Controlling the Structural Integrity of Injection Molded Parts in Debinding and Sintering by Experimental Design

The preservation of the structural integrity of injection molded Fe-8% Ni in debinding and sintering was studied using four spherical ball specimens having diameters of 10 mm, 20 mm, 30 mm and 40 mm. Different degrees of defects existed in the as-molded specimens due to jetting during molding, which subsequently transformed into cracks when the debinding conditions were not properly controlled. The manifestation of molding defects during debinding was most severe for specimens having a green diameter of 40 mm, but could be avoided by optimizing the extraction temperature in solvent debinding and the heating rate in thermal debinding. For the processing conditions selected in the experimental trials which were designed using the Taguchi method, distortion as a result of slumping could be reduced to a magnitude close to the ±0.3% tolerance commonly quoted for metal injection molded parts.