Hot runner injection mold design for paper holder
Time：2021-09-13 13:58:49 / Popularity： / Source：
It can be seen from Figure 1 that structure of plastic part is a flat and complex shell. There are local protrusions on both sides of fixed mold to provide guidance for paper output. This surface has multiple paper-through positions, which need to be smooth to reduce contact area between paper and surface to reduce friction. There are multiple bone positions in movable mold part to increase strength and rigidity. Bone position of movable mold is also over paper surface, top of bone position is rounded, it is required to be smooth, and paper should not be prevented from flowing out of this surface to front side. There are 3 undercuts on both sides of plastic part, and slider core needs to be designed. There are 3 undercuts in movable mold part, and it is necessary to design inclined top demoulding.
Please refer to attached PDF for product drawings of plastic parts. Product drawing specifies dimensional tolerances and technical requirements of product in detail. Technical requirements stipulate that mold release agents (release agents) must not be used during injection molding. Injection molding material mixed with recycled materials does not exceed 25%, and detailed dimensional tolerances are shown in the product drawing.
Size of plastic part is large, and mold design cavity is ranked as 1 cavity. When mold design cavity is arranged, three sliders are arranged on operating side and non-operating side of mold. Since gating system uses hot runner injection, mold base is a non-standard mold base 7095, which is a large mold. In order to increase rigidity of mold, 4 ø35 positioning pins are added to fixed mold. Since hot runner system generates a large lateral force in manifold during injection molding, diameter of positioning pin here should not be less than ø30. In most cases, standard guide posts are used instead. In movable mold part, ø20 positioning pins are added between B plate and square iron, between square iron and bottom plate. On four sides of mold base, zero-degree positioning blocks are respectively designed for precise mold clamping. This zero-degree positioning block must be customized by mold blank manufacturer and cannot be added later.
Design of full inlays requires comprehensive consideration of various factors, and a reasonable determination of number of large inserts. Breaking up and making inserts must take into account design of water transportation, layout of ejection system, and processing efficiency of machine tool. 3D diagram of water transportation is shown in Figure 4. Specific to each insert, it is necessary to consider that each insert has a reasonable processing benchmark, it can be processed by wire cutting or grinder as much as possible, and EDM processing or corner cleaning should be avoided as much as possible. Small inserts are all designed with hanging tables, and screws cannot be used to fix them.
Through development of DFM activities, on the one hand, mold manufacturers intervene in customer product design stage to consolidate relationship with customers, assist customers in improving product design capabilities, provide professional knowledge, optimize and improve product quality, reduce potential problems, and provide customers with a full range of solutions. At the same time, they have a more in-depth understanding of customer product design intentions and can better control subsequent costs. On the other hand, for mold manufacturers, since they can fully communicate with customers on various technical issues in the early stage of project during DFM activities, it lays a good foundation for opening a good mold review meeting, which is conducive to parallel development of product and mold design work, thereby shortening product and mold development cycle. Mold DFM file is shown in Figure 5.
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