Plastic injection molding machines are also called plastic injection molding machines or plastic injection machines. It is the main molding equipment for making thermoplastics or thermosetting materials into plastic products of various shapes by using plastic molding dies. Divided into vertical, horizontal, all-electric. Plastic injection molding machines can heat plastics and apply high pressure to molten plastics to make them eject and fill the mold cavity.
2 considerations edit
In order to do a good job in the management and prevention of injection molding machine failures, it is necessary to grasp the causes of the injection molding machine failures, accumulate data and data of frequent and typical failures, carry out failure analysis, attach importance to the study of failure laws and failure mechanisms, and strengthen daily maintenance and inspection. And preparatory. The failure management process has the following 8 aspects:
1. Do a good job of propaganda and education, so that the operating workers and maintenance workers consciously record, statistics and analyze the failure of the injection molding machine, and put forward reasonable suggestions.
2. Closely combine the actual situation of injection production and the characteristics of the injection molding machine, and divide the injection molding machine in use into A, B, C three categories to determine the focus of fault management.
3. Use monitoring instruments to carry out planned monitoring of key parts of key injection molding machines, and timely find signs of failures and degradation information.
General injection molding machines also need to perform daily inspections, roving inspections, periodic inspections (including accuracy inspections), and intact condition inspections through human senses and general inspection tools, focusing on mastering the technical status and abnormalities of parts, mechanisms and parts that are prone to failure. Phenomenon information. At the same time, it is necessary to formulate inspection standards to determine the limits of normal, abnormal, and faulty injection molding machines.
4. Carry out failure analysis and train maintenance personnel of injection molding machines to master failure analysis methods.
5. The fault record is the basic data for the fault management of the injection molding machine and the original basis for fault analysis and processing. The record must be complete and correct. After inspecting and troubleshooting the injection molding machine maintenance workers at the site, they should carefully fill in the contents of the "Injection Mold Repair Sheet", and the shop mechanics analyze and report to the supervisor of the injection molding machine on a monthly basis.
6. In addition to the daily maintenance of the breakdown situation of the injection molding machine maintenance personnel in the workshop, the "failure repair list" and maintenance records should be compiled monthly. Through statistics, sorting and analysis of fault data, calculate the fault frequency and average fault interval of various injection molding machines, analyze the fault dynamics and major fault causes of a single injection molding machine, and find out the law of fault occurrence in order to highlight key measures. Countermeasures, feedback and analysis of failure information to the planning department in order to arrange preventive repair or improvement measures plan, can also be used as a basis for modifying the periodic inspection interval, inspection content and standards.
According to the statistically organized data, statistical analysis charts can be drawn. For example, a single dynamic analysis table for the failure of a single injection molding machine is an effective method for maintenance teams to visually manage faults and other problems. It is convenient for managers and maintenance workers to grasp various types of injection molding in a timely manner. In the event of machine failure, clear goals can be identified when determining maintenance countermeasures.
7. Through the daily inspection of the injection molding machine maintenance workers and the inspection of the injection molding machine status, the obtained status information and failure symptoms, as well as relevant records and analysis data, the workshop injection molding machine maintenance staff or repair team leader has problems with various types of injection molding machines. In time, arrange daily maintenance, make full use of production gap time or holidays, and prevent in advance to control and reduce failures. For some failure symptoms and hidden dangers, the daily maintenance can not afford, then feedback to the planning department to arrange planned repairs.
8. Develop a flowchart of fault information management. 
Investigate the function or state of injection molding gradually decrease with the use of time. Many failures will have some warning signs before they occur. This is the so-called potential failure. Its identifiable physical parameters indicate that a functional failure is about to occur. The functional failure indicates that the injection molding machine has lost its prescribed performance standards.
The regularity of the failure rate of injection molding machines over time is often called the bathtub curve. The change of the failure rate of injection molding machines with time is roughly divided into three phases: early failure period, occasional failure period, and wear-out failure period.
Early failure period
The injection molding machine is in the early failure period, and the failure rate at the beginning is very high, but the failure rate decreases rapidly over time. The early failure period is also called the run-in period for mechanical products. The length of this period varies depending on the design and manufacturing quality of the product and system. The failures during this period are mainly caused by defects in design, manufacturing, or improper use of the environment.
2. Incidental failure period
The injection molding machine enters into the occasional failure period, and the failure rate is generally stable, and tends to a fixed value. During this time, failures occur randomly. During the occasional failure period, the failure rate of the injection molding machine is low and stable. Therefore, it can be said that this is the good condition or normal working period of the injection molding machine. This section is called effective life.
Infrequent failures often result from improper design, poor use, and poor maintenance. Therefore, by improving the design quality, improving the use management, strengthening the monitoring diagnosis and maintenance, etc., the failure rate can be reduced to a low level.
3. Attrition failure period
In the later stages of injection molding machine use, the failure rate started to rise. This is caused by wear, fatigue, aging, corrosion, etc. of the injection molding machine parts. If overhaul is performed at the inflection point, that is, at the beginning of the wear failure period, the failure rate can be reduced economically and effectively.
The three stages of the change in the failure rate curve of the injection molding machine truly reflect the change in the failure rate of the injection molding machine from running-in, commissioning, normal work to overhaul or scrap. Strengthening the daily management and maintenance of the injection molding machine can extend the occasional failure period. Accurately finding the inflection point can avoid excess repairs or the expansion of the repair range to obtain better investment benefits. 
cause of issue
When the injection molding machine fails, in order to ensure the fast and effective troubleshooting and troubleshooting, a certain procedure must be followed. This procedure is roughly as follows.
Symptom analysis while keeping the scene live
1. Ask the operator
(1) What happened? Under what circumstances? When did it happen?
(2) How long has the injection molding machine been running?
(3) Was there any abnormal phenomenon before the failure occurred? What audible or audible and visual alarm signal? Is there smoke or odor? Are there any mistakes, please pay attention to the inquiry method?
(4) Is the control system operating normally? Has the operating procedure changed? Are there any special difficulties or abnormalities during operation?
2. Observe the overall machine status and various operating parameters
(1) Are there any obvious anomalies? Is the part blocked or damaged? Is the hydraulic system loose or leaking? Are the wires 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. Inspection monitoring indicating device
(1) Check that all readings are normal, including pressure gauges and other instrument readings, and oil level.
(2) Check whether the filters, alarms and interlocking devices, motion output or display are normal.
4. Jog injection molding machine inspection (under the allowable conditions)
Check intermittent, long-lasting, fast-forward or slow-forward conditions to see if the output is affected under these conditions, and if it may cause damage or other danger.
The second step is to check the injection molding machine (including parts, components and circuits)
1. Use sensory examination (continuing the process of in-depth observation)
1 see: whether the plug and socket are abnormal, whether the motor or pump is operating normally, whether the control and adjustment position is correct, whether there are traces of arcing or scorching, whether the fuse is good or bad, whether the liquid leaks, and whether the lubricating oil path is unobstructed.
2 touch: vibration of the injection molding machine, the heat of the element (group), the temperature of the oil pipe, and the state of the mechanical movement.
3Listen: There is no abnormal sound.
4 Smell: whether there is burnt smell, leaky smell, other odors.
5 check: changes in the shape and position of the workpiece, changes in the performance parameters of the injection molding machine, abnormal line inspection.
2. Evaluation results
Evaluate whether the fault judgment is correct, whether the fault clue is found, and whether the inspection results are consistent.
The third step is to determine the location of the fault.
1. Identify system structure and determine test method
Consult the injection molding machine manual to identify which structure the injection molding machine uses, what method to use for testing, what testing methods are needed, what test parameters or performance parameters may be obtained, under what operating conditions to test, what safety measures must be followed, and whether Operational license.
2. System detection
Adopt technology suitable for system structure detection. At appropriate test points, compare the results obtained with input and feedback with normal values or performance standards to identify suspicious locations.
Step 4 Repair or replace parts
Find the cause of the failure, repair and take preventive measures against the failure of the injection molding machine; check the relevant parts to prevent the failure from spreading.
2. Replacement of accessories
Correctly assemble and replace the replacement parts, and pay attention to the relevant parts. Replaced parts for repair or scrap.
The fifth step is performance measurement
1. Start the injection molding machine
After the components are assembled and debugged, the injection molding machine is started, manually (or jog), and then no-load and load measurement are performed.
2. Adjust the load changing speed from low to high, load from small to large, and the system pressure cannot exceed 140kg / cm2. Measure the performance according to the specified standards.
3. Expand the scope of performance test
As required, the performance test range is gradually expanded from local to system. Pay attention to the operating status of the system in the non-fault zone. If the performance meets the requirements, it will be delivered for use. If it does not meet the requirements, the fault location will be determined again.
Step 6 Record and feedback
1. Collect valuable information and data, such as the time of the injection molding machine failure, the phenomenon of failure, downtime, repair hours, repair parts, repair effects, unresolved problems, settlement costs, etc., and store it in the file according to the required 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. Report the relevant faults to the competent authority according to the procedures and feed them back to the injection molding machine manufacturing unit or the injection molding machine equipment maintenance contractor. 
1. Noise and vibration of oil pump
The cause of the failure:
1. The oil pump motor is installed differently.
2. The coupling is loose.
3. Internal failure of the oil pump.
4. The oil level is too low. Inhale air from the strainer or joint to the oil.
5. Inhale air from the moving shaft of the motor.
6. The oil filter is blocked by oil pollution.
7. The return oil pipe is loose to suck in air or oil pipe on the oil surface, and mix the air into the oil.
Method of exclusion:
1. Concentricity should be adjusted to within 0.1MM.
2. Correct the coupling.
3. Repair or replace the oil pump.
4. Increase the amount of oil above 400mm in the oil filter and joint position.
5. Replace the rotating shaft seal ring.
6. Clean the oil filter and filter the oil.
7. Clean the oil filter and filter the oil.
8. Tighten the oil return pipe and extend the oil return pipe under the oil surface.
The cause of the failure:
1. The motor bearing is damaged.
2. The motor coil winding is faulty.
3. The motor wiring is wrong, and the noise increases when the system pressure rises.
Method of exclusion:
1. Replace the connecting bearing.
2. Replace or repair the motor.
3. Refer to the wiring diagram for wiring again.
Third, the total pressure valve noise (overflow valve)
1. There is air in the front cavity of the pilot valve of the relief valve.
2. The damping hole on the main valve core of the relief valve is blocked by oil. 3. The pilot valve and the valve seat are not tightly matched.
4. The spring is deformed or installed incorrectly.
5, the remote port oil flow is too large.
6. The viscosity of hydraulic oil is too low or too high.
7. Resonance with components in the circuit.
Method of exclusion:
1. Strengthen the seal, and repeatedly lift and adjust the pressure several times to exhaust.
2. Clean the valve body to make the damping hole unobstructed.
3. Repair or replace.
4. Overhaul and replace the spring.
5. Reduce the remote mouthpiece.
6. Replace the oil.
7. The pressure setting of other components cannot be close to the pressure setting value of the relief valve.
4. Noise of Hydraulic Cylinder (1) Air is mixed in the oil or the air in the hydraulic cylinder is not completely exhausted, and cavitation is generated under the action of high pressure, which causes large noise. In this case, exhaust the air in time.
(2) The cylinder head oil seal is too tight or the piston rod is bent, and it will also generate noise due to other forces during the movement. In this case, you must replace the oil seal or straighten the piston rod in time.
Fifth, pipeline noise. Pipe noise is usually caused by too many dead bends in the hydraulic pipe or loose fixing sleeves. Therefore, try to avoid dead bends on the line of the hydraulic pipeline and check the tightness of the ferrule in time. 
3 common faultsedit
Before repairing the injection molding machine, it is necessary to fully understand the working principle of the machine, such as electrical principle, hydraulic principle and mechanical principle. Secondly, we must follow the four steps of the ancients to see a doctor: look, smell, ask, and cut. Keep a clear head, don't be impatient, first figure out which faults are electrical, hydraulic, and mechanical. Simple distinctions can be made according to the following steps:
The following are general faults and handling methods for reference
First, the oil pump motor does not start
1. The motor can't turn, and at the same time it makes an abnormal sound, immediately turn off the emergency stop button, check whether the fuse is blown or loose, and then check whether the three-phase power of the motor is normal
2. When the motor start button is pressed, there is no possibility that the motor sounds like the button switch, the AC contactor wire is loose, or the thermal relay is activated.
3. The oil pump is stuck causing the motor not to rotate (at this time, the motor has some sound)
4. The motor burns out. Repair and find the cause according to the original specifications (such as phase failure, overload, poor AC relay contacts, loose contact of the motor wire, or unbalanced and unstable three-phase power voltage).
Second, the motor can turn, but can not afford pressure or large pump
1. The electromagnetic coil of the small pump electromagnetic relief valve or pressure proportional valve is not attracted or the internal valve core is stuck by debris. Remove and clean it. At the same time, check whether the solenoid coil is burned, the wiring is loose, or the contact is poor.
2, the oil pump is damaged, repair or replace the oil pump
3, the oil level is too low, causing the pump to empty
4. Is the oil filter blocked?
5. Whether the motor is reversed and commutated
6. There is air in the oil pump.
7. The main valve core controlling the relief valve of the big pump is stuck, remove the relief valve for cleaning
Third, the mold is not closed
1. The wiring of the safety door travel switch is loose or damaged, and the safety door travel is not depressed. Check SQ1, SQ2, and SQ3.
2.SQ4 limit switch is closed
3.The mold clamping solenoid valve is stuck or the solenoid valve socket is loose.
4.The formation switch of the thimble back is not closed
5. System pressure is not available: repair according to item (2)
Fourth, no injection or slow
1. The injection pressure is low and the speed is too slow: increase the injection pressure and increase the injection speed
2. Plastic heating temperature bottom: increase temperature
3. The nozzle is clogged, remove the heating and cleaning
4.The injection time is too short
5.The injection solenoid valve is stuck
6, injection solenoid valve must not be electric. Check electrical reasons
Fifth, do not preform or preform too slowly
1. The pre-mold end travel switch has been closed.
2.The one-way throttle valve is closed
3, the material temperature is too low, increase the material temperature
4, pre-plastic solenoid valve is stuck, remove and clean
5. Pre-molding pressure is too low, increase pre-molding pressure
6. The screw enters the foreign body and jams the screw. Disassemble screw cleaning, barrel cleaning
7, the hydraulic motor is broken, the bearing is stuck
6. The screw rotates during pre-plasticization, but does not feed
1.Back pressure is too high
2. There is insufficient cooling water at the feeding port, and the material in the feeding port is "bridged"; adjust the water volume and remove the plastic block with sticky structure
3. Out of stock
5, the back pressure is adjusted too high, lower the back pressure
7.Can't adjust or difficult to adjust
1.The system pressure is adjusted to the bottom
2. The rear template tie rod nut is stuck due to impurities or lack of lubricating oil and grease; cleaning the tie rod nut and repairing, pay attention to the same axial clearance of the four nuts when installing, then add grease
3. The mold adjustment solenoid valve is stuck or the socket is loose: check and repair
4, mold adjustment hydraulic motor is damaged, repair or replace
Eight, the hydraulic oil is too high
1. The oil pump pressure is too high: appropriately lower the working pressure according to the plastic molding process
2. Insufficient oil quantity in fuel tank: add enough hydraulic oil
3. The oil cooler is used for a long time, it is full of scale, and the cooling effect is poor. Clean the cooler
4. The cooling water flow is not large enough, or the temperature of the cooling water is not low enough
Nine, semi-automatic operation failure
The semi-automatic operation of this machine is opened by the safety door, the stroke switch is closed, and the signal is sent to make the machine start the semi-automatic action, and then the mold is closed. After the SQ4 stroke switch is touched, the mold is closed and the injection is started. The injection time relay starts to count and the injection time reaches After that, pre-molding is started. After encountering the stroke switch at the end of pre-molding, flow prevention is started. After touching the flow-proof stroke switch, the cooling time relay starts counting. After the time is reached, the mold is opened, and then the mold is opened. After the mold terminates the stroke switch, it will perform the ejection action. When it encounters the ejection end of the stroke switch, it will perform the ejection action. After the ejection terminates the stroke, it waits for the safety door to open. In this way, the work is repeated. It can be seen from the above that if the manual is normal, it is generally caused by the absence of signals from the travel switch and time relay. According to the failure of the semi-automatic action at that stage in the mechanical cycle, the corresponding control elements are found based on the electrical and hydraulic schematic diagrams and checked to solve them. 
Precautions for downtime
If the injection molding machine is suspended, the remaining plastic must be sprayed clean or the plastic can be used to clear the remaining plastic in the injection cylinder or barrel through the injection molding machine. When the plastic fades, the number of sprays will increase. For minor repairs, the heater of the shot cylinder must be adjusted to a low value, such as 150 ° C, to minimize the possibility of thermal decomposition.
Before injection of thermally stable plastic (such as PS or PE), if the machine has been stopped for one night in advance, you only need to turn off the slide at the bottom of the hopper and the heater of the shot cylinder (only the heater of the nozzle), and spray the shot cylinder clean. clean. After the nozzle is completely cleaned, cool down the barrel as much as possible. After the injection molding machine has cooled down, turn off all equipment. The injection molding machine is fully prepared for reheating.
If the temperature of the injection cylinder or barrel is high, only the above steps need to be slightly changed to prevent the resin from thermal decomposition. For example, turn off the spray cylinder heater (only the nozzle heater is turned on), or cool the barrel as high as possible, during which the remaining resin is continuously sprayed. Close the slide at the bottom of the hopper, and then try to clear the oblique rubber in the barrel. If there is no plastic spray, you can turn off the equipment for next time.
If the plastic is decomposed or burned in the injection molding machine, it will eventually discolor, making the finished product a waste. In this case, the injection molding machine must be completely shut down and sprayed clean. The precautionary method is to spray a resin that is sensitive to heat with a plastic with high thermal stability, so that it can withstand subsequent heating.
Some plastics (such as POM, PVC) are easy to decompose. If the injection molding machine suddenly stops during injection, the nozzle heater should be turned on before continuing the injection molding. Only when the plastic has the nozzle melted, can the injection cylinder heater be activated. The temperature of the shot cylinder or barrel should be adjusted to about 140 ° C. Then raise the temperature to the processing temperature and spray the remaining plastic as soon as possible. Sprayed plastic must be placed in cold water. For other plastics to be modified, it is better to use natural or non-fire-resistant grades of PS or PE as spray cleaners; if the remaining materials are not sprayed thoroughly, mix POM with PVC or mix them successively.
Before stopping or switching to another plastic, you must check that the steps taken are correct. The material supplier has printed a booklet with sufficient information. You should read it carefully before operation to understand the "standard shutdown procedures" required for each plastic. The booklet should be placed next to the injection molding machine so that it can be accessed by the operator at any time. 
2. Source of information
3. Source of information
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5. Source of information
6. Precautions for plastic injection molding machine during shutdown Plastic injection molding machine. 2011-1-12 [Date of reference 2012-10-22]