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Instability of screw speed of injection molding machine

Update:26 Oct 2019
Summary:

The working speed of the screw of the injection molding […]

The working speed of the screw of the injection molding machine is unstable and is affected by the following factors:
1. The transmission V-belt is seriously worn and slips during work.
2. The center distance of the V-belt drive pulley is too small, so that the belt drive can not work correctly with the trapezoidal slope of the pulley.
3. The temperature of the heating material in the barrel is low, and the plasticization of the raw material is uneven, which causes the working torque of the screw of the injection molding machine to increase, which makes the screw speed of the injection molding machine unstable.
4. Damage to the thrust bearing of the injection molding machine screw.

 

The effect of unstable working speed of the injection molding machine screw on the quality of plastic products:
1. The geometric shape size error of the product is large;
2. the product will often appear horizontal wrinkles;
3. The surface of the product is rough, brittle or partially lumpy.
The speed of the injection screw should be selected according to the injection molding conditions.
(1) The rated screw speed of the injection molding machine. When injecting PS, the plasticizing ability and screw speed of the material to be processed are calibrated by 50%-60% of the nominal plasticizing amount.
(2) Determine the screw speed based on the large line speed allowed by the polymer.
High screw speed: n=V/πD
V----The large line speed allowed by the polymer. General polymer V = 80cmm / S, heat-sensitive polymer V = 1.8cm / s
D----screw diameter (cm)
(3) According to the shear rate r allowed by the polymer, the V in the above formula can be changed to r and then determined.
When adjusting the screw speed, start from the lower speed and gradually adjust to the higher speed, and then determine the screw speed.