Poor size
Shaped product is less than size
the reason
Most of the material on the earth has the property of thermal expansion and contraction, and the same resin, so the molded product starts to shrink after being formed, and it is cooled until it is equal to the normal temperature, but the problem is that if the final shrinkage is too large In this case, the size of the molded product becomes too small. As a result, the resulting size is small. One of the reasons for this is that, when the initial size of the mold is determined, the basic shrinkage of various resins is taken into consideration and the value thereof is calculated as For reference, however, even if the shrinkage factor is considered to be smaller than the standard size, the shrinkage of the molded product that actually shrinks during the actual process is carried out. Therefore, it is necessary to re-correct the mold in the above situation.
The second is related to the environment in which it is molded. These include the dry state of the material, the mixing ratio of the materials, the molding conditions, etc., but the most important is the molding conditions, because the mold temperature and injection pressure can make the shrinkage. Because of the increase, it is necessary to pay attention. In general, if the injection pressure is increased, the molded product will increase in size, and if the mold temperature is increased, the size tends to become smaller. If these are easy to understand, they are: The size of the product is proportional to the injection pressure, injection time; inversely proportional to the mold temperature
The third phenomenon is that in the long-term mass production, the waste gas generated from the material during injection is accumulated in the mold. Therefore, the filling property of the material is not good and a defect of small size occurs. Regarding the content related to the exhaust gas, The key problem is that it cannot be done without any defects in injection molding of precision plastics, because defect is an important issue, so we will consider it in detail in the future.
Forming measures
Increase injection pressure
Reduce the mold temperature
Extend injection and cool down time
Make sure the type of molding machine and the mold are suitable.
Mold countermeasures
The place where the new mold is not reprocessed well
In mass production, this kind of situation occurs due to the wear of the mold or the obstruction of the exhaust gas. First, the mold is completely cleaned and the exhaust gas is washed off and then re-formed. It must be confirmed.
Bad size
Shaped product is larger than size
It is a phenomenon that is completely opposite to the one in which the size is small, which is called a large size defect. Therefore, the content of the defect is the same as the case where the size is small. First, the size of the mold is not correctly produced. The second problem is the molding environment. The third reason is that the surface of the mold is acidified due to the exhaust gas, which is caused by erosion.
Forming measures
Reduce injection pressure
Increase mold temperature
Reduce injection and cooldown
Check whether the molding machine is suitable for the mold
Mold countermeasures
Will lead to re-correction of the oversized part