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Practical injection molding machine information!

Update:10-10-2020
Summary:

njection molding machine is one of the equipment common […]

njection molding machine is one of the equipment commonly used in the plastics processing industry. Usually it has to work for a long time. Therefore, how to ensure the normal and stable operation of the injection machine in continuous production is a worthy consideration for both the injection machine manufacturer and the user. To solve the problem, from the perspective of users, regular preventive maintenance is an effective way to ensure the normal operation of the injection machine under the premise of correct selection of the injection model.

The so-called preventive maintenance is a series of preventive work and inspections to prevent machine failures and prolong the working life of various parts. For example, the sudden occurrence of failures that cause production shutdowns can be turned into foreseeable and planned shutdown repairs or overhauls; it can be timely Discovery and replacement of damaged parts can prevent chain damage, etc., which are the purpose of preventive maintenance.

1. Preventive maintenance

A hydraulic part

1. Hydraulic oil volume

Insufficient oil will cause the oil temperature to rise easily, and the air will easily dissolve into the oil, which will affect the oil quality and the normal operation of the hydraulic system. Insufficient oil is usually caused by oil leakage or loss during repairs. For this reason, daily attention should be paid to check whether there is leakage If necessary, replace worn seals and tighten loose joints as soon as possible. After maintenance, check the amount of oil in the fuel tank and replenish it in time.

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 designed according to a selected pressure oil viscosity, but the viscosity will change with the oil temperature, which will affect the work of the system. Components, such as oil cylinders, hydraulic valves, etc., reduce 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 the seal and cause it to harden and crack; if the temperature is too low, the processing energy will be consumed and the operating speed will be reduced. Therefore, it is necessary to pay close attention to the working temperature of hydraulic oil. There are many reasons for high oil temperature, but most of them are due to oil circuit failure or cooling system failure.

3. Hydraulic oil quality

One of the important properties of hydraulic oil is its chemical stability, that is, oxidation stability. Oxidation is the most important factor that determines the effective service life of hydraulic oil. The insoluble matter such as wood tar, sludge and carbon residue generated by oxidation will pollute the hydraulic system, increase the wear of hydraulic components, reduce various gaps, block small holes, and eventually cause The hydraulic system is malfunctioning. The oxidation rate of hydraulic oil depends on many factors such as itself and working conditions, among which temperature is one of the main factors. Therefore, it is necessary to use suitable hydraulic oil and regularly check the oxidation degree of hydraulic oil (judged from the darker color of the oil itself) ), it is absolutely necessary to actively change the oil after a certain number of working hours.

4. Oil filter cleaning

The oil filter plays a role in cleaning the hydraulic oil, so the oil filter should be cleaned every three months to keep the oil suction pipe unblocked, and check the oil filter for damage.

5. Cooler cleaning

The cooler should be cleaned once a year, or according to whether its working capacity is reduced. Blockage or fouling inside the cooler will affect the cooling efficiency. The cooling water should be soft (mineral-free).

Two electrical parts

1. Wire connector inspection

Unfastened wires in the connector will cause high temperature or spark damage at the connector position. A poor connector will also affect the signal transmission; the connector on the contactor will be easier to loose due to the vibration of the electromagnetic action, so it is necessary to check the wire connector regularly Position and tighten.

2. Electric motor

Generally, the motor is air-cooled. The accumulation of dust causes difficulty in heat dissipation. Therefore, it is cleaned regularly every year. A motor overload cutoff is usually installed in the circuit. The limit current of the protection device is adjustable and should be adjusted according to the motor power. At the same time, once the overload protector is activated, it should be determined to check whether there is a lack of phase, a bad contact or the oil temperature is too high before pressing the return position switch.

3. Heating cylinder and thermocouple

The heating cylinder should be checked regularly to ensure that it is fastened to ensure effective heat transfer. The burning of the heating cylinder is not easy to detect in normal production. For this reason, pay attention to the working condition of the temperature controller and 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, and the local overheating of the connection causes the interface to oxidize and damage.

4. Electromagnetic contactor

The contactor used for the electric heating part has a faster loss rate due to its frequent action. If the main contact is overheated and melted and bonded, it may cause the heating temperature to be out of control. Therefore, if the contact is overheated, it makes a noise or it is very hot when breaking. 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 to the injection molding machine, the normal operation of the microcomputer part and its related auxiliary electronic board has raised the influence of the fluctuation of the power supply voltage, the temperature and humidity of the working environment, the shock resistance of the installation and the interference of external high-frequency signals. In order to meet higher requirements, to maintain the normal operation of the fans for ventilation and heat dissipation in the control box, use high-precision power supply and stabilized equipment to supply power, and try to reduce the influence of external vibration on the control box. These problems should be solved and regularly an examination.

Three mechanical parts

1. Template parallelism

The parallelism of the template can best reflect the condition of the clamping part. The non-parallel template will make the product unqualified and increase the wear of the equipment and mold. The parallelism of the template can be initially reflected by the movement of the tail plate during mold clamping and the appearance analysis of the product, but the exact situation needs to be detected by instruments such as a dial indicator. The adjustment of the parallelism of the template must be carried out by a familiar person in steps, otherwise improper adjustment will cause greater damage to the machine.

2. Mold thickness adjustment

The mold thickness adjustment system should be used regularly to adjust the mold thickness from the thickest to the thinnest to ensure smooth movement. For machines that use the same mold for a long time, this inspection must be performed to avoid malfunctions.

3. Central lubrication system

All mechanical moving parts need to have proper lubrication, and the central lubrication system is one of the must-haves for current injection molding machines. The amount of oil in the central lubrication system should be checked frequently to see if it is full. The lubricating oil used must be clean and free of impurities to ensure that all lubricating positions have lubricating oil supply. If the oil pipe is blocked or leaking, it should be replaced or repaired immediately. Most mechanical wear occurs due to lack of lubrication, so adequate attention must be paid to lubrication.

4. Keep all movements smooth

Vibration or unsmooth movement may be caused by improper speed adjustment, speed change and uncoordinated time, or mechanical or oil pressure adjustment. This kind of vibration will accelerate the wear of the mechanical parts and loosen the tightened screws, so vibration should be reduced and avoided.

5. Bearing inspection

When the bearing is working, there are abnormal noises, or the temperature rises, it means that the inside of the bearing has been worn out, and it should be checked or replaced in time and refilled with grease.

6. Injection system

The injection screw, check ring and barrel form the heart of the injection molding machine, which determines the quality and efficiency of the processing, and they must be kept in good working condition. First, take necessary measures to prevent non-plastic debris from mixing into the plastic material flow, and then pay attention to checking the correct gap between the screw and the barrel, and the check ring and the barrel. The normal gap should be able to seal the plastic backflow and produce plastic When it is found that the melting action is slow, the melting material has spots and black spots, or the product is unstable, check the wear of the screw, check ring and barrel.

2. Causes and solutions of some common faults

One oil temperature is too high

The abnormal increase in oil temperature may be caused by abnormal cooling system or high heat generated by oil pressure components during operation.

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