Defects And Solutions For Injection Molding

- Jul 13, 2018-

5. Overflow


The focus of processing on the overflow should be mainly on the improvement of the mold. In terms of molding conditions, it is possible to reduce the fluidity. Specifically, the following methods can be used:

(1) Reduce the injection pressure.

(2) Lower the resin temperature.

(3) Select materials with high viscosity grades.

(4) Reduce the mold temperature.

(5) Grinding the mold surface where the overflow occurs.

(6) Use a harder mold steel.

(7) Improve the clamping force.

(8) Adjust the joint surface of the accurate mold and so on.

(9) Increase the mold support column to increase rigidity.

(10) Determine the size of the different exhaust slots according to different materials.


6. Weld marks


The weld line is caused by the front end portion of the molten resin from different directions being cooled and not being completely fused at the joint. Under normal circumstances, it mainly affects the appearance and affects painting and plating. In severe cases, it has an effect on the strength of the product (especially in the case of fiber reinforced resins).


Can be improved by referring to the following items:

(1) Adjust molding conditions to improve liquidity. For example, increase the resin temperature, increase the mold temperature, increase the injection pressure and speed.

(2) Adding an exhaust groove, and providing a push rod at the place where the weld line is generated is also advantageous for exhausting.

(3) Minimize the use of release agents.

(4) Set the process flash as the place where the weld line is produced, and then cut and remove after molding.

(5) If only the appearance is affected, the four positions can be changed to change the position of the weld line. Alternatively, the portion where the weld mark is produced may be treated as a dark glossy surface or the like.