12 Options For Dealing With Undershot Of Iinjection Molded Parts

- Jul 02, 2018-

8. The nozzle hole is damaged or partially blocked. When the seat is retracted, the nozzle and the mold are continuously impacted for a long time, so that the injection hole becomes smaller and smaller, that is, the flow passage becomes smaller, and the area specific volume of the strip increases, which causes the cold material to block the nozzle hole. Or consume too much injection pressure. The nozzle is to be removed for repair or cleaning, and the end position of the injection base is properly reset to reduce the impact force to a reasonable value.


9. Collar wear. The wear gap between the check ring and the thrust ring on the screw head is large, and it cannot be effectively cut off during injection, so that the melted material at the front end has a countercurrent flow and loses the injection component, resulting in incomplete parts.


The method for verifying the wear of the rubber ring is: after the completion of the injection in the previous cycle, the manual operation mode is changed, and the injection pressure and the speed are adjusted to a lower value, and then the stocking is completed. At this point, when observing the manual injection of rubber, the degree of hindrance of the position indicator of the screw is hindered, that is, the degree of leakage of the rubber ring is checked. The less obstructed, the greater the degree of leakage.


For plastic rings with a large degree of wear, they should be replaced as soon as possible, otherwise they will be forced to produce, and product quality cannot be guaranteed.


10. Poor mold exhaust. During the injection process, the air in the cavity is too late to be discharged from the parting surface or the thimble gap, so that the last incoming melt is blocked by the continuously compressed high pressure in the cavity, leaving no resistance at the end of the flow. Fusion defects.


A suitable exhaust passage is set at the parting plane corresponding to the gas blocking position. If the choke position is not on the parting surface, the original shroud or thimble can be used to change the internal exhaust, or the gate position can be re-selected to allow the air to be discharged at the expected position.


11. The ribs are too thin or too deep. These are dead corners that are easy to store air. They are also difficult to mold. The rib rubber position should be thickened or the root angle should be increased. The most thorough method is to add exhaust measures.


12. The runner or gate channel is uneven. Due to continuous improvement of mold manufacturing technology and design level, most of the flow path design for single-head mold adhesive is reasonable and meets the molding requirements. This refers to the distribution of multi-cavity flow channels. Often, there are small differences in the gates, which can result in inhomogeneous flow of components injected into the mold cavities, causing some of the cavities to fill up and some of the cavities still lacking.