[TAIZHOU HUANGYAN XINGTAI PLASTIC MOULD CO., LTD.]
Injection molding is a method of producing shapes for products which are usually injection molded from rubber and plastic. Injection molding can also be divided into injection molding and die casting. Injection molding machine (referred to as injection machine or injection molding machine) is the main molding equipment for making thermoplastic or thsermosetting materials into plastic products of various shapes by using plastic molding die. Injection molding is realized by injection molding machine and mold.
Some injection molding processes that affect the strength of injection molded parts:
1) Increasing the injection pressure can increase the tensile strength of PP injection molded parts
PP material is more elastic than other hard rubber materials, so the density of injection molded parts will increase with the increase of pressure. This characteristic is relatively obvious. When the density of the plastic part is increased, its tensile strength naturally increases, and vice versa.
However, when the density is increased to the maximum value that the PP itself can reach, the pressure is increased and the tensile strength does not continue to increase. On the contrary, the residual internal stress of the molded part is increased, and the injection molded part becomes brittle, so it should be stopped.
Other materials have similar situations, but the extent of the difference will vary.
2) Mold heating oil injection can improve the strength of steel and nylon parts
Nylon and POM materials are all crystalline plastics. The mold is sprayed with hot oil machine to transport the hot oil, which can slow down the cooling rate of the injection molded parts and improve the crystallinity of the plastic. At the same time, due to the slowdown of the cooling rate, the residual internal stress of the injection molded part is also reduced. Therefore, the impact resistance and tensile strength of nylon and POM parts injection molded by hot oil machine are correspondingly improved.
It should be noted that the size of the injection molded parts of the nylon and POM parts injected with the hot oil machine may be somewhat different, and the nylon parts may be larger.
3) The melt speed is too fast, even if it is 180 °C, it will be glued.
Under normal circumstances, pvc90 degree material is injected at 180 °C, the temperature is enough, generally there will be no raw rubber problem. However, it is often because the operator does not pay attention to the reason, or in order to speed up the production and intentionally speed up the melting speed, so that the speed of the screw retreating is quite fast, for example, it takes only two or three seconds, the screw retreats to the maximum melting amount. In more than one position, the time during which the PVC material is heated and stirred is seriously insufficient, resulting in a problem of the temperature of the melt and the uneven mixing of the raw rubber, so that the strength and toughness of the injection molded part become quite poor.
Therefore, when molding PVC materials, be careful not to adjust the melt speed to 100 rpm or more. If you must adjust it quite quickly, remember to raise the material temperature by 5 to 10 °C, or increase the back pressure of the melter to match it. Also pay attention to check whether there is any raw rubber problem. Otherwise, it is very likely Caused a great loss.
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