Injection molding machines are capable of molding plastic products with complex shapes and precise dimensions or with metal inserts at a time. They are widely used in national defense, electromechanical, automotive, transportation, building materials, packaging, agriculture, culture, education, health and daily life. Life in all areas. The injection molding process has good adaptability to the processing of various plastics, has a high production capacity, and is easy to implement automation. In the rapid development of the plastics industry today, injection molding machines occupy an important position both in quantity and variety, and thus become one of the fastest growing and most productive machines in the plastics machinery industry. China's plastics processing companies are located in all parts of the country, and the technical level of equipment is uneven. Most of the processing companies' equipment needs technological transformation. Over the past few years, the technological progress of China's presses industry has been remarkable. In particular, the gap between the technological level of injection molding machines and foreign brand-name products has been greatly reduced. Significant changes have been made in the level of control, internal product quality and appearance. Selecting domestically produced equipment can also produce products with comparable quality to imported equipment, with less investment. These create conditions for the technological transformation of the company. To have good products, we must have good equipment. The wear and corrosion of equipment is a natural law. With this rule, people can prevent or reduce equipment wear and corrosion, extend the life cycle of the equipment, and ensure the equipment's good rate. In order to strengthen the use, maintenance, and management of plastics machinery, relevant departments in China have formulated related standards and implementation rules that require the equipment management and production companies to “scientifically manage, use, and lubricate the equipment properly.†Careful maintenance, regular maintenance, planned maintenance, improved equipment availability, and the equipment is always in good condition.This article has written about the knowledge and technical information of the injection molding machine maintenance and maintenance for the management of equipment management and production companies and technical personnel Plastic injection molding technology was developed from the late 19th century to the early 20th century based on the principle of die casting, and is one of the most commonly used methods in plastics processing. The method is applicable to all thermoplastic plastics and partially thermoset plastics (about the total amount of plastics 1/3 of the amount.) 1.1 Working principle of injection molding machine The working principle of injection molding machine is similar to that of injection syringe. It uses the thrust of screw (or plunger) to melt the melted state (ie, viscous flow). The plastic of the state) is injected into a closed mold cavity, and after curing, the product is obtained. Arts process Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding - melting plasticization - pressure injection - filling cooling - opening the mold taking parts. After taking out the plastic parts, the mold is closed again for the next cycle. 1.2 Structure of Injection Molding Machine Injection molding machine is divided into plunger injection molding machine and screw injection molding machine according to the plasticization method; The operation modes are divided into automatic, semi-automatic, and manual injection molding machines.(1) Horizontal Injection Molding Machine: This is the most common type, in which the mold clamping portion and the injection portion are on the same horizontal center line, and the mold is opened in the horizontal direction. Its features are: short body, easy operation and maintenance, low center of gravity, stable installation, automatic drop by gravity after ejecting the product, and easy automatic operation.At present, the injection molding machine on the market adopts this type (2) Vertical Injection Molding Machine: The mold clamping part and the injection part are on the same vertical center line, and the mold is opened in the vertical direction. Easy to insert inserts, loading and unloading the mold more convenient, materials falling from the hopper can be more uniform plasticized, but the product is not easy to automatically drop after the top, you must manually remove, easy to achieve automatic operation.Vertical injection molding machine should be used for small Injection molding machines generally use more than 60 grams of injection molding machines, and large and medium-sized ones are not suitable for use.(3) Angle injection molding machines: The injection direction and the mold interface are on the same surface, which is especially suitable for machining centers. It is not allowed to leave traces of flat products with gate marks. It covers an area smaller than that of horizontal injection molding machines, but inserts placed in molds are liable to sloping down. This type of injection molding machine is suitable for small machines. Die-spindle type injection molding machine: It is a special multi-station operation injection molding machine, characterized by the use of a rotating disc type mold structure, the mold rotates around the shaft.This type of injection molding machine gives full play to the plasticization of the injection device The ability to shorten the production cycle and increase the production capacity of the machine makes it particularly suitable for the production of large quantities of plastic products requiring a long cooling set-up time or requiring more auxiliary time due to the placement of inserts. However, due to the large and complex mold clamping system, the clamping force of the mold clamping device is often small, so this injection molding machine is used in the production of plastic shoe soles and other products. General injection molding machines include injection devices, mold clamping devices, hydraulic systems, and electrical control systems. The basic requirements for injection molding are plasticization, injection and molding. Plasticization is the prerequisite for achieving and ensuring the quality of molded products. In order to meet the requirements of molding, injection must ensure sufficient pressure and speed. At the same time, due to the high injection pressure, a high pressure is generated in the mold cavity accordingly (the average pressure in the mold cavity is generally between 20 and 45 MPa, see Table 1), so a sufficient clamping force must be provided. It can be seen that the injection device and the mold clamping device are key components of the injection molding machine. 1.4 Operation of Injection Molding Machine 1.4.1 Action Procedure of Injection Molding Machine Nozzle forward→injection→maintain pressure→pre-plastic→shrinkage→nozzle retreat→cooling→open mold→top ejection→back needle→open door→close door→clamping→nozzle advance . 1.4.2 Injection Molding Machine Operation Items: The injection molding machine operation items include control keyboard operation, electrical control cabinet operation and hydraulic system operation. The injection process operation, feeding operation, injection pressure, injection speed, ejection type selection, temperature and current and voltage monitoring of the barrel, adjustment of injection pressure and back pressure are performed. 1.4.2.1 Injection Process Action Selection: The general injection molding machine can be operated manually or semi-automatically and fully automatically. Manual operation is in a production cycle, each action is achieved by the operator toggle the operating switch. It is usually used when the test machine adjusts the mold. During semi-automatic operation, the machine can automatically complete a working cycle, but after each production cycle is completed, the operator must pull open the safety door, remove the work piece, close the safety door, and the machine can continue production in the next cycle. In fully automatic operation, the injection molding machine can automatically enter the next working cycle after completing a work cycle. There is no need to stop and control and adjust during normal continuous operation. However, it should be noted that if automatic work is required, (1) do not open the safety door halfway, otherwise the automatic operation is interrupted; (2) feed in time; (3) if you use electric eye sensor, you should pay attention not to cover the electric eye. In fact, in the fully automatic operation, it is usually also necessary to temporarily stop halfway, such as spraying mold release agent to the machine mold. In normal production, semi-automatic or fully automatic operation is generally used. When the operation starts, the operation mode (manual, semi-automatic, or fully automatic) should be selected according to the production needs, and the manual, semi-automatic, or fully automatic switch should be dialed accordingly. The semi-automatic and fully automatic working procedure is determined by the line itself. The operator only needs to change the speed and pressure, the length of the time, the number of thimble, etc. on the surface of the electric cabinet. It will not be caused by the operator's mis-key. Make the work program appear confused. When each action in one cycle is not adjusted properly, manual operation should be selected first, after confirming that each action is normal, then semi-automatic or fully automatic operation is selected. 1.4.2.2 Selection of Preplasticizing Action According to whether pre-plastic feeding before or after filling, whether the nozzle leaves the mold, the injection molding machine generally has three options. (1) Fixed feeding: Before and after pre-molding, the nozzles are always attached to the mold, and the injection seat does not move. (2) Pre-feeding: The nozzles are pre-molded with the mold, the pre-molding is completed, the injection seat is back, and the nozzle leaves the mold. The purpose of this method is to use the mold injection hole to assist the nozzle during pre-molding to avoid the molten material flowing out from the nozzle when the back pressure is high. After the pre-molding, the nozzle and the mold can avoid heat transfer for a long time and affect the heat transfer. The respective temperature is relatively stable. (3) After feeding: After the injection is completed, the injection seat is retreated, the nozzle leaves the mold and is then pre-molded, and the pre-molding is completed and then the seat is advanced. This action is suitable for plastics with particularly narrow processing temperatures. Due to the short contact time between the nozzle and the mold, heat loss is avoided and solidification of the melt in the nozzle hole is avoided. After the injection is completed and the cooling timer is timed, the pre-molding operation starts. The rotation of the screw melts the plastic and pushes it in front of the screw head. Due to the one-way valve functioned by the back-and-forth ring of the screw, the molten plastic accumulates on the front end of the barrel and forces the screw backwards. When the screw is retracted to a predetermined position (this position is determined by the travel switch, the distance to control the screw retreat, to achieve quantitative feeding), the pre-plastic stop, the screw stops rotating. This is followed by a retracting action. The retraction is a slight axial retraction of the screw. This action allows the pressure of the molten material collected at the nozzle to be relieved, and overcomes the problem of “retaining flaws†caused by the imbalance of the pressure inside and outside the barrel. phenomenon. If retraction is not required, the retraction stop switch should be adjusted to the proper position so that the retraction stop switch is pressed at the same time that the pre-plastic stop switch is pressed. When the screw is retracted to move back to the pressure stop switch, the retraction stops. Then the injection begins to recede. When the injection seat retreats to the pressure stop switch, the injection stop stops. If the fixed feeding mode is adopted, the position of the limit switch should be adjusted. General production mostly uses fixed feeding methods to save injection seats and retreat operation time, speed up the production cycle.
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