Seven parameter standards set by the injection molding process

Injection speed: the injection speed is slow, the plastic is carried out in the mold cavity, there will be more heat loss, the flow viscosity increases, and the use pressure loss increases; higher injection speed can often get higher accuracy and less deformation For the molded products, only through the areas of thin and thick meat, fierce changes, corners and other areas, it is easy to produce poor appearance, and it is also prone to problems such as poor exhaust, criticism, and incorrect pressure switch.

Switching of holding pressure: Switching too early, the finished product size is easy to be insufficient, or even short shots, and the surface is sunken, otherwise the excessive compression is formed, the small size is too large, the flash, whitening, deformation, and the mold is damaged ; Switching of holding pressure, usually with injection stroke (position), time and other control methods.

Holding pressure setting: If the holding pressure is too high, overfilling will occur, which will cause the plastic that has entered the mold cavity to flow backward; the correct and appropriate holding pressure setting should enable the screw to pass the pressure holding switch Continue to advance to the lower pressure of the target point as the principle; during the holding phase, the internal pressure of the mold cavity gradually decreases due to the cooling of the plastic, so the holding pressure should be appropriate

Setting of holding time: The holding time should be maintained until the gate condenses. It is meaningless if it is too long, but if the time is too short, it is easy to reverse flow, which makes the part near the gate easy to sag and insufficient size; keep the time appropriate Generally, it should be judged by the stability of the weight; the gate is small, the mold temperature is low, and the pressure holding time should be set shorter, if the contrary is the case, set it for a longer time.

Cooling time setting: the plastic is cooled in the mold cavity, most of them start at the end of the holding pressure switch and end the mold opening. The theoretical cooling time = holding time + post cooling time; the theoretical time required should be that the product can be smooth Ejection (non-deformation) as the principle, its length varies with the thickness of the molded product, material, and mold cooling speed; gate thickness and mold temperature will affect the holding time (the cooling time set by the machine, that is, after cooling) Time) If the gate is large and the mold temperature is high, the holding time should be properly extended, otherwise, the holding time should be appropriately reduced.

Mold temperature setting: If the mold temperature is set too low, the melt flows in the mold cavity, and the temperature drops faster, which increases the material flow resistance, so the pressure loss increases, the internal stress increases, and the mold temperature increases. Intraluminal pressure.

High mold temperature setting: increase the crystallinity and more uniform structure of the molded product, reduce the residual internal stress, deformation and increase strength, reduce the flow resistance of the material during filling, reduce the pressure loss, make the product appearance good gloss, but easy to occur The burrs increase the part near the gate and reduce the depression in the part far from the gate, so that the bonding line becomes smaller and the cooling time is increased.