First, the working speed of the screw of the injection molding machine is unstable, which is affected by the following factors:
1. The transmission V-belt is seriously worn and slips during operation.
2. The center distance of V-belt drive pulley is too small, which makes the belt drive and the trapezoid bevel of pulley not work correctly.
3. The temperature of the heating material in the barrel is low and the plasticization of the raw material is uneven, which results in the increase of the working load torque of the screw rotation of the injection molding machine and the instability of the screw rotation speed of the injection molding machine.
4. The thrust bearing of injection molding machine screw is damaged.

Second, the influence of the unstable working speed of the screw of injection molding machine on the quality of plastic products:
1. The geometrical shape and size error of the products are large;
2. Products will often appear horizontal wrinkles;
3. The surface of the product is rough, easy to crack or hard block appears locally.