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Common defects of MIM metal injection molding and their solutions (1)

Categories: ZCMIM NewsStars: 3StarsVisit: -Release time: 2019-03-20 10:30:00
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MIM Metal injection molding is a kind of complex process, which is made of metal powder mixed with binder, heated by injection machine and thermoplastic extruded into mold cavity by screw . The affect conditions include time, pressure, speed and temperature. As a result, black line, air pattern, short shot, bubbles, shrinkage, flush and other problems may occur in the process of injection process.

1.During injecting, it is easy to cause poor extrusion and blackening on the surface of green part, which is called black line. sink marks or cracks are easy to appear on the surface of green parts after sintering at these black marks positions, which will seriously affect the appearance and mechanical properties of the products. Black marks can be solved by increasing the position of the injection gate (such as making it in fan or increasing the main flowing tunnel) to disperse pressure. It is also possible to make texture on mold so as to slow down the flow rate of feedstock surface. If thickness of product is enough, the injection gate can be made in the thick area. In this way, feedstock can be buffered to wash against mold surface to reduce black mark.

2.In process of injection, fast flowing of powder solution impacted mold cavity, resulting in poor air discharge, then appear air pattern on product surface. After sintering, the air pattern will become flow mark, which can be improved by magnetic grinding or polishing if it not serious, Serious air pattern will make product surface have mark or shade off after PVD, By adding exhaust on the mold, adjusting injection speed can improve air pattern defect . 

3.During injection, residue material adhere to mold will result in short of material on product. It can be improved by strengthening polish mold, enlarge draft angle, or smooth mold pattern, at the same time, cleaning mold with a brush from time to time during injection can also reduce short shot issue.

Keywords in the article: MIM Metal injection molding
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