prepare the punched paper tape on a typewriter-like tape punching

machine

METHODS OF LISTING THE CO-ORDINATES OF POINTS IN NC SYSTEM:

There are two methods of mentioning the co-ordinates of points programming for an NC system:


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1. Absolute System

2. Incremental System

In the absolute system, the co-ordinates of points are mentioned with respect to one reference

point, that is , datum. In the incremental system, the co-ordinates are written in the programme wi

respect to the previous point. Referring to fig the co-ordinates of points A and B, in the two systemare given as below:

Absolute System

X-co-ordinate Y-co-ordinate

Point A 5

Point B 10

Incremental System

Point A 5

Point B 5

APPLICATIONS OF NC MACHINES

The major applications of NC machines are:

1. For parts, which are complex and it will not be possible to manufacture them very accurately

on conventional machines, due to human error involved.

2. For parts which are frequently subjected to design changes.

3. Repetitive and precision quality parts which are to be produced in low to medium batch

quantity.

4. In situations where the investment on tooling and fixture inventory will be high if the parts are

made on conventional machine tools.

5. To cut down lead time in manufacture.

ADVANTAGE:

1. Greater accuracy.

2. Lesser production cost per piece due to reduction in lead time and also set up time.

3. Improved product quality and provision of higher order of repeatability.

4. High production rates as the machining conditions (feeds and speeds) are optimized and the

non-machining times are reduced to minimum.


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5. Less scrap due to consistent accuracy and absence of operator errors.

6. Reduced inventory of parts in process because parts can be made economically in smalle

quantities.

7. Less operator skill is required to run NC machine.

8. Due to reduced idle time, the machine utilization is better.

9. Changes in part design can be incorporated very easily and at a low cost by simply changing

parts of tape program.

10.Excellent reliability as the control equipment now is virtually all made of solid state modules.

11.Lower tooling costs as expensive jigs and fixtures are not required.

12.Reduced cycle time and increased tool life.

The major disadvantage of NC machines is their costs. Therefore, the machines must haveefficient use to justify the investment. Programming of NC machines has been greatly simplified

machine availability above 95% is common.


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EX NO: 1

DATE:30/08/2010

AIM:


PROGRAM:

N0010 G53 X-170 Y-160 Z-140

N0020 G53

N0030 T1.1

N0040 M06

CNC MILLING


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N0050 G90 G94 G97 F200 S1200

N0060 G00 X10 Y10 Z5

N0070 G01 Z-1 F200

N0080 G01 X50 Y10

N0090 G01 X50 Y50

N0100 G01 X10 Y50

N0110 G01 X10 Y10

N0120 G00 Z5

N0130 G74

N0140 M05

N0150 M30

RESULT:

Thus the program was created and verified.


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EX NO: 2DATE:13/09/2010

AIM:


PROGRAM:

N0010 G53 X-170 Y-160 Z-140

N0020 G53

N0030 T3.3

CNC MILLING


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N0040 M06

N0050 G90 G94 G97 F200 S2000 M03

N0060 G00 X20 Y10 Z5

N0070 G01 Z0 F200

N0080 G22 N2

N0090 G91 G01 Z-1 F100

N0100 G90 G01 X40 Y10

N0110 G02 X50 Y20 I10 J0

N0120 G01 X50 Y40

N0130 G02 X40 Y50 I0 J10

N0140 G01 X20 Y50

N0150 G02 X10 Y40 I-10 J0

N0160 G01 X10 Y20

N0170 G02 X20 Y10 I0 J-10

N0180 G24

N0190 G20 N2.4

N0200 G00 Z5

N0210 G74

N0220 M05

N0230 M30


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RESULT:



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EX NO: 3

DATE:13/09/2010

AIM:

To create a manual CNC path program for the given work piece .

PROGRAM:

N0010 G53 X-170 Y-160 Z-140

MILLING SUBROUTINE


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N0020 G53

N0030 T3.3

N0040 M06

N0050 G90 G94 G97 F200 S2000 M03

N0060 G00 X20 Y10 Z5

N0070 G01 Z0 F200

N0080 G22 N2

N0090 G91 G01 Z-1 F100

N0100 G90 G01 X40 Y10

N0110 G03 X50 Y20 I0 J10

N0120 G01 X50 Y40

N0130 G03 X40 Y50 I-10 J0

N0140 G01 X20 Y50

N0150 G03 X10 Y40 I0 J-10

N0160 G01 X10 Y20

N0170 G03 X20 Y10 I10 J0

N0180 G24

N0190 G20 N2.4

N0200 G00 Z5

N0210 G74

N0220 M05

N0230 M30


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EX NO: 4

DATE:20/09/2010

AIM:


PROGRAM:

N0010 G53 X-170 Y-160 Z-140

N0020 G53

N0030 G54 X-140 Y-130 Z-140

N0040 G54

MIRRORING


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N0050 T1.1

N0060 M06

N0070 G90 G94 G97 F200 S2000 M03

N0080 G22 N2

N0090 G00 X0 Y0 Z5

N0100 G00 X0 Y20

N0110 G01 Z-1 F200

N0120 G01 X10 Y20

N0130 G01 X20 Y10

N0140 G01 X20 Y0

N0150 G00 Z5

N0160 G24

N0170 G11

N0180 G20 N2.1

N0190 G10

N0200 G12

N0210 G20 N2.1

N0220 G10

N0230 G11

N0240 G12

N0250 G20 N2.1

N0260 G10

N0270 G00 Z5

N0280 G74

N0290 M05

N0300 M30


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RESULT:



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EX NO: 5

DATE:27/09/2010

AIM:


PROGRAM:

N0010 G53 X-175 Y-145 Z-145

N0020 G53

N0030 T1.1

N0040 M06

DRILLING


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EX NO: 6DATE:4/10/2010

AIM:


PROGRAM:

N0010 G53 X-175 Y-145 Z-145

N0020 G53

N0030 G54 X-145 Y-115 Z-145

N0040 G54

N0050 T3.3

RECTANGULAR POCKETING


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EX NO: 7

DATE:9/10/2010

AIM:


PROGRAM:

N0010 G53 X-175 Y-145 Z-145

N0020 G53

N0030 G54 X-140 Y-130 Z-145

CIRCULAR POCKETING


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N0040 G54

N0050 T3.3

N0060 M06

N0070 G90 G94 G97 F200 S3000 M03

N0080 G00 X0 Y0 Z5

N0090 G88 X0 Y0 Z0 I2 J20 B1 C2 D0.5 H0 L0 F80

N0100 G00 Z50

N0110 M05

N0120 M30

RESULT:


cnc lab record arun ridwan

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