What are the causes of the decrease in the strength of plastic products, and how should plastic manufacturers solve them?

(1) Defect characteristics

The main manifestation of the decrease in the strength of Plastic Products is that the strength of the plastic product is lower than the predetermined strength during the plastic manufacturing process, which makes the plastic part unable to withstand the predetermined load.

(2) Causes of defects and their elimination methods

The decrease in the strength of plastic parts is affected by many factors, mainly including injection molds, plastic molding process, injection molding equipment, plastic part structure, and raw materials. The specific analysis is as follows.

1) Injection mold

(1) If the mold temperature used by the plastic manufacturer is too low, the plastic melt will cool down quickly after entering the mold, which will cause stress concentration and decrease in strength. For this, the mold temperature should be appropriately increased.

(2) If the draft angle of the mold produced by the injection molding manufacturer is too small, it is difficult to demold. When the mold is demolded with strong force, the local stress of the plastic part is too large, so its structure is also damaged, resulting in a decrease in strength. For this, the draft angle should be appropriately increased.

(3) If the ejector device used by the plastic factory is not balanced, the plastic part is subjected to eccentric force during demolding, which increases the local stress and causes a decrease in strength. For this, the ejector device should be checked or re-set.

(4) If the mold produced by the plastic supplier has a rough inner surface of the mold cavity, it will cause demolding difficulties. When the plastic part is demolded with strong force, the plastic part will be damaged, resulting in a decrease in strength. For this, the inner surface of the mold cavity should be repaired to make it smooth and clean.

(5) If the gate position is not appropriate, such as being placed in a place where the transverse load is applied, the structure at the gate position of the resulting plastic part will be affected and weakened, and the strength will be greatly reduced. For this, the gate position should be changed.

2) injection molding process

(1) If the melt temperature is too high, the melt will degrade and change its properties, resulting in a decrease in strength. For this, the melt temperature should be reduced.

(2) If the injection pressure is too low, the melt filling performance will be poor, resulting in a decrease in strength. For this, the injection pressure should be appropriately increased.

(3) If the mold temperature is too low, the melt forming performance will be damaged, resulting in a decrease in strength. For this, the mold temperature should be appropriately increased.

(4) If the holding pressure is too low, the melt will not be dense, resulting in a decrease in strength. For this, the holding pressure should be appropriately increased.

(5) If the melt has poor fluidity, poor fusion occurs during pouring, resulting in a decrease in strength. For this, the fluidity of the melt should be increased.

3) injection molding equipment

(1) If the injection screw and barrel are worn out and the gap increases, the plasticizing ability will decrease, which will cause the plastic part to decrease in strength. For this, the injection screw and barrel should be checked and the screw or barrel should be replaced if necessary.

(2) If the injection molding machine has a small capacity and a low plasticizing ability, the strength of the resulting plastic part will decrease. For this, the plasticizing ability of the injection molding machine should be checked and a large-capacity injection molding machine should be used if necessary.

4) Plastic part

(1) If there are sharp corners, gaps, etc. on the plastic part, stress will be concentrated here, which is the weakest point of strength. For this, such shapes should be avoided as much as possible during design.

(2) If the wall thickness of the plastic part varies greatly, stress will be concentrated here, resulting in a decrease in strength. For this, the wall thickness should be gradually transitioned.