EPT 221
Engineering Design
Manufacturing Process Selection
Objectives of Lecture
 Differentiate and select primary, secondary ,
and tertiary processes
 Understand and apply methods to select
appropriate manufacturing processes
 Estimate the costs of manufacturing a
product.
How would we manufacture a
mountain bike ?
Seat
Post
Rear Brake
Rear
Derailleur
Saddle
Top
Tube
Down
Tube
Pedal
(Courtesy of Trek Bicycle, 2002)
Handle Bar
Fork
Front
Brake
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
Changes?
 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
Part / Mfg. Process
Considerations
1. Production Volume
2. Part Size (overall)
3. Shape Capability (features)/
geometric complexity
boss/depression 1D
boss/depression >1D
holes
undercuts (int./ext.)
uniform walls
cross sections - uniform/regular
rotational symmetry
captured cavities
Types of manufacturing
processes
Manufacturing
Processes
Deformation
Extrusion
Forging
Rolling
Bar drawing
Wire drawing
Casting
Centrifugal
Die casting
Investment
Permanent mold
Sand casting
Sheet
Metal
Bending
Blanking
Drawing
Punching
Shearing
Spinning
Polymer
Processes
Blow molding
Casting
Compression molding
Extrusion
Injection Molding
Thermoforming
Transfer molding
How is the input
material changed?
Machining
Boring
Drilling
Facing
Grinding
Milling
Planing
Turning
Sawing
ECM, EDM
Finishing
Anodizing
Honing
Painting
Plating
Polishing
Assembly
Automated
Bonding
Brazing
Manual
Riveting
Soldering
Welding
Bulk Deformation
 To change the shape or form of bulk material
caused by compressive or tensile yielding.
 Rolling
 Extrusion
 Drawing
 Forging
Rolling
 Two or more cylindrical
rollers plastically compress
material, forming sheets,
bars and rods.
 Hot rolling requires less work
but an oxidized surface finish
 Cold rolling requires more
work but increases the yield
strength of the material and
produces superior surface
finish.
Rolling
bloom
structural
ingot
slab
coil
sheet
billet
bar
rod
Extrusion
 Heated metal plastically
yields as it is pushed through
a die, producing long pieces
with a constant crosssection.
 Size: 40-foot in length
Ram
 Economical production
quantities: 1,000 to 100,000
pieces
 Materials: ductile metals
(e.g. aluminum, steel, zinc,
copper, magnesium)
Extrusion
die
Cross
sections
Billet
Drawing
 Process of producing a wire,
bar or tube by pulling on a
material until it increases in
length accompanied with a
reduction in its crosssectional diameter.
 Size: bar size range 1/8 to 6
inches in cross-section, wire
size range 0.001 to 3/8
inches.
 Material: ductile metals (e.g.
aluminum, steel, copper)
Drawing
die
Cross
sections
Billet
Pulling
force
Forging (closed-die)
Ram pressure
Blocked
preform
Flash
Gutter
 A process in which material is plastically compressed
between 2 halves of a die set by hydraulic pressure
or the stroke of a hammer.
 Size: maximum size limit roughly 36 inches
 Economic production quantity: 1,000 to 100,000
pieces
Casting Processes
 The process in which molten metal is
poured into a cast to solidify.
 Sand casting
 Die casting
 Investment casting
Sand casting (closed-mold)
Cope
Flask
Parting
line
Core
Riser
Sprue
Runner
Drag
Gate
 Uses sand mold. The mold is destroyed to remove the part.
 Mold size ranges from inches to feet. (e.g. as mold cast for
industrial engine blocks as large as 12 feet in cross section and
30 feet long)
 Economical production quantity: very small i.e. 1 to 10
 Material: all ferrous and nonferrous metals
 Parts produced have a granular surface finish.
Die casting
 Molten metal is injected





under high pressure into
permanent die set usually
made of steel.
Molten
Die casting is faster than
metal
sand casting but can more
expensive.
Smoother surface finishPlunger
than
sand-cast parts.
Size: maximum part size 30
x 30 inches to parts less
than an inch.
Economic production
quantity: over 10,000
Material: low-melting-point
metals (e.g. aluminum, zinc,
magnesium, brass)
Stationary Moving
die
die
Ejector
pins
Sprue
Parting line
Investment casting (lost wax casting)
 Molten metal solidifies in a
ceramic cast made by
coating a wax pattern with
liquid slurry, then dried.
 Wax is melted out and
ceramic mold is destroyed
after part solidifies.
 Material: alloy of aluminum,
zinc, magnesium, brass,
steel, stainless steel.
 Economic production
quantity: less than 10,000
pieces
Investment casting
4-part pattern tree
Ceramic mold
(hardened slurry)
Molten metal
solidifies in cast
Ceramic mold is
removed
Wax pattern
is cast
Wax removed
by melting
Polymer Processes
 Part shapes are created by solidification
of thermoplastic polymers or curing of
thermosetting polymers.
 Results in little waste of raw material and
require few, if any, finishing operations
 Compression molding
 Transfer Molding
 Blow molding
 Injection molding
Compression molding
Heated
mold
Ram Pressure
Charge
Part
 Charge of thermoset or elastomer is formed between heated
mold halves under pressure while the polymer cures.
 Compression molds are simpler than injection molds (no sprue,
runners, risers)
 Size: minimum part size of the order of 1/8 to ¼ inch in crosssection
 Economic production volume: more than 10,000 pieces
Transfer molding
Ram pressure
Ram
Heated
mold
Charge
Sprue
Part
Blow molding
Molten
parison is
extruded
Extruder
air injector
parison
Mold
halves
close
Air
blown
into
parison
Part is
removed
Blow moulding
 A molten parison of
thermoplastic material
injected with air, then
expands to the shape of
the mold.
 Is used to produce
hollow parts within thin
walls.
 Size: maximum size of
about 3 feet in diameter
Injection moulding
 Thermoplastic pellets are melted and injected under
high pressure into a metal mold.
 Size: maximum part size less than 24 x 24 inches,
minimum part size are of the order of 1/8 to ¼ inch in
cross-section
 Economic production quantity: more than 10,000
Sheet Metalworking
 The permanent deformation of thin metal











sheets by bending and shearing forces
produced by mechanical or hydraulic forces.
Often called stamping forces.
Produces parts of moderate complexity.
Size: less than 24x24inches
Economic production quantity: more than
10,000
Material: alloys of steel and aluminum
Bending
Blanking
Drawing
Punching
Shearing
Spinning
 Shearing : cutting or separating sheet metal
along a straight line.
 Blanking: shearing of a smaller, shaped
piece, called a blank, from the stock.
 Punching: produces slots, notches, extruded
holes, and holes.
 Embossing: forming plastic indentations to
form ribs, beads, or lettering on the surface of
metal.
Sheet metal drawing
Punch ram
Punch
Blank
holder
Die
Blank
Clamp
force
Drawn part
 Punch plastically deforms a blank sheet material into
a die, forming cupped-, box-, or hollow-shaped parts
 Products: soda cans, ammunition cartridge casings,
and pots and pans.
Solidification processes
molten material
freezing
solid Part
Casting Processes
Polymer Processes
Sand Casting
Injection Molding
Die Casting
Blow Molding
Investment Casting
ThermoForming
Centrifugal
Compression Molding
Add to your
notes
Flow (voids, flash)
Cooling time (cycle time)
Temperature
Mold complexity
Warpage
Post processing
Costs (materials, tooling, processing)
Machining
 The removing of material from the workpiece
by a sharp cutting tool that shears away chips
of material to create a desired form or
features.
 It is a subtractive process that produces
manufactured waste and can, therefore be
expensive.
 Often used as a secondary process to true-up
critical dimensions or surfaces or to smooth
the surface finish.
 Often used for low-volume production.
Machining processes
Manufacturing
Processes
Deformation
Extrusion
Forging
Rolling
Bar drawing
Wire drawing
Casting
Centrifugal
Die casting
Investment
Permanent mold
Sand casting
Sheet
Metal
Bending
Blanking
Drawing
Punching
Shearing
Spinning
Polymer
Processes
Blow molding
Casting
Compression molding
Extrusion
Injection Molding
Thermoforming
Transfer molding
Machining
Boring
Drilling
Facing
Grinding
Milling
Planing
Turning
Sawing
ECM, EDM
Finishing
Anodizing
Honing
Painting
Plating
Polishing
Assembly
Automated
Bonding
Brazing
Manual
Riveting
Soldering
Welding
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 (EDM) - by means of a spark.
Machining process
considerations
solid material
machining
material removed
sawing, turning, boring, milling,
drilling, grinding, ECM
Add to your
notes
hardness, strength of material
shear forces = strong jigs & fixtures
tool/bit wear, replacement
size of workpiece, fit machine?
volume removed
rate of removal, hp needed
tolerances
operator skill, CNC
costs (materials, tooling, processing)
Finishing
 Preparing the final surface for aesthetics and
protection from the environment.
 Cleaning: wire brushing is used to remove grit and
scale, and chemical solutions, including acid baths,
are used to remove oily films
 Protection: polymers and ceramics requires little
protection from the environment. Metals, however,
require some surface treatment with oil-and-water
based painting providing the least expensive coating.
Steels are often plated with chrome, cadmium, or
zinc). Aluminum alloys are usually anodized (a
chemical surface treatment).
Finishing processes
Manufacturing
Processes
protection?
Deformation
Extrusion
Forging
Rolling
Bar drawing
Wire drawing
Casting
Centrifugal
Die casting
Investment
Permanent mold
Sand casting
Sheet
Metal
Bending
Blanking
Drawing
Punching
Shearing
Spinning
Polymer
Processes
Blow molding
Casting
Compression molding
Extrusion
Injection Molding
Thermoforming
Transfer molding
Machining
Boring
Drilling
Facing
Grinding
Milling
Planing
Turning
Sawing
ECM, EDM
Finishing
Anodizing
Honing
Painting
Plating
Polishing
Assembly
Automated
Bonding
Brazing
Manual
Riveting
Soldering
Welding
Surface roughness
Assembly
 The process of putting together all the components
of a product before shipping.
 Operation include handling, insertion, and/or
attachment of parts.
 Handling: grasping, moving, orienting, and placing
parts, before insertion or attachment.
 Attachment: either
- Permanent: welding, brazing, soldering, adhesive
bonding, rivets, eyelets, staples, shrink fits, press fits,
or
- Temporary: threaded fasteners such as screws,
nuts and bolts, snap fits.
Assembly processes
– fastening / joining of 2 or more
components
Manufacturing
Processes
Deformation
Extrusion
Forging
Rolling
Bar drawing
Wire drawing
Casting
Centrifugal
Die casting
Investment
Permanent mold
Sand casting
Sheet
Metal
Bending
Blanking
Drawing
Punching
Shearing
Spinning
Polymer
Processes
Blow molding
Casting
Compression molding
Extrusion
Injection Molding
Thermoforming
Transfer molding
Machining
Boring
Drilling
Facing
Grinding
Milling
Planing
Turning
Sawing
ECM, EDM
Finishing
Anodizing
Honing
Painting
Plating
Polishing
Assembly
Automated
Bonding
Brazing
Manual
Riveting
Soldering
Welding
permanent?
Process / Material
Screening
Process-First Approach
Part Information
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 /regular)
rotational symmetry
captured cavities
Material First Approach
Application Information
1. Applied Loads
magnitude
cyclic nature (fatigue)
rate (slow, impact)
duration (creep)
2. Ambient Conditions
temperature
moisture
sunlight (ultra-violet)
chemical liquids/vapors
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
Processes
compatible
materials & processes
Material-Process
Compatibility
thermosets
Thermoplastics
Refractory metals
Nickel & alloys
Titanium and alloys
Magnesium & alloys
Zinc & alloys
Copper & alloys
sand casting
investment casting
die casting
injection molding
structural foam
blow molding - extr
blow molding - inj
rotational molding
Bulk
Deformation
impact extrusion
cold heading
closed die forging
powder metal
hot extrusion
rotary swaging
Metal
Removal
machined from stock
ECM
EDM
Profile Generation
Wire EDM
Sheet
Forming
sheet metal bending
thermoforming
metal spinning
© R. J. Eggert, BSU (Based on data from Boothroyd, Dewhurst & Knight) pg 47
Legend
Aluminum & alloys
Stainless Steel
Materials Compatibility
Alloy Steel
Carbon Steel
Cast Iron
Processes
Solidification
Shape Attributes
ME 488 Design for Manufacture & Assembly
Normal practice
Less common
Not applicable
revision
9/02/03
Shape generation capability (of
processes)
Process Capabilitites for Shape Generation
Alignment Features
Integral Fasteners
DFA Index
Not capable (N)
Feature (M)ust
Accepted / Rejected
sand casting
investment casting
die casting
injection molding
structural foam
blow molding - extr
blow molding - inj
rotational molding
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
YU
YU
YU
YU
YU
M
M
M
Y
Y
Y
Y
Y
N
N
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
YU
Y
Y
Y
N
N
N
M
M
N
N
N
N
N
N
Y
N
M
N
N
N
N
N
N
N
N
4
5
4
5
4
3
3
2
3
5
5
5
4
4
4
2
1
2
3
5
3
3
3
1
8
12
12
15
11
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
2
2
A
A
A
A
A
R
R
R
Bulk
Deformation
impact extrusion
cold heading
closed die forging
powder metal
hot extrusion
rotary swaging
Y
Y
Y
Y
Y
N
N
N
Y
N
N
N
Y
Y
Y
Y
Y
N
N
N
Y
YU
M
N
Y
Y
Y
Y
Y
M
YU
YU
Y
Y
Y
N
N
N
N
N
N
N
N
N
N
N
N
N
Y
Y
N
YU
Y
N
3
3
3
3
2
1
3
3
2
3
2
1
1
1
1
1
3
1
7
7
6
7
0
0
0
0
0
0
0
0
0
0
0
0
1
1
A
A
A
A
R
R
Metal
Removal
machined from stock
ECM
EDM
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
N
N
N
N
Y
N
N
2
3
3
3
4
4
2
1
1
7
8
8
0
0
0
0
0
0
A
A
A
Profile Generation
Wire EDM
Y
N
Y
Y
Y
Y
N
N
Y
2
2
3
7
0
0
A
Sheet
Forming
sheet metal bending
thermoforming
metal spinning
Y
Y
N
Y
Y
N
M
M
M
Y
Y
N
Y
Y
M
Y
Y
N
N
N
Y
N
N
N
N
N
N
4
3
1
3
3
1
4
3
1
0
0
0
0
0
0
1
1
2
R
R
R
Processes
Solidification
Shape Attributes
Part consolidation
Process
Evaluation
Draft Free Surfaces
N
Enclosed
N
Captured Cavities
N
Regular Cross Section
N
Axis of Rotation
N
Uniform-Section
N
Uniform-Wall
N
Depressions >1D
N
Design
For
Assembly
Depressions 1D
ME 488/588 Design for Manufacture & Assembly
Date:
9/2/03
Engineer:
R. J. E.
Part Name:
no features part
Part Data Input:
N
© 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
fixtures
jigs
tool bits
TMC
= M
+T
labor
electricity
supplies
O/H
(deprec.)
+P
Material costs per part, cM
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 is
cM = cw (wp + ww ) = cw (wp +  wp )
cM = cw wp (1+ )
Tooling cost per part, cT
Let
T= total cost of molds, fixtures per production run
q = number of parts per run
Then tooling cost per part, cT
cT= T/q
e.g. sand casting
cT = ($10,000/run) / (5000 parts/run) = $2.00/part
Processing cost per part, cP
Let
ct = cost per hour, (machine rate + labor)
t = cycle time (hours per part)
then
cP = ct t
e.g. sand casting
cP = ($30/hr) (0.3 hrs/part) = $9/part
Total cost per part
Cost per part,
c=
cM
+
c = cw wp (1+ ) +
cT
+
cP
T/q
+
ct t
e.g. sand casting
c=
$1.05
c=
$12.05 / part
+
$2.00 +
$9.00
(6.6)
Example
 Assume that our company is
considering making a part
out of low-strength metals or
thermoplastics. Three
A
processes appear
Mfg. Process Sand casting
compatible with the required
Material Aluminum alloy
feature shapes: sand
casting, injection, and
Part weight (lb)
1
machining. The marketing
alpha
0.05
department estimates that
1
the company should produce Material cost ($/lb), cw
about 5,000 pieces. Data
Tooling cost ($), T
10000
gathered to select the
Production quantity, q
5000
material and manufacturing
Cycle time (hrs/part), t
0.3
process are shown in the
table below. Determine the
Machine rate ($/hr)
30
cost per part.
Part cost ($/part)
12.05
Alternative
B
Injection molding
ABS
3
0.01
0.25
35000
5000
0.03
100
10.7575
C
Machining
Bronze alloy
2
0.2
0.75
1500
5000
0.6
75
47.1
Run quantity is important!
Cost ($/part)
1000
100
10
1
0
1000
2000
3000
4000
5000
6000
Production quantity
A
B
C
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 waste
4) 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)
Case Study- Aero engine
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