Injection molded parts are warped, come here to see the solution

Injection molded parts are warped, come here to see the solution

There are many reasons for the warping of plastic molded parts, such as too fast mold release, high mold temperature, uneven mold temperature and asymmetric runner system.

The two biggest possibilities are:

1. The thickness of the plastic part is uneven or the corners are not smooth enough, so it cannot cool and shrink evenly, resulting in warping and deformation.

2. For some flat plastic parts, the runner gate has to be located at the corner of the gate for the sake of beautiful appearance. When injecting, the molten plastic can only be injected into the mold cavity at high speed from one end, so the plastic solidified in the mold cavity is straightened to the same direction (called orientation). The stress is very high; these molecules are pulled back to their original state when they are de-moulding, thus deforming.

In order to make the molten plastic fill the mold cavity smoothly, the design should try to avoid the following points:

l The thickness of the same plastic part varies too much;

l Excessively acute angles exist;

l The buffer zone is too short, so that the thickness change is very different.

From the gate analysis, the design of the mold should ensure that the plastic can enter the mold cavity smoothly, so the runner should avoid using a right-angle turn, and the turning point is more suitable for the arc transition area, so the short and thick runner is the most ideal, which will help reduce fluid resistance and fluid orientation phenomena.

However, the problem to be considered is that an excessively large gate will increase runner waste and also affect the appearance of the plastic part. In addition, if you are worried that the gate is too large and the waste will increase, you can consider adding a certain proportion of Qiagen silicone powder to increase the fluidity of the raw material to reduce fluid resistance, ensure the normal discharge of the gate, and prevent the deformation of the finished product.

The size of the cross-sectional shape of the runner will change with the amount of injection and the shape of the product. After the part of the product that is difficult to form is thickened, the main channel should also be relatively enlarged, so that the cross-sectional area of the main channel is equal to the sum of the cross-sectional areas of the drainage channels.

Technological solution:

1. The finished product has not cooled down when it is ejected → reduce the mold temperature

→Extended cooling time

→Reduce raw material temperature

2. The shape and thickness of the finished product are asymmetrical → after demolding, fix it with a setting frame

→Change molding design

3. Too much filler → reduce injection pressure, speed, time and dose

4. The feeding of several gates is uneven → change the gate

5. The ejection system is unbalanced → improve the ejection system

6. Uneven mold temperature → adjust the mold temperature

7. The raw material near the gate is too loose and too solid → increase or decrease the injection time