In order to study the effect of injection speed on distribution of metal powder for the metal injection molding (MIM), we observed the specimens, MIMed at injection speed of 10%, 30%, 70% and 90% against maximum speed, by using an acoustic microscope. We compared acoustic images with back scattering electron images of the MIMed specimen, and found that the acoustic images can show distribution of metal powders.
As the results of observation on the acoustic images, difference of distribution of metal powders on specimen MIMed at each injection speed could he distinguished. On the acoustic images of the specimen MIMed at 10% injection speed, especially, irregular distribution of metal powders and flow marks were clearly observed at a position remote from the molding gate of the specimen. And at 90%, jetting was observed. Therefore, in the case of compound and injection condition used in this study, the obtained results showed that 10% injection speed is too slow and 90% is too fast to make sound MIMed specimens.