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Design Considerations for Powdered Metal -
Ridgway Powdered Metals

1. The shape of the part must permit ejection from the die. Not permitted:

• Undercuts
• Holes at right angles to the direction of pressing
• Reverse tapers
• Reentrant angles
• Threads (external or internal)
• Diamond knurls or horizontal serrations
  
  

2. The shape of the part should be such that the powder is not required to flow into thin walls, narrow splines or sharp corners.

• Parts with thin walls, narrow splines or sharp corners can be made by P/M
• Minor changes in design will result in better parts at lower cost
  
  

3. The shape of the part should permit the construction of strong tooling.

• Simplify shapes
• Allow a reasonable clearance between the top & bottom punch faces during pressing
• Make dies and punches without sharp edges
• Length-to-diameter ratios of holes should be limited to 4:1
  
  

4. The shape of the part should make allowance for the length to which thin-walled parts can be compacted.

• Preferred maximum length for thin-wall, hollow cylindrical parts =
  (2 _ x Part Diameter)
• The above ratio can be increased to 4 or more times part diameter for parts with thicker walls.
  
  

5. The part should be designed with as few changes in section thickness as possible.

• The number of levels in the part should not exceed the number of pressing actions available in the compacting press
• With too many levels, density varies considerably and part quality becomes a problem
• Make parts according to constraints of available press motions and machine additional levels
• Best tool life is obtained when diameter difference between different levels is large
  
  

6. Take advantage of the fact that certain forms can be produced by P/M which are impossible, impractical or uneconomical to obtain by any other method. (Examples):

• Involute gear forms
• Keys and keyways can be formed
• Parts requiring controlled weight in specific sections