1. 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

2. How would we manufacture a mountain bike ?
Handle Bar
Top
Tube
Seat
Post
Saddle
Fork
Rear Brake
Down
Tube
Front Brake
Rear
Derailleur
Pedal
(Courtesy of Trek Bicycle, 2002)

3. 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?

4. Parts undergo sequence of processes
Changes?
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

5. 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/regular
rotational symmetry
captured cavities

6. Types of manufacturing processes
How is the input material changed?

7. Deformation processes
Rolling
Extrusion
Drawing
Forging

8. Rolling (of ductile materials)
Rollers in compression
thick slab
thin sheet
Plastic deformation

9. Rolling
slab
bloom
billet
sheet
coil
bar
rod
structural
ingot

10. Extrusion
Ram
Cross
sections
Extrusion die
Billet

11. Drawing
Pulling force
Cross
sections
Drawing die
Billet

12. Forging (closed-die)
Blocked
preform
Gutter
Ram pressure
Flash

13. Casting Processes
Sand casting
Die casting
Investment casting

14. Sand casting (closed-mold)
Core
Riser
Sprue
Runner
Drag
Flask
Cope
Gate
Parting
line

15. Die casting Parting line Plunger Sprue Moving die Stationary die
Ejector pins
Molten
metal

16. Investment casting Ceramic mold (hardened slurry) 4-part pattern tree
Wax pattern
is cast
Wax removed
by melting
Molten metal solidifies in cast
Ceramic mold is removed

17. Sheet Metalworking
Bending
Blanking
Drawing
Punching
Shearing
Spinning

18. Sheet metal drawing Punch ram Punch Blank holder Clamp force Die Blank
Drawn part
Clamp
force
Blank holder
Die
Punch
Punch ram

19. Polymer Processes Compression molding Transfer Molding Blow molding
Injection molding

20. Compression molding
Charge
Heated mold
Part
Ram Pressure

21. Transfer molding
Charge
Ram
Heated
mold
Sprue
Part
Ram pressure

22. Molten parison is extruded
Blow molding
Extruder
air injector
parison
Part is
removed
Air
blown
into
Mold halves
close
Molten parison is extruded

23. Injection molding Shear-heating Cavity half of mold Core half
Ejector pins
Moving
Feed hopper
Sprue
Fixed
Barrel
Pellets
Mold closure direction
Parting plane/surface

24. Example of a box …with no undercuts
core
cavity
parting
line
mold closure
direction
plastic
injection
ejector pins

25. Internal undercuts core cavity parting line closure direction plastic
injection
ejector pins

26. External undercuts ejector pins parting line core cavity closure
plastic
injection
ejector pins
closure
direction

27. Solidification processes
solid Part
molten material
freezing
Casting Processes
Sand Casting
Die Casting
Investment Casting
Centrifugal
Polymer Processes
Injection Molding
Blow Molding
ThermoForming
Compression Molding
Recall
Flow (voids, flash)
Cooling time (cycle time)
Temperature
Mold complexity
Warpage
Post processing
Costs (materials, tooling, processing)
considerations
Add to your notes

28. Machining processes

29. 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.

30. Surface roughness

31. Machining process considerations
solid material
machining
material removed
sawing, turning, boring, milling,
drilling, grinding, ECM
Recall
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)
considerations
Add to your notes

32. Finishing processes
protection?

33. Assembly processes – fastening / joining of 2 or more components
permanent?

34. Process / Material Screening

35. Product function is interdependent
Material
Properties
Product
Function
Manufacturing
Processes
Product
Geometry

36. Are materials compatible with mfg. process?
Properties
Manufacturing
Processes
compatible
materials & processes

37. Material-Process Compatibility

38. Is process capable of producing part geometry?
geometry & processes
Manufacturing
Processes
Product
Geometry

39. 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

40. Depressions 1D, >1D 1D
>1D

41. Uniform wall (thickness) but…
Varying cross section
Constant cross section

42. Uniform cross section (constant cross section)
Non-uniform wall thicknesses

43. Axis of rotation (symmetry)

44. Regular cross section (regular pattern)
Regular (i.e.pattern)
Regular (i.e.pattern)
not-regular

45. Enclosed (hollow)
And, rotationally molded parts

46. Draft free surfaces No draft With draft Core Riser Sprue Runner Drag
Flask
Cope
Gate
Parting
line

47. Shape generation capability (of processes)

48. 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)

49. 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

50. 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 ) (6.2)
cM = cw wp (1+ ) (6.3)
e.g. sand casting
cM = ($1/lb)(1lb/part)(1+.05) = $1.05/part

51. 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

52. Processing cost per part
Let
ct = 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

53. 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 = $ $ $9.00
c = $12.05 / part

54. Example costs for 5000 part run

55. Run quantity is important!
A-Sand casting B-Inj.Molding C-Machining

56. How can we lower the cost of parts?
c = cw wp (1+ ) + T/q + ct t (6.6)
      
purchase less expensive materials,
keep our finished part weight low
produce little manufactured waste
design simple parts that result in less expensive tooling
make many parts production run (i.e. batch)
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)

57. 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