Selecting and Planning the Process of Manufacture

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Selecting and Planning theSelecting and Planning theProcess of ManufactureProcess of Manufacture

Dr.Dr. PulakPulakM.M. PandeyPandey

http://http://paniitpaniit..iitdiitd.ac.in/~.ac.in/~pmpandeypmpandey


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The manufacturing process selected must beThe manufacturing process selected must be

an economical balance of materials,an economical balance of materials,manpower, product design, tooling andmanpower, product design, tooling and

equipment, plant space, and many otherequipment, plant space, and many other

factors influencing cost and practicality.factors influencing cost and practicality. The process must be selected in such a wayThe process must be selected in such a way

that the produced product will be acceptablethat the produced product will be acceptable

to the consumerto the consumerfunctionally, economicallyfunctionally, economically

and appearanceand appearance--wisewise..

IntroductionIntroduction


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Fundamental Rules for the selection andFundamental Rules for the selection and

Planning of a Manufacturing ProcessPlanning of a Manufacturing Process

1.1. The process must assure a product that meets all designThe process must assure a product that meets all design

requirements of quality, function and reliabilityrequirements of quality, function and reliability2.2. Daily production requirement must be metDaily production requirement must be met

3.3. Full capacity of the machine and its tooling should beFull capacity of the machine and its tooling should be

utilizedutilized4.4. Idle operator and idle machine time must be reduced toIdle operator and idle machine time must be reduced to

minimumminimum

5.5. The process must provide the maximum utilization ofThe process must provide the maximum utilization ofthe minimum amount of materialthe minimum amount of material

6.6. The process should be flexible enough to accommodateThe process should be flexible enough to accommodatereasonable changes in designreasonable changes in design


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7.7. The process should be designed to eliminate anyThe process should be designed to eliminate anyunnecessary operations and combine as manyunnecessary operations and combine as manyoperations as are physically and economicallyoperations as are physically and economically

practicalpractical

8.8. Capital expenditure that must be amortized overCapital expenditure that must be amortized overshort periods must be kept as low as possible.short periods must be kept as low as possible.

9.9. The process must be designed with the protectionThe process must be designed with the protectionof both the operator and the workpiece in mindof both the operator and the workpiece in mind

10.10. The process should be developed so that the finalThe process should be developed so that the final

product will be produced at a minimum cost to theproduct will be produced at a minimum cost to theenterprise as a wholeenterprise as a whole


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The Engineering ApproachThe Engineering Approach

Establish the process objectivesEstablish the process objectives

Collect all the facts about the problemCollect all the facts about the problem

Plan alternative processesPlan alternative processes

Evaluate alternative processesEvaluate alternative processes

Develop a course of actionDevelop a course of action

Follow up to assure action and check resultsFollow up to assure action and check results


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Using Materials More EconomicallyUsing Materials More Economically

Better stock utilization through materials controlBetter stock utilization through materials control

Sale of scrapSale of scrap

ReRe--usable materialsusable materials

MaterialMaterial cost balance sheetcost balance sheet

Process effects materials costProcess effects materials cost

Lack of proper workpiece controlLack of proper workpiece control Wrong manufacturing processWrong manufacturing process

Improper stock selectionImproper stock selection

Improper handlingImproper handling Incomplete inspection at early stages of manufacturingIncomplete inspection at early stages of manufacturing

Incorrect operation sequenceIncorrect operation sequence


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Eliminating OperationsEliminating Operations

The cost of processing can be reduced byThe cost of processing can be reduced by

eliminating unnecessary operations. Thiseliminating unnecessary operations. This

can be achieved in number of ways and arecan be achieved in number of ways and are

accomplished through proper planning.accomplished through proper planning.

ChangingChangingproduct designproduct design..

Changing the operation sequence.Changing the operation sequence.

Changing theChanging thebasic processbasic process..Combining operations.Combining operations.


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Combining operationsCombining operations By simulatingBy simulating

Simulation involves those combinations where two or moreSimulation involves those combinations where two or more

elements of an operation, or two or more operations areelements of an operation, or two or more operations areperformed at the same time.performed at the same time.

Example: series of hole to be drilled simultaneously using aExample: series of hole to be drilled simultaneously using amultiple spindle drill press.multiple spindle drill press. Cuter are specially designedCuter are specially designed..

By integratingBy integrating Where several individual elements of an operation or group ofWhere several individual elements of an operation or group of

operations are combined in succession but not simultaneously.operations are combined in succession but not simultaneously.

Taping is done after drilling hole on the same set up by justTaping is done after drilling hole on the same set up by justchanging the tool.changing the tool. Typical example.Typical example.

Both simulation and integration are employed profuselyBoth simulation and integration are employed profuselyin todays highly mechanized and automated industry.in todays highly mechanized and automated industry.


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Advantages of combined operationsAdvantages of combined operations

Improved accuracyImproved accuracy

Reduced labor costReduced labor cost Reduced plant fixed costReduced plant fixed cost

Less tooling requiredLess tooling required

Less handling requiredLess handling required

Fewer setupsFewer setups

Smaller in process inventorySmaller in process inventory

Less scrapLess scrap

Fewer inspection points requiredFewer inspection points required


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Limitations of combined operationsLimitations of combined operations

Maintaining tool accuracyMaintaining tool accuracy

Possible higher tool costsPossible higher tool costs

Maintaining dimensions for several baselinesMaintaining dimensions for several baselines

Combination tooling subject to downtimeCombination tooling subject to downtime More costly setupsMore costly setups

More costly scrapMore costly scrap

Compromises on operational speedCompromises on operational speed

Chip disposalChip disposal


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Selection of Proper ToolingSelection of Proper Tooling

In selecting dies, jigs or fixtures for a givenIn selecting dies, jigs or fixtures for a given

process, there are three essentialprocess, there are three essential

considerations that demand the attention ofconsiderations that demand the attention of

process engineerprocess engineer

Quality of the productQuality of the product

Total volume to be producedTotal volume to be produced

Required rate of productionRequired rate of production


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Effect of operational speed on performanceEffect of operational speed on performance

and economyand economy Cutting speed influences the rate of production andCutting speed influences the rate of production and

performance economy.performance economy.

Assuming product quality can be achieved isAssuming product quality can be achieved isindependent of the speed, there are two divergentindependent of the speed, there are two divergentopinions.opinions.

Greater is the machine speed, greater its output and lowerGreater is the machine speed, greater its output and lowerproduct unit cost.product unit cost.

Speed should be held so that longerSpeed should be held so that longertool lifetool life is achieved.is achieved.

With the change in tool life due to change in operationalWith the change in tool life due to change in operational

speed the overall production time will be effected duespeed the overall production time will be effected dueto reto re--sharpening and resetting the tool.sharpening and resetting the tool.

Minimum cost analysisMinimum cost analysis and/orand/ordiminishing returndiminishing return

analysisanalysis are carried out to evaluate the situation.are carried out to evaluate the situation.


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Minimum Cost AnalysisMinimum Cost Analysis

In minimum cost studies, it is found thatIn minimum cost studies, it is found that

when changes occur in a common variablewhen changes occur in a common variable

(in this case it is operational speed), the(in this case it is operational speed), the

change may modify other cost aspects of thechange may modify other cost aspects of the

problem in such a way that the combinedproblem in such a way that the combined

effect produces a minimum value.effect produces a minimum value.


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Diminishing Return AnalysisDiminishing Return Analysis When the value of common variableWhen the value of common variable

(cutting speed) is increased, there will be a(cutting speed) is increased, there will be acorresponding increase in the return (maycorresponding increase in the return (may

be volume or profit) up to a point wherebe volume or profit) up to a point wherereturn is no longer a proportional. This pointreturn is no longer a proportional. This pointis called the point of diminishing returns.is called the point of diminishing returns.Furthermore, if the common variableFurthermore, if the common variablecontinues to increase, the return willcontinues to increase, the return will

ultimately reach a point beyond which itsultimately reach a point beyond which itsvalue will start to decrease. This point isvalue will start to decrease. This point iscalled point ofcalled point ofmaximum returnsmaximum returns..


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The Make and Buy DecisionsThe Make and Buy Decisions The decision to manufacture a product in itsThe decision to manufacture a product in its

entirely or to produce any part or all of itentirely or to produce any part or all of itprimarily dependent upon a combination ofprimarily dependent upon a combination offactors like:factors like:

1.1. Volume requiredVolume required

2.2. CostCost

3.3. Life of the productLife of the product

4.4. Degree of product standardizationDegree of product standardization5.5. Degree of manufacturing specializationDegree of manufacturing specialization

6.6. Alternative source of supplyAlternative source of supply

7.7. Reliability of supplierReliability of supplier


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Casting redesigned to eliminate foundry andCasting redesigned to eliminate foundry and

machining operationsmachining operations

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Effect of cutting speed on volume, unitEffect of cutting speed on volume, unit

cost and total profitcost and total profit

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Selecting and Planning the Process of Manufacture