Difficulties thin wall mold
Demand for the production of small and light parts has become so thin-walled injection molding machine most need to increase performance. "Thin Wall" is usually defined by the wall thickness of less than 1mm of the portable electronic parts. Large car parts, the "thin wall" can be 2mm. In short, thin-walled products requires a change process: higher pressure and speed, shorter cooling time, changing part ejection and gate arrangement. The following is a thin-wall injection molding machines and molds for injection requirements.
Injection machine: standard injection molding machine can be used to produce a variety of thin-walled products. The current performance of the new injection molding machine considerably more than 10 years ago. Material, gate technology and design advances, further broadening the standard injection machine performance filling of thin-walled parts. However, due to the continuous reduction in thickness, a need for a more specific, the performance of high-speed and high-pressure injection machine. For example, a thickness of less than 1mm of electronic parts, filling time of less than 0.5 seconds and the injection pressure exceeding 210MPa is normal. For thin-wall injection of hydraulic injection molding machine is designed with reservoir pressure, can frequently driven injection and clamping. High-speed and high-performance all-electric injection molding machine and electric / hydraulic injection molding machine also appeared. To be able to withstand the minimum pressure, the clamping force of the new injection molding machine must be 5 to 7 tons / inch (projected area). Further, when the wall thickness is increased to reduce the injection pressure, large templates help reduce bending. Thin-walled products with the rod injection machine template thickness ratio of 2: 1 or lower. The production of thin-walled products, loop injection speed and pressure as well as other processing parameters control helps control at high pressure and high-speed filling and packing.
As for the injection volume, large diameter barrel too often, the proposed injection volume of 40% to 70% of the barrel capacity, thin-walled products significantly shorten the overall molding cycle, it is possible to reduce to a minimum the amount of injection cylinder capacity of 20 % ~ 30%. User when the injection must be very careful, because the material, the small injection volume means that the material in the barrel longer residence time, which will lead to performance degradation products. Mold: Speed is a key factor in the success of thin-walled injection. Rapid filling and high pressure can be a high speed molten thermoplastic material into the mold cavity, thereby preventing the gate freeze. If a standard parts completed within two seconds of filling, then the mold thickness reduction of 25%, it is possible to reduce the filling time by 50%, just one second. One of the advantages is that when the thin-walled injection molding to reduce the thickness, less need to cool the material. With the reduction in the thickness of the molding cycle can be shortened by half. Set reasonable melt conveying device does not prevent hot runner and runner shorten the molding cycle. Use hot runner and sprue bushing helps to shorten the molding cycle to a minimum. In addition, you should also take into account the mold timber. P20 steel is widely used in the conventional molded article, but due to the higher pressure of the thin-walled injection molding, the mold must be made very strong. H-13 and other hard steel for Mould adds additional safety factor. However, the cost may be higher than the mold sturdy 30% to 40% of the standard mold. But the increased costs would normally be offset by increased production performance.