Several considerations for processing plastic molding
Injection molding is one of several aspects of injection molding. Five elements that meet the needs of injection molding are temperature, speed, pressure, position, and time. Keys to the quality of the controlled molded product is that a qualified product requires control of the above factors. Most quality problems often encountered in injection molding come from quality anomalies caused by five points that are not well controlled.
1. During the processing of plastic molding, the temperature is the first step of injection molding.
Temperature can be divided into the temperature of drying, material, and mold. These are some of the most important factors. The drying temperature is to dry polymer in advance to ensure molding quality, dry and wet of polymer are in a certain amount, normalization of plasticizing (melting) of polymer for smooth filling and molding; Temperature is an important condition for skin size, appearance, and molding cycle. Control affects the cooling rate of the product in the cavity and the appearance quality of the product.
2. In the plastic molding processing process, the speed is divided into the speed of injection molding, melt temperature, loosening, opening, and closing mold, ejector forward and backward.
An increase in injection speed will affect the increase of filling pressure. It will increase flow length, ensure product quality. The high-speed injection is suitable for long-flow products. Melt speed affects plasticizing ability, which is an important parameter for the quality of plasticizing ability. The higher speed, the higher the melt temperature, the stronger plasticizing ability. Loosening speed is to reduce melt specific volume so that the internal pressure of the melting chamber is reduced to prevent its outflow. Opening and closing speed is One of the important conditions to ensure the production and operation of the machine. Ejector forward and reverse speed is to ensure that product is smoothly demolded without deforming product and cracking.
3. Pressure is divided into the pressure of injection, holding, back, mold clamping, mold protection, and ejection.
During the processing of plastic molding, the injection pressure is used to overcome pressure loss of melt from nozzle-runner-gate-cavity to ensure that cavity is filled. Holding pressure is to reduce excessive injection pressure of workpiece which cause mold burst or bend. Backpressure is to avoid impurities in the mold under a high-speed and pressure state which causes mold crushed. Ejection pressure is to prevent the product from being detached from the mold surface and causing defects.
4. In plastic molding processing, the time is divided into a time of cooling, sol, drying, cooling, melting, drying, cycle, injection, and pressure holding.
Molding of product requires a certain period. Injection time determines the size of the product. Holding time is to prevent melt backflow, cooling shrinkage. Cooling time ensures the product solidifies and prevents deformation. Melting time is to ensure melt is sufficient. Drying time Ensure that product does not become elongated, bad, and other factors.
In injection molding processing, there are often unfavorable causes such as damage to the appearance of defective products, wave marks, spray marks, scratches, peeling, bubbles, and film removal that are all affected by the above five factors.
5. In the plastic molding processing process, the position can be divided into a position of mold opening, ejection backward stroke, metering stroke, injection stroke, buffer amount.
The mold opening position is to ensure normal operation of demolding take-up. Ejector retracting stroke has the effect of partial spring reset on ejector limit protection; the Metering stroke is to ensure that there is enough plastic filling mold to ensure product quality. Buffering amount prevents mechanical failure of screw head from coming into contact with nozzle, and precision can be controlled.