When injection molding production, do you often encounter floating fiber problems, exposed fiber is glass fiber exposed on the surface of the product, relatively rough, appearance is more difficult to accept, the possible causes of analysis: When adding this kind of filler, it is generally the use of physical mixing method, so only the glass fiber is evenly dispersed in the middle of the plastic, but after the plastic melts, the mixture will appear different degrees of separation (depending on the proportion of the added and the length of the glass fiber, and the temperature of the raw material also has a certain degree of influence)

Why the glass fiber is 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 more easy 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 of these attached to the river bank and stay. Because the flow rate of the water along the river bank is slowed down by the resistance, this is similar to the surface layer when filling. So these branches are exposed in the injection molding, which is the glass fiber, which is the floating fiber.

This is because the flow of glass fiber relative to plastic is much worse, and the flow of plastic in the mold is a fountain flow (fountain effect), from the middle to both sides of the way to flow, so the best flow is definitely to the front, the poor flow will stay on the surface of the mold (PP and other raw materials when the combination line and the final part of the color is different, the same reason, Only in the most front is generally waxy, and the color powder is separated, especially the most obvious color master, because the color master is generally used as the carrier PE), and the fire retardant mold surface adsorption of fire retardant is also this reason.

Generally using the following methods can reduce the proportion of floating fiber:

1. Increase the filling speed

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

2. Increasing the 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 becomes smaller as far as possible. And let the middle melt layer of the plastic flow as thick as possible, so that the skin layer on both sides as thin as possible, so that it is like a smooth river bank can not retain the same truth. RHCM uses this principle to achieve the appearance of no floating fibers.

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

This is to minimize the possibility of glass fiber separation in the plastic box, generally speaking, the impact on the floating fiber is minimal, and the effect is not large in actual operation. However, this can be a good solution to the 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 and high oxygen gas environment!

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