MECH152-L27(1.0) - 1
Design for Manufacture
Manufacturing Processes
Review
MECH152-L27(1.0) - 2
Manufacturing
Manufacture
Shape
forming
Shape
change
Finish
Assembly
Handle
Handle
Handle
Handle
Primary
manufacturing
Secondary
manufacturing
Tertiary
manufacturing
Join
Shape forming
Machining
Coating,
treatment
Fasten
Inspect
Inspect
Inspect
Inspect
Insert
MECH152-L27(1.0) - 3
Process Planning
Given the engineering drawing:
– Drawing interpretation
– Material evaluation, Production volume and
rate, Tolerance and surface finish, and process
selection
– Selection of machine and tooling
– Setting process parameters
– Tooling and fixtures
– Selecting quality assurance methods
– Costing
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Combined Routing Sheet /
Operation List
Part No.:
Part Name:
Revision:
Matl.:
Size:
Planner:
No
Operation
Page No.:
Date:
Dept.
M/C
Tooling
Gauges
G856
.
10
Face; rough & finish turn to
360.075 dia. and 300.1 length; Face shoulder to
80.05 and finish turn to 450.05 dia.
L
325
20
Reverse: face to 1200.1 dia. length; finish turn to
450.05 dia.; Drill 25 +0.15 -0.05 dia. hole
L
325
30
Drill & Ream 3 radial holes at 9.50.05 dia
D
114
40
Mill 120.1 wide x 9.50.075 deep slot
M
50
Mill 180.1 wide x 9.50.075 deep flat
M
Setup
Time
Cycle
Time
1.0h
6.12m
0.5h
3.10m
F512
0.3h
2.50m
240
F321
0.3h
1.80m
240
F322
0.3h
1.45m
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Primary Manufacturing Processes
• Casting
• Molding
• Powder Metallurgy
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Sand Casting – Pros & Cons
Pros:
• Produce parts with
complex geometries, both
internally and externally.
• Possible to net shape with
no further manufacturing
required.
• Large parts can be
produced.
• Wide choice of metals.
• Suitable for mass
production.
Cons:
• Poor dimensional control for
some processes
• Poor surface finish for some
processes
• Limitation on mechanical
properties
• Safety hazard
• Environmental hazard
MECH152-L27(1.0) - 7
Expendable Mold Casting Shell Mold
Pros:
– Smoother surface finish than sans casting.
– Surface finish of 2.5 m can be obtained.
– Good dimensional accuracy  0.25 mm on
small to medium size parts.
– No further machining is needed.
– Capability for automation lowers the cost for
larger quantities.
Cons:
– More expensive metal pattern, especially for
small batch.
MECH152-L27(1.0) - 8
Expendable Mold Casting Vacuum Mold
Sand held together by vacuum pressure.
Pros:
– Sand can be recovered unlike shell mold.
– No chemical binder, and therefore no special
treatment for the sand.
– No water mixed with the sand and therefore no
moisture related problems
Cons:
– Relative slow
– Not readily adaptable to mechanization.
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Expendable Mold Casting Expanded Polystrene Mold
Pros:
– Pattern need not be removed.
– No cope /drag is needed, all features are built
into the pattern.
– Possibility for automated production.
Cons:
– The pattern is not reusable.
MECH152-L27(1.0) - 10
Expendable Mold Casting Investment
Casting
Pros:
– Capability to cast parts with great complexity and
intricacy.
– Close dimensional control ( 0.076 m tolerance).
– Good surface finish.
– Wax can be recovered and reuse.
– Additional machining normally not required.
Cons:
– Normally cater for smaller parts.
– Relatively expensive.
MECH152-L27(1.0) - 11
Expendable Mold Casting Plaster Mold and Ceramic Mold
• Similar to sand casting in terms of process.
• Plaster mold is for lower temperature alloys
while ceramic mold is for higher
temperature alloys.
Pros:
– Good surface finish and dimensional control.
– Capability to make thin cross sections.
Cons:
– Curing takes too long to render it unsuitable for
volume production.
MECH152-L27(1.0) - 12
Permanent Mold Casting Basic
Permanent
Mold
Pros:
– Good surface finish and close dimensional
control.
– More rapid solidification, finer grain structure,
stronger castings.
Cons:
– Generally limited to lower melting point metals.
– Simpler part geometries as mold is permanent.
– Mold cost is expensive and thus cater for volume
production.
MECH152-L27(1.0) - 13
Permanent Mold Casting Die Casting
Pros:
–
–
–
–
–
–
High production rates are possible.
Economical for large quantities.
Close tolerances are possible ( 0.076 mm).
Good surface finish.
Thin sections are possible (down to 0.5 mm).
Rapid cooling, fine grain, high strength.
Cons:
– melting point of metals.
– shape restriction.
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Casting
MECH152-L27(1.0) - 15
Molding
• Tolerances
MECH152-L27(1.0) - 16
Powder Metallurgy - Pros
• Net shape manufacturing
• Minimum wastage of material
• Production of porous parts, typically for
self-lubricating applications
• Produce parts from material difficult to
process
• Produce parts with special alloying content
• Good dimensional control
• Can be automated for economic production
MECH152-L27(1.0) - 17
Powder Metallurgy - Cons
• High tooling and equipment cost.
• Expensive raw material.
• Difficulty with storing and handling of
powder.
• Limiting in geometry as the powder does
not flow readily in die.
• Inhomogeneity of produced part.
MECH152-L27(1.0) - 18
Powder Metallurgy
Design Considerations
• Large batch size to make it cost effective,
typically over 10,000.
• Controlled porosity parts.
• Special alloying elements parts.
• Limited geometry to allow die opening.
• Built-in chamfers and radii.
• Minimum wall thickness of 1.5 mm and
minimum hole diameter of 1.5 mm.
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Secondary Manufacturing Processes
Machining
•
•
•
•
•
•
•
Turning, Boring
Drilling
Reaming
Milling
Shaping
Broaching
Sawing
MECH152-L27(1.0) - 20
MECH152-L27(1.0) - 21
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Tertiary Manufacturing Processes
• Grinding and Abrasive Processes
– Grinding
– Honing, Lapping, Super-finishing, Polishing
and Buffing
• Non-traditional Machining and Thermal
Cutting Processes
–
–
–
–
Mechanical Energy Processes
Electrochemical Machining Processes
Thermal Energy Processes
Chemical Machining
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Surface Roughness Values
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Tertiary Manufacturing Processes
Application Considerations
Very small holes below 0.125 mm diameter. (Laser beam
machining, LBM)
Holes with large depth-to-diameter ratio, d/D>20. (ECM or
EDM)
Holes that are not round (ECM or EDM)
Narrow slots in slabs or plates (ECM, LBM, EDM, water
jet, abrasive jet)
Micromachining (PCM, LBM, EBM)
Shallow pockets and surface details in flat parts (Chemical
machining)
Special contoured shapes for mold and die applications
(EDM or ECM)
MECH152-L27(1.0) - 25
Tertiary Manufacturing Processes
Application Considerations
Special shapes for which the non traditional processes are appropriate (a) very small diameter holes, (b) holes with
large depth-to-diameter ratios, (c) nonround holes, (d) narrow, non-straight slots, (e) pockets, and (f) die sinking
MECH152-L27(1.0) - 26
Tertiary Manufacturing Processes
Materials Consideration
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Tertiary Manufacturing Processes
Machining Characteristics
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Case Study
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Product Specification
• Final product specification will be issued
after:
– Prototyped is designed, fabricated, and tested
– Cost analysis after trail batch es
• Dimension – specified in the drawing
• Material – Grey cast iron
• Maintenance – the bolting arrangement
should incorporate standard parts.
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Product Specification
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Product Specification
MECH152-L27(1.0) - 32
Drawing Interpretation
• Review the part drawing to determine the
primary manufacturing process: casting or
forming
– Casting – tooling fabrication
– Forming – tooling fabrication or direct stock
purchase
• Secondary manufacturing process:
machining
– Overall stock size and material
– Tolerance & surface finish requirements
MECH152-L27(1.0) - 33
Material Evaluation
•
•
•
•
•
Light weight
Hard with good wearing resistance
Low cost
Good casting properties
Good machinability
• Batch size - 350
MECH152-L27(1.0) - 34
Manufacturing Considerations
•
•
•
•
•
•
•
•
•
•
•
•
•
the 100 mm and 50 mm bores cannot deviate from the nominal size by more than
0.01mm;
the 100 mm diameter bore must also be perpendicular to the flange face within 0.1 mm
tolerance zone;
the 100 mm and 50 mm bores must be machined to a surface finish of 0.1m;
the flange face and centreline of the 12 mm hole must be parallel to each other to within
a tolerance zone of 0.1mm;
the flange face must be machined to a surface finish of 0.8m;
the 12 mm hole must be perpendicular to the component centreline within a 0.01 mm
tolerance zone;
all holes must not deviate by more than 0.1 mm of the nominal size;
all holes must have a surface finish of 1.6m;
all spotfaces must not deviate by more than 0.1 mm of the nominal size;
all spotfaces must have a surface finish of 0.8m;
all fillets are R7 unless otherwise stated;
the general dimensional tolerance is 0.5mm;
the general surface finish is 12.5m.
MECH152-L27(1.0) - 35
Process Selection
• Suitable for grey cast iron (sand casting /
investment casting)
• Meet general dimensional tolerance of ±0.5
mm
• Meet general surface finish of 12.5 µm
• Produce economically 350 per batch
• Meet the tolerance specifications stated in
the drawing
MECH152-L27(1.0) - 36
Process Selection
• Investment casting
• Holes assumed to be drilled with the help of
drill jigs.
• Processes:
– Turning – for the flange face
– Drilling – for the holes and spotfacing
– Grinding – for the 100 mm and 50 mm
bores
MECH152-L27(1.0) - 37
Process Sequencing
• Stock produced by investment casting with 2
mm machining allowance
– Wax pattern, flasking, bake, mold, stock removal
• Machine the flange face by turning
– Rough facing with 0.2 mm left for fine finishing
• Machine spotfaces by drilling
• Machine holes by drilling
• Machine bores by grinding
– Internal grinding each 100 mm and 50 mm
holes in four passes
MECH152-L27(1.0) - 38
Tooling and Fixtures
• Turning/facing tool – facing
• Spotfacing - 20 mm and 25 mm spot
drills
• Drilling - 10 mm and 12 mm twist drills
• Grinding - 20 mm internal grinding wheel
MECH152-L27(1.0) - 39
Tooling and Fixtures