Medical Mould

Selection of molds is very strict, because medical injection molding are all finished in clean room. First, mold materials need stainless steel materials, and need to do matching surface treatment, such as vacuum heat treatment, PVD coating, laser heat treatment and so on. Plastic materials of medical device products often have medical grade PP, PVC, ABS, PSU, POM, PA, etc., which have high strength, are corrosive, have wear resistance and high transparency, etc. Requirements for medical injection molding are relatively high as precision mold. Commonly used mold steels are imported S136, 2316, S136H, NAK80, etc., to meet high corrosion resistance and high polishability. Because of large number of cavities and large batch size of medical injection molding for medical consumables, hardness and wear resistance of injection molding materials are very high. Hardness of commonly used medical injection molding steel is suitable around HRC48-56. It can ensure strength of mold and good polishing performance.
There are many different design requirements for mold forming structures. There are many transparent parts for medical consumable products. Products should choose hot runners as much as possible to reduce trace of fusion. When using cold runners, soft PVC should minimize size of runners; Device products are small in size and large in volume. Therefore, automatic unloading and shearing gates should be used to ensure production efficiency and quality; disposable medical device products have many transparent tubular parts. Pay attention to feeding position of gate and Z-fixing method of dynamic model during design to avoid improper selection of gate position and core fixing method, resulting in uneven material flow during injection molding, which causes core to be elastically deformed, product is uneven or not filled, wall thickness is uneven. Extension tube shape product should pay attention to adopt appropriate exhaust method. Inlet port runner should open overflow well according to molding condition of product to avoid difficulty of molding product due to closed gas. Mold cooling system should adopt multiple sets of separate cooling water channels to reasonably control dynamic mold temperature to control deformation of product. In addition, many medical device products involve problem of push-and-seal sealing. Core of mold forming should be designed to straighten body and not to design draft angle, and to ensure that mold release is normal without strain, so that design cooling should be uniform and provide a higher mold temperature, core surface needs to be treated, and special requirements are required on demolding method to ensure quality and precision of product after injection.
Manufacturing precision of medical injection molding is high as precision mold, because products are in contact with blood and liquid medicine entering human body. Injection molding products related to medical equipment are definitely not allowed to have existence of burr, and many of them are directly matched by plastic parts to achieve sealing and pressure resistance effect, multi-cavity product compatibility requirements. So processing precision of mold core is extremely high, and machining precision of some cores is less than 0.005mm. Surface of mold core is required to ensure that Ra value is 0.20 or more. These precisions have basically reached high manufacturing precision of imported precision equipment. Protection and special handling are required on polishing process of mold.
In general, there is not much difference in structure between medical injection molding and traditional mold, which is mainly reflected in control of processing technology and processing precision. Use environment of medical injection molding is relatively harsh.

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