02 Selecting Manufacturing Processes

8/3/2019 02 Selecting Manufacturing Processes

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Selecting manufacturing processes

Manufacturing process decisions Deformation processes Casting processes Sheet metalworking Polymer processing Machining Finishing Assembly

Material compatibilities / Process capabilities Material costs, Tooling costs, Processing costs



How would we manufacture a mountain bike ?

Top

Tube

Rear

Derailleur

Front Brake

Rear Brake

SaddleSeat

Post

Pedal

Handle Bar

Down

Tube

Fork

(Courtesy of Trek Bicycle, 2002)



Manufacturing process decisions

How do we choose the specific manufacturingprocesses?

How do the selected materials influence the choice of manufacturing processes?

Would product function or performance issuesinfluence our choice of processes?

What criteria should we use to select processes?

Which criteria are more important? Who will make the final decisions?



Parts undergo sequence of processes

Primary - alter the (“raw”) material’s basic shape or form.

Sand casting

Rolling

Forging

Sheet metalworking Secondary - add or remove geometric features from the basic forms

Machining of a brake drum casting (flat surfaces)

Drilling/punching of refrigerator housings (sheet metal)

Trimming of injection molded part flash

Tertiary - surface treatments

Polishing

Painting

Heat-treating

Joining

Changes?



Part / Mfg. Process Considerations

1. Production Volume

2. Part Size (overall)

3. Shape Capability (features)

boss/depression 1D

boss/depression >1D

holes

undercuts (int./ext.)

uniform walls

cross sections - uniform/regularrotational symmetry

captured cavities



Types of manufacturing processes

ExtrusionForgingRollingBar drawing

re raw ng

Deformation

CentrifugalDie castingInvestmentPermanent mold

an cast ng

Casting

BendingBlankingDrawingPunching

ear ngp nn ng

SheetMetal

Blow moldingCastingCompression moldingExtrusionn ect on o ng

ermo orm ngTransfer molding

PolymerProcesses

BoringDrillingFacingGrinding

ngan ng

TurningSawingECM, EDM

Machining

AnodizingHoningPaintingPlating

o s ng

Finishing

AutomatedBondingBrazingManual

vet ngo er ng

Welding

Assembly

ManufacturingProcesses

How is the inputmaterial changed?



Deformation processes

Rolling

Extrusion

Drawing Forging



Rolling (of ductile materials)

Plastic deformation

Rollers in compression

thick slab

thinsheet



Rolling

slab

bloom

billet

sheetcoil

bar rod

structural

ingot



Extrusion

Ram

Cross

sections

Extrusion

die

Billet



Drawing

Pulling

force

Cross

sections

Drawing die

Billet



Forging (closed-die)

Blockedpreform

Gutter

Ram pressure

Flash



Casting Processes

Sand casting

Die casting

Investment casting



Sand casting (closed-mold)

CoreRiser

Sprue

Runner

Drag

Flask

Cope

Gate

Parting

line



Die casting

Parting line

Plunger

Sprue

Moving

die

Stationary

die

Ejector pins

Molten

metal



Investment casting

Wax pattern

is cast

Wax removed

by melting

Molten metal

solidifies in castCeramic mold is

removed

Ceramic mold

(hardened slurry)4-part pattern tree



Sheet Metalworking

Bending

Blanking

Drawing Punching

Shearing

Spinning



Sheet metal drawing

Blank Drawn part

Clampforce

Blank holder

Die

Punch

Punch ram



Polymer Processes

Compression molding

Transfer Molding

Blow molding Injection molding



Compression molding

Charge

Heated

mold

Part

Ram Pressure



Transfer molding

Charge

Ram

Heated

moldSprue

Part

Ram pressure





Injection molding

Shear-heating

Cavity half

of mold

Core half

of mold

Ejector pins

Moving

Feed hopper

Sprue

Fixed

Barrel

Pellets

Mold closure directionParting

plane/surface



Example of a box …with no undercuts

core

cavity

parting

line

moldclosure

directionplastic

injection

ejector

pins



Internal undercuts

core

cavity

parting

line

closuredirection

plastic

injection

ejector

pins



External undercuts

core

cavity

parting

line

plastic

injection

ejector

pins

closure

direction



Solidification processes

Casting Processes

Sand Casting

Die Casting

Investment Casting

Centrifugal

Polymer Processes

Injection Molding

Blow Molding

ThermoForming

Compression Molding

solid Partmolten material freezing

Flow (voids, flash)

Cooling time (cycle time)

Temperature

Mold complexity

Warpage

Post processing

Costs (materials, tooling, processing)

Add to yournotes



Machining processes

ExtrusionForgingRolling

ar raw ngWire drawing

Deformation

CentrifugalDie castingInvestment

ermanent moSand casting

Casting

BendingBlankingDrawing

unc ngShearingSpinning

Sheet

Metal

Blow moldingCastingCompression molding

xtrus onInjection MoldingThermoformingTransfer molding

Polymer

Processes

BoringDrillingFacing

r n ngMillingPlaningTurningSawing

,

Machining

AnodizingHoningPainting

at ngPolishing

Finishing

AutomatedBondingBrazing

anuaRivetingSolderingWelding

Assembly




Machining – removal of material…

Sawing – using a toothed blade. Milling – from a flat surface by a rotating cutter tool.

Planing – using a translating cutter as workpiece feeds.

Shaping - from a translating workpiece using a stationary cutter.

Boring - increasing diameter of existing hole by rotating the workpiece.

Drilling- using a rotating bit forming a cylindrical hole.

Reaming – to refine the diameter of an existing hole.

Turning - from a rotating workpiece.

Facing - from turning workpiece using a radially fed tool.

Grinding - from a surface using an abrasive spinning wheel.

Electric discharge machining - by means of a spark.



Surface roughness



Machining process considerations

sawing, turning, boring, milling,

drilling, grinding, ECM

material removedsolid material machining

hardness, strength of material

shear forces = strong jigs & fixtures

tool/bit wear, replacement

size of workpiece, fit machine?

volume removedrate of removal, hp needed

tolerances

operator skill, CNC

costs (materials, tooling, processing) Add to your

notes



Finishing processes

xtrus onForging

o ng

Bar drawingre raw ng

Deformation

entr ugaDie castingnvestment

Permanent moldan cast ng

Casting

en ngBlanking

raw ng

Punchingear ng

p nn ng

Sheet

Metal

ow mo ngCasting

ompress on mo ng

Extrusionn ect on o ng


Polymer

Processes

or ngDrilling

ac ng

Grindingng

an ngTurning

aw ngECM, EDM

Machining

no z ngHoning

a nt ng

Platingo s n g

Finishing

utomateBonding

raz ng

Manualvet ng

o er ngWelding

Assembly


protection?



Assembly processes – fastening / joining of 2 or more components

xtrus onForging

o ng

Bar drawingre raw ng

Deformation

entr ugaDie castingnvestment

Permanent moldan cast ng

Casting

en ngBlanking

raw ng

Punchingear ng

p nn ng

Sheet

Metal

ow mo ngCasting

ompress on mo ng

Extrusionn ect on o ng


Polymer

Processes

or ngDrilling

ac ng

Grindingng

an ngTurning

aw ng,

Machining

no z ngHoning

a nt ng

Platingo s ng

Finishing

utomateBonding

raz ng

Manualvet ng

o er ngWelding

Assembly


permanent?



Process / Material Screening

Process-First Approach Material First Approach

Part Information Application Information

1. Production Volume 1. Applied Loads

2. Part Size (overall) magnitude

3. Shape Capability (features) cyclic nature (fatigue)boss/depression 1D rate (slow, impact)

boss/depression >1D duration (creep)

holes 2. Ambient Conditions

undercuts (int./ext.) temperature

uniform walls moisturecross sections –

(uniform /regular)

sunlight (ultra-violet)

rotational symmetry chemical liquids/vapors

captured cavities 3. Safety/Legal (FDA, UL)

4. Cost



Product function is interdependent

Material

Properties

Product

Function

Manufacturing

Processes

Product

Geometry



Are materials compatible with mfg. process?

Material

Properties

Manufacturing

Processescompatible

materials & processes



Material-Process Compatibility

ME 488 Design for Manufacture & Assembly Materials Compatibility

Processes S h a p e A t t r i b u t e s

C a s t

I r o n

C a r b o n

S t e e

l

A l l o y

S t e e

l

S t a

i n l e s s

S t e e

l

A l u m

i n u m

& a

l l o y s

C o p p e r

& a

l l o y s

Z i n c

& a

l l o y s

M a g n e s

i u m

& a

l l o y s

T i t a n

i u m

a n

d a

l l o y s

N i c k e

l & a

l l o y s

R e

f r a c t o r y m e t a

l s

T h e r m o p

l a s t i c s

t h e r m o s e t s

Solidification sand casting

investment casting

die casting

injection molding

structural foam

blow molding - extr

blow molding - inj

rotational molding

Bulk impact extrusion

Deformation cold heading

closed die forging

powder metal

hot extrusion

rotary swaging

Metal machined from stock

Removal ECMEDM

Profile Generation Wire EDM

Sheet sheet metal bending

Forming thermoforming

metal spinning

© R. J. Eggert, BSU (Based on data from Boothroyd, Dewhurst & Knight) pg 47 revision 9/02/03

Legend Normal practice

Less common

Not applicable



Is process capable of producing part geometry?

Manufacturing

Processes

Product

Geometry

“capable” geometry & processes



Process-first selection approach

Part Information

1. Production Volume (run qty)

2. Part Size (overall)

3. Shape Capability (features)

boss/depression 1D

boss/depression >1D

holes

undercuts (int./ext.)uniform walls

uniform cross sections

regular cross sections

rotational symmetry

captured cavities



Depressions 1D, >1D

1D

>1D



Uniform wall (thickness) but…

Varying cross section Constant cross

section



Uniform cross section (constant cross section)

Non-uniform wall thicknesses



Axis of rotation (symmetry)



Regular cross section (regular pattern)

not-regularRegular(i.e.pattern)

Regular(i.e.pattern)



Enclosed (hollow)

And, rotationally moldedparts



Draft free surfaces

CoreRiser

Sprue

Runner

Drag

Flask

Cope

Gate

Parting

line

With draft

No draft



Shape generation capability (of processes)ME 488/588 Design for Manufacture & Assembly Process Capabilitites for Shape Generation

Date: 9/2/03

Engineer: R. J. E. Design

Part Name: no features part For Process

Part Data Input: N N N N N N N N N Assembly Evaluation

Processes S h a p e A t t r i b u t e s

D e p r e s s i o n s 1 D

D e p r e s s i o n s > 1 D

U n i f o r m - W a l l

U n i f o r m - S e c t i o n

A x i s o f R o t a t i o n

R e g u l a r C r o s s S e c t i o n

C a p t u r e d C a v i t i e s

E n c l o s e d

D r a f t F r e e S u r f a c e s

P a r t c o n s o l i d a t i o n

A l i g n m e n t F e a t u r e s

I n t e g r a l F a s t e n e r s

D F A I n d e x

N o t c a p a b l e ( N )

F e a t u r e ( M ) u s t

A c c e p t e d / R e j e c t e d

Solidification sand casting Y Y YU Y Y Y Y N N 4 3 1 8 0 0 A

investment casting Y Y YU Y Y Y Y N N 5 5 2 12 0 0 A

die casting Y Y YU Y Y Y N N N 4 5 3 12 0 0 Ainjection molding Y Y YU Y Y Y N N N 5 5 5 15 0 0 A

structural foam Y Y YU Y Y Y N N N 4 4 3 11 0 0 A

blow molding - extr Y Y M N Y Y M Y N 3 4 3 0 0 2 R

blow molding - inj Y Y M N Y YU M N N 3 4 3 0 0 2 R

rotational molding Y Y M N Y Y N M N 2 2 1 0 0 2 R

Bulk impact extrusion Y N Y N Y YU N N Y 3 3 1 7 0 0 A

Deformation cold heading Y N Y N Y YU N N Y 3 3 1 7 0 0 A

closed die forging Y Y Y Y Y Y N N N 3 2 1 6 0 0 A

powder metal Y N Y YU Y Y N N YU 3 3 1 7 0 0 A

hot extrusion Y N Y M Y Y N N Y 2 2 3 0 0 1 R

rotary swaging N N N N M N N N N 1 1 1 0 0 1 R

Metal machined from stock Y Y Y Y Y Y Y N Y 2 3 2 7 0 0 A

Removal ECM Y Y Y Y Y Y N N N 3 4 1 8 0 0 A

EDM Y Y Y Y Y Y N N N 3 4 1 8 0 0 A

Profile Generation Wire EDM Y N Y Y Y Y N N Y 2 2 3 7 0 0 A

Sheet sheet metal bending Y Y M Y Y Y N N N 4 3 4 0 0 1 R

Forming thermoforming Y Y M Y Y Y N N N 3 3 3 0 0 1 R

metal spinning N N M N M N Y N N 1 1 1 0 0 2 R

© R. J. Eggert, BSU (Based on data from Boothroyd, Dewhurst & Knight) revision 9/02/03



Manufacturing costs

Total Manufacturing Cost = Material + Tooling + Processing

raw mat’ls molds labor

fixtures electricity jigs suppliestool bits O/H

(deprec.)

TMC = M + T + P (6.1)



Material costs per part

Let M = total materials costs (raw, bulk)

q = production quantity

Then material costs per part, cM iscM = M/q = (cost/weight x weight) / number of parts

Let’s reorganize the variables in the equation above

cM = [cost/weight] [weight/number of parts]= (cost/weight) (weight/part), and therefore

cM = cost/part



Material cost per part (continued)

Letcw = material cost per unit weight, andwp = weight of finished partww= weight of wasted material, scrap

= ratio of wasted material weight / finished weight= ww / wp

Then the material cost per part, cM iscM = cw (wp + ww ) = cw (wp + wp ) (6.2)c

M

= cw

wp

(1+ ) (6.3)

e.g. sand castingcM = ($1/lb)(1lb/part)(1+.05) = $1.05/part



Tooling cost per part

LetT= total cost of molds, fixtures per production runq = number of parts per run

ThencT= T/q (6.4)

e.g. sand casting

cT = ($10,000/run) / (5000 parts/run) = $2.00/part



Processing cost per part

Letct = cost per hour, (machine rate + labor)

t = cycle time (hours per part)

then cP = ct t (6.5)

e.g. sand casting

cP = ($30/hr) (0.3 hrs/part) = $9/part



Total cost per part

Cost per part,

c = cM + cT + cP

c = cw

wp

(1+ ) + T/q + ct

t (6.6)

e.g. sand casting

c = $1.05 + $2.00 + $9.00

c = $12.05 / part



Example costs for 5000 part run

Alternative

A B C

Mfg. Process Sand casting Injection molding Machining

Material Aluminum alloy ABS Bronze alloy

Part weight (lb) 1 3 2

alpha 0.05 0.01 0.2

Material cost ($/lb), cw 1 0.25 0.75

Tooling cost ($), T 10000 35000 1500

Production quantity, q 5000 5000 5000

Cycle time (hrs/part), t 0.3 0.03 0.6

Machine rate ($/hr) 30 100 75

Part cost ($/part) 12.05 10.7575 47.1



1

10

100

1000

0 1000 2000 3000 4000 5000 6000

Production quantity

C

o s t ( $ / p a r t )

A B C

Run quantity is important!

A-Sand casting B-Inj.Molding C-Machining



How can we lower the cost of parts?

c = cw wp (1+ ) + T/q + ct t (6.6)

1) purchase less expensive materials,

2) keep our finished part weight low

3) produce little manufactured waste4) design simple parts that result in less expensive

tooling

5) make many parts production run (i.e. batch)

6) choose a manufacturing process that has a lowcycle time & cost per hour

Goal: minimize the sum of the terms!(not any one term in particular)



Summary

Manufacturing process decisions Deformation processes Casting processes Sheet metalworking

Polymer processing Machining Finishing Assembly

Material compatibilities / Process capabilities Material costs, Tooling costs, Processing costs

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02 Selecting Manufacturing Processes