Significance of improving the surface quality of plastic bottle cap mold processing

The surface geometric features of the products produced by the plastic bottle cap mold are formed by replicating the working surface of the mold. Therefore, the surface roughness of the plastic bottle cap mold is directly reflected on the surface roughness of the product. The smaller the surface roughness value of the mold, the smaller the surface roughness value of the produced product. Therefore, the quality of the processed surface has an impact on the performance of the plastic bottle cap mold, as follows.

(1) Effect of mold surface roughness on product release

In the manufacture of plastic bottle cap molds, in order to facilitate the demolding of the product, a demolding slope is often created when processing the working surface of the mold. The smaller the surface roughness value of the mold, the easier the demoulding of the product, and the smaller the required demoulding slope; the larger the value of the mold surface roughness, the more difficult it is to demould the product, and the larger the required demoulding slope. When the demolding slope of the mold is small, the surface roughness value of the mold should have a sufficiently small value, and it is also required that the direction of the polishing texture is consistent with the demoulding direction; otherwise, it is easy to scratch the surface of the product, which will seriously lead to failure to demold and damage for products and cores, this problem is particularly prominent in the manufacture of metal die-casting molds.

(2) The influence of the surface quality of mold parts on the fatigue strength of parts

Under the action of alternating loads, the microscopically uneven valleys and defects in the surface layer of the parts are likely to cause stress concentration and fatigue cracks, resulting in fatigue damage to the parts.

The work hardening of the surface layer of the plastic bottle cap mold can improve its wear resistance and prevent the appearance of fatigue cracks in the surface layer. However, if the degree of chilling and hardness of the surface layer of the part is too large, it is easy to produce cracks, so the degree of chilling and hardness of the part and the depth of hardening should be controlled within a certain range.

The residual stress of the surface layer also has a great influence on the fatigue strength of the part. When there is residual compressive stress in the surface layer, it can delay the expansion of fatigue cracks and improve the fatigue strength of the part; When there is residual tensile stress in the surface layer, it is easy to cause cracks on the surface of the part and reduce its fatigue strength.

(3) How mold parts' surface roughness affects the components' susceptibility to corrosion

Surface roughness of parts has a significant impact on their ability to resist corrosion. The easier it is for corrosive materials to build up on a part's surface, and the stronger the corrosion and penetration, the deeper the valley. Consequently, lowering the parts' surface roughness can increase their resistance to corrosion.

(4) Effect of surface roughness of mold parts on fit properties

For matching parts that require relative motion, the size of the parts will change due to wear and tear, which will affect the matching properties of the parts. Improper selection of the surface roughness of the parts will speed up the wear of the parts, and the reasonable gap obtained during assembly will increase rapidly, and a new set of plastic bottle cap molds will soon lose their normal working ability. Therefore, when it is required to cooperate with molds with small precision gaps, not only the size and geometric accuracy of the mating surface but also a certain surface roughness must be guaranteed. Also in the interference fit, if the surface of the parts is rough, the convex peaks on the mating surface will be flattened after assembly, the effective interference between the fittings will be reduced, the connection strength between the mating parts will be reduced, and the reliability of the fit will be affected. Therefore, for surfaces with matching requirements, a smaller surface roughness must be specified.

In short, improving the quality of the mold processing surface is very important to improving the performance of the plastic bottle cap mold and the life of the plastic bottle cap mould.