How to protect the injection molding machine

Therefore, how to ensure the normal and stable operation of injection molding machines in continuous production is a problem worthy of attention and effort for both injection molding machine manufacturers and users. From the user's point of view, regular preventive maintenance is an effective way to ensure the normal operation of injection molding machines under the premise of the correct selection of injection molding machines.

The so-called preventive maintenance is a series of preventive work and inspection to avoid machine failure and prolong the working life of various parts, such as the sudden occurrence of production stoppage failure into a foreseeable and planned downtime repair or overhaul; the timely detection and replacement of damaged parts can prevent chain damage, etc. are the purpose of preventive maintenance.

I. Preventive maintenance work

A. Hydraulic part

1. Hydraulic oil quantity

Insufficient oil will cause the oil temperature to rise easily. Air is easy to dissolve in the oil and affect the oil quality and the normal work of the hydraulic system, insufficient oil is usually caused by oil leakage or loss during repair, so daily attention should be paid to check whether there is a leaky part, early replacement of worn seals, tighten the loose joints, etc., after maintenance to check the oil tank oil quantity, timely replenishment.

2. Hydraulic oil temperature

The ideal working temperature of the hydraulic system should be between 45 ℃ -50 ℃, the reason is that the hydraulic system is based on a selected pressure oil viscosity and design, but the viscosity will change with the oil temperature, which in turn affects the work of the system components, such as cylinders. Hydraulic valves, etc., so that the control accuracy and response sensitivity are reduced, especially in the case of precision injection machines.

At the same time, high temperatures will also accelerate the aging of the seals to make them harden. If the temperature is too low, the processing energy consumption will be large and the operation speed will be reduced. Therefore, it is necessary to pay close attention to the working temperature of hydraulic oil. Oil temperature is too high for a variety of reasons but mostly attributed to the failure of the oil circuit or cooling system failure.

3. Hydraulic fluid oil quality

One of the important properties of hydraulic oil is its chemical stability, i.e. oxidation stability. Oxidation is the most important factor to determine the effective service life of hydraulic oil, oxidation generated by wood tar. Sludge and carbon residue and other insoluble substances will contaminate the hydraulic system and increase the wear of hydraulic components. Reduce various gaps. Clogging of small holes. Eventually, this lead to the failure of the hydraulic system.

The speed of oxidation of hydraulic oil depends on itself and working conditions and other factors, of which temperature is one of the main factors, so use the right hydraulic oil and regularly check the degree of oxidation of hydraulic oil (from the oil itself, the color turns dark and judgment), more than a certain number of working hours after the initiative to change the oil is absolutely necessary.

4. Oil filter cleaning

The oil filter plays the role of cleaning hydraulic oil, so the oil filter should be cleaned every three months to keep the oil Ga suction pipe open and check whether the oil filter is damaged.

5. Cooler cleaning

The cooler should be cleaned once a year or according to whether its working capacity is reduced.

B. Electrical part

1. Wire connector inspection

The wire with unfastened joints will cause high temperature or sparks to damage the joints, and poor joints will also affect the transmission of signals; the joints on the contactor will be easier to loosen due to the vibration of electromagnetic action, so it is necessary to check the position of the wire joints and tighten them regularly.

2. Motor

Generally, the motor is air-cooled, dust accumulation will cause heat dissipation difficulties, so every year for regular cleaning, usually in the circuit is equipped with a motor overload cut-off device, the protection device is adjustable for the limited current, according to the motor power for appropriate selection, at the same time once the overload protector is activated, should be sure to check whether the under-phase. Poor contact or oil temperature is too high before pressing the reset switchback.

3. Heating cylinder and thermocouple

The heating cylinder should be checked periodically for tightness to ensure effective heat transfer. In normal production, it is not easy to detect the burning of the heating cylinder, so pay attention to the work of the temperature controller to determine whether the heating cylinder is normal. In addition, the common damage to the heating cylinder is the wire connection, due to poor joints, contact resistance increases so that the local overheating of the connection leads to oxidation and destruction of the interface.

4. Electromagnetic contactor

Contactor for the electric heating part because the action is more frequent, the loss of speed is also faster, if the main contact overheating melting bonding may cause the heating temperature out of control, so if the contact is found to have overheating phenomenon. Rattle or fire when breaking is very large, it means that it is about to be damaged and should be replaced as soon as possible.

5. Computer control part

With the application of microcomputer control technology in the injection molding machine, the normal operation of the microcomputer part and its related auxiliary electronic board on the fluctuation of the power supply voltage, the temperature, and humidity of the working environment. Humidity, the installation of anti-vibration, and external high-frequency signal interference have put forward high requirements, to maintain the normal operation of the fan for ventilation and heat dissipation in the control box, the use of high-precision power supply regulator power supply, trying to reduce the impact of the control box by external vibration, these aspects of the problem should be effectively addressed and regularly checked.

C. Mechanical parts

1. parallelism of the template

The parallelism of the mold plate can best reflect the condition of the clamping part, and the non-parallelism of the mold plate will make the product unqualified and increase the wear and tear of the equipment and mold. The parallelism of the mold plate can be reflected by the movement of the tail plate during clamping and the analysis of the appearance of the product, but the exact situation needs to be tested with a percentage meter and other instruments. The adjustment of the parallelism of the mold plate must be carried out by familiar personnel according to the steps, otherwise, the improper adjustment will cause more damage to the machine.

2. Mould thickness adjustment

The mold thickness adjustment system should be used regularly to adjust the mold thickness from the thickest to the thinnest back and forth once to ensure smooth action.

3. Central lubrication system

All mechanical moving parts need to have proper lubrication, and the central lubrication system is one of the necessities of an injection molding machine. The oil quantity of the central lubrication system should be checked frequently to make sure it is full, and the lubricant used should be clean and free of impurities to ensure that all lubrication positions are supplied with lubricant. The oil pipe should be replaced or repaired immediately if it is found to be blocked or leaking. Most of the mechanical wear and tear is due to the lack of lubrication, so to have enough attention to lubrication. 4.

4. Keep the smoothness of each movement

Motion vibration or smoothness may be due to improper speed adjustment, speed change, and time inconsistency or mechanical. Oil pressure adjustment caused. This kind of vibration will make the mechanical parts wear faster and loosen the tightened screws, so it should be reduced and avoided.

5. Bearing inspection

Bearings in the work of strange sound, or temperature rise that means the internal bearing has been worn, should be timely inspection or replacement, and re-inject grease.

6. Injection system

Injection screw. The stop collar and barrel form the heart of the injection molding machine and determine the quality and efficiency of the process. First of all, take necessary measures to prevent non-plastic debris from mixing into the plastic material flow, and then pay attention to check the proper alignment between the screw and barrel. The normal clearance should be able to seal the plastic backflow and produce the shearing effect required for plasticization when the melt is found to be slow. When you find that the melt is slow, there are spots and black spots on the melt, or the product is unstable, you should check the screw. Check the wear of the screw, the non-return ring, and the barrel.

II. The causes and solutions of some common failures

A. Oil temperature is too high

The oil temperature may rise abnormally because the cooling system is not normal or the oil pressure components are working with high heat.

1. Cooling system is not normal

1) Insufficient supply of the cooling system, such as water valve not fully opened, insufficient water pressure or pump flow does not meet the needs, etc. 2) Blocked pipes, such as filters. Cooling tower or water pipe blockage.

(3) Cooling water temperature is too high, such as cooling tower cooling capacity is not enough, or damaged or the temperature is too high.

2. High heat generated by the hydraulic system

(1) Oil pump damage, internal parts wear at high-speed rotation to generate high heat.

(2) improper pressure adjustment, the hydraulic system in a long-term high-pressure state, and overheating.

(3) Internal leakage of hydraulic components, such as damaged directional valves or damaged seals, resulting in heat generated when high-pressure oil flows through small spaces.

B. Noise generation

Abnormal noise generation indicates that there are parts damaged or improperly adjusted, and the cause should be identified and repaired immediately according to the location of the noise.

1. Insufficient hydraulic oil in the oil tank, oil pump inhalation air, or oil filter dirt blockage will cause oil pump oil shortage, resulting in oil bubble discharge impact vane and generate noise, the solution is to check the amount of oil, to prevent inhalation air and clean the oil filter.

2. high viscosity of hydraulic oil. Increase the flow resistance, need to replace the appropriate hydraulic oil.

3. Due to the oil pump or motor bearing or vane damage, the concentricity of the coupling deviation caused the noise, must adjust the concentricity or replace the parts.

4. The directional valve fails to respond but still functions, such as valve core wear, internal leakage. Burr blockage. Inflexible movement, solenoid valve failure due to insufficient current will also produce noise. The solution is to clean the valve core, the valve core wear must be replaced with new parts, the current must be stable and sufficient.

5. hydraulic components damage or oil pipeline blockage of hydraulic oil flow at high speed when the noise is generated.

6. mechanical part failure, bearing wear, or mechanical lack of lubricating oil or lose parts, should find out the reason to tighten or replace the parts, to ensure that there is sufficient lubricating oil.

C. Product production is unstable or unqualified

In a stable production cycle, the quality of the finished product is unstable, which may be caused by the wear of mechanical parts or improper adjustment.

1. screw. Non-reverse ring. Wear and tear of the barrel.

2. Internal leakage due to damage to the seal inside the injection cylinder.

3. Unstable temperature control of the heating cylinder.

4. Pressure. Speed control part malfunction.