CNC machine tools are high-efficiency and complex automated machine tools with high technological content, such as machines, electricity, and instruments. In the running process of machine tools, components will inevitably have different degrees of failure and different types of failures. Therefore, familiar with the machinery The characteristics of faults, and the common methods and means of mastering the mechanical fault diagnosis of CNC machine tools, play a significant role in determining the causes and elimination of faults.
First, the principles and basic requirements for the troubleshooting of CNC machine tools 1.1.
Mainly include the following aspects: 1) Fully investigate the phenomenon of failure, the first investigation of the operator, the detailed inquiry of the entire process of failure, some of what happened, what measures were taken. Then make a detailed survey of the site; 2) When looking for the cause of the failure, the idea must be broad. Whether it is integrated electrical equipment or mechanical and hydraulic pressure, as long as it may cause the cause of the failure, it should be listed as comprehensively as possible. Then make comprehensive judgments and optimization choices to determine the most likely cause of failure; 3) first mechanical and electrical, first static and dynamic principles. Before troubleshooting, first of all you should take care to eliminate mechanical failures. In the running state, dynamic observation, inspection and testing are performed to find faults. However, if a destructive fault occurs after power is applied, the danger must be eliminated before power is applied.
1.2 Fault diagnosis requirements.
In addition to rich professional knowledge, the personnel who perform numerical control fault diagnosis operations need to have a certain hands-on ability and practical operation experience, require the staff to combine practical experience, be good at analysis and thinking, and analyze the causes of faults through the actual operation of the faulty machine tool. No change should be made to achieve the same effect. Complete maintenance tools and diagnostic instruments are indispensable. Commonly used tools include screwdrivers, pliers, wrenches, and soldering irons. Commonly used detection instruments include multimeters, oscilloscopes, and signal generators. In addition to this, the staff also needs to prepare the necessary technical information, such as the electrical machinery principle drawing of the numerical control machine tool, the structure layout drawing, the numerical control system parameter manual, the maintenance manual, the installation, the operation, the use instruction and so on.
Second, the idea of fault handling Different numerical control system design ideas vary, but no matter what kind of system, their basic principles and composition are very similar. Therefore, when the machine tool fails, the maintenance personnel must have a clear idea of troubleshooting: investigate the fault site, confirm the fault phenomenon, the nature of the fault, should fully grasp the fault information, so that "more brains, careful hands" to avoid the expansion of the fault . According to the mastered fault information, the complexity of the fault is clarified, and all the doubt points of the fault location are listed. Preparation of necessary technical information, such as machine tool manuals, electrical control schematics, etc., based on which to analyze the causes of failures, formulate troubleshooting plans, require open-minded thinking, and should not limit the faults to a certain part of the machine tool.
After determining the troubleshooting plan, use a multimeter, oscilloscope, and other measurement tools to verify and detect faults with test methods, locate the fault location step by step, and confirm whether the fault belongs to an electrical fault or a mechanical fault. Is it systematic or random? Is it self-failure or external failure and so on. Troubleshooting. Usually the problem is solved immediately after finding the cause of the problem.
Third, troubleshooting methods and examples of faults CNC machine tools CNC system is the core of CNC machine tools, its reliable operation, is directly related to the entire equipment operation is normal or not. The following summary summarizes some methods for determining and troubleshooting CNC machine tools.
3.1 Intuitive Law 1: A five-axis CNC boring and milling machine produced by Germany's MAHO company. The numerical control system is a Philips system. In a transmission NC program, due to improper handling, the transmission interface of the CPU board was burned out. The CPU board was removed and carefully observed, and it was found that there were noticeable burn marks at the RS232 interface. Observe carefully under the magnifying glass, and reconnect the disconnected part: replace a 8255 chip, install it on the machine, input the machine parameters, and the machine will return to normal. The CPU board has been running so far and is in good condition.
3.2 Analysis of self-diagnosis function Law 2: A 16-meter large vertical lathe produced by a Wuhan heavy-duty machine tool factory suddenly appeared No. 43 alarm in one processing (the PLC was not ready to work). Read fault code 34 in ISTACK and consult the Siemens 840C Diagnostic Manual, which reads: Interface-DMP Module Startup Error. Check all DMP modules including hand-held units and find that the DMP module backplane connected to the ground control console is not powered. Check the electrical drawing for an air switch trip that provides the voltage and close the fault and disappear.
3.3 PLC program analysis method Numerical control machine tool is the most, the most frequent breakdown is that some logic functions of the machine tool cannot be realized. At this time, it is necessary to combine the electrical schematics, PLC programs, hydraulic schematics, and other data for analysis to find out the cause of the fault and repair or replace the parts, so that the CNC machine tool can resume normal work.
Example 3: The 16-meter-long vertical lathe produced by the Wuhan Heavy Machine Tool Plant mentioned above was suddenly found to have spilled oil out of the X-axis tank in large quantities during use. Check the oil line and did not find the blockage phenomenon, check the electrical schematic diagram to find the oil supply only the X-axis timing lubrication and fixed lubrication. With the real-time monitoring of the programmer PG720, the output point Q11.4 of the control relay 9KY50 found in PB10 is as follows:
PB1O paragraph 5
AT40: Loading T40
LKT030.3; set T40 time to SET41 for 300 seconds; load to T41
ANT41; Loading T41
LKT002.2: Set T41 to 2 seconds for SET40; load to T40
CDB32; Call DB32 Block A (0D0.10; X-axis forward motion signal 0D0.11; X-axis negative motion signal)
AT40; flip control 0T38; power control lubrication lubrication = Q11.4; control 9KY50 relay PLC control here is enough in the X axis movement, the use of T40 and T41 not set flip time to output Q11.4 The control has reached the effect of regular lubrication. Monitor PLC status discovery logic is running normally, monitor 9KY50 found out completely according to the PLC program control output, and then check the hydraulic solenoid valve, whether or not the PLC output solenoid valve is in the normally-on state, it is enough to say that at any time. Remove the 9KY50, measure it with a multimeter, and find that the normally open contacts are stuck, replace the new intermediate relay, and troubleshoot.
3.4 Replacement of Law 4: A 500-ton programmable press produced by the German company Wändäden with an electronic cam controller. In the course of one use, the electronic cam controller alarms, the content is the system breakdown, causes the entire machine tool to rake. The electronic cam device was removed and it was found that it had two identical circuit boards, and the alarm red LED indicator on one circuit board was on, and the other one was completely normal. After the transfer, the fault occurred and it was proved that one of the hardware was faulty. When the board was removed, a total of eight pluggable chips were found. Four of the chips were swapped and compared again. The fault phenomenon did not shift. Then the remaining two chips were swapped and the faulty phenomenon was transferred. So far, the problem has been identified. chip. However, since this chip is an EPROM chip, a program in a good EPROM chip is written into the EPROM chip of the same type that is purchased using a writing machine, and the failure phenomenon disappears after installation. The elimination of this failure is completely replaced by the replacement method, gradually narrowing the scope of the failure, identifying the cause of the failure and eliminating it.
IV. After the confirmation of troubleshooting and the troubleshooting of the aftermath work, the maintenance work cannot be completed yet. It is still necessary to analyze the underlying causes of the fault from both technical and managerial aspects, and take appropriate measures to avoid the recurrence of the fault. If necessary, mature equipment can be used to retrofit and improve the equipment according to site conditions.
After a while, ask about the operating conditions of the operator's machine tool, and conduct a thorough inspection of the fault point again. Finally, make a maintenance record, and record the entire process of maintenance in detail, including maintenance time, model specifications of replacement parts, and failure analysis. From the process of troubleshooting, discover what you lack, develop a learning plan, and ultimately enrich yourself.
