CNC machine tool technology brief
From:Taian Haishu Machinery Co.,Ltd. Updatetime:2012-1-17 10:34:05 Views：
CNC Maintenance Technology Brief
As electronic technology and automation technology, digital technology more widely. Microprocessor-based, large scale integrated circuit as a symbol of CNC equipment in our production, introduction and promotion of a large number of applications, they give the machinery manufacturing industry to create the conditions, and bring great benefits. At the same time, because of their nature, complexity and characteristics of high intelligence, in the maintenance of the theory, techniques and tools have undergone a leap change.
CNC maintenance techniques not only to safeguard the normal operation of the premise, the development and improvement of numerical control technology also played a huge role in promoting, so now it has become a specialized discipline. In addition to any CNC equipment is a kind of process control equipment, which requires it in real-time control of every moment of accurate work. Any part of the fault and failure, so that the machine will shut down, resulting in the production halt. Thus the principle of numerical control system so complex and sophisticated structure of the device for repair it is very necessary.
Here we have from the basic structure of modern CNC system to start to explore the numerical control system diagnosis and repair.
1, the composition and characteristics of the CNC system
Numerical control system on the world wide range of different forms, form the structure has its own characteristics. These structural features derived from the basic requirements for the initial system design and engineering ideas. Control systems such as point and continuous path control systems have different requirements. For the T system and the M system, there are also very different, the former suitable for rotary part processing, which is suitable for special-shaped non-rotating body parts processing. For different manufacturers, the historical development factors and vary in their complexity factors, strengths and weaknesses in the design may be thinking. For example, the United States Dynapath system uses a small board structure, combined with easy and flexible replacement board, FANUC system in Japan is a large plate structure tends to make it conducive to reliability of the system, prompting the system MTBF rate continues to increase. In either system, however, they constitute the basic principles and are very similar. Generally the entire CNC system consists of three major components, namely the control system, servo system and position measuring system. Process control system according to the interpolation operation workpiece, issue control instructions to the servo drive system; servo drive system control instructions amplified by the servo motor driven mechanical movement required; measuring system detects the movement of mechanical position or speed, and feedback to the control system, to fix the control instructions. This three-part combination, form a complete closed-loop control of the CNC system.
Control system mainly consists of bus, CPU, power supply, memory, control panel and display, digital control unit, programmable logic controller control unit and data input / output interface, etc.. The latest generation of numerical control system also includes a communications unit, it can complete the CNC, PLC's internal and external high-data communications network. Servo drive system including servo drives and motors. Position measurement system is mainly used grating or radial grating incremental position encoder.
CNC system's main features are: high reliability: because once the CNC system failure, which caused huge economic losses; have a higher ability to adapt to the environment, because the numerical control system is generally for industrial control machine, its working environment for the workshop environment, requiring It has the vibration, heat, moisture, and various industrial sources of interference in the ability to work under environmental conditions; interface circuit complexity, numerical control system with a variety of CNC equipment and external equipment, matched to handle the production process at the various situations to adapt to a variety of process equipment requirements, and thus the interface circuit complexity, and work frequently.
2, a modern CNC system the basic conditions for maintenance work
2.1 The basic conditions for maintenance staff
To carry out maintenance work was good or bad depends primarily on the staff conditions. Maintenance staff must have the following requirements:
1) a high degree of responsibility and good work ethic;
2) extensive knowledge, computer skills, basic analog and digital circuits, automatic control and motor drive, detection technology and machining technology with certain aspects of the basic knowledge of foreign languages;
3) After a good technical training, information on the CNC, drive and PLC works, to understand CNC programming and programming languages;
4) be familiar with structure, with strong hands-on experimental skills and operational capability;
5) to master a variety of commonly used (especially live) test equipment, instruments and tools.
2.2 Maintenance means the conditions should have
1) ready to commonly used spare parts, accessories;
2) micro-electronic components are readily available to the actual support or supply;
3) the necessary repair tools, instruments, meters, wiring, computer. Best to have a small programming system or programmer to debug support equipment;
4) Complete information, manuals, schematics, maintenance manuals (including CNC operating instructions) and interface, adjustment and diagnostics, driver manual, PLC instructions (including the PLC user program alone), components, forms, etc..
2.3 Preparation before repair
After receiving the user's direct request, should be as direct contact with the user to quickly access site information, site conditions and fault information. Such as the CNC machine tool spindle drive into the given type, alarm indication or symptoms, whether the user-site spare parts. Accordingly, pre-analysis of the possible cause of the malfunction and location, and then before the departure to the scene, ready to relevant technical information and service tools, equipment parts, etc., so that there is prepared away.
3, on-site maintenance
On-site maintenance is a malfunction of CNC machine tools (mainly NC part) for the diagnosis, identify the fault location to the corresponding normal parts replacement, so that the machine back to normal operation. This process is the diagnosis of your system or peripheral circuit testing, to determine whether the fault, fault location and the exact location of that fault. Positioning from the machine to strip, in some cases even locate components. This is a major part of the maintenance work.
3.1 CNC system fault diagnosis
1) determine the initial data is usually more full-time, through data analysis to determine the fault lies, or failure to take the phenomenon of interface signal discrimination method according to the site may fail, but then failed with this site in accordance with the specific characteristics, one by one site inspection, preliminary identification. In practice, it may be a way can be found in failure and exclusion, sometimes need a variety of methods and use. Determine the point of failure for a variety of methods depends on the mastery of equipment failure to grasp the depth of the principles and structure.
2) alarm processing ① system alarm processing: CNC system failure, usually in the control panel display or on the fault signal and the corresponding information. Usually the operation manual or system manual adjustments are detailed in the alarm number, alarm content and approach. Since the alarm system set a single, complete, tight, clear, repair may be based on information given after each alarm and approach themselves. ② machine alarm and operation of information processing: machine tool manufacturer based on the electrical characteristics, application PLC program, the machine interface, that can reflect the failure of the electrical control or operating information to a specific symbol, is given by the display, and through specific key to see a more detailed description of the alarm. Machine Tool Plant of these alarms can provide troubleshooting manual processing, you can use the control panel or circuit programmer and PLC based process to identify the corresponding signal state, according to the logic to find the point of failure for processing.
3) No alarm or alarm malfunction can not be handled when the PLC system can not run, the system is down or the system does not alarm, but not working properly, need to occur before the system failure status information, use of the available theoretical basis for analysis, make the right judgments. The following describes the fault diagnosis and troubleshooting methods.
Fault Diagnosis
1, the conventional test method
Visual: visual fault board, carefully check for blown fuses, burnt components, smoke, cracking, with or without foreign body circuit phenomenon. This board can determine whether the over-current, over voltage, short circuit and other issues.
Hand touch: touch and jiggle components, in particular, RC, semiconductor devices loose sense, this can check out some broken legs, Weld and other issues.
Power: First, check with a multimeter between the availability of power supply circuit, you can access without the appropriate power, whether visual smoke, ignition and other phenomena, whether the abnormal hand-touch heating components, as can be found in some of the more significant failures, and reduce the maintenance range.
2, the instrument measurement
When the system fails, the use of conventional electrical testing instruments, tools, system schematics and parts of machine fault circuit voltage, power, pulse signals for measured to determine failures. If the power supply input voltage overrun, causing the power control network can be measured voltage voltmeter or voltage tester with real-time monitoring to rule out other causes. In case of position control loop circuit failure can be measured oscilloscope signal state, or whether the oscilloscope to observe the signal output phase, with or without interference. For example, a factory in Shanghai in troubleshooting, system alarms, position loop hardware failure, found to have interference with the oscilloscope signal, we connected in the circuit using capacitance method to filter out the system is working properly. Such as the reference point of a system unable to return to the case, check whether the oscilloscope can be used zero mark pulse, if no consideration is a measure of system damage.
1) with programmable interrupt controller state analysis of PLC: programmable logic controller failure, the cause of the interruption to interrupt the way the stack memory. Programmer can use the system to stop the state, bring up the interrupt stack and stack blocks, according to the instructions of the reasons for it, to identify failures. Programmable logic controller in the maintenance of which is the most common effective and fast way.
2) Interface signal check: check by using a programmable logic controller interface signals the machine control system, and the right signals and interface compared to manual will also identify the corresponding point of failure.
3) Diagnosis spare substitution method: a modern CNC system using modular design, divided into different modules according to different functions, with modern technology, the increasing scale integrated circuit technology is more complex, according to conventional methods, it is difficult to fault location to a small area, but once the system failure, in order to reduce downtime, we can block the function and symptoms, initially to determine the possible fault module, spare parts to replace it with a diagnosis so quickly determine the faulty module. In the absence of diagnostic parts of the same case can be used on-site replacement or compatible module checks for modern CNC maintenance, a growing number of cases using this method of diagnosis, and then replace the damaged module with spare parts, allowing the system to work . Maximum extent possible, reduce downtime, when using this method attention must be conducted in the state power, but also carefully check the circuit board version, model, a variety of markers, whether the same jumper for the machine data and position potentiometer should make a record, stitches should be good signs.
4) the use of system self-diagnostic function to determine: a modern full-function CNC numerical control system, especially with strong self-diagnostic capabilities, when the monitoring system through the implementation of the various parts of the work, time to determine fault, alarm information is given, and make the appropriate action to avoid accidents. Sometimes, however, when the hardware fails, you can not police, and some numerical control system can be different LED blink rate or different combinations to make the appropriate instructions, these instructions can help us with the use of a failure to accurately diagnose the location of the template . Such as SINUMERIK 8 system based on MS100 CPU board and four on the control panel lights FAULT lamp light off combinations can determine the fault location.
The diagnostic methods, in practice there is no strict time limits, it may be a way to be able to troubleshoot a variety of methods may also be required simultaneously. Its effect depends on the principle and structure of the system to understand and grasp the depth and the amount of maintenance experience.
3.2 Fault analysis of numerical control system
CNC system based on the composition, working principle and characteristics, combined with our experience in maintenance, the common phenomenon of fault location and fault analysis are as follows
1) This is the numerical position loop control system to issue commands, and with the position detection system compared to the #118alue of the feedback to further the key to complete the control task. It has a high frequency of work, and to link with the peripheral, so prone to failure.
Common faults are: ① position control loop alarm: open circuit may be measured; measurement system damage, internal damage to the digital control unit. ② not issued instructions on the movement, may drift too high, positive feedback, digital control unit failure; measuring cell damage. ③ measurement component failure, the general performance without feedback #118alue; not return the machine reference point; high speed pulse generator leakage alarm may be due to grating or read head is dirty; grating bad.
2) servo drive system power servo drive systems and power grids, and other associated mechanical systems, and work has been in frequent starting and running, so this is more part of the fault.
The main faults are: ① system damage. Generally due to network voltage fluctuations or voltage shocks. Poor power quality in most parts of China, will bring the voltage gauge machine, especially an instant gauge, without specific voltage monitoring device, it is difficult to measure, in reason to find fault, it should be noted, as well as Some are due to special causes damage. If a factory in the factory due to lightning and fleeing into the grid substation caused damage to more than one machine tool servo system. ② no control instructions, and the motor at high speed. This failure is due to the speed loop open-loop or positive feedback. For example, X or Z-axis machine instructions in case of non-high-speed operation, which is caused by positive feedback. Because the system zero drift, in the case of positive feedback, it will quickly add the motor running at high speed; If we reverse the feedback line, the machine is operating normally. Again, start the motor on the operation of machine tools, and faster and faster, until the maximum speed. This is due to the speed loop open, the system can not suppress drift caused. If the machine speed feedback wire to the ground line will cause the phenomenon. ③ processing mainly the surface, take the circular interpolation axis when changing the Boss, or motor speed crawling or vibration, such failures are generally due to improper adjustment of the servo system, the gain of the shaft and the motor system does not equal or caused by improper matching, the solution is adjusted to optimize. ④ insurance blown, or motor overheating, even burn, such failures are generally mechanical load is too large or stuck.
3) some of the power supply system is to maintain the energy to work to support part of it a direct result of failure or malfunction is caused by system downtime or damage to the entire system. Usually in the United States and Europe, relatively few such problems in the design considerations in this area much, but in China due to power fluctuations, poor quality, but also hidden like a high-frequency pulse interference of this kind, coupled with human factors (such as a sudden wind up power, etc.). For these reasons can cause a power failure or damage control. In addition, the numerical part of the operating system data, setting data and processing procedures normally stored in RAM memory, the system power, the power reserve by lithium batteries, or to maintain. Thus, down a long time, plug the power or memory, can cau, , se data loss, the system can not run.
4) programmable logic controller logic interface, CNC control, database management knives, hydraulic start, etc., mainly by the PLC to achieve, to accomplish these control samples must be taken of each control point status information, such as broken electrical, servo valve , lights, etc. Thus it is with a wide variety of outside sources and implementation of various components are connected, change frequently, so the likelihood of failure are more, but the type of failure is also changing.
5) other due to environmental conditions, such as interference, temperature, humidity exceeds the allowable range, improper operation, improper parameter settings, may result in downtime or failure. There is a factory of CNC equipment, shortly after the loss of NC power ready signal, the system does not work, checked that the body temperature is high, because the ventilation filter has blocked, causing the temperature sensor movement, replace the filter, the system works . Do not follow the rules and plug circuit board, with or without electrostatic protection measures are likely to cause damage or system downtime.
General in the NC system design, use and maintenance must be considered the site of frequent failure to give the alarm, the alarm circuit work, on the one hand on the screen or the control panel shows alarm information, a protection of the other interrupt instruction, the system to stop working in order to identify failures and maintenance.
3.3 troubleshooting
1) Initial reset method under normal circumstances, due to transient faults caused by the alarm system, the available hardware reset or turn the system power switch to clear the fault, if the system is working storage area due to power down, plug the circuit board or battery voltage caused confusion, you must initialize the system clean, removing the former should pay attention to make copies of data records, if the initialization failure persists, the hardware diagnostics.
2) parameters change, the program more Dhamma is to determine the system parameters based on system functions, parameter settings may cause system errors or failures of a function is invalid. Sometimes, because of procedural errors can cause the user downtime, which can quickly search the system checks to correct all errors, in order to ensure its proper operation.
3) regulation, regulation is the best method of adjusting one of the most simple way. By potentiometer adjustment, correction system failure. If a military plant maintenance, the system displays the screen chaos, the adjusted properly. Factory in Shandong, the spindle and the brake when the belt starts slipping, because the spindle load torque, and drives the ramp time setting is too small, the adjusted properly.
Adjust the system to optimize the servo drive system and mechanical system is being dragged to achieve the best match of the integrated adjustment method, the solution is simple, with a single or multi-line recorder storage function with dual trace oscilloscope, respectively. observe instructions and speed feedback or current feedback response relationship. By adjusting the speed regulator and integral time scale factor to make the servo system to achieve the higher dynamic response without oscillation of the best working condition. In the field without an oscilloscope or recorder case, based on experience, that regulate the motor start-up, and then adjusted to reverse slowly until you can eliminate shock.
4) replace the method with a good spare parts spare parts replacement diagnose bad circuit board, and do the appropriate initialization starts, so that the machine quickly put into normal operation, and repair or rework bad board, which is the most common troubleshooting methods .
5) to improve power quality and power supply method now commonly used to improve power supply fluctuations. Can be used for high-frequency interference
Capacitor filter, these preventive measures to reduce the power supply board failure.
6) maintenance company information tracking method according to the actual work appear accidental failure to continuously revise and improve the system software or hardware. These changes to the information in the form of maintenance to continue to provide maintenance personnel. This as a basis for troubleshooting, troubleshooting can be completely correct.
3.4 maintenance precautions
1) remove a block from the machine on the circuit board should pay attention to record its corresponding position, connect the cable number, for fixed installation of the circuit board, it should be removed before the corresponding crimp parts and screws for the record. Demolition under the pressure parts and screws should be placed on a dedicated box, so as not to lose, assembly, the box should be all things to spend, otherwise the assembly is not complete.
2) The soldering iron should be placed easily in front, away from the circuit board repair. Tip should be properly repaired to meet the integrated circuits of welding, soldering bumps and avoid other components.
3) Measure the resistance between the lines, should be off the power, the measured resistance should be measured twice red and black table document exchange, to a large resistance for the reference #118alue.
4) Most of the brush circuit board with solder mask, the measurement should be to find the appropriate spot as a test point, do not eliminate solder film, and some insulation board with all the brush, only scratch the solder joint at the insulation with a blade layer.
5) should not be arbitrarily cut off the printed circuit. Some maintenance personnel have some experience in appliance repair, used to break check, but on the CNC equipment are mostly double-sided circuit board or multi-hole plate of metal plates, printed circuit thin and dense, easy to weld once cut off, and the tangent easy to cut when the adjacent line, Furthermore some point, cut off a one line, and can not make it and line out, a few lines need to cut off the job.
6) The components should be free to replace them. Some maintenance personnel to determine the faulty components in the absence of circumstances that only the feel of a component is broken, replace them immediately, so that a higher rate of false positives, remove the human component failure rate is higher.
7) Remove the element should be used to suction devices and suction tin tin rope, should hard to take. The same should not be prolonged heating pad and repeat the demolition to avoid damage to the pad.
8) The replacement of the device, the pin should be an appropriate treatment, welding, soldering should not be used acidic oil.
9) record on the line switch, jumper position should not be arbitrarily changed. Control checks for more than two poles, or exchange components of the board when the note marked components, in order to avoid confusion, resulting in a good board will not work.
10) identify the circuit board's power configuration and type, according to inspection requirements, or all of the power supply, respectively. Should be noted that high-voltage, direct access to some high-voltage circuit board, or board a high-voltage generator, to be properly insulated, the operation should pay special attention.
4, numerical control machine tool commissioning
CNC machine tool is a high-tech mechatronics machine, buy a CNC machine tool users, the security to boot correctly, debugging is a crucial step. This step is correct or not to a large extent determines the CNC machine can play this normal economic efficiency and service life of its own, this manufacturer of CNC machine tools and user-plant issues are at stake. CNC machine boot, the following steps should be commissioning.
4.1 Visual inspection before power
1) Check the electrical machine to open the machine electrical control box, check the relays, contactors, fuses, servo motor speed, the control unit connector, spindle motor speed control unit for loose sockets, if loose should be back to normal state, the lock The connector must be tight body lock, a switch box of the machine be sure to check the socket on the adapter box, loose wiring, there is some locking mechanism to lock.
2) CNC CNC electric electric box check box to open the door, check the types of interface socket, servo motor feedback cable socket, spindle pulse generator outlet, manual pulse generator outlet, CRT sockets, etc., if loose to re-plugged, there is locking mechanism must be locked. Check the various printed circuit board according to the instructions on the setting of short-circuit terminals must comply with the state machine factory set, do wrong should be re-set, in general, need to re-set, but the user must set short-circuit terminal state make the original records.
3) quality inspection check all wiring terminals. Including the strength of electrical parts in the assembly, machine tool manufacturing plant to wiring terminals and the motor power line terminals, each terminal should be tightened with a screwdriver until the screw with the screwdriver does not move up, be sure to tighten all electrical outlets tight.
4) Check all solenoid valve solenoid valve should be hand-drive several times, in order to prevent a long time without power caused by the adverse action, such as abnormal, should be ready record in power, confirm that repair or replacement.
5) Check the limit switch limit switch operation check all the flexibility and fixity is solid, that adverse action is not strong or fixed should be dealt with immediately.
6) Check the control panel buttons and switches on the button and switch inspections of all control panel buttons, switches, light wiring, found errors should be addressed immediately, check the CRT socket and wiring on the unit.
7) Check the requirements of a good ground ground, ground measurement tools, grounding resistance can not be greater than 1Ω.
8) Check the power supply phase sequence phase sequence table with input power of the phase sequence check to confirm the input supply phase sequence and machine tool calibration throughout the power phase sequence should be absolutely consistent. A second wiring devices, such as power transformers, secondary wiring must confirm the consistency of the phase sequence. Throughout to ensure the absolute correct phase sequence. Supply voltage should be measured at this time, make a record.
4.2 The total voltage of the connected machine
Machine connected to the mains, check the CNC electric box, spindle motor cooling fan, cooling fan electrical box machine steering is correct, lubrication, hydraulic oil, etc. signs and machine lights are normal, the fuse for damage, such as abnormal maintenance outage immediately, no exceptions can proceed.
Measuring strong electric voltage of each part, especially for CNC and servo unit with the initial level of power transformer voltage, and make records.
Observe whether the oil spill, especially for indexable turret, clamping, as well as chuck spindle gear, etc. The hydraulic clamping cylinder and solenoid valve. If leakage power should be repaired or replaced immediately.
Press the power button the power CNC, CNC turned on the power, observe the CRT display, until the normal screen so far. If the ALARM display, look for faults and to remove, re-transmission should be checked at this time.
Open CNC power, according to the information given on the location of the test terminal voltage measurement at all levels, a deviation should be adjusted to a given #118alue, and make records.
The state placed in the appropriate position switch, such as Japan FANUC system should be placed in MDI mode, select the Parameters page. Bit-by-one by one to check the parameters parameter list should be brought in line with the random. If there are inconsistencies in the argument, should find out the meaning of each parameter and then decide whether to modify, such as backlash compensation #118alues ??may be inconsistent with the parameters table, which can be processed at any time during the actual modification.
The state selector switch placed in the JOG position, jog speed on the most low-end, respectively, positive and negative directions of the coordinates to move the operation, and a hand press and to move the direction corresponding to the overtravel protection switch, verify the protective effect reliability, then, then the ultra-slow process testing, process validation super hit block installation is correct.
Will switch back to the zero position the state to complete the traverse, reference point return operation is not complete can not perform other operations. In this case the result should be the first action item, and then for the first four operations.
Position of the state JOG or MDI switch position, the manual gearshift testing, validation will be placed in the lowest position the spindle speed control switch, for reversing the spindle of the file test operation of the spindle speed and accuracy of displayed and then gradually increases the speed to maximum speed, the stability of the spindle operation.
Manual rail lubrication test, so there is good rail lubrication.
Rapid changes in overshoot gradually switch and feed override switch, free to move the knife to observe the speed of change is correct.
4.4 MDI test
Measure the actual speed of the machine tool spindle lock switch on the connected position, with manual data entry instructions, any changed files to the spindle, speed test, measure the actual speed of the spindle and the spindle speed display to adjust the error should be limited to 5% within.
Turret or tool holder for the election of knife blade test its purpose is to check seat or positive, reverse positioning accuracy and correctness.
Function tests according to the ordering situation is different, different functions, depending on the circumstances of each functional test. To prevent accidents from happening, the best first test machine lock, then release the machine to test.
EDIT function tests will be placed EDIT selector switch position status, self-preparation of a simple procedure, as much as possible, including a variety of functions and auxiliary functions command instructions to move the machine size is limited to the maximum stroke, at the same time to increase, delete, and modify .
The state test will automatically lock the machine, with the establishment of procedures for air running test to verify the correctness of the program, then release the machine, respectively, the feedrate override switch, ultra-fast transfer switch, spindle speed overshoot switch to a variety of changes, Switch to machines in a variety of changes in the above case of a full run, after the overshoot at the switch to 100%, so that the machine fully operational, observe the work of the machine is normal. At this point, be considered a start-end CNC machine tools.
5, the technique of handling maintenance, debugging
After repairs in the field should fill maintenance records, lists the necessary spare parts list, create a user profile, for the failure time, the phenomenon of diagnostic methods, using troubleshooting methods, if there are remaining issues should be well documented, so Each failure has not only documented, but can also be accumulated maintenance experience.
Number of Machinery Manufacture Co., Ltd. Taian Hai Technology Center feeds
February 22, 2011
