one, Two are not conducive to solve the problem of shrinking temperature conditions
1) mold temperature is too low to solve the problem of shrinkage
Hard plastic shrinkage problem Mold temperature is not conducive to solve the shrinking problem
The problem of shrinkage of hard plastic parts (shrinkage of the surface and shrinkage of the internal part) is caused by the shrinkage of the melt when the melt shrinks, and the space left by the concentrated shrinkage can not receive the defect caused by sufficient replenishment of the melt from the direction of the water inlet. Replenishment factors will affect us to solve the problem of shrinking.
Most people are aware that mold temperature is too high prone to shrinkage problems, usually like to reduce the mold temperature to solve the problem, but sometimes if the mold temperature is too low, it is not conducive to solve the problem of shrinkage, which many people do not notice.
Mold temperature is too low, melt too fast cooling, farther away from the nozzle at a thicker glue bit, due to the middle part of the cooling too fast and was closed the channel of the refill, the distance will not be sufficient melt Supplement, resulting in more difficult to solve the problem of shrinkage, thick plastic parts shrink the problem is particularly prominent.
Furthermore, the mold temperature is too low, is not conducive to increasing the overall shrinkage of injection molded parts, so that the amount of concentrated shrinkage, shrinkage problems even more serious.
Therefore, in resolving difficult shrinkage problems, it is helpful to remember to check the temperature of the mold.Experienced technicians often touch the surface of the mold cavity by hand, each of which has its proper mold temperature, for example PC material shrinkage problems, if the Sheng ⑺ ⑺ 埽 s hole will be better to improve, but the mold temperature is too high, the plastic parts will shrink the problem.
2) melt temperature is not conducive to solve the problem of shrinkage
The same is the majority of people know that the melt temperature is too high, the plastic parts prone to shrinkage problems, the appropriate lower temperature 10 ~ 20 ℃, shrinkage problems will be improved.
However, if the injection part shrinks somewhere thicker parts, then the melt temperature is adjusted too low, for example, close to the lower limit of injection molding melt temperature, but not conducive to solve the problem of shrinkage, and even more serious, injection molding The thicker the case, the more obvious.
The reason is too low similar to the mold temperature, melt condensation too fast, from the shrunk to the nozzle can not form a larger temperature difference between the shrink, shrinking shrinking channel premature will be sealed, the problem solved It becomes more difficult.It can also be seen from this, the faster melt adhesive condensation is not conducive to solve the problem of shrinkage, PC material is a very fast condensation of raw materials, so its shrinkage problem can be said that a big problem injection molding .
In addition, the melt temperature is too low is also not conducive to increasing the amount of overall shrinkage, resulting in an increase in the amount of concentrated shrinkage, thus exacerbating the problem of shrinkage.
Therefore, it is very important to check if the temperature of the melt is too low when adjusting the harder shrinkage problem. In addition to looking at the thermometer, it is more intuitive to check the temperature and fluidity of the melt with the air jet method .
two, Injection speed too fast is not conducive to solve the problem of serious shrinkage
Solve the problem of shrinkage, the first thing that comes to mind is to increase the injection pressure and extend the injection time, but if the injection speed has been tuned quickly, it is not conducive to solve the problem of shrinkage.So sometimes shrink is difficult to eliminate, it should cooperate with the reduce injection Speed to solve.
Reduce the injection rate, can walk in front of the melt and the water inlet to form a larger temperature difference, which is conducive to the melt from near to the order of solidification and shrinkage, but also conducive to shrinking water farther away from the position Get a higher pressure to replenish, the problem will be of great help to solve.
Due to lower injection speed, walking in front of the melt temperature is lower, the speed has slowed down, the injection molding parts will not be easy to batch front, injection pressure and time can be longer and longer, which is even more beneficial Solve the problem of serious shrinkage.
In addition, the effect will be more pronounced if slower, more stressful, longer end-of-fill and step-down and pressure-hold methods are used, so when it is not possible Slow speed of plastic injection, from the late injection of this method is also a good remedy.
However, it is worth reminding that the filling is too slow but will not help to solve the problem of shrinkage, because when the cavity is full, the melt is completely frozen, just like the melt temperature is too low, there is no Ability to retract the shrinking afar.