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MFGE 404

Computer Integrated Manufacturing

CIM

A T I L I M U N I V E R S I T Y

Manufacturing Engineering Department

Lecture 3 Computer Aided Process Planning - CAPP

Fall 2005/2006Dr. ale! A"A#$#%

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Defning Process planning Process planning can be defned as the systematic

determination o the detailed methods by which workpieces

or parts can be manuactured economically and competitively

rom initial stages (raw material orm) to fnished stages(desired orm).

Initial FormFinal Form

eometrical eatures! dimensional si"es! tolerances!materials! and surace fnishes are analy"ed and evaluatedto determine an appropriate se#uence o processingoperations.

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Defning Process planning In general, the inputs to process planning are

design data,

raw material data,

facilities data (machining data, tooling data, xture data,

etc.),

quality requirements data, and

production type data.

The output of process planning is the process plan.

The process plan is often documented into a specic formatand called process plan sheet,

process sheet, operation sheet, planning sheet, route sheet, route plan, or part program.

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$ process plan is an important document or production

management. %he process plan can be used or

Management of production, ssurance of product quality,

!ptimi"ation of production sequencing, and

#etermination of equipment layout on the shop $oor.

Defning Process planning

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Defning Process planning

%ecent research results ha&e also demonstrated thatprocess planning plays an important role in 'omputer

Integrated Manufacturing 'IM

Process planning is the key link for integrating design andmanufacturing

the process plan provides necessary

inormation or technical and e#uipmentpreparation! such as& tools,igs and xtures, machines,

inspection de&ices, raw material stoc*s, in&entory plans, purchasing plans,

personal requirements, etc.

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Defning 'omputer $ided Process planning '$PP

'omputer ided +rocess +lanning ('++) can edened as the functions which use computers to

assist the wor* of process planners.

The le&els of assistance depend on the di-erentstrategies employed to implement the system.

ower level strategies only use computersfor storage and retrie&al of the data for theprocess plans which will e constructedmanually y process planners, as well as forsupplying the data which will e used in theplanners new wor*.

*igher level strategies use computers toautomatically generate process plans for some

wor*pieces of simple geometrical shapes.

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Defning 'omputer $ided Process planning '$PP

'++ a *ey factor in '#/'M integration ecause it isthe lin* etween '# and 'M.

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Defning 'omputer $ided Process planning '$PP

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+enefts o '$PP

,.-eduction in process planning time.

.-eduction in the re#uired skill o the processplanner.

/.-eduction in costs due to e0cient use o

resources.

1.Increased productivity.

2.Production o accurate and consistent plans.

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$pproaches o '$PP

In general! three approaches to '$PP aretraditionally recogni"ed&

the &ariant approach,

the generati&e approach, and

the hyrid (semi0generati&e) approach

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%he 3ariant approach o '$PP The &ariant approach, which is also called retrie&al

approach, uses a group technology (1T) code to select a

generic process plan from the existing master processplans de&eloped for each part family and then edits to

suit the requirement of the part. 2ariant approach is commonly implemented with 1T

coding system. 3ere, the parts are segmented into

groups ased on similarity and each group has a masterplan.

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$dvantages o 3ariant approach o '$PP

,.4nce a standard plan has been written! a

variety o components can be planned.

.Programming and installation arecomparatively simple.

/.%he system is understandable! and theplanner has control o the fnal plan.

1.It is easy to learn and easy to use.

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,.%he components to be planned are limited to

previously planned similar components.

.56perienced process planners are stillre#uired to modiy the standard plan or the

specifc component.

/.Details o the plan cannot be generated.

1.3ariant planning cannot be used in anentirely automated manuacturing system!

without additional process planning.

Disadvantages o 3ariant approach o '$PP

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%he enerative approach o '$PP

In a generati&e approach, a process plan for eachcomponent is created from scratch without human

inter&ention. These systems are designed toautomatically synthesi"e process information tode&elop a process plan for a part

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1enerati&e '++ systems contain the logic to usemanufacturing data bases, knowledge bases and suitale

part descriptionschemes to generate a process plan for aparticular part.

%he enerative approach o '$PP

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$dvantages o enerative approach o '$PP

,.'onsistent process plans can be generated

rapidly.

.7ew components can be planned as easily as

e6isting components.

/.It has potential or integrating with anautomated manuacturing acility to providedetailed control inormation.

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%he *ybrid (8emienerative) approach o '$PP

$ hybrid planner! or e6ample! might use a

variant! %based approach to retrieve an

e6isting process plan! and generative

techni#ues or modiying this plan to suit the

new part

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9ain 8teps o '$PP 8ystems

Identifcation o part specifcations.

8election o blanks or stock.

8election o machining operations.

8election o machine tools.

8election o cutting tools.

'alculation o cutting parameters.

eneration o setup plans.

8election o work holding devices (f6tures).

'alculation o times and costs.

eneration o process plans