Highlight products for injection molding enterprises is really a difficult problem to deal with, because it can not hide external defects, even the dust in the workshop will cause different degrees of product defects, such as troma, pitting, contamination, etc., so the environment is also one of the key factors affecting this kind of products.

The white fog on the surface of the product is white from the visual point of view, so it is not obvious in the white product, and the black highlight is the most obvious, as shown in Figure 1.

The product is made of PP material, and the surrounding surface shows large and small white markings, like the symptom of cloud, which is classified as white fog here.

Analyze the reasons:

There is a certain gap between plastic and plastic in the feeding stage, which is brought into the barrel after shearing by the screw. In the process of shearing by the screw, physical changes will occur inside the material, from the glass state to the high elastic state, from the high elastic state to the viscous flow state.

This change of process may be only a few seconds - seconds between, (according to the machine or product size) in such a short time to transform a complex process, injection molding defects also occurs, the space between the plastic is compressed gas to internal melting, when in plasticizing fails to discharge the gas to the outer cylinder, existing gas is wrapped into the molten material is injected into the mold cavity, Whether the mold can be discharged smoothly depends on whether the exhaust of the mold is good, then the phenomenon of fog trapped gas or burning is generated.

Apparently, white fog was trapped gas a phenomenon, a lot of personnel engaged in injection molding technology for burning is trapped gas, or trapped gas exhaust trough, this is unscientific, burnt due to air trapping is too serious, gas in high pressure, high speeds are compressed not release partial combustion, the combustion temperature can reach 600-800 ℃, instantly This is the highest state of trapped air.

Solutions

How can we make the best gas discharge and not produce white fog phenomenon?

1. In terms of mold

Exhaust is not entirely by the mold to solve, for PP material characteristics, the temperature range is very wide, its flow performance is superior, if the mold exhaust slot is too large or the position is wrong, can not be correct exhaust, but also easy to produce bad flash, so the correct exhaust is useful.

2. In terms of technology

It is very effective to master the correct tuning skills in practical work.

1) If the screw rotation speed is reduced, the melt temperature can be uniform, and the opportunity of enrolling air is small, such as the screw rotation speed is too fast, the opportunity of enrolling air is more; The melt is subjected to a large shear force of screw, friction heat generation leads to uneven melt temperature, and melt decomposition producesair.

2) Increasing the mold temperature can benefit high pressure and slow filling to gain time. If the mold temperature is too low, the product surface is prone to premature freezing, and slow filling cannot be achieved, which may lead toshort ofplastic material.

3) Reduce the injection speed, the faster the speed, the faster the gas compression, the higher the temperature. The slower the speed, the slower the gas compression, the more conducive to gas expulsion.

4) clamping force, the greater the clamping force, the worse the cavity surface exhaust effect, the smaller the clamping force, the better the cavity surface exhaust effect.

If you have anything different comments, kindly please contact us Green Vitality Industry Co.,Ltd at any time.