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.
4. Cool
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.
more information www.plastic-injectionmoulding.com
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