DFM Powder Metallurgy.pptx

1. Reference:
James G. Bralla, Design for manufacturability Hand book,
McGraw Hill Publications
By
Pradeep N B
Assistant Professor
Department of Mechanical Engineering
JNNCE, Shivamogga
Design Consideration for Powder Metallurgy
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2. The shape of the compact must be kept as simple and
uniform as possible.
Provision must be made for ejection of the green
compact without damaging the compact.
P/M parts should be made with the widest acceptable
tolerances to maximize tool life.
Part walls should not be less than 1.5 mm thick;
thinner walls can be achieved on small parts; walls
with length to thickness ratios above 8:1 are difficult to
press.
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3. ➢Steps in parts can be produced if they are simple and their size
doesn’t exceed 15% of the overall part length.
➢Letters can be pressed if oriented perpendicular to the pressing
direction. Raised letters are more susceptible to damage in the
green stage and prevent stacking.
➢Flanges or overhangs can be produced by a step in the die.
➢ A true radius cannot be pressed; instead use a chamfer.
➢Dimensional tolerances are on the order of ±0.05 to 0.1 mm.
Tolerances improve significantly with additional operations such
as sizing, machining and grinding.
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4. Die geometry and design features for powder-metal
compaction
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5. Poor and Good Designs of P/M Parts
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6. Design Features for Use with Unsupported Flanges or
Grooves
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7.  Thin walls and projections create fragile tooling.
 Holes in pressing direction can be round, square,
D-shaped, keyed, splined or any straight-through
shape.
 Draft is generally not required.
 Generous radii and fillets are desirable to extend
tool life.
 Chamfers, rather the radii, are necessary on part
edges to prevent burring.
 Flats are necessary on chamfers to eliminate
feather-edges on tools, which break easily.
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8. Basic rules for the design of P/M parts
– Shape of the part must permit ejection from die
– Powder should not be required to flow into small cavities
– The shape of the part should permit the construction of strong
tooling
– The thickness of the part should be within the range for which
P/M parts can be adequately compacted
– The part should be designed with as few changes in section
thickness as possible
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9. Parts can be designed to take advantage of the
fact that certain forms and properties can be
produced by P/M that are impossible, impractical, or
uneconomical by any other method
The design should be consistent with available
equipment
Consideration should be made for product
tolerances
Design should consider and compensate for
dimensional changes that will occur after pressing
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11. Financial Considerations
 Die design
 must withstand 700 MPa, requiring specialty designs.
 Can be very automated
1500 parts per hour not uncommon for average size part
60,000 parts per hour achievable for small, low complexity parts in
a rolling press.
 Typical size part for automation is 1” cube
 – Larger parts may require special machines (larger surface area, same
pressure equals larger forces involved)
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