The reasons that affect the plasticization of the screw

Update:17-05-2019
Summary:

Back pressure One. Increasing the back pressure can inc […]

Back pressure

One. Increasing the back pressure can increase the work of the screw on the molten resin, eliminate the unmelted plastic particles, increase the density and uniformity of the raw materials in the material tube; b, the back pressure is used to increase the temperature of the barrel, and the effect is most significant; The back pressure is too large, and the heat sensitive plastic is easily decomposed. Low viscosity plastics can cause runny, back pressure is too small, and the finished product may have air bubbles.

Screw speed

The rotation speed of the screw directly affects the shearing force of the plastic in the spiral groove; the shallow groove of the bay absorbs the heat source quickly, which is sufficient to soften the plastic during compression, and the frictional heat energy between the screw and the barrel wall is low, suitable for high-speed rotation and increasing plasticizing ability; c, large screws should not rotate quickly to avoid plasticization unevenness and excessive frictional heat; d, for plastics with higher heat sensitivity, if the screw speed is too large, the plastic is easy to decompose; usually, each size of the screw has a certain The speed range is generally 100 150 rpm; if it is too low, the plastic will not melt, and if it is too high, the plastic will burn.

Electric temperature setting

Melting the chilled plastic remaining in the barrel and screw to promote the rotation of the screw, providing some of the heat required for the plastic to melt; set the temperature 10 ° C lower than the melt temperature (partially provided by frictional heat); nozzle temperature Adjustments can also be used to control problems such as flow, condensation (plug) and wire drawing.