CAUSES AND SOLUTIONS OF INJECTION MOLDING DEFECT FLOATING FIBER

So why is the glass fiber exposed?

When shooting glue, the flow of the material is different from the flow of the liquid (liquid is Newton flow, plastic is non-Newton flow), but there is a more interesting and easier to understand. We should have seen the river inside, in the river there are some branches and other debris, often along the coast there are some such attached to the river bank and stay. Because the flow rate of water along the river bank is slowed by resistance, this is similar to the surface layer during filling. So these branches in the injection molding, that is, the glass fiber exposed, that is, the floating fiber.

This is because the flow of glass fiber is much worse than that of plastic, and the flow of plastic in the mold is a fountain flow (fountain effect), flowing from the middle to both sides, so the best flow is definitely to the front, and the poor flow will stay on the surface of the mold (the same reason why the combination line and the final part of the color are different when doing PP and other raw materials, Only at the very front is generally waxy, and the separation of color powder, especially the most obvious color masterbatch, because the masterbatch is generally made of PE as the carrier), and the adsorption of fire retardant on the surface of the fire retardant mold is also this reason.

Generally the following methods can be used to reduce the proportion of floating fibers:

1. Increase filling speed

After increasing the speed, although the flow rate of glass fiber and plastic is different, the proportion of the relative speed difference is small compared to the high-speed glue, just like the river will never have branches left in the rapids.

2. Increase mold temperature

This effect is the largest, increasing the mold temperature is to reduce the contact resistance of the glass fiber and the mold, so that the speed difference between the glass fiber and the plastic is as small as possible. And make the molten layer in the middle of the plastic flow as thick as possible, and make the skin layer on both sides as thin as possible, so that it is like a smooth river bank can not retain the branches of the same reason. RHCM is to use this principle to achieve the appearance of no floating fiber.

3. Reduce the temperature of the metering section of the screw and reduce the amount of sol

This is to minimize the possibility of glass fiber separation in plastic boxes, generally speaking, the impact on floating fibers is minimal, and the effect is not large in actual operation. But, uh, this is good for burning. This is because after increasing the glass fiber, the volume of the glass fiber is much larger than that of the plastic, so it is easy to block the exhaust channel, so it is difficult to exhaust in the end, and the glass fiber is easy to burn in the high-pressure high-oxygen gas environment