The principle of injection molding machine

Date：2011/12/6 17:47:23

Injection molding machine has a complex shape to a shape, size, precision, or with metal inserts dense texture of the plastic products are widely used in national defense, electronics, automotive, transportation, building materials, packaging, agriculture, culture, education health and daily all areas of life. Injection molding of various plastics processing has a good adaptability, high capacity and easy to automate. The rapid development in the plastics industry today, both in quantity and injection molding machine or varieties have played an important role, the production of plastic molding equipment, the total number of 20% - 30%, making it the fastest growing plastic machinery, production volume one of the largest models. According to statistics from 1996 - 1998, 8383 China's exports of injection molding machine (sets), imported injection molding machines 42959 (sets), in which injection molding machine in China in 1998 production reached 20,000 units, its sales accounted for total sales of presses 42.9%. The working principle of injection molding machine and injection with a syringe similar, it is with the screw (or plunger) of thrust, will have a good molten plastics (ie, viscous flow) closed well into the plastic injection mold cavity, The products obtained after curing shaping process. Injection molding is a cyclic process, with each cycle including: dosing - molten plastics - pressure injection - filling the cooling - Kai-mode pickup. Remove the plastic parts and then re-closed mode, the next cycle. Injection molding is a cyclic process, with each cycle including: dosing - molten plastics - pressure injection - filling the cooling - Kai-mode pickup. Remove the plastic parts and then re-closed mode, the next cycle.
General injection molding machine including injection device, clamping devices, hydraulic systems and electrical control systems and other parts.

        Injection device: its main role is to make plastics plastic evenly into the molten state, and with sufficient pressure and injection speed will melt into the mold. It mainly consists of plastics parts (barrel, screw, or plunger, nozzle, etc.), hopper, screw gear (motor oil, etc.), injection cylinder, move the cylinder block composed of injection.

        Clamping device: it is to ensure that mold is closed and the achievement of a reliable opening and closing action, and take out the product model parts. As the melt at high pressure into the mold cavity in order to produce products without causing locking mold flash or affect product quality, we must put enough of the mold clamping force (ie, clamping force). Clamping device includes a fixed template, mobile template, after the wall, before and after the template used to connect the rod, clamp cylinder, the top of the cylinder, transfer mode devices and other components.

        Hydraulic system and electrical control system: it is to ensure that pre-injection molding machine according to process requirements (such as pressure, speed, temperature, time, etc.) and action program to work effectively and accurately set the power and control systems.

        Generally screw-type injection molding machine process: first by adding granular or powdered plastic cylinder machine, and through the rotation of the screw and barrel wall heating the plastic to become molten state, and mold and injection machine front seat shift, snapping the nozzle mold gate road, then the oil pressure to the injection cylinder Walter, screw forward to the high pressure and faster speed will melt into the closed mold temperature is lower , after a certain period of time and keep the pressure (also known as pressure), cooling, so that curing can mold removal products (packing the cavity to prevent reflux in the melt, add material to the mold cavity, and to ensure that products have a certain density and dimensional tolerances). The basic requirement is injection molded plastics, injection and molding. Plastics molding products to achieve and guarantee the quality of the premise, and to meet the requirements of molding, injection must ensure there is enough pressure and speed. Meanwhile, high pressure injection, corresponding to the cavity produced in a high pressure (the average cavity pressure is generally between 20 ~ 45MPa), so there must be large enough clamping force. Thus, the injection mold device is a device harmony key component injection molding machine.

        Injection molding machine of action program
Mold closed → → → injection nozzle forward → → packing → pre-plastic nozzle loose back → back → cooling → → top of the mold → → needle back door.

        Injection molding machine operation program: injection molding machine operations include control keyboard operation, electrical and hydraulic control system operating system operating in three areas. Separate injection process action, feeding movements, injection pressure, injection speed, the top choice of type, cylinder temperature of each of the monitoring, injection pressure and back pressure regulation, etc.

        The evaluation of plastic products are mainly three aspects, first is the appearance of quality, including integrity, color, gloss, etc.; second is the relative position between the size and accuracy; third is the appropriate use of physical properties, chemical properties, electrical properties. These quality requirements and product use occasions, according to the different requirements of different scales. Products, mainly due to defects in the mold design, manufacturing precision and wear and tear and so on. But in fact, plastic processing plants often suffer from technical staff to use technology to make up the face of the mold problem and the effectiveness of defect is not caused by a difficult situation.
Regulation of the production process technology is to improve product quality and yield the necessary means. As the injection molding cycle itself is very short, if the process conditions are handled badly, waste will be endless. In the adjustment process when the best time to change only one condition, to observe several times, if the pressure, temperature, time all the words with the tune, it could easily lead to confusion and misunderstanding, a problem do not know what reason. Adjustment process measures, the means are manifold. For example: to solve the problem there is dissatisfaction with products Note dozen possible solutions, to select the crux of the problem-solving one or two major programs, in order to really solve the problem. In addition, the solution should also pay attention to the dialectical relationship. For example: the emergence of depression products, sometimes to raise the melt temperature, sometimes to reduce the feed temperature; sometimes to increase the quantity, and sometimes to reduce the fluxes. Reverse steps to recognize the feasibility of solving the problem.

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