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Abstract
An analysis has been performed on the selective removal of particles from the edges and thin lands on green iron powder compacts. The voids created as a result of this ‘picking’ are believed to be due to large (+ 125 μm (+ 120 mesh)) particles in the iron powder mix. Microscopic examinations indicated that in all cases picking occurred within isolated regions of large pore and particle size. Two possible independent causes for this problem have been advanced: segregation of large particles within the feed shoe during die filling; and an uneven load distribution across the face of a part due to the presence of tooling impressions on the upper punch. A series of follow up tests showed no change in the relative position of the large pore size region with upper punch orientation. Therefore, by deduction, particle segregation is advanced as the main cause of the observed picking. Suggestions are presented to alleviate this problem. PM/0495