Both imported and domestic injection molding machines have the following characteristics:
1. The injection molding machine has a large investment in fixed assets, a large production scale, a large consumption of raw materials, high labor productivity, and a large output value. It is a form of production organization with high labor efficiency.
2. The injection molding machine is organically combined by machinery, hydraulics, electrical appliances, special accessories, etc., according to the needs of injection molding processing technology, with a high degree of automation and close correlation with each other; The injection molding machine can run continuously for 24 hours in 3 shifts. If one of the components of the injection molding machine fails, it will lead to downtime.
3. Although the operation of the injection molding machine is simple and there are few workers, the technical content of the management and maintenance of the injection molding machine is high and the workload is also large.
Therefore, in order to ensure that the injection molding machine is always in good condition, it is necessary to strengthen the management of the injection molding machine and strictly control the failure of the injection molding machine. In order to achieve the purpose of reducing the failure rate, reducing maintenance costs and prolonging the service life.
Injection molding machine failure generally refers to an event or phenomenon in which an injection molding machine or system loses or reduces its specified function in use. The injection molding machine is equipped by the enterprise to meet the requirements of the production process of injection molding products. The function of the injection molding machine reflects its value in the production of injection molding products and the degree of guarantee for injection molding production. In the production of modern injection molding machines, due to the complex structure of injection molding machines, the degree of automation is very high, and the connection between hydraulic, electronic control and machinery is very close.
Therefore, if the injection molding machine fails, even if it is a partial failure, it will cause the entire injection molding machine to stop production. Injection molding machine failures directly affect the quantity and quality of injection molding products.
1. Classification of injection molding machine failures
Injection molding machine failures are varied and can be classified from different angles.
1. According to the state of failure, it can be divided into:
(1) Progressive failure. It is caused by the gradual deterioration of the initial performance of the injection molding machine, and most of the failures of the injection molding machine belong to this type of failure. This kind of fault is closely related to the wear, corrosion, fatigue and creep of electronic control and hydraulic mechanical components.
(2) Sudden failure. It is the result of a combination of adverse factors and accidental external influences that are beyond the limits of the injection molding machine. For example, the screw is broken due to the overload of the barrel entering the iron; Breakdown of the electronic board of the injection molding machine due to high-pressure serial insertion. Such failures often occur suddenly, without warning.
Sudden failures mostly occur in the use stage of injection molding machines, often due to defects in design, manufacturing, assembly and materials, or operation errors and illegal operations.
2. According to the nature of the fault, it can be divided into:
(1) Intermittent failures. The injection molding machine loses some of its functions in a short period of time and can be restored with a little repair and commissioning without the need to replace parts.
(2) Permanent failure. Some parts of the injection molding machine are damaged and need to be replaced or repaired to be brought back into service.
3. According to the degree of impact of the failure, it can be divided into:
(1) Complete failure. This results in a complete loss of function of the injection molding machine.
(2) Partial failure. This leads to the loss of some functions of the injection molding machine.
4. According to the cause of failure, it can be divided into:
(1) Abrasive failure. Failure due to normal wear and tear of the injection molding machine.
(2) Misuse failures. Failures caused by operational errors, improper maintenance.
(3) Inherently weak faults. Due to design problems, there are weak links in the injection molding machine, and failures occur during normal use.
5. According to the danger of failure, it can be divided into:
(1) Dangerous failure. For example, the safety protection system loses its protection function due to failure when it needs to be moved, resulting in personal injury and injection molding machine failure; Failure caused by the failure of the hydraulic and electronic control system, etc.
(2) Security failures. For example, the safety protection system acts when it is not needed; Failure of the injection molding machine to start when it does not start.
6. According to the occurrence and development law of injection molding machine failure, it can be divided into;
(1) Random failures. The timing of the failure is random.
(2) There is a rule failure. There is a certain pattern in the occurrence of failures.
Each type of failure has its main characteristic, the so-called failure mode, or failure state. The fault states of various injection molding machines are quite complicated, but they can be summarized into the following types: abnormal vibration, mechanical wear, input signal can not be accepted by the computer, solenoid valve has no output signal, mechanical hydraulic components rupture, proportional linear misalignment, hydraulic pressure drop, hydraulic leakage, oil pump failure, hydraulic noise, circuit aging, abnormal sound, oil quality deterioration, power supply voltage drop, no output of the amplifier plate, temperature runaway and others. The proportion of various failure modes varies depending on the type of injection molding machine.
2. Fault analysis and troubleshooting procedures
In order to ensure that fault analysis and elimination are fast and effective, certain procedures must be followed, which are roughly as follows.
Step 1: Perform symptom analysis in the case of keeping the scene
1. Ask the operator
(1) What went wrong? Under what circumstances did it happen? When did it happen?
(2) How long has the injection molding machine been running?
(3) Is there any abnormal phenomenon before the failure? What are the audible or visual alarm signals? Is there any smoke or odor? Is there any misoperation (pay attention to the way you ask)?
(4) Is the control system operating normally? Are there any changes to the operating procedures? Are there any particular difficulties or abnormalities in the operation?
2. Observe the condition of the whole machine and various operating parameters
(1) Are there any obvious anomalies? Are the parts jammed or damaged? Is there any looseness or leakage in the hydraulic system? Are the wires cracked, bruised or burned?
(2) What are the changes in the operating parameters of the injection molding machine? Are there any obvious interfering signals? Are there any obvious signs of damage?
3. Check the monitoring and indication device
(1) Check whether all readings are normal, including the readings of pressure gauges and other instruments, and the height of the oil level.
(2) Check whether the filter, alarm and interlock device, action output or display are normal.
4. Jog injection molding machine inspection (under allowable conditions)
Inspect intermittent, persistent, fast-forward, or slow-forward conditions to see if these conditions affect output and may cause damage or other hazards.
Step 2 Check the injection molding machine (including parts, components and wiring)
1. Sensory examination (the process of continuing in-depth observation)
(1) Look: whether the plug and socket are abnormal, whether the operation of the motor or pump is normal, whether the control adjustment position is correct, whether there are traces of arcing or scorching, whether the fuse is good or bad, whether the liquid is leaking, whether the lubricating oil circuit is unblocked, etc.
(2) Touch: the vibration of the injection molding machine, the heat of the components (components), the temperature of the tubing, and the state of mechanical movement.
(3) Listen: whether there is any abnormal sound.
(4) Smell: whether there is burnt smell, leakage odor, and other peculiar smells.
(5) Check: changes in the shape and position of the workpiece, changes in the performance parameters of the injection molding machine, and abnormal line inspection.
2. Evaluate the results of the examination
Evaluate whether the fault judgment is correct, whether the fault clues are found, and whether the inspection results are consistent.
Step 3 Determine the location of the fault
1. Identify the system structure and determine the test method
Consult the instructions of the injection molding machine to identify which structure the injection molding machine is, what method is used to test, what means of testing are required, what test parameters or performance parameters may be obtained, under what operating conditions the test is carried out, what safety measures must be observed, and whether an operating license is required.
2. System detection
Tests are carried out using the technology that is most suitable for the system structure. At the appropriate test points, the results obtained from the input and feedback are compared to normal values or performance standards to identify suspicious locations.
Step 4 Repair or replacement
1. Repair
Find the cause of the failure, repair the injection molding machine failure and take preventive measures; Inspect the relevant parts to prevent the spread of faults.
2. Replacement
Correctly assemble and debug replacement parts, and pay attention to relevant parts. Replaced parts are repaired or scrapped.
Step 5 Perform performance measurement
1. Start the injection molding machine
After the assembly and commissioning of the parts, the injection molding machine is started, first manually (or joged), and then the no-load and load determination are carried out.
2. Adjust the load change speed from low to high, the load from small to large, the maximum system pressure can not exceed 140kg/cm2, and the performance is measured according to the specified standard.
3. Expand the scope of performance test
According to the need, gradually expand the scope of performance test from local to systematic. Pay attention to the system health in the non-fault area. If the performance meets the requirements, it will be delivered, and if the requirements are not met, the fault location will be redetermined.
Step 6 Record and give feedback
1. Collect valuable information and data, such as the time of failure of the injection molding machine, the fault phenomenon, the downtime, the repair man-hours, the replacement parts, the repair effect, the problem to be solved, the settlement cost, etc., and store them in the file according to the specified requirements.
2. Statistical analysis
Regularly analyze the use records of injection molding machines, analyze downtime losses, revise the memo catalog, find key measures to reduce maintenance operations, study the failure mechanism, and propose improvement measures.
3. According to the procedure, the relevant faults are reported to the competent department, and fed back to the injection molding machine manufacturing unit.
3. Procedures for the development of fault management
In order to do a good job in the fault management of injection molding machines, it is necessary to grasp the causes of failures, accumulate data and data on frequent failures and typical failures, carry out failure analysis, pay attention to the study of failure laws and failure mechanisms, and strengthen daily maintenance, inspection and pre-repair. There are 8 aspects of the fault management deployment process.
1. Do a good job in publicity and education, so that operators and maintenance workers consciously record, count and analyze the faults of injection molding machines, and put forward reasonable suggestions.
2. Closely combine the actual injection molding production and the characteristics of the injection molding machine, and divide the injection molding machine into three categories: A, B and C, so as to determine the focus of fault management.
3. Use monitoring instruments to monitor the key parts of the key injection molding machine in a planned manner, and find the signs of failure and deterioration information in time.
Generally, the injection molding machine should also carry out daily spot checks, patrol inspections, regular inspections (including accuracy inspections), and intact state inspections through human senses and general testing tools, focusing on grasping the technical status and abnormal phenomena of parts that are prone to failure. At the same time, it is necessary to formulate inspection standards to determine the boundaries of normal, abnormal and faulty injection molding machines.
4. Carry out failure analysis and train injection molding machine maintenance workers to master failure analysis methods.
5. Fault record is the basic data for the fault management of injection molding machine, and it is the original basis for fault analysis and processing, and the record must be complete and correct. After the injection molding machine maintenance workers carry out on-site inspection and fault repair, they should fill in carefully according to the content of the "Injection Molding Machine Fault Repair Form", and the workshop mechanics shall statistically analyze and submit to the injection molding machine management supervisor on a monthly basis.
6. In addition to grasping the fault situation on a daily basis, the workshop injection molding machine maintenance staff should collect the "fault repair order" and maintenance records on a monthly basis. Through the statistics, collation and analysis of fault data, the failure frequency and average failure interval of various injection molding machines are calculated, the fault dynamics and key fault causes of a single injection molding machine are analyzed, and the occurrence law of failure is found out, so as to highlight the key points and take countermeasures, and the fault information is sorted out and analyzed and fed back to the planning department, so as to arrange preventive repair or improvement measures plan, and can also be used as the basis for modifying the regular inspection interval, inspection content and standards.
According to the statistical data, statistical analysis charts can be drawn, such as a single injection molding machine fault dynamic statistical analysis table is an effective way for the maintenance team to visually manage the fault and others, which is not only convenient for managers and maintenance workers to grasp the failure of various types of injection molding machines in a timely manner, but also has a clear goal when determining the maintenance countermeasures.
7. Through the daily inspection of maintenance workers and the status inspection of injection molding machines, the status information and fault signs obtained, as well as relevant records and analysis data, the workshop injection molding machine maintenance personnel or repair team leader will arrange daily maintenance in time for the existence of various types of injection molding machines, make full use of production gap time or holidays, and prevent in advance, so as to control and reduce the occurrence of failures. For some fault signs and hidden dangers, if the daily maintenance is not affordable, it will be fed back to the planning department to arrange planned repair.
8. Formulate a fault information management flow chart.
Fourth, the failure law of injection molding machine
Studying the law of faults is very beneficial to the formulation of maintenance countermeasures and even the establishment of a scientific maintenance system. During the use of the injection molding machine, its performance or state gradually decreases with the passage of time. Many failures are preceded by some warning signs, the so-called latent failures, with recognizable physical parameters that indicate an imminent functional failure and a functional failure that indicates that the injection molding machine has lost its specified performance standards.
The variation of the failure rate of injection molding machines over time is often referred to as the bathtub curve. The failure rate of injection molding machines can be roughly divided into three stages: early failure period, occasional failure period and wear and tear failure period.
1. Early failure period
The injection molding machine is in the early failure period, and the failure rate is very high at the beginning, but the failure rate decreases rapidly over time, and the early failure period is also called the running-in period for mechanical products. The length of this time varies depending on the quality of the product, system, design, and manufacturing. Failures that occur during this period are mainly caused by defects in design, manufacturing, or improper use environment.
2. Occasional failure period
The injection molding machine enters the period of occasional failure, and the failure rate is roughly in a stable state and tends to be fixed. During this time, failures occur randomly. During the period of occasional failure, the failure rate of the injection molding machine is the lowest and stable. Therefore, it can be said that this is the optimal condition or normal working period of the injection molding machine. This segment is called active life.
Failures during the occasional failure period are mostly caused by improper design, use and poor maintenance. Therefore, the failure rate can be reduced to the lowest level by improving the design quality, improving the use management, and strengthening the monitoring, diagnosis and maintenance.
3. Wear and tear failure period
In the later stages of the injection molding machine's use, the failure rate begins to rise. This is caused by the wear, fatigue, aging, corrosion, etc. of injection molding machine parts. If an overhaul is carried out at the inflection point, i.e. at the beginning of the attrition failure period, the failure rate can be reduced cost-effectively.
The three stages of the failure rate curve of the injection molding machine truly reflect the law of the failure rate change of the injection molding machine from running-in, commissioning, normal operation to overhaul or scrapping, and strengthen the daily management and maintenance of the injection molding machine, which can prolong the occasional failure period. Accurately identifying the point of failure avoids over-repairs or extended repair areas for optimal injection molding investment.
