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What should I do if the injection molding of plastic products is not perfect?

Release time:

2021-09-15

What should I do if the injection molding of plastic products is not perfect?

The imperfection of plastic products after injection molding is a very common problem in the plastic processing and production process, but it is also relatively easy to solve. When it is really impossible to solve it by technological means, it can be improved from the perspective of the design and manufacture of plastic molds, which can generally be solved.

(1) The mold gating system is defective. The runner is too small, too thin, or too long, adding fluid resistance. The diameter of the main flow channel should be added, the flow channel and the branch flow channel should be formed into a circle, the flow channel or the mouth is too large, the shooting force is not enough, and the flow channel and gate are blocked by impurities, foreign matter or carbon. The runner and gate are rough and scratched, or have sharp angles, and the surface roughness is poor, which affects the flow of materials;

There is no cold slug well in the runner or the cold slug well is too small, and the opening direction is wrong; for multi-cavity molds, the runner and gate size distribution balance should be carefully arranged, otherwise there will be thick and short gates near the sprue. In the case that the cavity can be filled but other cavities cannot be filled, the diameter of the runner should be increased to reduce the pressure drop of the melt flowing to the end of the runner, and the pressure drop of the cavity farther from the runner should be increased. Gate, so that the injection pressure and flow rate of each cavity are basically the same.

(2) The mold plan is unfair. Too many molds, too many turns, improper selection of feed inlet, too narrow runner, insufficient number of gates or improper method. The section of the finished plastic product is very thin, and the thickness of the entire finished product or part should be added, or an auxiliary runner or gate should be arranged near the insufficient filling;

It is common for unsatisfactory parts to be formed due to insufficient venting in the mold cavity. This defect mostly occurs in the corners of the finished product, deep depressions, thin-walled parts surrounded by thick-walled parts, and thin bottoms formed by side gates. the bottom of the shell, etc.

The plan to remove this defect includes the establishment of effective exhaust channels, and the selection of reasonable gate positions to make it easier for air to be displaced in advance. When necessary, a portion of the air trapped area of the cavity is specially made into an insert, so that air can escape from the hole in the insert. For multi-cavity molds that are prone to unbalanced gate distribution, the number of injection cavities should be reduced if necessary to ensure that other cavity parts pass.