Close this search box.
Home » Blog » Causes and Solutions of Plastic Molding Shortcomings (1)

Causes and Solutions of Plastic Molding Shortcomings (1)

Incorrect operating conditions, damaged machines, and molds can cause many molding shortcomings, and some solutions are provided below for reference. To reduce the downtime and find out the cause of the operation problem as soon as possible, the operator should record all the best injection molding conditions on the “Injection Molding Conditions Record Sheet” for future reference when solving the problem.


1. Incomplete finished product.

The causes of the issue are as follows.

(1) The plastic temperature is too low, increasing the melt cylinder temperature.

(2) Injection pressure is too low, increase the injection pressure.

(3) Injection volume is not enough to increase the injection volume.

(4) The gate bushing and injection nozzle do not fit properly, and the plastic overflows to readjust its fit before the injection time is too short.

(5) The injection speed is too slow to speed up the injection speed.

(6) Improper adjustment of low pressure and readjustment.

(7) Mold temperature is too low, increase the mold temperature.

(8) Mold temperature is not uniform. Readjust the mold water pipe.

(9) Mold exhaust is not good. Add a moderate exhaust hole in the proper position.

(10) The temperature of the injection nozzle is not low.

(11) Uneven glue feeding reopens the mold overflow position.

(12) The sprue or spillway is too tiny to increase the sprue or spillway.

(13) Insufficient lubricant in the plastic increases the lubricant.

(14) Backpressure is not enough. Increase back pressure slightly.

(15) Over rubber ring, melt screw wear and tear removal inspection and repair.

(16) Insufficient injection volume replaces the giant injection molding machine.

(17) The product is too thin to use nitrogen injection.


2. Product shrinkage.


Causes of failure.

(1) Insufficient glue in the mold.

(2) Insufficient melt glue amount to increase the amount of melt glue.

(3) Injection pressure is too low to high injection pressure.

(4) Backpressure is not high enough backpressure.

(5) Injection time is too short, a long injection time.

(6) Injection speed is too slow and fast.

(7) Unbalanced spillway mold spillway is too tiny or positioned.

(8) Injection nozzle hole is too thin. The plastic solidifies in the sprue bushing, reducing the backpressure effect. The whole mold or replace the injection nozzle material temperature is too high low material temperature.

(9) Improper mold temperature, whole proper temperature.

(10) Cooling time is not enough to extend the cooling time.

(11) The accumulation pressure section is too much, injection glue termination should be at the forefront.

(12) The product itself or its ribs and column position is too thick review the finished product design injection glue volume is too large, replacing the more acceptable injection molding machine.

(13) Over rubber ring, melt glue screw wear removal, and overhaul.

(14) The gate is too small, plastic solidification loss of support backpressure to increase the size of the gate.


3. Finished products sticky mold.


Causes of failure in treatment methods.

(1) Filler is too full to reduce the injection pressure. The time, speed, and injection volume injection pressure are too high to reduce the injection pressure.

(2) Too much injection glue volume reduces the amount of injection glue.

(3) The injection time is too long to reduce the injection time.

(4) The material temperature is too high to reduce the material temperature.

(5) Uneven feeding makes part of the overfill change the size or location of the overflow.

(6) The mold temperature is too high or too low, adjust the mold temperature and the relative temperature on both sides of the mold. There is a mold release chamfer to repair the mold to remove the chamfer.

(7) The surface of the mold is not smooth, polished in the mold.

(8) Mold release caused by vacuum opening or ejection slow down, or mold plus air intake equipment injection cycle is too short to enhance cooling.

(9) Insufficient mold release agents slightly increase the amount of mold release agents.


4. Sprue (water spout) sticky mold.


Failure causes treatment methods.

(1) Injection pressure is too high to reduce the injection pressure.

(2) The plastic temperature is too high to reduce the plastic temperature.

(3) The sprue is too large to modify the mold.

(4) Sprue cooling is not enough to extend the cooling time or reduce the cooling temperature sprue release angle is not enough to modify the mold to increase the angle.

(5) The sprue bushing and the injection nozzle do not fit correctly. Readjust its fit. The inner surface of the sprue is not bright, or there is a mold release chamfer, to repair the mold.

(6) No sprue grab pin, add grab pin.

(7) Filler is too full to reduce the injection volume, time, and speed.

(8) Insufficient release agents, slightly increase the number of release agents.

Share this post