(1) temperature. Temperature has a significant influence on the performance of vertical Injection Molding Machine plastic extrusion and preform. Enhance the Vertical Injection Molding Machine heating temperature results in the following: the ability to reduce the melt viscosity, improved melt flow, reduce the power consumption of vertical injection molding machine; may be appropriate to enhance the screw speed, without affecting the mixing plastics materials effect; help to improve the intensity with the brightness of the final product; help improve the transparency of the final product. However, the melt temperature is too high, easy to produce extruded parison sagging weight, causing the parison wall thickness longitudinal uneven; prolong parison blow cooling time; expand shrinkage of the final product; make pvc and other heat-sensitive plastic degradation, the parison strength Pc and other engineering plastics is significantly reduced. Therefore, we should follow this principle to set the heating temperature of the extruder, that is both smooth and uniform extruded parison, and not leave under the premise of the transmission system overload, to ensure a higher melt parison strength should be possible to adopt a lower heating temperature.
When the heating temperature is set vertical injection molding machine, feed zone temperature should be relatively low, to prevent blockages in the charging port affect delivery of materials; high temperature compression section, in favor of mixing plastics materials; extruded sections temperatures can fall below the compression section, and higher than the feed zone, conducive to the stability and uniform feed to the nose.
Heating apparatus Shenzhen vertical injection molding machine, generally adopt the electric heater, and air-cooled machine placement, to adjust the heating temperature of the vertical injection molding machine. To control the heating temperature deviation extruder, often adopt the proportional (P) Integral (I) derivative (D) temperature controller. Their role are:
① proportional action. Heating current with temperature deviation proportional relationship exists, the smaller the heating current, the temperature deviation is also smaller.
② integral action. Heating current is proportional to the time integral of the temperature deviation. Thus, even if the deviation is very small, after a certain time, it can also eliminate the static error, improve temperature control system static accuracy.
③ derivative action. Heating current is proportional to the temperature differential deviation of time. So, the faster the temperature deviation occurs, the corresponding change in the amount of heating current is also larger, can enhance the ability of the heating system to the outside world a sudden disturbance.
Because of these effects, PID temperature controller allows the temperature deviation of the extruder control within ± 1 ℃, the power consumption is also reduced by about half.
(2) Melt pressure. Head into the melt pressure should be uniform. Vertical injection molding machine appropriate to enhance the melt pressure, can make the material mixing uniformity, so that stability of the parison and final article. For high molecular weight polyethylene, high density polyethylene with a low density polyethylene blend, coloring with masterbatch polymer melt pressure sufficient parison can have a good appearance, reduce the "crystallization point" with the clouds shaped pattern. However, due to debris blocking stencil head, causing the melt pressure is too high, will increase the vertical injection molding machine load and machine damage, should be replaced, cleaning panels to maintain a stable pressure head into the melt. Adoption of low melt flow rate resin, extruder reduce the heating temperature, improve the extruder screw speed, etc., can enhance the melt pressure extruder.
To control the pressure of the melt extrusion, melt pressure measuring instruments can be installed at the discharge section of the vertical injection molding machine. Melt pressure measuring instrument commonly used in a mechanical pressure gauge, hydraulic (oil, grease, mercury) pressure gauge, pneumatic gauges, electrical pressure gauges and the like.
(3) Melt conveying speed. Melt conveying speed is large, the amount of vertical extrusion molding machine. Lifting the conveying speed of the melt, the weight can improve sagging parison, increasing the wall thickness of the parison. Melt conveying speed increases with the diameter of the screw increases, less affected by the head pressure. Enhance the extruder screw speed with the heating temperature, can be improved accordingly melt conveying speed. However, when the screw speed upgrade to a certain value, prone to melt fracture phenomenon. In the vertical injection molding machine plastic extrusion experience, these three factors are interdependent. At the same time, these three factors requires low volatility. If the temperature, pressure, melt conveying speed greater volatility, not only the parison wall thickness uniformity, repeatability subsequently deteriorated, but also the final product mechanical properties and dimensional stability with a greater difference in performance fell.