Single chip microcomputer STM32L151CCU6

Photocoupler

In the actual work, the author has encountered many failures without alarm, and the maintenance is more difficult. The diagnosis and maintenance methods of such faults are now described below with reference to examples.

1X axis does not perform automatic return to reference point action

The machine tool is a JCS-018 vertical machining center produced by a research institute, and the numerical control system is FANUC-BESK7M. After the fault occurs, there is no alarm prompt on the CRT, and there is no alarm indication in all parts of the machine. However, the manual X-axis can be moved. After the X-axis is manually moved to the reference point, the machine can perform normal machining again, and the above phenomenon is repeated after the machining is completed.

Based on the above situation, we judge: the NC system and the servo system are fault free. Considering that the fault occurs during the X-axis reference point return, it is suspected that the fault is related to the change of the parameters of the X-axis reference point. However, when we are in TE mode, the parameters related to the X-axis reference point with the address F are adjusted. Examined, but found that these parameters are normal.

From the working principle of the CNC machine tool, the axis reference point is related to the origin position of the axis and the position of the reference point in addition to the parameters. Check the limit switch of the X-axis reference point on the machine and find that it has failed due to oil stains, that is, it is always on. Therefore, when the machining program is completed, the system considers that it has returned to the reference point, and therefore, the X axis does not return to the reference point. After cleaning and repairing the travel switch, the fault is eliminated.

2 During the automatic machining process, there is no exchange action on the A and B workbenches.

The machine is a MKC-500 horizontal machining center produced in Hungary and the CNC system is SIEMENS820M. When the fault occurs, the machine tool processing program has executed the M06 function in the L60 subroutine, the curtain has been opened, but the A and B work stations have no exchange action, the program is in the stop state, and there is no alarm display on the CNC system.

From the machine tool station exchange flow chart, it can be seen that when the A and B work stations are exchanged, there are two conditions that must be met: one is that the curtain must be opened; the other is that the work table should be in a relaxed state and raised. Check the above two conditions: (1) the curtain has been opened and the conditions are met. (2) The workbench is not raised, the conditions are not met, that is, the workbench is still in the clamped state. According to the machine manual, the clamping and loosening of the rotary table are related to the SP03 pressure relay, and the plc input point corresponding to the SP03 pressure relay is E9.0. When the machine is in the normal machining state, the rotary table is clamped, E9.0=1; when the machine is in the exchange state, the rotary table is relaxed, E9.0=0, ready for A and B workbench exchange. According to its working principle, in order to exchange the workbench, E9.0=0, the workbench should be relaxed, even if the SP03 pressure relay is disconnected.

We found that the SP03 pressure relay failed due to oil contamination. After cleaning and repairing, adjust to the workbench exchange, E9.0=0; when the workbench is processed, E9.0=1. Troubleshooting.

3The robot does not change the tool in automatic machining

The machine tool is a KT1400 vertical machining center produced by a research institute, and the numerical control system is FANUC0 system. The inspection found that the robot does not change the tool in the automatic control mode, and there is no alarm. In the manual mode, the tool can be changed, and the tool can be automatically processed after the tool change.

According to the above inspection, we judge that the numerical control system and the servo system are fault-free. Considering that the movement of the tool magazine motor and the robot is controlled by the Fuji inverter alone, the inspection is focused on the inverter. The tool magazine and tool change actions are accurate when observing the manual status. Observing the automatic state, the tool magazine rotates normally, and the tool change is not normal. Check that the NC control signal has been sent and the control contactor has also been engaged, indicating that the tool change signal has been sent to the frequency converter. Check the working condition of the inverter and find that the operating frequency is 35Hz when the tool is changed manually, and the operating frequency is only 2Hz when the tool is automatically changed. At such low frequencies, the robot can of course not perform a normal tool change. The reason for the failure is that when the robot is changing the tool, the substation suddenly loses power, causing the robot to be stuck when the tool is changed, and the above-mentioned failure occurs after the power is restored. After resetting its frequency to 35 Hz, the fault is removed and the robot returns to normal.

4 The rotary table is in the process of lifting or rotating, the odd positioning is correct, and the even positioning is not allowed.

The machine and system are as described in Fault 2. After the fault occurs, the machine does not have any alarm. When the positioning is not correct, the machine can't work, but after the workbench is lifted again, the positioning is correct, and the machine can continue to work. Based on this fault phenomenon, we suspect that the rotary encoder on the rotary table motor is loose or misaligned. However, it is not possible to eliminate the fault by repeatedly adjusting the rotary encoder and modifying the parameters related to the rotary encoder.

The drive system is the same as the magazine motor drive system, and we use the replacement method for exchange. When the magazine drive system is changed to the rotary table, the fault is eliminated. When the rotary table drive system is changed to the magazine, the tool magazine will fail to find the correct tool number. Through this inspection, we determined that the workbench drive system has failed. The drive system is the SIMODRIVE 611-A feed drive. By consulting the driver system manual and analyzing the failure of the drive system, it is agreed that the drive has no hardware failure. The above-mentioned faults are mainly caused by the wear of the mechanical moving parts after long-term operation, the performance changes of the electrical components, etc., which cause the servo system and the driven mechanical system to not achieve the best match. It can be known from the technical data that this situation can be achieved by adjusting the speed controller KP and the integration time TN to achieve the optimal operating state of the servo system with high dynamic response characteristics without oscillation. After we fine-tune the rotary table drive system with reference to the KP scale and TN scale on the magazine motor drive, the fault is eliminated.

No alarm faults account for a large proportion of the failure of CNC machine tools. Faults are usually caused by external conditions such as power supply voltage, hydraulic pressure, pneumatics, oil pollution, and ambient temperature. As described in Faults 1, 2, and 3 herein. In addition, after a long time of use, the CNC machine tool will cause problems in the matching of the system and the mechanical part due to aging of components and wear of mechanical parts, resulting in no alarm failure, as described in Fault 4 of this paper. Therefore, paying attention to the use environment of CNC machine tools and strengthening the maintenance of CNC machine tools is the fundamental way to reduce the probability of occurrence of no alarm failure, and is an important means to ensure the normal operation of CNC machine tools.