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Gas-assisted injection molding

by:CSSSLD     2021-01-23
In general, error of precision injection molding machines manufactured should be in & plusmn; 0. Within 5%, injection pressure fluctuations is relatively stable, the control system can match and gas control unit, air floating device by the nitrogen generator, control unit and nitrogen recycling equipment. Stationary control unit is the pressure control valve installed directly in the injection molding machine, electronic control system in injection molding machine control box, that is, the control unit and the injection molding machine is even as a whole.

the location of the thermocouple to the correct temperature control has a decisive role. In general, are the requirements for the position of the thermocouple heat slower. If the small distance between the heater and the flow channel, to set the thermocouple, thermocouple can be set up near the port near a heater. Gas assisted injection molding technology is in the 1980 s began using a new technology, it combines the advantages of structural foam molding and injection molding together, can reduce the pressure of the melt in the mold cavity, and can avoid structural foam molding of rough surface, can be on the premise of guarantee the quality of products greatly reduce the production cost, has the good economic efficiency.

activity core method is set in the mold cavity core activities, first of all make the core activities in the longest stretch out position, the injection molding of plastic melt in cavity until cavity and pressure, and then inject gas, activity cores from the cavity exit to give up the required space, retreated to the shortest stay active core out higher gas pressure to achieve the feeding position. Because of the gas-assisted molding by controlling the amount of plastic injection mold cavity open control parts of hollow ratio and the shape of the airway, so the gas-assisted molding injection volume and injection pressure of injection molding machine high accuracy requirements.

gas-assisted molding technology process is first to inject the plastic melt in the mold cavity, and then to the plastic melt in the injection of compressed gas, with the aid of the role of the gas drive parts of plastic melt into the mold cavity, the plastic forming and intact hollow section shape. This process compared with common injection molding, one more gas injection phase, and plastics mold release before instead of plastic melt injection pressure of gas by pressure.

forming parts of gas in the formation of the hollow part called the airway. Compressed gas nitrogen is generally selected because of its cheap, easy and does not react with plastic melt. Depending on the specific process, molding in gas-assisted molding can be divided into standard, deputy cavity displayed, melt flow method and the activity of four core method. Standard is displayed to the mold cavity inject the first accurate weighing of plastic melt.

the sprue bushing also known as the gate. When the sprue bushing with less than 20 mm, the height of the heat flow but I don't have to set up special heating device, by means of injection molding processing and the temperature of the heat flow but heating can, if the height is more than 20 mm, you need to configure the annular heater. Runner bushing in the plastic melt flow layer thickness should be greater than 5 mm, and to set up the taper so that cleaning up. Runner bushing with the way the heat flow but has three, the hot-pressing way the thread, flange cooperation way, way. These three ways, prevent leakage is the most effective way to hot pressing, flange cooperate with screw fastening and with stainless steel o-rings to prevent leakage, plastic thread cooperate way is convenient for assembly, but easy to leak.

vice cavity is displayed outside of the mold cavity set a pair of cavity can be the same as the cavity. First vice cavity, close to the injection molding of plastic melt in cavity until cavity and pressure, and then open cavity, the cavity inside the injection gas, due to the penetration of the gas excess melt into the cavity. When the gas penetration to a certain degree of closed cavity, higher gas pressure of the melt in the cavity pressure and finally open mold ejection plastic parts. Vice cavity with the method of melt flow and molding in similar, different is the backflow of melt mold no vice mold, gas injection spare not melt into the deputy cavity, but is expected to flow back to the injection molding machine barrel.

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