First, the
injection molding size is too small
The molded product is smaller than the specification size
the reason
"Hot expansion and contraction" I believe that everyone has heard that the resin is the same, so the molded product begins to shrink after being formed and is cooled to the same temperature as normal temperature, but the problem is that if the final shrinkage is too large, the molded article The size becomes too small, and as a result, the size is too small. One of the reasons is that the initial shrinkage of the various resins is taken into consideration when determining the initial mold size, and the numerical value is calculated as a reference, but even It is considered that the size of the molded product in which the shrinkage ratio shrinks during actual operation is smaller than the specification size, and therefore it is necessary to correct the mold in the above case. Secondly, it is related to the environment at the time of forming. Among them, there are problems such as the dry state of the material, the mixing ratio of the materials, the forming conditions, etc., but the most important is the forming condition, because the mold temperature and the injection pressure can cause the shrinkage amount. If it is increased, it is necessary to pay attention. In general, if the injection pressure molded article is raised, the size will become larger. If the mold temperature is raised, the size will become smaller. These are easily understood: forming The size of the product is proportional to the injection pressure and injection time; it is inversely proportional to the mold temperature. The third is that in the phenomenon that long-term mass production often occurs, the exhaust gas generated from the material during the injection is accumulated in the mold, so that the filling property of the material is not good and the size is small, and the content related to the exhaust gas is in the middle. The key issue is that there is no shortage of precision plastics for injection molding. Because defects are more important issues, we will consider them in detail in the future.
Countermeasures during forming
Increase injection pressure
Reduce mold temperature
Extended injection and cooling time
Confirm that the type of molding machine and the mold are suitable.
Mold countermeasure
Reworked bad place in case of new mold
In the mass production process, such a situation occurs because of the wear of the mold or the obstruction of the exhaust gas. First, the mold is completely cleaned, the exhaust gas is washed away, and then formed, and it must be confirmed.
Second, the injection size is too large
The molded product is larger than the specification size
The phenomenon that is completely opposite to the small size is called the size is too large. Therefore, the content of the bad cause is the same as the small size. First, the size on the mold is not correctly produced. The second is the problem of the forming environment. The third is because the surface of the mold is acidified and eroded because of the exhaust gas. The situation caused by the time.
Molding countermeasure
Reduce injection pressure
Increase mold temperature
Reduce injection and cooling time
Check if the type of molding machine is suitable for the mold.
Mold countermeasure
The part that caused the larger size will be re-corrected.
