Procedure for filling the amount of plastic in the mold cavity
Pre-adjust a certain metering so that a small amount of melt (buffer amount) remains at the end of the cnc-machining screw near the end of the injection stroke, and further apply injection pressure (two or three times) according to the filling situation in the mold Injection pressure), add a little melt. In this way, the product can be prevented from sinking or the shrinkage rate of the machining uhmw plastic product can be adjusted.
Program control of screw back pressure and speed
The high back pressure can make the melt material get strong shear, and the low speed can also make the plastic in the barrel get longer plastic machining time. Therefore, the control of simultaneous programming of back pressure and speed is used more frequently.
For example: in the screw metering full stroke, firstly high speed and low back pressure, then switch to lower speed and higher back pressure, then switch to high back pressure and low speed, and finally plasticize under low back pressure and low speed. In this way, most of the pressure of the melt at the front of the screw is released, and the rotational inertia of the screw is reduced, thereby improving the accuracy of screw measurement.
Excessive back pressure often causes the degree of discoloration of the colorant to increase; the mechanical wear of the pre-plastic mechanism and the barrel screw increases; the machining uhmw cycle is prolonged, and the production efficiency decreases; the nozzle is prone to salivation and the amount of recycled material increases; even if the self-locking type is used If the back pressure of the nozzle is higher than the designed spring locking pressure, it will also cause fatigue damage. Therefore, the back pressure must be adjusted appropriately.