Main points of design of injection mold for test tube bracket

Time：2020-07-17 09:25:55 / Popularity： / Source：

Product drawing of test tube holder is shown in Figure 1. Maximum external dimensions of product are 143.40 mm*24.50 mm*105.00 mm, average thickness of plastic parts is 2.0 mm, material of plastic parts is PP, shrinkage rate is 1.016, and weight of plastic parts is 11.70 grams. Technical requirements for plastic parts are that there must be no defects such as peaks, incomplete injection molding, flow lines, pores, warpage, silver lines, cold materials, spray lines and other defects.

It can be seen from Figure 1 that plastic part is shaped as a semi-circle, and a simple bracket with a semi-circular cross-section. Hook part has a hook hole formed by a long hole and a round hole. Difficulty of mold design lies in following two points: one is how to judge direction of mold opening and further determine parting surface; the other is choice of gate location and how to avoid deformation of plastic part. Difficulty of mold processing is processing of parting surface. Because parting surface is an arc surface, height is high and low, plastic is PP material, it is easy to produce burrs. Therefore, processing of parting surface requires high-speed machining to make parting surface fit well.
Production volume of plastic parts is huge, and mold design cavity layout is 1 out of 4; mold frame is Fudeba mold base MDC SC3555 A150 B130 C90 H, and AB plate is made of P20 steel. Mold is exported to Germany. If mold base used in the early export mold is not HASCO standard mold base, but Longji or Fudeba mold base, guest will request AB plate to be made of P20 steel. Furthermore, guests will request that thimble plate is also made of P20, all of which are to ensure quality of mold. Design two conical positioning parts staggered on parting surface to ensure mold clamping accuracy. Important concept of mold design for European and American customers is steel selection and heat treatment hardness. Steel used in this set of mold is 1.2344, and heat treatment hardness is HRC48~52.
Choice of mold opening direction is the most important link in determining mold design drawing. In this set of molds, when choosing mold opening direction, two points are mainly considered. The first hook hole is designed in moving mold to make slider simple; at the same time, gating system is in a higher position, which makes main runner shorter. Actual mold design drawing is shown in Figure 2.

Figure 1 Test tube bracket product picture

After plastic independent runner enters parting surface, it enters each cavity separately in 4 ways, adopt one point injection for each cavity to submerge front mold.
Export mold adopts hard mold design after heat treatment, and production process needs to be considered. Heat treatment will deform steel. Therefore, layout design is that two cavities are on a mold core, and a total of two mold cores are required. Separating mold core can reduce deformation and facilitate production. Manufacturing process of hard mold is as follows: spare material precision grinding (remaining margin), rough machining cavity, remaining margin, screw hole drilling, tapping, drilling water transportation; heat treatment; fine grinding shape, lower frame; finishing cavity. Die-saving polishing, etc. Therefore, design of hard mold must take into account heat treatment and its deformation. Only with careful thinking can a reasonable mold be designed.
Slider core-pulling system is designed at hook part, driven by inclined guide column, and shovel is backhoeed in rear mold. In mold exported to Europe, when slider backhoe mechanism can be designed, it cannot be omitted and must be designed. Moreover, inclined guide column core pulling mechanism is the first choice.
Design of mold temperature control system is very important, which is conducive to controlling injection cycle and reducing deformation of plastic parts. While front and rear molds are designed of water transportation, heat insulation plates are designed on both front and rear molds to prevent heat loss.
Ejection of plastic parts is ejected with a eject pin, which can fully meet needs of ejection of plastic parts.

Figure 2 mould drawing of test tube holder

Figure 3 3D drawing of the test tube holder mold

Gud Mould Industry Co., Ltd

Main points of design of injection mold for test tube bracket

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