Injection molding machine often causes failure and maintenance

Whether imported or domestic injection molding machines have the following characteristics:

1. Injection molding machines have large investment in fixed assets, large scale of production, consumption of raw materials, high labor productivity, and large production value. It is a form of production organization with higher labor efficiency.

2. The injection molding machine consists of machinery, hydraulics, electrical appliances, and special fittings, etc. In accordance with the needs of the injection molding process technology, organically combines together, with a high degree of automation and close connection between each other; the injection molding machine can be operated continuously in 3 shifts of 24 hours. If a component of the injection molding machine fails, it will cause a shutdown.

3. Although the operation of the injection molding machine is simple and the number of workers is small, the technical content of the injection molding machine management and maintenance is high and the workload is also large.

Therefore, 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 reduce the failure rate, reduce maintenance costs and extend the life of the purpose.

Failure of an injection molding machine generally refers to an event or phenomenon in which an injection molding machine or system loses or reduces its prescribed function during use. The injection molding machine is equipped by the company to meet the production process requirements of injection molding products. The function of the injection molding machine embodies its value in the production of injection molding products and the assurance of injection molding production. In the modern injection molding machine production, due to the complex structure of the injection molding machine and the high degree of automation, the hydraulic, electronic control, and mechanical connections are very close. Therefore, the injection molding machine malfunctions, 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.

First, the classification of injection molding machine failure

Injection molding machine failures are varied and can be classified from different perspectives.

1. According to the status of failure, it can be divided into:

(1) Fading failure. It is due to the gradual deterioration of the initial performance of the injection molding machine, and most of the injection molding machine failures fall into this type of failure. This type of fault is closely related to the processes of wear, corrosion, fatigue, and creep of electrical controls and hydraulic mechanical components.

(2) sudden failure. It is caused by various unfavorable factors as well as occasional external influences, which exceeds the limits that the injection molding machine can withstand. For example, the screw breaks due to the overload of the cylinder into the iron, and breaks through the electronic board of the injection molding machine due to the high pressure. Such failures often occur suddenly without any prior warning.

Sudden failure occurs in the use 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 faults. The injection molding machine loses some of its functions in a short period of time and can be restored with minor repairs and adjustments without replacement of parts.

(2) Permanent failure. Some parts of the injection molding machine have been damaged and need to be replaced or repaired before they can be used again.

3. According to the degree of influence of the fault, can be divided into:

(1) Complete failure. Lead to the complete loss of function of the injection molding machine.

(2) Local malfunction. Loss of some of the functions of the injection molding machine.

4. According to the causes of faults, they can be divided into:

(1) Abrasion failure. Failure due to normal wear of the injection molding machine.

(2) Misuse faults. Fault caused by incorrect operation and improper maintenance.

(3) inherent weaknesses. Due to design problems, the injection molding machine appeared weak links and caused failures during normal use.
5. According to the risk of failure, can be divided into:

(1) Dangerous failure. For example, a safety protection system loses protection due to a malfunction when it needs action, resulting in personal injury and failure of the injection molding machine; failure caused by failure of the hydraulic electric control system.

(2) Security failure. For example, the safety protection system will act when no action is required; the injection molding machine will fail to start when it starts.

6. According to the occurrence of injection molding machine failure, the development of the law can be divided into;

(1) Random failure. The time of failure is random.

(2) There is a rule failure. The occurrence of failure has a certain law.

Each type of fault has its main characteristics, the so-called failure mode, or fault conditions. The failure status of various injection molding machines is quite complex, but it can be summarized as follows: abnormal vibration, mechanical wear, input signals cannot be accepted by the computer, solenoid valve has no output signal, mechanical hydraulic components are broken, proportional linear misalignment, hydraulic pressure Pressure drop, hydraulic leakage, oil pump failure, hydraulic noise, circuit aging, abnormal sound, oil degradation, power supply voltage drop, amplifier board no output, temperature out of control and others. Different types of injection molding machines have different percentages of failure modes.

Second, failure analysis and troubleshooting procedures

In order to ensure quick and effective failure analysis and elimination, certain procedures must be followed. This procedure is roughly as follows.

The first step is to perform symptom analysis while keeping the scene

1. Ask the operator

(1) What happened? Under what circumstances? When did it happen?

(2) How long has the injection molding machine been operated?

(3) Are there any abnormalities before the failure? What sound or sound and light alarm signal? Is there smoke or odor? Is there an error-free operation (note the way of asking)?

(4) Is the control system operating normally? Is there a change in operating procedures? Is there any special difficulty or abnormality during operation?

2. Observe the condition of the whole machine and various operating parameters

(1) Are there any obvious anomalies? Is there any block or damage to the parts? Is the hydraulic system loose or leaking? Has the wire broken, scratched or burned?

(2) What are the changes in the operating parameters of the injection molding machine? Is there any obvious interference signal? Is there any obvious damage signal?

3. Check the monitoring indicator device: (1) Check that all readings are normal, including pressure gauges and other meter readings, oil level conditions. (2) Check if the filter, alarm, interlock, operation output or monitor is normal.

4. Jog the injection molding machine to check (under allowable conditions) Check the condition of intermittent, persistent, fast-forward or slow-move to see if the output is affected under these conditions and may cause damage or other hazards. Step 2 Check the injection molding machine (including parts, components, and lines) 1. Use sensory inspection (continue the process of further observation) 1 Look for: whether the plug and socket are abnormal, whether the motor or pump is operating normally, and 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 leaks or not, and whether the lubricant path is unimpeded. 2 touch: vibration of the injection molding machine, the heat of the unit (set), the temperature of the tubing, and the state of the mechanical movement. 3 Listen: There is no abnormal sound. 4 sniffing: There is no smell, leakage odor, other odor. 5 check: change of the shape and position of the workpiece, change of the performance parameters of the injection molding machine, abnormal inspection of the circuit. 2. Assess the inspection results to assess whether the fault diagnosis is correct, whether the fault cues 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 Check the injection molding machine specification to identify which injection molding machine is The structure, what methods are used for testing, what test methods are required, what test parameters or performance parameters may be obtained, under which operating conditions the tests are performed, which safety measures must be followed, and whether an operating license is required. 2. System detection uses the most suitable technology detection for the system structure. At the appropriate test point, the suspicious position is found by comparing the results of input and feedback with normal values ​​or performance criteria.

Step 4 Repair or Replacement 1. Repair Find the cause of the malfunction, repair the injection molding machine and take preventive measures; check the relevant parts to prevent the failure from spreading. 2. Replace the correct assembly and commissioning replacement parts, and pay attention to the relevant parts. Replaced parts are repaired or scrapped.

Step 5: Performance Measurement 1. Start the injection molding machine after starting injection molding machine parts assembly and debugging, first manually (or jog), then carry out no-load and load measurement. 2. Adjust the load change speed from low to high, the load from small to large, the system pressure can not exceed 140kg/cm2, according to the provisions of the standard performance measurement. 3. Extend the range of performance tests As needed, gradually expand the range of performance tests from the local to the system. Pay attention to system operating conditions in non-faulty areas. If the performance meets the requirements, it is delivered for use. If it does not meet the requirements, the fault location is re-determined.

Step 6 Record and feedback 1. Collect valuable data and data, such as injection molding machine failure time, failure phenomenon, downtime, repair work hours, repair parts, repair effects, pending problems, settlement fees, etc. The required requirements are stored in the file. 2. Statistical analysis, regular analysis of injection molding machine usage records, analysis of downtime losses, revision of memorandum catalogs, search for key measures to reduce maintenance operations, study failure mechanisms, and propose improvements. 3. According to the procedure, the relevant faults are reported to the competent authority and fed back to the injection molding machine manufacturer.

Third, the failure management of the deployment process, to do a good job injection molding machine fault management, must master the cause of the failure, accumulate frequent failures and typical failures of the data and data, carry out failure analysis, pay attention to the law of failure and failure mechanism research, strengthen daily Maintenance, inspection and pre-repair. The fault management deployment process has the following 8 aspects. 1. Do a good job of publicity and education, so that operators and maintenance workers consciously record, statistically analyze and analyze the failure of the injection molding machine, and put forward reasonable suggestions. 2. Incorporating closely the actual conditions of injection molding production and the status of the injection molding machine, the existing injection molding machine is divided into three categories, A, B, and C, to determine the focus of fault management. 3. Use monitoring equipment to carry out planned monitoring of the key parts of key injection molding machines, and to detect signs of failure and deterioration information.

In general, the injection molding machine must also carry out daily inspections, tour inspections, periodic inspections (including accuracy inspections), and intact inspections through human senses and general inspection tools to focus on the technical status and abnormalities of the parts, mechanisms, and parts that are prone to failure. Phenomenological information. At the same time, inspection standards should be established to determine the boundaries of normal, abnormal and faulty injection molding machines.

4. Carry out fault analysis and train injection molding machine maintenance technicians to master fault analysis methods.
5. The fault record is the basic data to realize the fault management of the injection molding machine, and is the original basis for the fault analysis and processing. The record must be complete and correct. After the injection molding machine maintenance worker conducts inspections and troubleshooting at the site, he shall fill it out in accordance with the contents of the “Failure Repair Manual for Injection Molding Machines,” and the mechanics of the workshop shall analyze monthly statistics and report to the supervisor of injection molding machines. 6. Workshop injection molding machine maintenance personnel, in addition to the daily grasp of fault conditions, should be a monthly collection of "fault repair orders" and maintenance records. Through statistics, collation and analysis of failure data, the failure frequency and average failure interval of various injection molding machines are calculated. The failure dynamics and key failure causes of a single injection molding machine are analyzed, and the occurrence rule of failure is identified to focus on Countermeasures: Feedback the failure information to the planning department to arrange for preventive repairs or improvement measures. It can also be used as a basis for modifying periodic inspection intervals, inspection contents, and standards.

According to statistical data, statistical analysis charts can be drawn. For example, single injection molding machine fault dynamic statistical analysis table is an effective method for maintenance teams to visually manage faults and other problems. It is convenient for managers and maintenance workers to grasp all types of injection molding in time. In the event of a machine failure, it can also have a clear goal in determining the maintenance strategy.

7. Through the daily inspection of maintenance workers and the status of the injection molding machine, status information and failure indications obtained, as well as relevant records and analysis data, the maintenance staff or repair team leader of the workshop injection molding machine Arrange daily maintenance, make full use of production gap time or holidays, and be sure to prevent the former to control and reduce the occurrence of failures. For some failure symptoms, hidden dangers, and day-to-day maintenance can not afford, then feedback to the planning department to arrange repairs.

8. Formulate fault information management flow chart.

Fourth, the failure of the injection molding machine

Studying the law of failure is very beneficial to the formulation of maintenance measures and the establishment of a scientific maintenance system. During the use of the injection molding machine, its performance or state gradually decreases with the use of time. Many failures have some harbingers before they occur. This is called potential failure. The identifiable physical parameters indicate that a functional failure is imminent, and the functional failure indicates that the injection molding machine has lost the specified performance standards. The variation of the failure rate of injection molding machines over time is often called the tub curve. The failure rate of injection molding machines varies over time in three stages: early failure period, accidental failure period, and wear-out failure period.

1. In the early failure period, the injection molding machine was in an early failure period and started to have a high failure rate. However, with the passage of time, the failure rate rapidly decreased. The early failure period was also referred to as the running-in period for mechanical products. The length of this period varies depending on the product and system design and manufacturing quality. The failures that occurred during this period were mainly caused by defects in design and manufacturing, or due to improper use of the environment.

2. Infrequent failure period, injection molding machine into the human accident period, the failure rate is roughly in a stable state, tending to a fixed value. During this time, the fault occurred randomly. During the accidental failure period, the injection molding machine has the lowest failure rate and is stable. Therefore, it can be said that this is the best state or normal working period of the injection molding machine. This section is called the effective lifetime.

Infrequent failures are caused by poor design, improper use, and poor maintenance. Therefore, the failure rate can be reduced to the lowest level by improving the design quality, improving the use of management, and strengthening monitoring and diagnosis and maintenance. 3. In the period of wear and tear failure, the failure rate began to increase at the later stage of the use of injection molding machines. This is due to wear, fatigue, aging, corrosion, etc. of injection molding machine parts. If the overhaul is performed at the inflection point, which is the beginning of the failure period, the failure rate can be reduced economically and effectively.

The three stages of the change of the injection molding machine's failure rate curve truly reflect the regularity of the injection molding machine from running-in, debugging, normal operation to overhauling or scrapping failure rate, strengthening the daily management and maintenance of the injection molding machine, and prolonging the accidental failure period. Accurately identifying inflection points can avoid excessive repairs or expansion of repairs to obtain the best investment benefits.

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