Mold information

Failure Analysis and Solution of Dustbin Mould


Dustbin Mould encounters various problems in production […]

Dustbin Mould encounters various problems in production. For the problem of the trouble of the dustbin mould, I made the following analysis:

1. It is difficult to remove the gate

During the injection moulding process, the gate is stuck in the sprue bushing and is not easily peeled off. When the mould is opened, the product is cracked. In addition, the operator must use the tip of the copper rod to knock out from the nozzle, so that it can be released after being loosened, which seriously affects the production efficiency.

The main reason for this failure is that the smoothness of the taper hole is poor, and there is a knife mark in the circumferential direction of the inner hole. Secondly, the material is too soft. After a period of use, the small end of the tapered hole is deformed or damaged, and the curvature of the spherical surface of the nozzle is too small, resulting in the gate material. A rivet head is produced here. The taper hole of the sprue sleeve is difficult to process. Standard parts should be used as much as possible. If you need to process it yourself, you should also make a special reamer. The taper hole needs to be ground to Ra0.4 or higher; in addition, the gate pull rod or the gate ejecting mechanism must be provided.

2. Large-scale dustbin mould moving mode offset

The large moulds are displaced due to the different filling rates and the influence of the weight of the dustbin mould during the mould 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 surface of the guide post is pulled and damaged. In severe cases, the guide post is bent or cut, and even the mould cannot be opened.

In order to solve the above problems, a high-strength positioning key is added on the parting surface of the dustbin mould, one on each side and the most convenient and effective one is to use a cylindrical key. The perpendicularity of the guide post hole to the parting surface is critical. During processing, after clamping with the movable and fixed mould alignment positions, the boring is completed once on the trampoline, which ensures the concentricity of the moving and fixed hole and minimizes the vertical error. In addition, the heat treatment hardness of the guide post and the guide sleeve must meet the design requirements.

3. Dustbin mould guide column damage

The guide post mainly plays a guiding role in the dustbin mould to ensure that the moulding surfaces of the core and the cavity do not touch each other under any circumstances, and the guide post cannot be used as the force receiving member or the positioning member.

In several cases, the dynamic and fixed modes will produce a large lateral offset force when injecting. When the wall thickness of the plastic part is not uniform, the flow rate of the material flow through the thick wall is large, and a large pressure is generated here; the side of the plastic part is asymmetrical, such as the dustbin mould of the stepped parting surface, and the opposite sides are subjected to The counter pressure is not equal.