The influence factors of injection molding processing and forming process of injection products
varieties of plastic injection molding processing and forming process of the crystallization taxiing on high volume change, high pressure injection molding processing, the molten material viscosity difference is small, the interlaminar shear stress is small, large elastic rebound after demoulding, so the shrinkage can be just the right amount of reduced injection tooling, injection molding processing at high temperature, shrinkage, but the direction is small.
when the pressure injection molding processing pressure increase is molten material shear effect, also increase the liquidity, especially sensitive, POM, PE, so control injection molding processing of forming time pressure to control liquidity. Molding, also can control the material temperature, mold temperature and injection molding processing factors such as pressure, injection speed to properly adjust the filling conditions to meet the needs of the molding.
products injection molding process
molding is mass production of some complex shape parts used when a processing method. Specific refers to the material will be heated to melt by high pressure into the cavity, after cooling solidification, molded products.
a, temperature control,
1, cylinder temperature, the injection molding process, the need to control the temperature of the material barrel temperature, nozzle temperature and mould temperature, etc. The first two main influence plastic plasticizing temperature and flow, and then a temperature is mainly influence plastic flow and cooling. Each kind of plastic flow with different temperature, the same kind of plastic, due to different sources or brand, the flow temperature and decomposition temperature is little different, this is due to the different average molecular weight and molecular weight distribution, plastic in different type of injection machine of plasticizing process is also different, so choose the cylinder temperature is not the same.
2, nozzle temperature, nozzle temperature is usually slightly below the cylinder. High temperature, this is to prevent the molten material in straight through the nozzle possible & quot; Salivate phenomenon & quot; 。 Nozzle temperature also cannot too low, otherwise will cause early setting of melting and the nozzle clogging, or due to early coagulation material into the cavity affect the performance of the products.
3, mold temperature, mold temperature has great influence on the intrinsic properties of the products and apparent quality. Mold temperature is determined by the size of the plastic, of crystalline products and structure, performance requirements, and other process conditions, Melting temperature, injection speed and injection pressure, molding cycle, etc. ) 。
2, pressure control
in the process of the injection pressure including the plasticization and injection pressure, and directly affect the quality of plastic plasticizing and products.
1, the plasticizing pressure: ( Back pressure) USES screw injection machine, screw at the top of the molten material in the screw rotating back pressure is called the plasticizing, which is also called back pressure. The size of the pressure can be found on the overflow valve to adjust the hydraulic system. In injection, the size of the plasticizing pressure is depending upon the design of the screw, the product quality requirements, and the type of plastic and needs to change, if the situation and the screw rotation speed is constant, increase plasticizing pressure will strengthen shearing action, which will raise the temperature of the melt, but will reduce the plasticizing efficiency, increase the current and leakage flow, increase the driving power.
in addition, the increase of plasticizing pressure often can make the melt temperature uniformity, color mixing and discharge gas in the melt. The decision of the general operation, the plasticizing pressure should be on the premise of guarantee the products quality is lower, the better, the specific values are vary with the varieties of the plastic, but usually rarely more than 20 kg/cm2.
2, injection pressure: in the current production, almost all of the injection pressure of injection machine are in piston or screw at the top of plastic pressure ( By the oil pressure conversion) Shall prevail. Injection pressure in injection molding, the role of is, to overcome the flow resistance of plastic flowing from cylinder cavity, given the rate of molten material molding and compaction of molten material.
3, molding cycle
time required to complete an injection molding process, molding cycle, also known as the molding cycle. It includes the following several parts: molding cycle: molding cycle directly affect the labor productivity and utilization rate of equipment. In the process of production, therefore, should be on the premise of guarantee quality, try to shorten the molding cycle time of all.
in the molding cycle, injection time and cooling time. Important, they have a decisive influence on the quality of products. Mold filling time of injection time is directly on the mold filling rate, for the production of molding time is about 3 - general 5 seconds.
the holding time of injection time is the cavity pressure time, plastic in the large proportion in the whole injection time, usually about 20 - 120 seconds ( Thick parts can be up to 5 ~ 10 minutes) 。 At the gate before freezing, melting the holding time of how many, dimensional accuracy of products are affected, if in the future, no effect. The holding time. Value, known it depends on the material temperature, mold temperature and the mainstream and the size of the gate. If the size of the mainstream way and gate and process conditions are normal, usually that is product shrinkage range are obtained. Small pressure value shall prevail.
cooling time is mainly decided by the thickness of products, thermal and crystallization properties of plastics, and mould temperature, etc. The end of the cooling time should be in place to ensure that products mold release when not cause changes for the principle, general about cooling timeliness between 30 to 120 seconds, cooling time is too long is not necessary, not only reduce the production efficiency, the complex parts will also cause demoulding difficulty, even the forced demoulding will produce mold release stress.
the other molding cycle time, and is continuous and automatic and continuous production process and the degree of automation and so on.