Determination of the parting surface of the hottes

2022-08-05
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Determination of parting surface of plastic injection mold (Part 1)

in the manufacturing process of plastic injection mold, the problem of determining the parting surface is always encountered. It is a very complex problem, which is restricted by many factors, and it is often a matter of looking at one thing and losing the other. Therefore, when selecting the parting surface, we should grasp the main contradiction and give up the secondary factors. Different designers sometimes have different understanding of the main factors. Protein plastics are one of the most widely studied and used natural bio based high molecular plastics in the field of biodegradable materials, which is related to their own work experience. The choice of parting surface of some plastic parts is simple, clear and unique; Some plastic parts have many options to choose from. According to my work experience, it can be determined according to the following principles that heat treatable reinforced aluminum alloy thick plate is a class of high-tech and high value-added products:

a) ensuring that plastic products can be demoulded

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

b) make the cavity depth the shallowest

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

1) at present, EDM is mostly used for the processing of the mold cavity. These building blocks must be combined with billions of Lego building blocks currently in use in the world. The deeper the cavity is, the longer the processing time will be, which will affect the mold production cycle and increase the production cost

2) the depth of the mold cavity affects the thickness of the mold. The deeper the cavity, the thicker the moving and 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) the deeper the cavity depth is, the greater the difference between the actual dimensions of the upper and lower ends of the same size at the same mold pulling inclination, as shown in Figure 2. In order to control the specified dimensional tolerance, it is necessary to reduce the demoulding slope, resulting in difficulty in demoulding plastic parts. Therefore, the cavity depth should be the shallowest when selecting the parting surface

c) make the plastic part beautiful in appearance and easy to clean

although the plastic mold is very precise, after the plastic part is demoulded, there will be a circle of burrs on the parting surface, which we call flash. Even if these rough edges are cut off immediately after demoulding, he said, for example, 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

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