How to solve these four common problems in injection molding?

1、 Solution to bubble phenomenon during injection molding
According to the causes of bubbles, the countermeasures are as follows:
1. When the wall thickness of the product is large, the cooling speed of its outer surface is faster than that of the center part. Therefore, with the cooling process, the plastic resin in the center part shrinks and expands to the surface, resulting in insufficient filling in the center part. This situation is called vacuum bubble solution. The main methods are:
A. According to the wall thickness, determine the reasonable gate and gate size. Generally, the gate height should be 50%~60% of the wall thickness of the product.
B. A certain amount of supplementary injection material shall be reserved until the gate is sealed.
C. The injection time should be slightly longer than the gate sealing time.
D. Reduce the injection speed and increase the injection pressure.
E. Use materials with high melting viscosity grade.
2. The main solutions to the bubbles caused by the generation of volatile gases are:
A. Fully pre-dry.
B. Reduce the resin temperature to avoid producing decomposition gas.
3. The bubbles caused by poor fluidity can be solved by increasing the temperature of resin and mold and increasing the injection speed.
2、 Cause Analysis of Mainstream Sticking in Injection Molding
Causes and troubleshooting of main channel sticking during injection molding:
1. The cooling time is too short and the main channel has not solidified.
2. If the slope of the main channel is not enough, its demoulding slope should be increased.
3. The improper fitting size of the main runner bushing and the nozzle causes leakage.
4. The main channel is rough and there is no cooling well in the main channel.
5. If the nozzle temperature is too low, the temperature should be increased.
3、 Cause analysis of slow production during injection molding
Reasons and solutions for slow production during injection molding are as follows:
1. The plastic temperature and mold temperature are high, resulting in long cooling time.
2. If the glue melting time is long, the back pressure should be reduced, less recycled material should be used to prevent overhead, and the cooling of the feeding section should be sufficient.
3. The movement of the machine is slow, which can be properly accelerated by adjusting the oil circuit and circuit.
4. The design of the mold shall be convenient for demoulding and shall be designed as fully automatic operation as far as possible.
5. The manufacturing wall thickness is too large, resulting in too long cooling time.
6. Nozzle salivation hinders normal production. Self-locking nozzle shall be used or nozzle temperature shall be reduced.
7. If the heat supply of the material barrel is insufficient, the machine with large plasticizing capacity should be replaced or the preheating of the material should be strengthened.
4、 Cause analysis of dissatisfaction of injection molding products
The main reasons for the dissatisfaction of injection molding products are lack of materials and improper injection pressure and speed (including excessive pressure loss caused by resistance).
It may be caused by the following reasons:
1. Reasons for injection molding machine:
The plasticizing amount or heating rate of the machine is variable, so the machine with large plasticizing amount and heating power should be selected;
The wear of the screw and the barrel or the rubber head causes the material return and the actual filling modulus is not correct; The actual temperature of the barrel is too low due to the failure of heating system such as thermocouple or heating ring; The wear of the sealing element of the injection cylinder causes oil leakage or backflow, which cannot reach the required injection pressure; Pressure consumption is caused by excessive resistance caused by too small nozzle inner hole or improper nozzle center adjustment
2. Reasons for injection mold:
A. The mold temperature shall be appropriately increased due to the difficulty of feeding due to the low temperature of the part or the whole mold;
B. The distribution of the mold cavity is unbalanced, and the wall thickness of the part is too thin, resulting in excessive pressure consumption and poor mold filling. The wall thickness of the whole part or part shall be increased or the auxiliary flow or gate can be set near the insufficient filling area.
C. Pressure loss caused by too small flow channel of the mold; When it is too large, the glue injection will be weak; Too rough will cause dissatisfaction with the parts. The size of the runner should be set appropriately, and the transition between the main runner and the runner, or the turning of the runner itself should be applied appropriately
Arc transition.
D. Poor exhaust of the mold. The material entering the mold cavity is blocked by the pressure of the gas that can not be discharged, resulting in insufficient filling. The gap of the screw can be fully used to exhaust or the clamping force can be reduced to use the parting surface to exhaust. If necessary, the exhaust channel or air hole should be opened.