Flow Marks in Powder Injection Molding

Powder injection molding manufacture notes flow marks  is a common defect in MIM process. Let’ probe into the reason for flow marks defect based on past MIM parts experience.

Phenomenon:

The initial injected feedstock cool down rapidly, then generate interface with later injected feedstock, the flow marks refers to injection gate centered concentric circles mark.

The causes and treatment:
- the mold temperature is too low
- injection speed is too slow
-poor liquidity of raw material
- too small injection gate
-too low or uneven temperature for mould and feedstock
- no cold slug well or too small
-poor  product design,  thickness change big .

Original article link：http://www.zcmim.com/article/flowmarksinpowderinjectionmolding_1.html

Crazing Defect in MIM Process

Powder injection molding manufacture notes crazing  is a common defect in MIM process. Let’ probe into the reason for crazing defect based on past MIM parts experience.

When feedstock flows in mould,  the material near mould wall cool down faster than central hot melt interface, which will form shear stress for the central  hot melt interface, therefore crack occurs .

The causes and treatment:
- low quality mould , draft angle is insufficient
- too strong injection pressure or holding time is too long
- mold temperature is too low
- finished products cling to mould surface in vacuum status
- bad inserts design, or temperature is too low
- poor finished product design, change thickness greatly or  acute Angle

Original article link：http://www.zcmim.com/article/crazingdefectinmimprocess_1.html