Selecting manufacturing processes Manufacturing process decisions Deformation processes Casting processes Sheet metalworking Polymer processing Machining.

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 ?

TopTube

RearDerailleur

Front Brake

Rear Brake

SaddleSeatPost

Pedal

Handle Bar

DownTube

Fork

(Courtesy of Trek Bicycle, 2002)

Manufacturing process decisions

How do we choose the specific manufacturing processes?

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

Would product function or performance issues influence 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 castingRollingForgingSheet 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 PolishingPaintingHeat-treatingJoining

Changes?

Part / Mfg. Process Considerations

1. Production Volume2. Part Size (overall)3. Shape Capability (features) boss/depression 1D boss/depression >1D holes undercuts (int./ext.) uniform walls cross sections - uniform/regular rotational symmetry captured cavities

Types of manufacturing processes

E xtrus ionF org ingR o ll ingB ar d raw ingW ire d raw ing

D eform ation

C en trifugalD ie cas t ingInvestm entP erm anen t m o ldS and cas t ing

C ast ing

B end ingB lank ingD raw ingP unch ingS hear ingS p inn ing

S hee tM etal

B low m old ingC ast ingC om press ion m o ld ingE x trus ionIn jec tion M old ingT herm oform ingT ransfe r m o ld ing

P o lym erP rocesses

B oringD ril lingF ac ingG rind ingM ill ingP lan ingT urn ingS aw ingE C M , E D M

M ach in ing

A nod iz ingH on ingP a in tingP la t ingP o lish ing

F in ish ing

A utom atedB ond ingB raz ingM anualR ive tingS o lde r ingW eld ing

A ssem bly

M anufac tu r ingP rocesses

How is the input material

changed?

Deformation processes

Rolling Extrusion Drawing Forging

Rolling (of ductile materials)

Plastic deformation

Rollers in compression

thick slab

thin sheet

Rolling

slab

bloom

billet

sheetcoil

bar rod

structural

ingot

Extrusion

Ram

Crosssections

Extrusion die

Billet

Drawing

Pulling force

Crosssections

Drawing die

Billet

Forging (closed-die)

Blockedpreform

Gutter

Ram pressure

Flash

Casting Processes

Sand casting Die casting Investment casting

Sand casting (closed-mold)

Core Riser

Sprue

Runner

Drag

Flask

Cope

Gate

Partingline

Die casting

Parting line

Plunger

Sprue

Moving die

Stationary die

Ejector pins

Moltenmetal

Investment casting

Wax patternis cast

Wax removedby melting

Molten metal solidifies in cast

Ceramic mold is removed

Ceramic mold(hardened slurry)4-part pattern tree

Sheet Metalworking

Bending Blanking Drawing Punching Shearing Spinning

Sheet metal drawing

BlankDrawn part

Clamp force

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

Heatedmold

Sprue

Part

Ram pressure

Blow molding

Extruderair injector

parison

Part isremoved

Airblown into

parison

Mold halvesclose

Molten parison is extruded

Injection molding

Shear-heating

Cavity halfof mold

Core halfof mold

Ejector pins

Moving

Feed hopper

Sprue

Fixed

Barrel

Pellets

Mold closure directionParting

plane/surface

Example of a box …with no undercuts

core

cavity

partingline

mold closure

directionplastic

injection

ejector pins

Internal undercuts

core

cavity

partingline

closuredirection

plasticinjection

ejector pins

External undercuts

core

cavity

partingline

plasticinjection

ejector pins

closuredirection

Solidification processes

Casting ProcessesSand CastingDie CastingInvestment CastingCentrifugal

Polymer ProcessesInjection MoldingBlow MoldingThermoFormingCompression Molding

solid Part molten material freezing

Flow (voids, flash)Cooling time (cycle time)TemperatureMold complexity Warpage Post processing Costs (materials, tooling, processing)

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Machining processes

E xtrus ionF org ingR o ll ingB ar d raw ingW ire d raw ing

D eform ation

C en trifugalD ie cas t ingInvestm entP erm anen t m o ldS and cas t ing

C as t ing

B end ingB lank ingD raw ingP unch ingS hear ingS p inn ing

S hee tM etal

B low m old ingC as t ingC om press ion m o ld ingE x trus ionIn jec tion M old ingT herm oform ingT ransfe r m o ld ing

P o lym erP rocesses

B oringD ril lingF ac ingG rind ingM ill ingP lan ingT urn ingS aw ingE C M , E D M

M ach in ing

A nod iz ingH on ingP a in tingP la t ingP o lish ing

F in ish ing

A utom atedB ond ingB raz ingM anualR ive tingS o lde r ingW eld ing

A ssem bly

M anufac tu r ingP rocesses

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 removed solid material machining

hardness, strength of materialshear forces = strong jigs & fixtures tool/bit wear, replacementsize of workpiece, fit machine?volume removedrate of removal, hp neededtolerances operator skill, CNCcosts (materials, tooling, processing)

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Finishing processes

E xtru s ionF org ingR o ll ingB ar d raw ingW ire d raw ing

D eform a tion

C en trifugalD ie cas t ingInvestm entP e rm anen t m o ldS and cas t ing

C as t ing

B end ingB lank ingD raw ingP unch ingS hea r ingS p inn ing

S hee tM etal

B low m o ld ingC as t ingC om press ion m o ld ingE x tru s ionIn jec tion M old ingT herm oform ingT ransfe r m o ld ing

P o lym erP rocesses

B oringD ril lingF ac ingG rind ingM ill ingP lan ingT urn ingS aw ingE C M , E D M

M ach in ing

A nod iz ingH on ingP a in t ingP la t ingP o lish ing

F in ish ing

A u tom atedB ond ingB raz ingM anualR ive t ingS o lde r ingW eld ing

A ssem bly

M anufac tu r ingP rocesses

protection?

Assembly processes – fastening / joining of 2 or more components

E xtru s ionF org ingR o ll ingB ar d raw ingW ire d raw ing

D eform ation

C en trifugalD ie cas t ingInvestm entP erm anen t m o ldS and cas t ing

C as t ing

B end ingB lank ingD raw ingP unch ingS hear ingS p inn ing

S hee tM etal

B low m o ld ingC as t ingC om press ion m o ld ingE x tru s ionIn jec tion M old ingT herm oform ingT ransfe r m o ld ing

P o lym erP rocesses

B oringD ril lingF ac ingG rind ingM ill ingP lan ingT urn ingS aw ingE C M , E D M

M ach in ing

A nod iz ingH on ingP a in t ingP la t ingP o lish ing

F in ish ing

A u tom atedB ond ingB raz ingM anualR ive t ingS o lde r ingW eld ing

A ssem bly

M anufac tu r ingP rocesses

permanent?

Process / Material Screening

Product function is interdependent

Material Properties

ProductFunction

ManufacturingProcesses

ProductGeometry

Are materials compatible with mfg. process?

Material Properties

ManufacturingProcesses

compatiblematerials & processes

Material-Process Compatibility

ME 488 Design for Manufacture & Assembly Materials Compatibility

Processes Sh

ap

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ttrib

utes

Cast

Iron

Carbon S

teel

Alloy S

teel

Sta

inle

ss S

teel

Alu

min

um

& a

lloys

Copper &

alloys

Zin

c &

alloys

Magnesiu

m &

alloys

Titaniu

m a

nd a

lloys

Nic

kel &

alloys

Refr

acto

ry m

eta

ls

Therm

opla

stics

therm

osets

Solidification sand castinginvestment castingdie castinginjection moldingstructural foamblow molding - extrblow molding - injrotational molding

Bulk impact extrusionDeformation cold heading

closed die forgingpowder metalhot extrusionrotary swaging

Metal machined from stockRemoval ECM

EDM

Profile Generation Wire EDM

Sheet sheet metal bendingForming thermoforming

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

Legend Normal practiceLess commonNot applicable

Is process capable of producing part geometry?

ManufacturingProcesses

ProductGeometry

“capable”geometry & processes

Process-first selection approach

Part Information1. Production Volume (run qty)2. Part Size (overall)3. Shape Capability (features)

boss/depression 1Dboss/depression >1Dholesundercuts (int./ext.)uniform walls

uniform cross sectionsregular cross sectionsrotational symmetrycaptured 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 molded parts

Draft free surfaces

Core Riser

Sprue

Runner

Drag

Flask

Cope

Gate

Partingline

With draft

No draft

Shape generation capability (of processes)

Manufacturing costs

Total Manufacturing Cost = Material + Tooling + Processing

raw mat’ls molds labor  fixtures electricity jigs supplies tool 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 is

cM = 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)

Let cw = material cost per unit weight, and wp = weight of finished part ww= 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)cM = cw wp (1+ )

(6.3)

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

Tooling cost per part

Let T= total cost of molds, fixtures per production run q = number of parts per run

Then cT= 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

1

10

100

1000

0 1000 2000 3000 4000 5000 6000

Production quantity

Cos

t ($

/par

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 low3) 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 low

cycle 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