Injection screw is operated for a long time under high temperature, high pressure, high mechanical torque and high friction environment. The first few factors are required by process conditions, and loss caused by friction is inevitable. Generally, screw has undergone surface nitriding treatment to increase surface hardness, that is, to improve wear resistance. However, if cause of wear is ignored and wear is not minimized, working life of screw will inevitably be greatly reduced.
Product diagram of shield is shown in Figure 1. Maximum size of product is ø85.7 mm * 55.20 mm, average thickness of plastic part is 1.50 mm, material of plastic part is HIPS, shrinkage rate is 1.005, and weight of plastic part is 10.5 grams. Technical requirements of plastic parts are that there must be no defects such as peaks, underfilling of injection molding, flow lines, pores, warpage deformation, silver streaks, cold materials, jet lines, and bubbles.
Molding process of two inner side inclined slider core-pulling of plastic part and analysis of influence of mold forming structure on quality of plastic part are introduced, correct selection and design of gating system, design of mold forming part and assembly structure.
PC polycarbonate plastic is an almost colorless glassy amorphous polymer with good optical properties. PC high molecular weight resin has high toughness, Izod notch impact strength is 600~900J/m, heat distortion temperature of unfilled grades is about 130℃. Glass fiber can increase this value by ℃. Flexural modulus of PC can reach more than 2400MPa, resin can be processed into large rigid products.
There are many ways to exhaust mold cavity, but each method must be guaranteed: size of exhaust slot should be designed to prevent material from overflowing into slot while exhaust slot is exhausted; secondly, it should prevent clogging. Therefore, when measuring from inner surface of cavity to outer edge of cavity, height of venting groove above 6-12mm should be about 0.25-0.4mm.
【Abstract】In order to improve injection efficiency and material utilization of connecting rod components, hot runner technology is introduced. Design process includes plastic part analysis, mold design and assembly drawing design. It mainly introduces determination of design plan, selection of mold base and selection of hot runner system. Design process adopts UG full 3D design, which helps to make mold structure intuitive, to find problems and avoid unnecessary errors.
Failure analysis and troubleshooting methods: (1) Improper control of process conditions. Should be adjusted appropriately. (2) Injection capacity of injection molding machine is less than weight of plastic part. A larger injection molding machine should be used. (3) Cross section of runner and gate is too small. Should be increased appropriately. (4) Flow distance of melt in cavity is too long or there are thin-walled parts. Cold slug should be set. (5) Poor mold exhaust, and residual air in mold cavity causes insufficient injection. Exhaust system of mold should be improved. (6) Fluidity of raw materials is too poor. Resin with better flow properties should be used instead. (7) Temperature of barrel is too low, injection pressure is insufficient, or injection time of replenishment is too short, which will also cause short injection. Control amount of related process parameters should be increased accordingly.
When we adjust machine, we often sigh: If mold is transparent, it will be fine! In this way, you can see entire filling process of melt, see how and when defects occurred. When we design a certain glue injection process, whether glue injection process is actually completed according to envisaged requirements, whether starting point is set correctly, we hope to be able to see.
Add granular or powdered plastic into hopper of injection machine. Plastic is heated and melted in injection machine to keep it flowing, then injected into a closed mold under a certain pressure. After cooling and shaping, molten plastic solidifies into desired plastic part.
When plastic part has external thread features, demolding generally adopts opening cavity, ejecting plastic part from core to realize automatic demolding, which is conducive to simplifying mold structure; When demoulding is required in same direction as axial direction of external thread or in vertical direction, a special side core pulling mechanism needs to be designed for side core pulling and demolding. Layout of plastic part to be molded in mold opening plane is closely related to selection of mold release method. In the case that demolding can be completed, ayout of plastic part to be molded in mold should be considered in favor of simplifying mold structure, so as to reduce mold manufacturing cost and ensure reliability of mold mechanism.