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Frequent problems with injection molds

update:05-05-2019
abstract:

1. The gate is difficult to remove: In the injection mo […]

1. The gate is difficult to remove:
In the injection molding process, the gate is stuck in the sprue bushing and is not easy to escape. When the mold is opened, the finished product exhibits crack damage. In addition, it is necessary for the operator to knock out the nozzle from the top of the nozzle with a copper rod, so that it can be released after being loosened, which seriously affects the production power.
The primary factor of this shortcoming is that the gate cone has poor brilliance and the inner hole has a knife mark in the circumferential direction. Secondly, the data is too soft. After a period of time, the small end of the tapered hole is deformed or damaged, and the arc of the nozzle is too small, so that the gate material is riveted here. The taper hole of the sprue bush is more difficult to process. Standard parts should be used as much as possible. If you need to process it yourself, you should also confiscate or buy a special reamer. The tapered hole needs to be ground to Ra0.4 or higher. In addition, it is necessary to set the gate pull rod or the gate to eject.
2. Large mold moving mode offset:
The large molds are displaced due to the different filling rates, and are affected by the weight of the mold during the mold loading. In the above cases, the lateral offset force will be applied to the guide post during the injection. When the mold is opened, the outer surface of the guide post will be pulled and damaged. When the test is severe, the guide post will be bent or blocked, and the mold cannot be opened.
In order to deal with the above problems, a high-strength positioning key is added on each side of the mold parting surface, and the most simple and useful one is to select a cylindrical key. The straightness of the guide post hole and the parting surface is crucial. When the machining is performed, the moving and fixed mold are clamped in the orientation, and the boring is finished once on the trampoline, so as to ensure the concentricity of the moving and fixed hole, and Minimize straightness errors. In addition, the heat treatment hardness of the guide post and the guide sleeve is necessary to arrive at the request.

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