How are chamfers on a through hole handled in a powder metal analysis?

There are two different methods for creating this kind of chamfer part feature on powder metal parts during compaction. The first method involves using tapered steps in the face of the compaction punch to create the features on the part. This method does increase the cost of the required punch, but for all practical purposes this increase in cost is insignificant, especially for parts where the required punches are simple turned pieces. One drawback to using the tapered steps in the punch face for creating these features is the resulting variations in part density. The thinner sections of the part will have a higher density than the thicker sections. Another drawback is the required shape of the punch edges. Using this method to create the chamfers will result in thin delicate edges on the compaction punches, resulting in a reduction in the usable life of the compaction punch, and increasing the tooling cost per part somewhat. It is not possible to account for this reduction in the life of the compaction punch in the DFM Concurrent Costing software. The software internally estimates the expected life of each compaction punch required and uses that internally calculated value in the tooling cost calculations.

The method described above is generally applicable to part features with depths that are less than 15 percent of the part's depth in the direction of compaction. An alternative method can be used for features greater than 15%; this method assigns a part level to the chamfer feature. Assigning the level to the chamfer indicates that an individual compaction punch is used within the tooling to create the chamfer on the part. When analyzing parts produced using this method, analyze the chamfer level as though it were a simple flat step on the part.

A third possibility is to model the part with the number of upper and lower level changes inputs both set to zero and the resulting part geometry inputs entered.

If the variation in part density resulting from production by the first method described above is not tolerable, it's possible that the chamfers could be produced on the part through a secondary operation such as coining or machining. The cost of both of these secondary operations can be estimated using the DFM Concurrent Costing software; coining using the Coining/sizing required checkbox input in the powder metal main process; machining, by adding machine tool setups and operations following the Powder metals analysis.