Defects And Solutions For Injection Molding

- Jul 12, 2018-

2. Insufficient filling


The main reasons for insufficient filling are as follows:

(1) The resin capacity is insufficient.

(2) Insufficient pressure in the cavity.

(3) The resin has insufficient fluidity.

(4) The exhaust effect is not good.

 

As an improvement measure, we can mainly start from the following aspects:

(1) Lengthen the injection time to prevent the resin from flowing back before the gate is solidified due to the short molding cycle, and it is difficult to fill the cavity.

(2) Increase the injection speed.

(3) Increase the mold temperature.

(4) Increase the resin temperature.

(5) Increase the injection pressure.

(6) Expand the gate size. Generally, the height of the gate should be equal to 1/2~1/3 of the wall thickness of the product.

(7) The gate is placed at the maximum wall thickness of the product.

(8) Set the exhaust groove (average depth 0.03mm, width 3 to smm) or the exhaust rod. It is more important for smaller workpieces.

(9) A certain (about smm) buffer distance is left between the screw and the injection nozzle.

(10) Select materials with low viscosity grades.

(11) Add a lubricant.


3. Wrinkle and pockmark


The cause of this defect is essentially the same as the filling, but to a different extent. Therefore, the solution is basically the same as the above method. In particular, it is more necessary to pay attention to appropriately increasing the gate and the proper injection time for resins with poor fluidity (such as polyoxymethylene, PMMA resin, polycarbonate, and PP resin).


4. Shrink pit


The reason for the shrinkage pit is also the same as the filling deficiency. In principle, it can be solved by excess filling, but there is a danger of stress. The design should pay attention to the uniform wall thickness, and the ribs and studs should be reduced as much as possible. Wall thickness.