Pipe dream for powder metal manufacturing

Five different approaches to calibrate extruded pipes based on metal powder-based feedstocks were set up and tested. Vacuum calibration delivers the best results concerning geometrical accuracy and surface quality. Approaches using mechanical support of the moving extrudate sometimes suffer from friction between extruded material and supporting tool geometry. Thus air and vacuum pressures respectively, influencing the degree of friction, have to be controlled in small tolerances. Approaches using pressurised air do also have cooling effects on the extruded material and thereby additionally support achieving a dimensional stability of the green part. Sintering tests still have to be carried out but it is expected that calibration will have no major influence on the product's final properties such as strength and density. Also, combinations of different calibration approaches should be tested in future investigations.