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Determination of Parting Surface of Plastic Injection Mould

Determination of Parting Surface of Plastic Injection Mould

In the process of plastic injection mould manufacturing, there will always be the problem of determining the parting surface. It is a very complex problem, which is restricted by many factors. Therefore, when selecting the parting surface, grasp the main contradiction and give up the secondary factors. Different designers sometimes have different understanding of the main factors, which is related to their own work experience. The selection of parting surface of some plastic parts is simple, clear and unique. Some plastic parts have many options.

Ⅰ. Ensure that the plastic products of the plastic injection mould can be demoulded

This is a primary principle, because the purpose of setting the parting surface of plastic injection mold is to smoothly remove the product from the cavity. According to this principle, the parting surface should preferably be on the largest contour line of plastic products, preferably on a plane, which is perpendicular to the opening direction. The whole profile of parting shall be reduced, and there shall be no concave convex shape affecting demoulding, so as not to affect demoulding.

Ⅱ. The cavity depth of plastic injection mould should be the shallowest

The depth of the mold cavity has the following three effects on the mold structure and manufacturing:

1. At present, the processing of plastic injection mold cavity mostly adopts EDM. The deeper the cavity, the longer the processing time, which affects the mold production cycle and increases the production cost.

2. The cavity depth of plastic injection mold affects the thickness of the mold. The deeper the cavity, the thicker the fixed mold. On the one hand, it is difficult to process. On the other hand, various injection machines have certain restrictions on the maximum thickness of the mold, so the cavity depth should not be too large.

3. At the same starting inclination, the deeper the cavity depth of plastic injection mold, the greater the difference between the actual dimensions of the upper and lower ends of the same size. In order to control the specified dimensional tolerance, it is necessary to reduce the demoulding slope, which leads to the difficulty of demoulding plastic parts. Therefore, when selecting the parting surface, the cavity depth should be the shallowest as possible.

Ⅲ. The plastic mold components have beautiful appearance and are easy to clean

Although the matching of plastic injection mold is very precise, there will be a circle of burrs on the parting surface after plastic parts are demoulded, which is called flash. Even if these burrs are cut off immediately after demoulding, they will still leave traces on the plastic parts and affect the appearance of the plastic parts. Therefore, the parting surface should not be set on the smooth surface of the plastic parts, which ensures the beautiful apprearance of plastic mold components.

Ⅳ. Try to avoid lateral core pulling of plastic injection mould

For plastic injection moulds, lateral core pulling should be avoided as far as possible. The structure of the lateral core pulling die is complex, which directly affects the size and matching accuracy of the plastic parts, consumes time and consumables, and the manufacturing cost increases significantly, so it can only be used as a last resort.

1. The parting surface of plastic injection mold should be easy to process

2. The accuracy of parting surface of high quality injection mold is an important part of the accuracy of the whole mold. It is required that the flatness and the parallelism of fixed mold mating surfaces are within the tolerance range. Therefore, the parting surface should be flat and perpendicular to the demoulding direction, so as to ensure the machining accuracy. If the parting surface is an inclined surface or curved surface, it will be more difficult to process, and the accuracy can not be guaranteed, which is easy to cause material overflow and flash.

To sum up, there are many factors affecting the parting surface of plastic injection mold. The general requirement is smooth demoulding to ensure the technical requirements of plastic parts, simple mold structure and easy manufacturing. After selecting a parting surface scheme, there may be some shortcomings, and then take other measures to make up for the existing problems, so as to select a parting surface close to the ideal.

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