Chapter 6Process Selection and Facility Layout

Process selection Deciding on the way production of

goods or services will be organized Major implications

Capacity planning Layout of facilities Equipment Design of work systems

Introduction

Forecasting

Product andService Design

TechnologicalChange

CapacityPlanning

ProcessSelection

Facilities andEquipment

Layout

WorkDesign

Process Selection and System Design

Variety How much

Flexibility What degree

Volume Expected output

Job Shop

Batch

Repetitive

Continuous

Process Selection

Types of Operations

INCREASED VOLUME

Project/Job Shop

Unit or Batch Mass/

Assembly

Continuous

Process Design

Project Processes (Fixed Position) Intermittent Flow Processes (Batch

Shops) Continuous Flow Processes (Flow

Shops) Processing Industries (Continuous)

Job Shop (Fixed Position)

People and material move Have limited duration Small scale Examples

Housing Ship building Dam Appliance Repair

Intermittent Flow Processes (Batch Shops)

No pattern exists between process of different products

Appropriate to service organizations Moderate volume Example:

Machine Shops Auto Repair Shops Commercial Bakery Classroom Lecture

Continuous Flow Processes (Flow Shops)

Sequences are the same (Standard Routes)

High volumes of standardized goods or services

Examples: Assembly Lines Car Wash

Processing Industries (Continuous Flow)

One primary input (gas, wheat, etc) is converted to multiple outputs

Very high volumes of non-discrete goods

Example: Petroleum Chemicals Food Industries

Process Characteristics

Characteristics Project Intermittent Continuous

PRODUCT      

Order Type Single Unit BatchContinuous or large batch

Flow of Product None Jumbled Sequence

Product Variety Very High High Low

Market type Unique Custom Mass

Volume Single Unit Medium High

Process Characteristics

Characteristics Project Intermittent ContinuousCAPITAL    

Inventory Medium High Low

EquipmentGeneral

PurposeGeneral

PurposeSpecial

Purpose

LABOR      

Skills High High Low

Task Type Non-routine Non-routine Repetitive

Process Characteristics

Characteristics Project Intermittent Continuous

CONTROL      

Production Difficult Difficult Easy

Quality Difficult Difficult Easy

Inventory Difficult Difficult Easy

EQUIPMENTGeneral

PurposeGeneral

PurposeSpecial

Purpose

Automation: Machinery that has sensing and control devices that enables it to operate Fixed automation Programmable automation

Automation

• Computer-aided design and manufacturing systems (CAD/CAM)

• Numerically controlled (NC) machines

• Robot

• Manufacturing cell

• Flexible manufacturing systems(FMS)

• Computer-integrated manufacturing (CIM)

Automation

Functional Areas Being Linked to Manage the Flow of Information

Design Handling of Materials Storage and Retrieval of

Information Control of Machine Tools

Design CAD

No longer limited to the top, side and front views

Can observe the rotation of the part about any axis on the screen

Generally, improves productivity in the drafting room by a factor of 3 or more

At GM, the redesign of a single auto model requires 14 months instead of 24 months

The time needed to design custom values reduced from six months to one

Handling of Materials

Data processing technology can be applied to the control of 3 general kids of machines in the factory: Machines that store, retrieve, or

transport materials Machines that process the materials Robots

Handling of Materials

Automatic storage and retrieval systems transfer pallets of material into or out of storage rack up to 100 feet high Mini Loaders

Hold drawers of small parts Automatic Warehouse

Automatic shuttle takes the place of the fork-lift truck and its human operations

Storage and Retrieval of Information

GT The formation of part families based on

design or manufacturing similarities (or both) Classification of parts speed up the design of

similar parts in the company Only 20% of the parts actually need new

design. 40% could be built from an existing design and the other 40% could be created by modifying an existing design.

Automatic guided vehicle

Control of Machine Tools

NC Machine tools run by programs

DNC Direct numerically controlled machine

tools Several computerized, NC machine

tools are linked by a hierarchy of computers

Control of Machine Tools FMS Flexible Manufacturing System It consists of an integrated collection of:

Automated Production Processes NC Robots

A material transport system An automated transfer line Robots

Control of Robots Robots

A programmable machine capable of moving materials and performing repetitive tasks.

Main features: They are flexible They eliminate the need for operators

Applications Loading and unloading of machine tools Jobs that are dirty, hazardous, unpleasant, or

monotonous

The Operating Capabilities of the Factory of the Future Economic order quantity approaches 1 Variety has no cost penalty (economy of slope) Rapid response to changes in product design,

market demand, and production mix Unmanned and continuous operation is

standard Consistent high levels of quality and accuracy

and repeatability introduce higher levels of certainty into the production planning and control activity

Layout: the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system

Facilities Layout

Requires substantial investments of money and effort

Involves long-term commitments Has significant impact on cost and

efficiency of short-term operations

Importance of Layout Decisions

Product layout Layout that uses standardized processing

operations to achieve smooth, rapid, high-volume flow

Process layout Layout that can handle varied processing

requirements Fixed Position layout

Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed

Basic Layout Types

Raw materialsor customer

Finished item

Station 2

Station 2

Station 3

Station 3

Station 4

Station 4

Material and/or labor

Station 1

Material and/or labor

Material and/or labor

Material and/or labor

Used for Repetitive or Continuous Processing

Product Layout

High rate of output Low unit cost Labor specialization Low material handling cost High utilization of labor and

equipment Established routing and scheduling Routing accounting and purchasing

Advantages of Product Layout

Creates dull, repetitive jobs Poorly skilled workers may not

maintain equipment or quality of output

Fairly inflexible to changes in volume Highly susceptible to shutdowns Needs preventive maintenance Individual incentive plans are

impractical

Disadvantages of Product Layout

Assembly Line Balancing Cycle time

The time required to produce one part is called the cycle time, or the maximum time allowed at any one work station

Assembly Line Balancing Given a cycle time, find the minimum

number of work stations or minimize the cycle time for a given number of work stations

Assembly Line Balancing - Example

Task Time (min) Immediate Predecessors

A 0.2 -----

B 0.3 A

C 0.2 A

D 0.25 A

E 0.15 B,C

F 0.3 D,E

Total 1.4

Assembly Line Balancing

Assembly Line Balancing

CYCLE TIME.30 C 1.40C = productive time/output rateC = (8hr x 60min) =.5 min

960Number of work stations, N = total time/CN = 140 = 2.8 =3

.5

Solution to Assembly Line Balancing Problem

Station Tasks Assigned Total Task Time Idle Time1 A, B 0.5 02 C, D 0.45 0.053 E, F 0.45 0.05

TOTAL 1.4 0.1

Assign tasks in order of most following tasks. Count the number of tasks that follow

Assign tasks in order of greatest positional weight. Positional weight is the sum of each task’s

time and the times of all following tasks.

Some Heuristic (intuitive) Rules:

Line Balancing Rules

Assembly Line Balancing Solution

Line Efficiency = Total Work Content

C x N Efficiency = 1.40 = .93 or 93% .5 x 3 Balance Delay = 1 – efficiency =

1-.93 = 7%

c d

a b e

f g h

0.2 0.2 0.3

0.8 0.6

1.0 0.4 0.3

Example 2

Station 1 Station 2 Station 3 Station 4

a b ef

d

g h

c

Solution to Example 2

1 2 3 4

5

6

78910

In

Out

Workers

A U-Shaped Production Line

Process Layout (functional)

Assume we have the following departments: Accounting (A) Production Planning (P) Customer Service (C) Sales (S)

What arrangement would be better?

A PC S

S CA P

Used for Intermittent processingJob Shop or Batch

Intermittent Process

Criteria Desirability ranking Volume of interaction Cost of interaction

Distance Time

Safety Facility Limitations

Can handle a variety of processing requirements

Not particularly vulnerable to equipment failures

Equipment used is less costly Possible to use individual incentive

plans

Advantages of Process Layouts

In-process inventory costs can be high Challenging routing and scheduling Equipment utilization rates are low Material handling slow and inefficient Complexities often reduce span of supervision Special attention for each product or customer Accounting and purchasing are more involved

Disadvantages of Process Layouts

Cellular Production Layout in which machines are grouped

into a cell that can process items that have similar processing requirements

Group Technology The grouping into part families of items

with similar design or manufacturing characteristics

Cellular Layouts

Process Layout - work travels to dedicated process centers

Milling

Assembly& Test Grinding

Drilling Plating

Process Layout - Example

Gearcutting

Mill Drill

Lathes

Grind

Heattreat

Assembly

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222

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Functional Layout

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Ass

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ly

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Lathe

Lathe

Mill

Mill

Mill

Mill

Drill

Drill

Drill

Heat treat

Heat treat

Heat treat

Gear cut

Gear cut

Grind

Grind

Cellular Manufacturing Layout – Group Technology