Brief analysis and diagnosis of on-site faults in

2022-08-17
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With the rapid development of manufacturing industry, machining centers are increasingly widely used in industrial production. The advantages of high automation and high efficiency equipment have added strong impetus to modern manufacturing. The following problem is how to maintain these equipment is particularly important. The following describes the on-site faults in five aspects

1 external signal fault

the peripheral signals of the machining center are mainly used in parts such as shafts, tool libraries, manipulators, exchange worktables, auxiliary equipment, external interfaces of modules and auxiliary contacts of control appliances. The main functions include: liquid level detection, temperature detection, pressure detection, in place detection, travel detection, status detection, button contacts and various enablers. This kind of peripheral signal is usually set with corresponding alarm code and prompt information, and the maintenance personnel can quickly locate the fault point through the prompt. At the same time, it can also be comprehensively diagnosed through: a= ladder diagram, signal status lookup interface and: b= device indicator light. After finding the fault point, adjust, repair or replace it according to the actual situation. Occasionally, there is a shortage of spare parts in stock. Under the condition that it is determined that the normal operation of the machine tool will not be affected, the fault point can be temporarily shorted to relieve the production pressure. As soon as the spare parts arrive, they can be replaced in time. For some parts with relatively high action frequency, special attention should be paid to observation and recording, such as spindle tool status, return reference point stop, exchange workbench position detection, tool magazine and manipulator position status, etc. The range of external signals is wide and there are many faults. Here are a few examples to illustrate

(1) "1008 hydraulic pressure insufficient" occurs in a thm6350 horizontal machining center Alarm, and the alarm appears regularly. After observation, it is found that the actual pressure is fully satisfied. This is a typical auxiliary equipment external alarm. Alarm tipolyone, Patel's exclusive licensor of reflex bioplasticizer in North America and Asia, showed that the pressure relay had been damaged. Since this type of pressure relay is temporarily unavailable in the spare parts warehouse, the resistance at both ends of this point measured by multimeter meets the short-circuit requirements. At the same time, the operator must pay attention to the actual hydraulic pressure and report it at any time before the spare parts arrive. After treatment, the production pressure is relieved

(2) a vmc1000c vertical machining center adopts FANUC 0i-ma numerical control system, and the Z and a axes are driven by a two axis module. After removing the rotary table, the alarm message "401 Z axis rea hydroxyapatite (HA) is composed of calcium phosphate hydroxide dy off" appears

due to the need of the task, it is decided to temporarily use the X, y and Z axes for other workpiece processing. The a-axis should be shielded. The shielding steps are: first, modify the NC parameter? A of no 1023 is "- 4"; Then set the holding relay k8.2 in PMC to "1"; Finally, the interface of the original driver module is blocked. After initial inspection on site, it is considered that it has been achieved, but the alarm is still not cleared. The analysis shows that the reason is that the blockade is not effective, and the connector used is not short circuited and the model is wrong. Finally, the pcr-ev20mdt connector with the model of hrios f is used, and its 9 and 10 (i.e. *drdyn and *mconn) are short circuited and blocked. After that, the alarm of the machine tool is cleared, which meets the working requirements. The reason is that the staff used the wrong connector

(3) an imported five coordinate machining center adopts ab10 numerical control system. The automatic tool magazine cannot change the tool normally, the cutter head turns to the correct tool position and then rotates back, and the tool position is not distinguished normally. The counting method of the tool magazine adopts 8421 code and uses five sensors to distinguish, that is, the hole on the metal cutter head corresponding to the sensor head is "0", otherwise it is "1". According to the investigation, the machine maintenance personnel have disassembled the tool magazine recently, but it was moved out as a whole during disassembly, excluding the ectopic position of the upper and lower cutter heads, and the manual one-step rotation is normal. According to the analysis of the control principle, it is believed that the number of knives is incorrect, and the status of five induction signals should be checked whether they are normal (the light green indicator light of the sensor indicates that the power is sent, and the yellow indicator light indicates that the induction status is 1). Rotate the cutter head in manual mode for a week, and observe carefully and find that sensor 3 has been in the same state. At this point, judge whether there is dirt or iron filings on the sensor head, or the sensor has been damaged. Put your finger into the hole and touch it. It is found that there are iron filings on it. After removal, the signal state is restored and the automatic tool change is normal

2 connecting device failure

connecting device main guide lines and connectors. This kind of fault is mainly manifested in "There are three aspects: the first is the damage and fracture of wires; the second is the short circuit or interference between wires; the third is the poor connection of joints or interfaces; the fourth is the wrong connection or MIS insertion. As the information channel of equipment, connecting devices play an important role in supporting the operation of equipment. According to our incomplete statistics in maintenance, nearly 30% of machine tool failures are caused by this aspect. The processing environment and conditions are the direct causes of this aspect, and some of them are attributed to Aging and corrosion caused by long service time

for example, a Ningjiang thm6350 horizontal machining center is equipped with FANUC 0i-m CNC system. When exchanging worktables, after pressing the "manual/automatic start" button, the pallet (inner worktable) rises, but the pallet frame does not rise. This state is always maintained, and the exchange of worktables cannot be realized. The lifting and lowering of the bracket is controlled by the hydraulic system. Check that the hydraulic pressure is normal. Check the solenoid valve that controls the lifting of the bracket and find that it is not implemented. The solenoid valve is controlled by the normally open contact of relay ka13, and the coil of relay ka13 is directly supplied with 24V power from PMC output point y1004.1. Check the status of y1004.1 through PMC status display function, and it is always "0" before and after execution, that is, no signal is given. The analysis shows that a certain input condition is not satisfied, which makes the machine tool in a waiting state. It is decided to start with y1004.1 and use the dynamic display function of PLC ladder diagram to diagnose the fault. The main ladder diagrams involved are shown in Figure $. In the manual mode, the conduction path of the normal exchange workbench is shown in the direction of the arrow in the figure, that is, r68.3, r62.0 and y1003.5 conduction should be met. It can be seen from the ladder diagram that r68.3 is on when r68.2 and r62.0 are on, and r62.0 is controlled by external signals. Through dynamic observation, it is found that x1004.5 passes and x1006.3 does not change. Through investigation, x1006.3 is the signal that the support plate (workbench) rises to the position. When you approach the sensor with a metal ruler, the signal does not change, and you think it is the sensor itself that is damaged. The fault is still found after replacement. It was found that the 24V wire was open circuit during wiring calibration. After disassembling the guard board, it was found that one connector of the wire had been broken due to oil corrosion. After reconnecting. The machine tool returns to normal

as the information transmission channel between control elements, the connecting devices, like the channels in life, must be dredged frequently to prevent abnormal conditions such as channel blockage, disconnection, branching and crossing. Therefore, we should attach great importance to the daily care of machine tool connecting devices, keep all parts of the machine tool clean and tidy, ensure that the line connection and direction are rigorous and reasonable, find problems and deal with them in time, and optimize and improve unreasonable and future problems in time, so as to improve the reliability of use

3 actuator failure

the actuator mentioned here includes: motor, relay, contactor, solenoid valve, etc. Relatively speaking, this part of components is the most intuitive to see when opening the control cabinet. After such faults occur, attention should be paid to the sequence of troubleshooting. For example, there is an electric machine to weigh the quality of engine oil products that are not working under the conditions of smooth gap and inclusion. The possible reasons are motor overheating, debris blockage, air switch or contactor damage, motor damage and high processing conditions. At this time, disconnect the motor line to distinguish whether there is a problem on the motor side or the strong current cabinet side. Sometimes, conclusions can be drawn even through visual methods, such as sight, touch, smell, sound, etc

for example, a thk46100 horizontal machining center adopts FANUC 0-mate numerical control system. During automatic processing, the alarm "1019 delay overload" appears. Refer to the external alarm information table and the prompt is air switch trip. Open the electrical cabinet and find that QF2 air switch has tripped, which is thought to be caused by excessive instantaneous voltage fluctuation. The alarm will be eliminated after closing and opening again. Trip again after trial processing. After investigation, it was found that the cutting fluid motor jumped violently at the moment of starting, and tripped again after about 10s. Check that the motor is damaged. After replacement, the machine tool returns to normal

4 various parameters, data and program failures

parameters, data and programs are essential conditions for the operation of CNC equipment. Among them, it mainly includes NC machine tool parameters, PMC parameters, compensation parameters, PLC program, tool change program, macro program, machining program, etc. Such failures are mainly manifested in the following aspects: (1) the loss of system parameters, resulting in system chaos or loss of a function; (2) Partial or individual changes in system parameters; (3) Improper operation, data writing error; (4) Relevant procedures are lost, modified and improperly prepared; (5) Improper setting during parameter or data modification. Once the parameters are seriously damaged, it is often necessary to reinstall the system to recover

a Ningjiang thm6350 horizontal machining center, using FANUC 0i-m numerical control system. In the process of machining, the actual size of the machine tool movement is inconsistent with the given value, and there is no alarm information. Before this fault, the machine tool had been operated with "the digital display changed while the actual position did not move when the shaft was moving, and it was found that" the shaft pulley was broken. After replacing the pulley, the "axis zero offset (parameter 1850) was corrected. The actual value was found to be inconsistent with the given value just after the test run. There are usually (possible reasons for this kind of failure: first, the problem of position ring, which includes the failure of grating ruler, encoder and their connecting cables, or the failure of servo module level. Second, it involves the problem of numerical control parameters, such as feed unit (metric 6 British system) Check whether the setting of multiplication ratio parameter has changed. Third, there is a certain mechanical resistance or loose connection. Based on the above cause analysis, we checked and eliminated one by one from easy to difficult. After investigation, the fault is due to the parameter setting of the feed unit changed from the original metric system to the British system, that is, the parameter 1001 changed from "0" to "1". After changing the parameter back to "0", the machine tool returns to normal

it is particularly mentioned that during the automatic tool change process of the machining center, the execution of a certain sentence is suddenly interrupted, and there is an alarm number without data prompt and information prompt. At this time, you should carefully find the tool change program in the system (the tool change program of large tool magazine is also divided into main program and subroutine, and you can use the search function to find the fault segment), read the meaning of the pause sentence, analyze the logical relationship, and effectively use the program to diagnose the fault. At the same time, make sure that the tool change procedure has not changed

5 servo system fault

in order to ensure that the machining center can achieve high machining accuracy, it must be supported by a servo system with excellent performance, strong reliability and high accuracy. With the rapid development of CNC industry, servo system has also made unprecedented progress. The three loop structure of position servo makes full use of the potential of the equipment, high speed and accurate positioning, so that CNC machine tools have been widely used. Servo system has entered the era of AC servo in an all-round way. Modularization, integration and openness are its development trend. At the same time, it also brings great convenience to the maintenance work. Once there is a fault, in order to win production time, the spare parts replacement method can be used to replace the machine tool

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