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Injection molding machine is one of the commonly used equipment in the plastic processing industry, usually it has to work for a long time, so how to ensure that the injection machine in continuous production normal and stable work, whether for the injection machine manufacturer or users is a worthy of attention and efforts to solve the problem, in terms of user perspective, in the correct selection of injection model under the premise, regular preventive maintenance is an effective way to ensure the normal operation of the injection machine. The so-called preventive maintenance is a series of preventive work and inspections to avoid machine failure and extend the working life of some parts, such as turning sudden failures that cause production downtime into foreseeable and planable shutdowns for repair or overhaul; The purpose of preventive maintenance is to find and replace damaged parts in time and prevent cascading damage. At the same time, in order to achieve the best injection molding machine performance and extend the service life, improve the durability of the machine, the machine regular inspection and corresponding repair and maintenance is completely necessary preventive maintenance work as follows:
Productivity: Reducing downtime and maintaining uptime can improve productivity;
Machine accuracy: timely replacement of aging or worn parts can maintain the accuracy level of the machine;
Part life: Regular replacement of vulnerable parts, proper adjustment and lubrication, and proper environmental conditions (temperature, humidity, dust adhesion) can extend the life of parts.
Preventive maintenance
Injection machine is a collection of hydraulic, electrical, mechanical and other technology in one of the equipment, with the maturity and development of various technologies, the combination of the three is closer, so the preventive maintenance of the injection machine work is according to hydraulic, electrical, mechanical three to describe.
Hydraulic section
Hydraulic oil volume
Insufficient oil will cause the oil temperature to rise easily, air is easy to dissolve into the oil and affect the normal operation of oil quality and hydraulic system, insufficient oil is usually caused by oil leakage or repair loss, for this daily should pay attention to check whether there is a leakage part, replace worn seals as soon as possible, tighten loose joints, etc., after maintenance to check the amount of oil in the tank, timely replenishment.
Hydraulic oil temperature
The ideal working temperature of the hydraulic system should be between 45 degrees and 50 degrees, because the hydraulic system is designed according to a selected pressure oil viscosity, but the viscosity will change with the oil temperature, which in turn affects the working components in the system, such as cylinders, hydraulic valves, etc., so that the control accuracy and response sensitivity are reduced, especially for precision injection machines. At the same time, too high temperature will also accelerate the aging of the seal, causing it to harden and chip; If the temperature is too low, the processing energy consumption is large, which reduces the operating speed. Therefore, it is necessary to pay close attention to the operating temperature of the hydraulic oil. There are various reasons for excessive oil temperature, but most of them are attributed to oil circuit failure or cooling system failure.
Hydraulic oil quality
One of the important qualities of hydraulic oil is its chemical stability, that is, oxidation stability. Oxidation is the most important factor determining the effective service life of hydraulic oil, oxidation generated wood tar, oil sludge and carbon residue and other insoluble substances will pollute the hydraulic system, and increase the wear of hydraulic components, reduce various gaps, plug small holes, and eventually cause the hydraulic system to fail. The oxidation rate of hydraulic oil depends on many factors such as itself and working conditions, of which temperature is one of the main factors, so to use suitable hydraulic oil, and regularly check the degree of oxidation of hydraulic oil (judging from the color of the oil itself), it is absolutely necessary to actively change the oil after a certain number of working hours.
During the use of the injection molding machine, it is necessary to frequently check the level of pressure oil, oil pump pressure and the cleanliness of pressure oil, and when encountering wet weather, the concentration of pressure oil must be checked daily, and the water pipe must be checked frequently to avoid water mixing in the pressure oil and causing the oil filter to blockage. Check the inside of the tank frequently to keep it clean and prevent debris from falling in. Replenish pressure oil on time. For the lubrication of each moving part, each stroke switch button, screw tightening, and whether the oil pipe and joint part leakage, etc., should be routinely checked once a week to maintain good condition, if loose, replace or tighten.
In addition, if a pressure oil is used for too long, the pressure oil can be replaced to extend the life of the oil switch, oil pump and seal.
Oil filter cleaning
The oil filter plays the role of cleaning the hydraulic oil, so the oil filter should be cleaned every three months to keep the oil pump suction pipe unblocked, and check whether the oil filter screen is damaged. Generally, the size of the filter should not be larger than 200 mesh.
Cooler cleaning
The cooler should be cleaned every two years, or according to whether its working capacity is reduced and cleaned, the internal blockage or fouling of the cooler will affect the cooling efficiency, and the cooling water should be selected soft (non-mineral) as the best.
Electrical section
Wire connector inspection
The wire with the joint is not tightened will cause high temperature or spark damage to the joint position, and the poor joint will also affect the transmission of the signal; The joints on the contactors are easy to loosen due to the vibration of electromagnetic action, so it is necessary to check the tightening of the wire joints regularly.
The contact points of the injection molding machine circuit must be kept in a tight state and there must be no loosening phenomenon. In order to avoid affecting the heat dissipation function of the electrical box, it is necessary to pay attention to the working performance of each exhaust fan at any time, and clean the dust on the dust filter and replace the dust filter in time.
Check all the wire connection points in the electrical box once according to the specified time to check whether the rubber shell of each wire is hardened to prevent leakage.
motor
Generally, the motor is air-cooled, dust accumulation causes heat dissipation difficulties, so regular cleaning every year, usually installed in the circuit motor overload cut-off, the limited current of the protection device is adjustable, should be according to the motor power to make an appropriate selection, and once the overload protector starts, should determine whether to check whether underphase, poor contact or high oil temperature before pressing the return switch.
Heating cylinders and thermocouples
The heating cylinder should be checked whether it is fastened to ensure effective heat transfer, and the burning of the heating cylinder in normal production is not easy to detect, so it is necessary to pay attention to the working situation of the temperature controller, from which to judge whether the heating cylinder is normal. In addition, the common damage of the heating cylinder is the wire connection, due to the poor joint, the contact resistance increases, so that the local overheating of the connection leads to the oxidation of the interface and damage.
Keep thermocouple contacts clean frequently.
AC contactor
The contactor used for the electric heating part because of the frequent operation, its loss rate is also faster, if the main contact is overheated and melted and bonded, it may cause the heating temperature to run out of control, so if the contactor is found to have overheating, making a noise or breaking when the fire is very large, it means that it will be damaged and should be replaced as soon as possible.
Computer control section
With the application of microcomputer control technology in injection molding machines, the normal operation of microcomputer parts and related auxiliary electronic boards on the fluctuation of power supply voltage, working environment temperature, humidity, installation of seismic resistance and external high-frequency signal interference are put forward higher requirements, for this reason to keep the control box ventilation and heat dissipation fans work normally, use high precision power stabilization equipment power supply, try to reduce the control box by external vibration influence, etc. are the basic requirements for normal work, should effectively solve these aspects of the problem and regular inspection.
Mechanical parts
1. Template parallelism
The parallelism of the template can best reflect the condition of the clamping part, and the non-parallelism of the template will make the product unqualified and increase the wear of equipment and molds. The parallelism of the template can be preliminarily reflected by the movement of the tail plate and the appearance analysis of the product during mold locking, but the exact situation needs to be measured with instruments such as dial indicators. The adjustment of the parallelism of the template must be carried out step by step by familiar personnel, otherwise the damage to the machine will be greater due to improper adjustment.
2. Mold thickness adjustment
The mold thickness adjustment system should be used regularly, and the mold thickness should be called back once from the thickest to the thinnest to ensure smooth action, and this inspection must be carried out for machines produced with the same mold for a long time to avoid failure.
3. Central lubrication system
All mechanical moving parts need to be properly lubricated, and a central lubrication system is one of the must-have for injection molding machines today. The amount of oil in the central lubrication system should be paid attention to frequently check whether it is full, and the lubricating oil used must be clean and free of impurities to ensure that there is a lubricating oil supply in all lubrication positions. When the oil pipe is found to be blocked or leaking, it should be replaced or repaired immediately. Most mechanical wear occurs due to lack of lubrication, so adequate attention should be paid to lubrication.
4. Keep each movement smooth
Vibration or unsmooth movement may be caused by improper speed adjustment, speed change and time incoordination, or mechanical and oil pressure adjustment. This type of vibration will accelerate the wear of the mechanical part and shake the fastened screws, so it should be reduced and avoided.
5. Bearing inspection
When the bearing part is working with abnormal noise, or the temperature rises, it means that the bearing has been worn inside, and it should be checked or replaced in time and re-injected with grease.
6. Injection system
The injection screw, check ring and barrel form the heart part of the injection molding machine, which determines the quality and efficiency of processing, and they must be kept in good working condition. First of all, take necessary measures to prevent non-plastic debris from mixing into the plastic raw materials, and then pay attention to check the correct gap between the screw and the barrel, the check ring and the barrel, the normal gap should be able to seal the plastic reflux and produce the shear effect required for plasticization, when it is found that the melt action is slow, the melt has spots and black spots, or the product forming is unstable, the screw, check the wear of the screw, check ring and barrel.
In addition, keep the motor and each oil switch clean, if the motor shell has dirt, can lead to its heat dissipation function, should be checked on time, find a problem in time repair, so that it can play a role, to ensure the normal operation of the machine. If the sealing ring of the machine is used for too long, it will naturally corrode, lose its effect, or play a bad function and cause oil leakage, it should be replaced according to the specifications. In addition, when the machine is out of use for too long or when it is necessary to inject different plastics, the remaining rubber material in the melting cylinder must be cleaned up, so as to facilitate the smooth progress of the melting process.
The service life of the injection molding machine depends not only on the high-quality quality assurance of the injection molding machine manufacturer, but also on the careful maintenance of the user to improve its reliability and durability.
Causes and solutions of some common faults
The oil temperature is too high
An abnormal rise in oil temperature may be caused by an abnormal cooling system or high heat generated by the oil pressure element during operation.
1. The cooling system is not normal
1) The cooling system supply is insufficient, such as the water switch is not fully opened, the water pressure is insufficient or the pump flow does not meet the needs.
2) Blocked pipes, such as clogged filters, cooling towers or water pipes.
3) The cooling water temperature is too high, such as insufficient cooling capacity of the cooling tower, or damage or high temperature.
2. The hydraulic system generates high heat
1) The oil pump is damaged, and the internal parts wear out when rotating at high speed to produce high heat.
2) The pressure adjustment is not appropriate, and the hydraulic system is overheated in a high-pressure state for a long time.
3) Internal leakage of oil pressure components, such as damage to directional valves or damaged sealing rings, causes heat generation when high-pressure oil flows through small spaces.
Noise generation
Abnormal noise generation, indicating that there are parts damaged or improper adjustment, should be according to the location of the noise to find out the cause of immediate repair.
1. The hydraulic oil in the oil tank is insufficient, the oil pump sucks in the air or the oil filter is blocked by dirt will cause the oil pump to lack oil, causing the bubbles in the oil to discharge and impact the blades and produce noise, the solution is to check the amount of oil, prevent air inhalation and clean the oil filter.
2. The hydraulic oil has high viscosity and increases the flow resistance, so it is necessary to replace the appropriate hydraulic oil.
3. Due to the damage of the bearing or blade of the oil pump or motor, the concentricity deviation of the coupling causes noise, and the concentricity must be adjusted or the parts replaced.
4. The directional valve reacts but the function is still there, such as valve core wear, internal leakage, burr blockage, inflexible movement, and the solenoid valve will also produce noise due to insufficient current failure. The solution is to clean the spool, the spool must be replaced with new parts if it is worn, and the current must be stable and sufficient. 5. Damage to hydraulic components or blockage of oil pipelines causes noise when hydraulic oil flows at high speed.
6. If the mechanical part fails, the bearing is worn or the machinery lacks lubricating oil or the parts are loose, the reason should be found to tighten or replace the parts to ensure that there is enough lubricating oil.
Unstable or unqualified product production
In a stable production cycle, the quality of finished products is unstable, mostly caused by wear or improper adjustment of mechanical parts.
1. Wear of screw, check ring and barrel.
2. Internal leakage caused by damage to the sealing ring in the injection cylinder.
3. The temperature control of the heating cylinder is unstable.
4. The pressure and speed control are partially abnormal.
Maintenance Summary
One. Daily maintenance items
1. Machine environmental hygiene
2. Oil temperature
3. Hinge lubrication system
4. Heating system
5. Cool the transport water
6. Emergency stop
7. Security mechanism effect
Two. Weekly maintenance items
1. Stroke and proximity switch inspection
2. Oil seepage
3. Butter lubrication part
4. Screws are loose
5. Amount of oil
Three. Quarterly maintenance
1. Wire connectors
2. Electric box hygiene
3. Oil pump, oil motor
4. Add butter
5. Power supply
Four. Annual maintenance matters
1. Fuel tank and pressure oil
2. The degree of insulation of the wire
3. Electric motor
4. Glue injection screw
5. Machine hinge
