Plastic raw materials processing mainly colloidal particles melt, flow, become the finished product, finalize the design after cooling is a process of heating and then cooling, and plastic from all the different shapes of particles changes to the process, the following will have different phase Angle to explain the process of machining.
1, melting heater (
Make raw material particles gradually melt into the fluid flow, mainly is suitable for temperature control in different raw materials, by high temperature will drive the flow of raw materials to speed up, can increase the efficiency of yield, but not necessarily can guarantee must achieve the right balance.
Another good effect with PP meet the characteristics of hot cracking, are the raw materials of production is best can let smoothly flowing to die, in order to avoid material shortage or backflow phenomenon produces, reflow on behalf of the raw material flow faster than output rate, finally causes the average flow efficiency increase is equal to the MFR, is one of the processing available methods, but also increasing MFR abnormal distribution may lead to instability, lead to defective rate may increase.
But PP products because of the application is not a product of the dimension precision is very high, so the effect also is not big.
2, screw PP processing is most are driven by the screw of liquidity, so the design of the screw influence is very big, diameter size affect the output, the compression ratio of the size influence pressure value also affect the output and the finished product effect, this also includes a variety of materials (
Pigment, additives and modification agent)
The mixing effect.
Friction material flow mainly depends on the heater, but the raw material turn spur liquidity also produces friction heat, so the screw compression ratio little drive the flow, speed must increase caused by friction heat energy will be more compression than big screw.
So often said that no teacher, plastic processing is teacher attentively understand the machine performance.
Raw material is heated not just heater, must and friction heat and smothering leave time.
So it's practical problems, experience makes for problem solving and efficiency.
Screw mixing effect is very good, if you need to design sometimes 2-phase different screw or biaxial screws and separate paragraphs screw mixing effect to all kinds of different form.
3, mold or die plastic to finalize the design depends on the mold or die, injection molding products is stereo, mold is more complex and shrinkage factor to consider, other are flat, strips, needle die head, continuous product for special shape is classified as alien, immediately after heating problems need to be paid attention to.
Plastic machine design most is like a needle tube, driven screw extrusion force will cause enormous pressure in small export, improve production efficiency.
When die design for the plane how to make the raw material evenly on the whole, the design of the coat hanger die is very important to pay attention to the pressure of the opportunity to add fish gills type pump stable raw material supply.
In addition to the sprue gate 4, cooling injection mold filling materials, cooling channel cooling materials design.
Extrusion forming, which is then roller cooling effect, the cooling channel to deal with the exception of also have air knife, cooling water spray directly on the blow bag, and hollow blowing cooling way.
5, extended product reprocessing extension will strengthen effect, such as packing tape on front and rear wheel drive rate differ that cause extension effect, finished to match the extension part tensile strain strengthen tore off not easily, but lateral is extremely easy to tear.
An extension of the molecular weight distribution will also affect the production effect, all the pressure out of the finished product including fiber has an extension of the range, vacuum and air pressure molding can also be seen as extensions of another form.
6, contraction of any raw material shrinkage problem, the reasons from the heat bilges cold shrink and crystallization of contraction caused by internal stress.
In general heat bilges cold shrink more easily overcome, can be on the processing to prolong cooling time, continuous pressure can be well done, crystalline materials from non-crystalline tend to have larger shrinkage difference, in terms of PP at about sixteen over one thousand, but ABS only about four over one thousand, this difference is very big part to overcome, in the mold or overcome tend to reduce shrinkage additives, drawing tablet, also often add LDPE to improve the necking of the problem.