Plastic raw materials are mainly particles melt processing, flow, cooling after shaping into finished products, is a cooling process after heating, but also to the process of changing the plastic particles from various shapes, the following will illustrate the various stages of the injection angles to process.
1. fuser unit heater (Heater) make raw material particles gradually melting into a fluid-like flow, mainly in various raw materials suitable for temperature control, the increase in temperature tends to become the raw material flow rate, increase efficiency but does not necessarily guarantee yield, We must obtain the appropriate balance. Another case of good results and characteristics of PP heat cracking, make the best material flowing smoothly when all production to die, in order to avoid the charge generating material shortage or reflux phenomenon, reflux representatives of material flow rate is faster than the output will eventually resulting in an average increase flow efficiency increase equal MFR, it is one of the available processing methods, but also caused abnormal distribution MFR may lead to increased stability, resulting in poor rate may increase. However, because the application of PP finished relationship is not very high dimensional precision products, so the impact is not great.
2. Screw PP screw machining vast majority are driven by liquidity, so the design influence of the screw is very large, aperture size affect output volume, the compression ratio can also affect the size of the impact pressure and finished products output volume effect, which also includes a variety of materials (masterbatch, additives and modifier) mixing effect. Material flows mainly by warmer, but turning friction materials to create friction heat will cause liquidity to accelerate, so the flow is smaller than the small screw compression drive, the speed must increase caused by friction heat must be better than the compression ratio of the screw more. So often we say plastic processing no master, try to understand who is the master machine performance. Not just the heater to heat the raw material only, it must be connected to the friction heat and smothering stay time and count. So it is practical problems, problem solving and experience contribute to the production efficiency. Screw mixing effect is particularly good if you need to, sometimes two-stage design different screw or twin-screw and screw is divided into segments to achieve a variety of different forms of mixing effect.
3. The mold or die plastic mold again relies on stereotypes or die, injection molding is a perspective view of the finished mold is also more complex and more to consider the shrinkage problem, others are all flat, strip, needle-like continuous product die If the special shape is classified as abnormal, you need immediate attention cooling stereotypes. Most plastics machinery design are like the syringe, screw extrusion force will drive enormous pressure in small exports, improve production efficiency. When the die is designed to plane how to feed evenly distributed over the entire surface, hanger die design is very important to pay attention to the opportunity to increase the pressure of the gill-type pump stable raw material supply.
In addition to injection mold runner gate perfusion material, there are also design cooling water cooling of the feed. Extrusion molding is against the inner wheel cooling water to achieve cooling effect, except there are air knife, cooling water poured directly on Inflation, and the like hollow blowing cooling.
5. The extension will extend the finished reprocessing enhancement, such as packing tape by varying the rate of front and rear wheel drive that is caused by the effect of the extension, the finished part with extending tensile pull strengthen not easy to tear off, but it very easy to tear the lateral. The molecular weight distribution also extends the Effect of high-speed production when all the pressure has ranged finished product comprises fibers extending vacuum and pressure forming can also be seen as another form of extension.
6. shrink materials have any questions shrinkage, shrinkage stress generated when reason comes from thermal expansion and contraction caused by the crystalline form. Generally easier to overcome thermal expansion and contraction, in the process to extend the cooling time, continuing to do a good job packing, crystalline materials tend to have a greater contraction than the amorphous difference to PP concerned about thousandths Sixteen, but ABS is only about four thousandths, very different in this part of the mold to be overcome, or is often added to reduce shrinkage additive overcome, press out flat LDPE often added to improve the necking problem.