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2.1 the composition of injection molding machine
A general-purpose injection molding machine mainly includes the following parts
Injection device, its main function is to make the uniform plastic into molten state, and at a certain pressure and velocity to a certain liquid injected into the mold cavity. So the injection device should have good plasticizing and accurate measurement of performance, and the injection of molten material can provide enough pressure and speed. Injection device by plasticizing unit commonly (barrel, screw, nozzle, etc.) hopper, metering device, screw transmission device, injection and mobile devices, etc.
Clamping device, clamping device: it is to ensure that the forming mold reliable closure and implementation of mold opening and closing action, namely the working parts of molding products. Because when injected into molten material also has certain pressure in the cavity, which requires the clamping device gives enough close to the mould force (usually called mould clamping force or clamping force) to prevent the pressure of molten material under the action of the mould is opened and lead to the precision of the products overflow edge or make products drop, the clamping device is mainly composed of template, tie rod, mold clamping mechanism, products of ejection device and exit, etc.
Hydraulic drive and electrical control system: injection molding is made of plastic melt, closing molds, injection molding, pressure maintenance, products curing finalize the design, mould opening out products process of continuous production process, such as hydraulic and electrical reservation is in order to ensure the injection moulding machine according to process requirements, pressure, speed, temperature, time and action program, accurate working drive and control system, set up by the direction of hydraulic parts mainly include power oil pump, valve, flow valve and pressure control valve; Accessory device; Line and the box body. Electrical part is mainly composed of dynamic action program and heating control.
2.2 the working process of the injection moulding machine
Each injection molding machine action program can not completely consistent, but need to complete the technology content of the basic process, its action is expressed as roughly
1, mold closing and tight
Injection molding machine molding cycle generally start from mold closing, mould rapid low-pressure closed in the first place, when moving die and die soon approach, mode of power system and automatic switch to low pressure, low speed, when confirm there is no foreign body in the mould, and then switch to high pressure and mold close tightly.
2, moved forward with injection injection device
Upon confirmation of the mold to achieve the required degree of close tightly after, the reach injection device, nozzle and the mould joint. When the nozzle and mold after fully fit, can to the injection cylinder connected to the pressure oil. Connects with the oil cylinder piston rod and the screw, with high speed will head the molten material into the cavity. At this point the screw head pressure acting on the molten material for injection force, also known as a pressure.
3, pressure maintenance
Into the cavity of the molten material, due to the low pressure mold cooling effect, make the injection shrinkage cavity of molten material. To produce quality density of the products, so the molten material still need to maintain a certain pressure to shrink. At this point, the screw pressure acting on the molten material, called the holding pressure, also known as the secondary stress.
4, product cooling and plasticizing
When the pressure in the cavity of molten material loss from gate (gate closed) when the possibility of reflux, injection pressure maintaining pressure in cylinder can remove (the clamping cylinder pressure can also be removed), make the products within the mold cooling stereotypes. At this point the screw under the driving of hydraulic motor rotation, will come from the mouth of granulated plastic and conveying, and make its plasticizing. As a result of the action of the screw head pressure melting, the screw back in rotating at the same time. Screw in plasticizing amount of backwards, which indicates that the screw head accumulates the amount of liquid volume. When the screw back to the measurement value, the screw is stop running, ready for the next injection. Products cooling and plasticizing general overlap in time, in general, plasticizing time less than products required screw cooling time.