Injection molded products refer to products that are heated, plasticized, and melted by an injection molding machine, and then injected into the cavity of the mold for molding. After cooling, the melt is solidified, and then demoulded. During the injection molding process, flash may occur (also known as overflow, burrs, burrs, etc.). Flash mostly occurs at the opening and closing positions of the mold, such as the parting surfaces of the movable mold and the static mold, and the parting surfaces of the slider. Flash at sliding fitting parts, insert clearances, ejector pin pores, etc. is largely caused by the failure of the mold or machine clamping force. Jiuzhi Plastic Network has summarized some reasons, as follows:
1. If the maximum clamping force of the machine is not enough, a machine with sufficient clamping force should be selected. The clamping machine hinge is worn or the sealing element of the clamping cylinder is worn, resulting in oil dripping or backflow, resulting in a decrease in the clamping force. If the heating system is out of control and the actual temperature is too high, check the thermocouple and
Is there any problem with the heating coil, etc.?
2. (1) Unbalanced distribution of the mold cavity or insufficient parallelism results in unbalanced forces, resulting in local flash and local dissatisfaction. The runner should be placed as close to the center of mass symmetry as possible without affecting the integrity of the part.
(2) Flash will be caused when the movable components and sliding core in the mold are unbalanced.
(3) When the mold is poorly vented, the pressurized air will expand the parting surface of the mold and cause flash. A good exhaust system should be set up, or an exhaust trench should be dug on the parting surface.
3. If the fluidity of the plastic is too high, or too much lubricant is added, the pressure, speed, temperature, etc. should be appropriately reduced, the amount of lubricant used should be reduced, and plastics with low fluidity should be used if necessary.
4. Processing and adjustment:
(1) If the set temperature, pressure and speed are too high, segmented injection should be used. Excessive injection time, holding pressure time and feeding amount will cause flash.
(2) During adjustment, the mold clamping machine hinge is not straightened, or the mold adjusting nut often moves when opening and clamping the mold, resulting in insufficient clamping force and flash.
(3) The parallelism between the adjusting head and the two poles is not enough or the adjusted system pressure is too high.
5. Reasons for repeated occurrence of flash and dissatisfaction of parts:
(1) When the particle size of plastic raw materials is very different, the amount of ingredients added will be uncertain.
(2) The wear of the screw's rubber head, rubber ring and rubber washer is too great, so that the molten material may slide and flow back between the screw and the barrel, causing flash or dissatisfaction.
(3) The cooling system at the inlet fails, causing the feed to adjust.
(4) The injection amount set in the barrel is insufficient, that is, the buffer pad is too small, which will cause more and less injection, resulting in flash or unsatisfied parts.
