Injection molding machine molding abnormal solutions and precautions

- May 14, 2019-

Injection molding machine molding abnormal solutions and precautions


If the pressure is too low, it will produce short shots and shrinkage; if the pressure is too high, the head will be full and burnt; if the internal pressure is high, the mold will be damaged and the machine will be damaged.

Injection speed:

The speed of the injection speed mainly determines the condition of the raw material flowing in the runner of the mold and in the finished product. If the speed is too fast, it will be full, burnt and sticky; too slow will cause short shots, shrinkage, and obvious bonding lines.

Shot temperature:

The heat and temperature required for proper melting of the raw materials during molding are different depending on the melting temperature and specific heat of each raw material. When the temperature is too low, the raw materials are unevenly melted, the short-term color is uneven, and the internal pressure of the finished product is high. If it is too high or too long, the flow will be too good to cause the finished product to produce hair, and the cooling temperature will easily cause the finished product to shrink; in severe cases, the raw material will be decomposed, deformed or even burnt.

Mold temperature:

The raw materials bring a lot of heat into the mold, the finished product will go part of the tropical part, and some of the heat will be dissipated into the air. Therefore, in order to keep the mold at a constant temperature, the frozen water, cold water, hot water and heat are sometimes passed in the mold. Oil or electric heating, the choice is to maintain a constant temperature in order to balance the pressure into and out of the mold. The mold temperature is too low, the finished product is prone to short shots, the surface is rough, the internal pressure is high, and the mold is applied. The mold temperature is too high. The finished product is easy to deform, shrink, and has a long surface gloss period.

Screw speed:

The screw has four functions of conveying, compressing, melting and measuring the source material. The function of the screw for melting is that three-fifths of the heat required to melt the material is the frictional heat generated by the rotation of the screw. Two-fifths are from the heat of the heating sheet and the baking material. The rotation speed of the screw is too slow, the plasticization of the raw materials is uneven, the cycle is extended too fast, the raw materials are easily overheated, and the hopper is easy to agglomerate.

Back speed:

When the screw rotates, the resistance when retreating is back pressure. The purpose of this resistance is to make the raw material conveyed by the screw, and the compression process is more compact. The air, water and gas decomposed in the raw material are compressed. The gas is discharged from the material tube to obtain a completely compressed plastic material before it is injected into the mold, and does not contain any other undesired gas, and has a particularly good effect on the appearance of the finished product. Therefore, the back pressure is too low, the finished product is easy to generate internal bubbles, the surface of the silver grain, the back pressure is too high, the raw materials are easy to overheat, the hopper is agglomerated at the material, the screw does not retreat, the cycle is extended, and the nozzle overflows.

Cooling and mold temperature control. The length of cooling and the temperature of the mold can affect the quality of the finished product. In the shrinkage of the finished mold and the dimensional tolerance, there is an absolute relationship between the brightness of the surface of the finished product and the cycle, which can be adjusted according to actual needs and experience.