Injection molding production, you often encounter the problem of floating fiber, dew fiber glass fiber is exposed on the surface of the product, relatively rough, the appearance of more difficult to accept, the possible causes Analysis: When adding such fillers, the general Is the use of physical mixing method, so only the glass fiber evenly dispersed in the middle of the plastic, but after the plastic melts, the mixture will appear in varying degrees of separation (depending on the added ratio and the length of the glass, and the temperature of the raw material is also certain Degree of influence)
Why that fiberglass exposed it?
In the injection of plastic, the material flow is different from the liquid flow (liquid Newton flow, plastic non-Newtonian flow), but there is a saying is more interesting and relatively easy to understand. You should have seen inside the river, in the river There are some branches and other debris, often in the coast along with some of these dependent on the river bank and stay, because the flow of water in the river bank due to resistance and slow down, this and fill the epidermis are similar, so these branches Injection, is the glass fiber exposed, that is, the floating fiber.
This is because the glass fiber flow is much worse than the plastic, and plastic flow in the mold is a fountain-like flow (fountain effect), from the middle to both sides of the flip way to flow, so the best mobility is sure to run to the most In front of poor liquidity will remain in the mold surface (PP and other raw materials to do when the line and the last part of the same color with the same reason, but in the forefront of the general is waxy, and toner separation, especially plus color mother The most obvious, because the masterbatch is generally used as a carrier PE), as well as fire retardant material on the surface of the adsorbent fire retardant is also the reason.
Generally use the following method can reduce the proportion of floating fiber:
1. Increase the filling speed
After increasing the speed, although the fiberglass and plastic have different flow rates, the relative speed difference is smaller than that of high speed plastic injection, just as the river will never leave the same branch in the rapids.
2. Raise the mold temperature
This effect is the largest, increase the mold temperature, is to reduce the glass fiber and mold contact resistance, so that the glass fiber and plastic speed difference as small as possible, and let the middle of the plastic flow of molten layer as thick as possible, so that both sides of the epidermis as much as possible Thin, so that like a smooth river bank can not keep the same token. RHCM is to use this principle to achieve the appearance of non-floating fiber.
3. Reduce the temperature of the screw metering section, to reduce the amount of sol
This is the plastic box glass fiber to minimize the possibility of separation, in general, for the smallest impact on the floating fiber, the actual effect is not great, but this can be a good solution to scorch.This is because the increase in glass fiber, The volume of glass fiber relative to the plastic is much larger, so it is easy to block the exhaust channel, it is difficult to exhaust in the end, and glass fiber in the high pressure and high oxygen environment is very easy to burn!