On the injection molded parts products, especially the raw materials are ABS, PP, PC, you will often see shiny stress marks on the surface of the product, ejector stress marks, into the sub stress marks, flesh thickness difference stress marks.
These apparent shiny and white marks are the results of internal stress, which is no more than orientation stress and cooling shrinkage stress. Irregular stress marks near the gate are typically caused by orientation stress, while the flesh thickness difference is the common result of orientation and shrinkage stress, while the ejector pin and slant pin stress marks are formed by more factors.
Generally, with the increase of pressure and time, the first one is the stress marks of flesh thickness difference, the stress marks of ejector pin, then the stress marks of flesh thickness difference, and finally the irregular stress marks near the gate (side view will be white and shiny), of course, it also depends on the specific structure of the product and the location of the inlet.
Therefore, when these stress marks appear, reducing the holding pressure and holding time is the most important, and understanding this, then start from here to modify the product design and mold design is more effective than molding adjustment
1. Product design.
The overall meat thickness is too thin or flowing end meat thickness is thicker leading to filling pressure and holding pressure is too large, need to add glue or flowing end steal meat. That is to say, when the holding pressure is reduced, see if the shrinkage can steal meat to improve, if not, it is necessary to add glue on the large side.
Try to avoid poor meat thickness, if there is a need to do a large differentiation.
The rib of the male mold to avoid doing too big leads to the mother mold having rib stress marks.
2. Mould design.
Gates are too small or the number is too small and unevenly distributed.
The movable parts with loose mold or unreasonable waterway configuration lead to high mold temperature.
3. Molding conditions.
The reasonable setting of holding pressure and time (lower).
Increase or decrease the mold temperature (increase can improve the filling and reduce the pressure; decrease is to make the surface shiny, the surface and stress marks close, generally speaking, reduce the mold temperature is the majority of options)
