How to determine the size of injection mold forming parts

Update:14-05-2021
Summary:

The so-called working size of the molded part refers to […]

The so-called working size of the molded part refers to the size of the directly molded part of the molded part, mainly the size of the cavity and the movable mold core.

Any plastic parts have certain geometrical shape and size requirements, grass cutter manufacturers among which the size accuracy requirements for matching requirements are higher. The size of mold forming parts must ensure that the size of the molded plastic part meets the requirements, and the factors that affect the size and tolerance of the plastic part are quite complicated.

① Manufacturing tolerances of molded parts.

a. The manufacturing tolerance of molded parts directly affects the manufacturing tolerance of plastic parts. When determining the dimensional tolerance of the molded part, 1/3 of the tolerance of the plastic part can be taken.

b. Before determining the forming size, you should first understand the nature and classification of each part size in order to determine the orientation of each part size and its tolerance.

②The size calculation of molded parts should consider the fluctuation factors of molding shrinkage: production process conditions of plastic parts, mold structure, operation methods, materials, etc. But the key requirement is that the molding shrinkage data must be correct

③ Pay attention to the control of the wall thickness of the product, generally it is better to be thinner than thick; pay attention to the control of the correction value: the movable mold should be properly positive, and the fixed mold should be properly negative for easy adjustment

④The dimensions of the molded parts need to be considered to facilitate the trimming after the mold trial.

⑤The assembly dimensions of the moving and fixed mold core parts are correctly selected according to the matching tolerance table, which is convenient for part production and maintenance

⑥ The manufacturing accuracy of molded parts is one of the important factors that affect the dimensional accuracy of plastic parts. The lower the processing accuracy of the molded parts, the lower the dimensional accuracy of the plastic parts. Practice has proved that the manufacturing tolerance of molded parts can be 1/3~1/6 of the tolerance of plastic parts, and then determined according to the standard tolerance value.