The difference between powder injection molding and other method which based on molding sometimes can be confused. Molding is often used in the traditional production of powder metallurgy, ceramics and carbides. Molding is the application of technology has longtime been used to form a wide range of materials–ranging from ceramics to pharmaceuticals. Molding use upper and lower punch to suppress the powder in the mold, such as suppression of aspirin tablets. Molding is often used to suppress high and low shapes, the production that easily ejected from the mold.In some cases, the pressure of form can reach 840MPa. However, because of needing to ejected the parts from the mold, so only can be complex shapes in the direction of suppressing. And suppression characteristics in the vertical direction is relatively small, even these features will be limited. In addition, there is friction between powder and mold, and the powder will have density gradients after molding. By contrast, the forming pressure of PIM is low and uniform. Density gradient caused by molding can lead to distortion during sintering, and homogeneous PIM stock after high-temperature sintering densification, the sizes are consistent. Therefore, pressed powder forming part has the following disadvantages:
1) In low-temperature sintering, avoid sintering densification.
2) After sintering usually use machining to correct a critical dimension.
3) If sintering to dense, dimensional consistency will be poor.
4) If sintering to thin dense, the performance may be relegated because of interstitial.
PIM avoid density gradient during high-pressure pressing, after sintering to dense, can be more stringent control.
Because of PIM parts have little pores, so their characteristics of performance are similar to other product that achieved from other material forming technology. It should be recognized that the cost of molding products are less cheaper, if the part’s shape and required performance can be achieved by compression molding, molding is the better choice. On the other hand, PIM method is suitable for the parts which are complex shape and high performance, both of them are difference in product performance, shape and cost, so two technologies are not competitors.