For automotive PM parts, it is well known that uniform powder filling is pretty important to guarantee the dimensional tolerance and the shape accuracy. A lot of powder filling methods and equipment were proposed for this issue, but there were less made practicable. A visual apparatus was developed for observing the powder behavior. Using this apparatus, it is clarified that the particle size segregation occurred, and the flowability of powders was pretty important for filling efficiency. In order to improve the flowability of powders in a feed shoe, an aeration powder filling method has been developed by blowing a small amount of gas into the feed shoe. This method is applied to the compacting of synchronizer hubs. As a result, machining of boss portion was eliminated by achieving the dimensional tolerance± 0.05mm, so net-shaping was achieved.
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