Analysis of common faults in injection molding machines

1Classification of Injection Molding Machine Faults

Injection molding machine faults are diverse and can be classified from different perspectives.

1. According to the fault occurrence status, 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 faults of the injection molding machine belong to this type of fault. This type of fault is closely related to the wear, corrosion, fatigue, and creep processes of electronic control and hydraulic mechanical components.

(2) Sudden malfunction. It is the combined effect of various unfavorable factors and accidental external influences, which exceeds the limit that the injection molding machine can withstand. For example, the screw is broken due to overload caused by the material barrel entering the iron object; Breakdown of the electronic board of the injection molding machine due to high voltage injection. Such failures often occur suddenly without any warning in advance.

Sudden failures often occur during the use stage of injection molding machines, often due to defects in design, manufacturing, assembly, and materials, as well as operational 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 the need to replace components.

(2) Permanent fault. Some parts of the injection molding machine have been damaged and need to be replaced or repaired before resuming use.

According to the degree of fault impact, it can be divided into:

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

(2) Localized fault. Causing the loss of certain functions of the injection molding machine.

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

The following types are identified: abnormal vibration, mechanical wear, input signals that cannot be accepted by the computer, no output signal from the solenoid valve, mechanical hydraulic component rupture, proportional linear imbalance, hydraulic pressure drop, hydraulic leakage, oil pump failure, hydraulic noise, circuit aging, abnormal noise, oil quality degradation, power pressure drop, no output from the amplifier board, temperature runaway, and others. The proportion of various failure modes of different types of injection molding machines varies.

2、 Fault Analysis and Troubleshooting Procedures

To ensure fast and effective fault analysis and troubleshooting, certain procedures must be followed, which are roughly as follows.

The first step is to conduct symptom analysis while maintaining the scene. 1. Ask the operator

(1) What malfunction has occurred? 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 fault occurs? What is the sound or light alarm signal? Is there any smoke or odor? Is there any incorrect operation (pay attention to the inquiry method)?

(4) Is the control system operating normally? Are there any changes to the operating procedures? Are there any special difficulties or abnormalities during operation?

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

(1) Are there any obvious abnormalities? Are there any jamming or damage to the parts? Is there any looseness or leakage in the hydraulic system? Are there any broken, scratched, or burnt wires?

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

3. Check the monitoring and indication device

(1) Check if all readings are normal, including pressure gauges and other instrument readings, as well as the oil level.

(2) Check if the filters, alarms, interlocking devices, action outputs, or displays are functioning properly.

4. Inch injection molding machine inspection (under allowable conditions) to check for intermittent, persistent, fast or slow feed conditions, and to see if these conditions affect output and may cause damage or other hazards.

The second step is to inspect the injection molding machine (including parts, components, and wiring). 1. Use sensory inspection (continue the process of in-depth observation). 1. Check whether the plug and socket are abnormal, whether the motor or pump operates normally, whether the control adjustment position is correct, whether there are signs of arcing or burning, whether the safety wire is in good condition, whether there is any liquid leakage, and whether the lubricating oil circuit is smooth. 2 touch: The vibration of the injection molding machine, the heat of the components, the temperature of the oil pipe, and the state of mechanical movement. 3 Listen: Is there any abnormal sound.

4 Nose: Check for burnt, leaking, or other odors.

5 checks: changes in the shape and position of the workpiece, changes in the performance parameters of the injection molding machine, and abnormal circuit checks. 2. Evaluation of inspection results

Evaluate whether the fault diagnosis is correct, whether the fault clues are found, and whether the inspection results are consistent.

Step 3: Determination of Fault Location

1. Identify system structure and determine testing methods

Refer to the instruction manual of the injection molding machine, identify which structure the injection molding machine is, what methods are used for testing, what testing methods are required, what testing parameters or performance parameters may be obtained, under what operating conditions the testing must be carried out, what safety measures must be followed, and whether an operating license is required.

2. System detection

Use the most suitable technology for system structure detection. At appropriate testing points, compare the results obtained from input and feedback with normal values or performance standards to identify suspicious locations.

Step 4 Repair or replace

1. Repair

Find the cause of the malfunction, repair the injection molding machine malfunction and take preventive measures; Check relevant parts to prevent the spread of faults.

2. Replacement

Properly assemble, debug, and replace parts, and pay attention to relevant components. Repair or scrap the replaced parts.

Step 5: Conduct performance measurement

1. Start the injection molding machine

After component assembly and debugging, start the injection molding machine, manually (or jog), and then perform no-load and load measurements.

2. Adjust the speed of load change from low to high, load from small to large, and the maximum system pressure should not exceed 140kg/cm2. Measure the performance according to the specified standards.

3. Expand the scope of performance testing

Gradually expand the scope of performance testing from local to system as needed. Pay attention to the operation status of the non fault zone system. If the performance meets the requirements, it will be delivered for use. If it does not meet the requirements, the fault location will be re determined.

Step 6 Record and provide feedback

1. Collect valuable information and data, such as the occurrence time, fault phenomenon, downtime, repair time, parts replacement, repair effect, unresolved issues, settlement costs, etc. of injection molding machine faults, and store them in the archives according to the specified requirements.

2. Statistical analysis

Regularly analyze the usage records of injection molding machines, analyze downtime losses, revise memo directories, find key measures to reduce maintenance operations, study fault mechanisms, and propose improvement measures.

3. Report relevant faults to the competent department according to the procedure and provide feedback to the injection molding machine manufacturing unit.

3、 Deployment Procedure for Fault Management

To do a good job in fault management of injection molding machines, it is necessary to understand the causes of faults, accumulate information and data on common and typical faults, conduct fault analysis, attach importance to the study of fault patterns and mechanisms, and strengthen daily maintenance, inspection, and pre repair. The deployment program for fault management has the following 8 aspects.

1. Do a good job in publicity and education, so that operators and maintenance workers can conscientiously record, count, and analyze injection molding machine faults, and provide reasonable suggestions.

2. Based on the actual production of injection molding and the characteristics of injection molding machine conditions, divide the injection molding machines in use into three categories: A, B, and C to determine the focus of fault management.

3. Use monitoring instruments to conduct planned monitoring of key parts of key injection molding machines, and timely detect signs of faults and deterioration information.

General injection molding machines also need to conduct daily spot checks, patrol inspections, regular inspections (including accuracy checks), and integrity checks through human senses and general testing tools, with a focus on mastering the technical status and abnormal phenomenon information of easily malfunctioning parts, mechanisms, and components. At the same time, inspection standards should be established to determine the boundaries between normal, abnormal, and faulty injection molding machines.

4. Conduct fault analysis and train injection molding machine maintenance workers to master fault analysis methods.

5. Fault records are the basic data for implementing fault management of injection molding machines, as well as the original basis for fault analysis and handling. The records must be complete and correct. After on-site inspection and fault repair by injection molding machine maintenance workers, they should follow& Ldquo; Injection Molding Machine Fault Repair Form& Rdquo; Fill in the content carefully, and the workshop mechanics will conduct monthly statistical analysis and submit it to the injection molding machine management supervisor.

6. Workshop injection molding machine maintenance personnel should gather on a monthly basis in addition to daily monitoring of fault situations; Ldquo; Fault Repair Order; Rdquo; And maintenance records. Through the statistics, organization, and analysis of fault data, the fault frequency and average fault interval of various injection molding machines are calculated. The fault dynamics and key fault causes of a single injection molding machine are analyzed to identify the occurrence patterns of faults, in order to highlight key measures and take countermeasures. The fault information analysis data is organized and fed back to the planning department to arrange preventive repair or improvement measures. It can also be used as a modification of the regular inspection interval The basis for checking the content and standards.

Based on the collected data, statistical analysis charts can be drawn. For example, the dynamic statistical analysis table for single injection molding machine faults is an effective method for maintenance teams to visually manage faults and other issues. It not only facilitates management personnel and maintenance workers to timely grasp the situation of various types of injection molding machine faults, but also has clear goals when determining maintenance strategies.

7. Through the daily patrol inspection of maintenance workers and the status inspection of injection molding machines, the status information and fault symptoms obtained, as well as relevant records and analysis data, will be promptly arranged by the workshop injection molding machine maintenance personnel or repair team leader to address the problems of various types of injection molding machines, fully utilizing production gap time or holidays, and achieving prevention first to control and reduce the occurrence of faults. For certain fault symptoms and hidden dangers that cannot be borne by daily maintenance, feedback will be given to the planning department to arrange planned repairs.

8. Develop a fault information management flowchart.

4、 Fault patterns of injection molding machines

Studying fault patterns is very beneficial for formulating maintenance strategies and establishing a scientific maintenance system. During the use of injection molding machines, their performance or condition gradually decreases over time. Before many faults occur, there are some signs, which are called potential faults. The identifiable physical parameters indicate that a functional fault is about to occur, and a functional fault indicates that the injection molding machine has lost the specified performance standards.

The variation pattern 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 over time: early failure period, occasional failure period, and consumption failure period.

1. Early failure period

The injection molding machine is in the early failure period, with a high initial failure rate, but the failure rate rapidly decreases over time. The early failure period is also known as the running-in period for mechanical products. The duration of this period varies depending on the design and manufacturing quality of products and systems. The faults that occurred during this period were mainly caused by defects in design and manufacturing, or by improper use of the environment.

2. Occasional failure period

The injection molding machine enters a period of occasional failure, and the failure rate is generally stable and tends to a constant value. During this period, the occurrence of faults is random. During the occasional failure period, the failure rate of the injection molding machine is the lowest and stable Therefore, it can be said that this is the optimal state period or normal working period of the injection molding machine. This section is called the effective lifespan. Occasional failures are often caused by improper design, use, and inadequate maintenance. Therefore, by improving design quality, improving usage management, strengthening monitoring, diagnosis, and maintenance, the failure rate can be reduced to the lowest level.

3. Loss and failure period

In the later stages of the use of injection molding machines, the failure rate began to rise. This is caused by wear, fatigue, aging, corrosion, etc. of injection molding machine components. If major repairs are carried out at the turning point, which is the beginning of the wear and tear failure period, the failure rate can be economically and effectively reduced.

The three stages of the failure rate curve change of injection molding machines truly reflect the law of the failure rate change from running in, debugging, normal operation to major repairs or scrapping. Strengthening the daily management and maintenance of injection molding machines can extend the occasional failure period. Accurately identifying inflection points can avoid excessive repair or expansion of repair scope, in order to achieve the best investment efficiency.
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