Bakelite injection molding machine
injection molding process parameters ①. Temperature A. Bakelite injection molding machine barrel temperature The barrel temperature should be between the viscous flow temperature (or melting point) and the thermal decomposition temperature. The temperature of the plunger barrel is 10-20°C higher than the temperature of the screw barrel. Plastic characteristics: Heat-sensitive plastics such as polyoxymethylene, polyvinyl fluoride, etc. must strictly control the maximum temperature of the barrel and the residence time in the barrel; the thermoplastic plastic with glass fiber should increase the barrel temperature due to poor fluidity. In order to prevent the melt from curing early in the barrel, the temperature of the barrel tends to take a small value. Plastic parts and mold structure: For thin-walled parts, the barrel temperature is higher than thick-walled parts; for parts with complex shapes or with inserts, the barrel temperature should also be higher. The temperature distribution of the barrel generally follows the principle of high front and low back, that is, the temperature of the rear section of the barrel (feeding port) is the lowest, and the nozzle temperature is the highest. For the screw injection machine
, in order to prevent thermal degradation of the plastic due to the shear friction heat between the screw and the melt, the melt and the melt, and the melt and the barrel, the temperature of the front section of the barrel can be slightly lower than the middle section. To judge whether the temperature of the barrel is appropriate, the air injection method can be used to observe or directly observe the quality of the plastic parts. During air injection, if the material flow is uniform, smooth, bubble-free, and uniform in color, the material temperature is appropriate; if the material flow is rough, silver wire or discoloration, it means that the material temperature is inappropriate. B. The temperature of the nozzle of the Bakelite injection molding machine is generally slightly lower than the maximum temperature of the barrel to prevent the molten material from drooling at the nozzle. But it should not be too low, otherwise the melt will have premature solidification at the nozzle and block the nozzle, or premature solidification will be injected into the mold cavity and affect the quality of the plastic parts. C. Bakelite injection molding machine mold temperature The mold temperature is determined by the characteristics of the plastic, the size and structure of the plastic part, performance requirements and other process conditions. Mold temperature ↑, fluidity ↑, density and crystallinity ↑, shrinkage rate and productivity ↓. The mold temperature is usually controlled by a constant temperature cooling medium; there is also a way to maintain a certain temperature by injecting the molten material into the mold to achieve a balance between natural heating and natural heat dissipation; in special cases, resistance wires and resistance heating rods can also be used to maintain a certain temperature. The mold is heated to keep the mold at a constant temperature. But no matter what, for the plastic melt, it is a cooling process. ②. Bakelite injection molding machine injection process pressure A. Bakelite injection molding machine plasticizing pressure (back pressure): refers to the pressure of the melt on the top of the screw when the screw retreats when the screw injection machine is used. The plasticizing pressure increases, the temperature of the melt and its uniformity are improved, the color materials are mixed uniformly, and the gas in the melt is discharged. However, the plasticization rate is reduced and the molding cycle is prolonged. In general operation, under the premise of ensuring the quality of plastic parts, the plasticizing pressure of Bakelite injection molding machine should be as low as possible, generally about 6MPa, and usually rarely exceed 20MPaB. Bakelite injection molding machine injection pressure: refers to the plunger or the top of the screw The pressure applied to the plastic melt. Function: Overcome the flow resistance of the melt flow during the filling process during injection, so that the melt has a certain filling rate; when the pressure is maintained, the melt is compacted and prevented from flowing backward. Size: It depends on the type of bakelite injection molding machine, the type of plastic, the mold structure, the mold temperature, the wall thickness of the plastic part, and the structure and size of the pouring system. Under normal circumstances: injection pressure of high-viscosity plastic> low-viscosity plastic; high injection pressure for thin-walled, large-area, and complex-shaped plastic parts; simple mold structure, larger gate size, lower injection pressure; plunger bakelite Injection pressure of the injection molding machine> screw bakelite injection molding machine; the barrel temperature and mold temperature are high, and the injection pressure is low. Recommended reading: (1) Bakelite injection molding machine, Bakelite injection molding machine brand, famous Bakelite injection molding machine manufacturer  (2) Bakelite vertical injection molding machine, Bakelite vertical injection molding machine brand, well-known Bakelite injection molding machine brand Injection Molding Machine Manufacturer【Machinery】
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