First of all, it is necessary to add granular or powdered plastic into the extruder barrel, and the plastic is melted by the rotation of the extruder screw and the heating of the outer wall of the extruder barrel. Then the machine closes the mold and moves the injection seat forward to make the nozzle close to the gate of the mold. Next, it is necessary to pass pressure oil into the injection cylinder to push the extruder screw forward so that the melt is injected at high pressure with a high speed into the closed mold with a lower temperature. After a period time of holding pressure, it can be solidified and formed through cooling. Next, the mold can be opened and you can take out the product (the purpose of holding pressure is to prevent the reflux of molten material in the cavity and fill the cavity with the material to ensure that the product has density and dimensional tolerance).
The basic requirements of injection molding are plasticization, injection and molding. Plasticization is the premise to realize and guarantee the quality of molding products. The injection must ensure sufficient pressure and speed to meet the requirements of molding. At the same time, due to the high injection pressure, correspondingly high pressure will be generated in the cavity (the average pressure in the cavity is usually between 20 and 45 MPa). Therefore, there must be sufficient clamping force. Therefore, it can be seen that the injection device and the mold device are the key components of the injection machine.
This is a necessary way to improve the quality and output of products. Since the injection cycle is very short, there will be an endless stream of waste products with insufficient process conditions. Several observations are required when adjusting the process to change only one condition at a time. If pressure, temperature, and time are all adjusted together, it is easy to cause confusion and misunderstanding and you will not know the reason if something goes wrong. The measures and means of adjusting double alloy screws are in many aspects.
(1) If the inner surface of the extruder barrel is not severely worn or scratched, it can be ground and polished on a lathe with an oilstone or emery cloth.
(2) When the inner surface of the extruder barrel is severely worn, it is necessary to check the depth of the wear groove first. The surface of the inner hole of the extruder barrel can be repaired after calculating whether there is a heat-treated hard layer on the inner wall of the extruder barrel after the wear layer is removed. After grinding, the inner surface roughness Ra of the extruder barrel should not be greater than 1.6 üm. The tolerance of the hole axis is precision processed according to GB1184-80 level 7. If there is no heat-treated hard layer on the inner surface of the barrel after the mold is repaired, it can be set with gold sleeves in the barrel. Also, the centrifugal casting method can be used to cast a layer in the inner wall of the barrel for use after machining and grinding.
