Injection molding machine is one of the common equipment used in plastic processing industry. Usually, it takes a long time to work. Therefore, how to ensure the normal operation of injection molding machine in continuous production is a concern for both injection molding machine manufacturers and users. In order to solve this problem, from the user's point of view, regular preventive maintenance is an effective way to ensure the normal operation of injection molding machine under the premise of correct selection of injection molding machine model. The so-called preventive maintenance is through a series of preventive work and inspection, to avoid machine failure and extend the working life of the components, such as the sudden failure of the downtime into a predictable, planned downtime maintenance or overhaul; find and replace damaged parts, can prevent chain damage and other preventive maintenance purposes.
A, preventive maintenance work (a), the hydraulic part 1. Insufficient hydraulic oil will lead to the oil temperature is easy to rise, air is easy to dissolve in the oil, affecting the oil quality and the normal operation of the hydraulic system, the amount of oil is usually insufficient For insufficient oil or maintenance losses, for this reason, attention should be paid to check the leakage parts, early replacement of worn seals, tighten the loose joints, etc.. After maintenance, the oil quantity of the oil tank should be checked and replenished in time.
2. hydraulic oil temperature The ideal working temperature of the hydraulic system should be between 45℃ and 50℃. The reason is that the hydraulic system is designed according to the selected viscosity of the pressure oil, but the viscosity will change with the change of oil temperature. In turn, it affects the working parts in the system, such as cylinders and hydraulic valves, thus reducing control accuracy and response sensitivity, especially for precision injection machines. At the same time, if the temperature is too high, it will accelerate the aging of sealing parts, making them harden and fracture. When the temperature is too low, the processing energy consumption is high and the operation speed is reduced. Therefore, the operating temperature of hydraulic oil must be closely monitored. There are many reasons for high oil temperature, but most of them are caused by oil circuit failure or cooling system failure.
3. hydraulic fluid One of the important characteristics of oily hydraulic fluid is its chemical stability, i.e. oxidation stability. Oxidation is the main factor that determines the effective service life of hydraulic fluid. The insoluble substances such as wood tar, sludge and carbon residue produced by oxidation will pollute the hydraulic system, increase the wear of hydraulic components, reduce various gaps and block small holes, eventually. It leads to the failure of the hydraulic system. The oxidation rate of hydraulic oil depends on many factors, such as itself and working conditions. Temperature is one of the main factors. Therefore, it is necessary to use suitable hydraulic oil and check the oxidation level of hydraulic oil regularly (from the color of the oil itself) ), and it is absolutely necessary to change the oil actively after a certain working time.
4. Cleaning of oil filter The oil filter plays the role of cleaning the hydraulic oil. Therefore, the oil filter should be cleaned once every three months to keep the oil suction pipe clear and to check whether the oil filter is damaged.
5. Chiller Cleaning Chillers should be cleaned once a year, or depending on whether their working capacity is reduced. Internal clogging or scaling of the chiller can affect the cooling efficiency. The cooling water should be soft water (no minerals).
(2) Electrical parts 1. Wire connectors Check the wires of the connectors, if not tightened, it may cause high temperature or spark damage to the connectors. The joints may also affect the transmission of signals; the joints on the contactor may vibrate due to electromagnetic action. It is easier to loosen, so it is necessary to check the position of the wire connectors and tighten them regularly.
2. motor Generally speaking, the motor is air-cooled. Dust accumulation makes it difficult to dissipate heat. Therefore, it should be cleaned regularly every year. Usually, motor overload circuit breakers are installed in the circuit. The limit current of the protective device is adjustable. The power supply is selected appropriately. Once the overload protector is activated, it should be determined whether the inverter is out of phase, has poor contact, or the oil temperature is too high before pressing the return switch.
3. The tightness of the heating tube and thermocouple heating tube should be checked to ensure effective heat transfer. In normal production, the burning of the heating tube is not easy to find. For this reason, pay attention to the work of the temperature controller to determine whether the heat Whether the tube is normal or not. In addition, a common damage to the heating tube is the wire connection. Due to poor connection, the contact resistance increases, causing the interface to overheat and the interface is damaged by oxidation.
4. The contactor of the electromagnetic contactor used in the electric heating part has a fast loss rate due to frequent movements. If the main contactor overheats and melts and bonds, it may cause the heating temperature to go out of control, so when the contactor is found to be overheated, it will make a sound or If the fire is very large when it is disconnected, it means that it is about to be damaged and should be replaced as soon as possible.
5. microcomputer control part With the application of microcomputer control technology on the injection molding machine, the normal operation of the microcomputer part and its related auxiliary electronic board has put forward higher requirements on the fluctuation of power supply voltage, temperature and humidity of the working environment, seismic resistance of the installation and interference of external high frequency signals. For this reason, the fan used for ventilation and heat dissipation inside the control box is kept in normal operation, and a high-precision power supply is used. Minimize the influence of vibration outside the control box. Aspects of the problem, and regular inspection.
(C), mechanical parts 1, the parallelism of the template The parallelism of the template zui can reflect the situation of the closing part of the mold, the template is not parallel will make the product unqualified and increase the wear and tear of equipment and mold. The parallelism of the template can be initially reflected by the movement of the tail plate and the appearance analysis of the product when the mold is closed, but the specific situation needs to be detected by the micrometer and other instruments. The adjustment of the parallelism of the mold plate must be carried out by familiar personnel according to the steps, otherwise improper adjustment will cause more damage to the machine.
2. Mould thickness adjustment should be done regularly by using the mould thickness adjustment system to adjust the mould thickness back and forth from zui thick to zui thin to ensure smooth movement, which is necessary to avoid failure for machines producing the same mould for a long time.
3. Central lubrication system for all mechanical activities need proper lubrication. The central lubrication system is one of the necessary equipment for the injection molding machine. The oil level of the central lubrication system should be checked frequently to see if it is full. The lubricant used should be clean and free of impurities to ensure that all lubrication locations are supplied with lubricant. Oil lines found to be clogged or leaking should be replaced or repaired immediately. Most mechanical wear occurs due to lack of lubrication, so pay enough attention to lubrication.
4, keep each movement smooth or unstable may be due to improper speed adjustment, speed change and time is not coordinated or mechanical, oil pressure adjustment. This vibration will accelerate the wear of mechanical parts and loosen the fastened screws, so the vibration should be reduced and avoided.
5. Bearing inspection If the bearing makes a strange noise or the temperature rises during operation, it means that the bearing is worn inside. They should be inspected or replaced in time and re-greased.
6. Injection system The injection screw, check ring and barrel constitute the core part of the injection molding machine, which determines the quality and efficiency of processing and must be kept in good working condition. First, take necessary measures to prevent non-plastic debris from mixing into the plastic stream. Also, pay attention to checking the correct clearance between the screw and barrel, and between the check ring and barrel. A normal clearance should seal the plastic backflow and produce plastic. For the action that requires shearing, the screw, check the wear of the screw, check ring and barrel when slow melt action, spots and black spots in the melt, or unstable products are found.
Second, some common causes of failure and solutions (a), the oil temperature is too high abnormally high oil temperature may be due to abnormal cooling system or hydraulic components work under too high a pressure caused by.
1. Cooling system is not normal. 1) Insufficient supply of cooling system. Such as the water raft is not fully opened, the water pressure is not enough or the flow rate of the pump does not meet the requirements.
2) Clogged pipes, such as filters, cooling towers or water pipes.
3) High cooling water temperature, such as insufficient cooling capacity of cooling tower, or damaged or high temperature.
2. High heat generated by hydraulic system. 1) Damaged oil pump, high heat generated by wear of internal parts during high speed rotation.
(2) improper pressure regulation, the hydraulic system in a long-term high-pressure state and overheating.
(3) internal leakage of hydraulic components, such as damaged reversing valves or damaged seals, high pressure oil flow through a narrow space to generate heat.
(2) abnormal noise generation, indicating that the parts are damaged or improperly adjusted. The cause should be repaired according to the location where the noise is generated.
1. Insufficient hydraulic oil in the oil tank. The suction of the oil pump or the dirt of the oil filter can cause the oil pump to be short of oil, causing bubbles in the oil to leak out and hit the blade to produce noise. The solution is to check the oil level to prevent air intake. Clean the oil filter.
2. High viscosity of hydraulic oil increases the flow resistance. It is necessary to replace the proper hydraulic oil.
3. Due to the oil pump or motor bearing or blade damage, the concentricity deviation of the coupling causes noise, it is necessary to adjust the concentricity or replace the parts. 4. The directional valve does not respond but still functions, such as spool wear, internal leakage, burr blockage, inflexible action, and solenoid valve failure due to insufficient current will also generate noise. The solution is to clean the spool, the spool must be replaced with new parts, and the current must be stable and sufficient.
5. The hydraulic components are damaged or the oil pipe is blocked, resulting in noise when the hydraulic oil flows at high speed.
6. The mechanical part is malfunctioning, the bearing is worn out or the machinery lacks lubricant or the parts are loose, the cause should be found and the parts should be tightened or replaced.
Make sure there is enough lubricating oil.
(C) Unstable or unsatisfactory product production Unstable quality of finished products in a stable production cycle may be due to wear or adjustment of mechanical parts.
1. Wear of the screw, check ring and barrel.
2. Damage to the inner seal of the injection barrel and internal leakage.
3. 3. Unstable temperature control of the heating cylinder.
4. 4. The pressure and speed control parts are not normal.
