DESIGN IMPROVEMENT OF DIE FILLING SHOE

摘要

Control of die filling is a problem that has persisted since the beginning of P/M parts manufacturing. The formation of air entrapment and the stacking of powder in long parts during scraping are known to be major concerns that influence strongly the reproducibility and uniformity of compact density. In this paper, a conventional shoe design is first modified to include: a new scraper design and a motorized agitator. A thorough experimental investigation with this filling system is presented using an instrumented press equipped with a specially designed tooling. The tooling can produce 11 slugs of different diameters distributed over the working surface of the feeding shoe. In addition, the tooling comprises a long piece to test powder stacking when the shoe retracts. Finally, 409 stainless steel powder is used. Compared with a reference test using typical industrial conditions, different parameters are studied. Among them are the powder level in the shoe, the position and angle of the tube, the tool motion and overfill, and the scraper design. In addition, two special forms of agitator in the shoe are tested. For all these tests, measurements of densities over the die are carried out and part-to-part variations are partly established. Finally, recommendations on an improved practice are provided.