Plastic products in many industries have been widely used, so the plastic processing method of plastic injection molding technology to carry out the latest research is of great significance. In this paper, the plastic injection molding technology in the gas-assisted injection molding, water-assisted injection, for example, analysis of its technical principles, characteristics, application and new development.
Plastic injection molding; technology; new development
As an important plastic processing method, plastic injection molding can produce a precise and complex plastic product with a shorter production cycle and an automated production method. After injection molding out of plastic products can be widely used in electronics, medical equipment, automotive and other industries. With the development of the economy, all walks of life should be at the lowest cost to participate in market competition, which requires plastic materials used in the lower cost of materials, a wider range of products in the size and appearance requirements, but also requires more and more The more accurate. After years of continuous practice, Plastic Injection Molding people in the injection industry, gas-assisted and water-assisted injection molding, precision injection molding, micro-injection, vibration injection, and so continue to research in various fields, and made some progress.
Plastic injection molding:
(1) plastic injection molding machine small capacity. When the quality of the product exceeds the actual maximum injection quality of the injection molding machine, it is clear that the amount of material is made better. If the quality of the product is close to the actual injection molding quality of the injection molding machine, there is a problem that the plasticization is not sufficient and the heating time in the barrel is insufficient. As a result, the appropriate melt can not be supplied to the mold in time. Plastic Injection Molding This situation only to replace the large capacity of the injection molding machine to solve the problem. Some plastics such as nylon (especially nylon 66) melting range is narrow, the greater the specific heat, the need for plasticizing capacity of the injection molding machine to ensure the supply of materials.
(2) thermometer shows the temperature is not real, bright high real low, resulting in material temperature is too low. This is due to temperature control devices such as thermocouple and its line or temperature millivolt failure, or because the distance from the heating point of the electric ring aging or burning, Plastic Injection Molding heating failure and never found or no timely repair replacement.
(3) nozzle hole diameter is too large or too small. It is too small, because the flow diameter is small, the specific volume of the material increases, easy to chill, plug the feed channel or consume the injection pressure; too large, the flow cross-sectional area, the plastic mold per unit area pressure is low A small situation. At the same time, non-Newtonian plastics such as ABS do not get a large shear heat and can not make the viscosity drop caused by filling difficult.
Nozzle and the main channel entrance with the bad, Plastic Injection Molding often occur outside the mold material, mold filled with dissatisfaction with the phenomenon. The nozzle itself or the main channel entrance spherical damage, deformation, and the impact of good cooperation with each other; Note mechanical failure or deviation, so that the nozzle and the main channel axis to produce tilt Displacement or axial compression surface detachment; nozzle diameter than the main channel inlet ball diameter, due to the edge of the gap, in the flash material squeeze gradually increase the axial thrust of the nozzle will cause the product note dissatisfaction.
(4) plastic frit blockage feed channel. As the plastic in the hopper dryer local melting agglomeration, or barrel feed section temperature is too high, or improper choice of plastic grade, or plastic containing too much lubricant will make the plastic into the feed port diameter position or screw From the screw deep groove within the premature melting, aggregates and fritters bonded to each other to form a "bridge", plug the channel or wrap the screw, with the screw rotation for circumferential sliding, can not move forward, Plastic Injection Molding resulting in material interruption or irregular fluctuations The This situation is only in the chisel channel, excluding the block before they can be fundamentally resolved.
(5) nozzle cold material into the mold. Injection molding machines are usually fitted with straight through nozzles due to pressure loss. However, if the barrel front and nozzle temperature is too high, or in the high pressure state of the front end of the barrel material is too much, resulting in "salivation", so that the plastic injection of the mold and open the case, accidentally first into the main channel entrance In the cooling effect of the template hardened, and hinder the smooth melt into the cavity. At this time, should reduce the barrel front and nozzle temperature and reduce the barrel of the storage capacity, reduce the back pressure to prevent the front end of the barrel melt density is too large.
(6) injection cycle is too short. As the cycle is short, Plastic Injection Molding the temperature is too late to keep up with the lack of material, when the voltage fluctuation is particularly evident. According to the supply voltage to adjust the cycle accordingly. Adjustment generally do not consider the injection and packing time, the main consideration from the completion of the adjustment to the screw back to the period of time, neither affect the filling molding conditions, but also to extend or shorten the material in the barrel of the warm-up time.