The detecting component is an important part of the CNC machine tool servo system. It plays the role of detecting the displacement and speed of each control axis. It feeds back the detected signal to form a closed loop system. The detecting component is an important part of the CNC machine tool servo system. It plays the role of detecting the displacement and speed of each control axis. It feeds back the detected signal to form a closed loop system. The measurement method can be divided into direct measurement and indirect measurement: direct measurement is to measure the linear displacement of the machine tool by linear detection component, and direct measurement commonly used detection components generally include: linear induction synchronizer, metrology grating, magnetic scale laser interferometer. The indirect measurement is to measure the linear displacement of the machine tool by the rotary type detection component. The commonly used detection components of the indirect measurement generally include: a pulse encoder, a resolver, a circular induction synchronizer, a circular grating and a circular magnetic grid.
Jinjitong reminds that when the machine tool has the following fault phenomenon, it should be considered whether it is caused by the failure of the detecting component:
1. Mechanical oscillation (when acceleration/deceleration):
(1) The pulse encoder has a fault. At this time, check whether the voltage of the feedback line terminal on the speed unit drops at a certain voltage. If there is a drop indicating that the pulse encoder is defective, replace the encoder.
(2) The pulse encoder cross joint may be damaged, causing the shaft speed to be out of sync with the detected speed and replacing the coupling.
(3) The tachogenerator fails, repairs, and replaces the tachometer.
2. Mechanical runaway (speeding):
In the case of checking the position control unit and the speed control unit, it should be checked:
(1) Whether the pulse encoder wiring is wrong, check whether the encoder wiring is positive feedback, and whether phase A and phase B are reversed.
(2) If the pulse encoder coupling is damaged, replace the coupling.
(3) Check if the tachometer generator terminal is connected reversely and the excitation signal line is connected incorrectly.
3. The spindle cannot be oriented or oriented in place:
Jinjitong prompts that when checking the orientation control circuit setting and adjustment, checking the orientation plate, and adjusting the spindle control printed circuit board, it should check whether the position detector (encoder) is defective. At this time, the encoder output waveform is measured. The normal waveform is as follows: :
4. Axis vibration feed:
Check whether the motor coil is short-circuited, whether the mechanical feed screw is well connected to the motor, and check whether the whole servo system is stable, check whether the pulse code is good, whether the coupling is stable and reliable, and whether the speed measuring machine is reliable.
5. An alarm caused by a program error or an operation error in the NC alarm. Such as FAUNUC 6ME system NC alarm 090.091. Jinjitong prompts that an NC alarm occurs, which may be caused by a main circuit failure and a feed rate that is too low. At the same time, there may be:
(1) Defective pulse encoder.
(2) The pulse encoder power supply voltage is too low. (At this time, adjust the power supply voltage to 15V, so that the voltage value on the +5V terminal of the main circuit board is within 4.95-5.10V).
(3) The reference point return cannot be performed normally without inputting a one-turn signal of the pulse encoder.
6. Hardware machine mold network gold machine pass prompt, servo system alarm number: such as FAUNUC 6ME system servo alarm: 416, 426, 436, 446, 456. Servo alarm of SIEMENS 880 system: 1364 Servo alarm of SIEMENS 8 system: 114, 104, etc. When the above alarm number appears, it may be:
(1) Axis pulse encoder feedback signal is broken, short circuit and signal loss, and A-phase and B-phase one-turn signals are measured by oscilloscope.
(2) The inside of the encoder is contaminated, dirty, and the signal cannot be received correctly.
There are 15 CNC equipments in our factory, including one Siemens 8 system machining center, two Siemens 880 system machining centers, four CNC cutting machines, three IRB2000 welding robots, and one CNCJ 800X8100 CNC bending machine. FAUNUC 6 system machining centers and 3 ordinary CNC lathes. Since the first YBM-90N Siemens 8 system machining center was used in 1991, the failure of the detection components has been greatly affected by the failures in the process of use. Proportion: The following is an analysis of several typical faults.
Fault 1: The division of the photoelectric encoder of the pulse encoder leads to inaccurate positioning of the worktable.
Fault phenomenon: The workbench of the Finnish VMC800 SIMES 880 vertical machining center is a double workbench. The two workpieces are processed through the exchange workbench. The workbench is positioned by the rat disc. The rat tooth plate is divided into 360 teeth, each tooth corresponds to 1°. The workbench moves up and down by the cylinder to realize the clutching of the work. The servomotor pulls the synchronous toothed belt, drives the table to rotate through the pulse encoder to detect the rotation angle and positioning of the workbench, and the workbench has a positioning fault in August 1996. The station can't correctly refer to the point. Every time the positioning error is different, whether it is automatic or manual, the angle is several angles, sometimes 1°, sometimes 2°, but the table is rotated several degrees, such as 30°, 60°, 90°. When the corresponding inversion is reversed by 30°, 60°, and 90°, the positioning is accurate. When a positioning error occurs, the NC 228* alarm display appears on the CRT.
Fault analysis: Query 228* alarm content: M19 selection is invalid, ie: M19 positioning program is not completed at runtime. At that time, we think that the M19 positioning program and the related NC MD are wrong, but the inspection program and data are normal. There may be several reasons for the positioning error of the table: (1) The synchronous toothed belt is damaged, causing the actual number of revolutions of the table to be inconsistent with the detected value; (2) the encoder coupling is damaged; (3) the measuring circuit is defective. Caused a positioning error.
Trouble-shooting: According to the above reasons, we checked the synchronous toothed belt and the encoder coupling, and found that everything is normal. After eliminating the above reasons, we judge that it is very likely that the fault caused by the measurement circuit is bad. This machine is made up of RAC. The 2:2-200 drive module drives the AC servo motor to form the Sl axis. The 6Fxl l21-4BA measurement module and a 1024-pulse photoelectric pulse encoder form the NC measurement circuit. When the workbench is faulty, check the workbench positioning PLC. Figure, PLC map board 4Al-C8 on the input points E9.3, E9.4, E9.5, E9.6, E9.7 is the relevant point of the table in the rotary joint positioning, the output board 4Al-C5 on the A2 .2, A2.3, A2.4, A2.5, A2.6 are the corresponding output points. Check these points, the working state is normal, the fault reason can not be judged from the PLC diagram, so we check the measurement circuit module 6Fx1 , 121- 4BA no alarm display is normal. Jinjitong prompts that during the positioning of the workbench, the oscilloscope is used to measure the feedback signal of the encoder to determine that the encoder is faulty. So we removed the encoder, removed the outer casing, and found that the photoelectric plate was close to the underlying indicating grating, and generated friction when rotating. The opaque portion of the inner ring of the photoelectric disk was rubbed and wiped by a light-transmitting ring, resulting in generation. Bad pulse signal, solved by replacing the encoder problem, now consider that the original alarm does not show the measurement circuit fault, because the encoder photoelectric disk has not been completely damaged, it is a random fault, the CNC can not truly display the real alarm content, so The alarm of the numerical control equipment does not completely explain the cause of the fault and needs to be analyzed in more depth.
Fault 2: The pulse encoder A phase signal error causes the axis motion to vibrate.
Fault phenomenon: FAUNUC 6ME system double-sided machining center In October 1996, the X-direction vibrates during the movement, and the NC416 alarm appears on the CRT.
Fault analysis: According to the fault phenomenon, we may analyze the causes of the faults as follows. (1) The speed control unit is faulty; (2) The position detection circuit is defective; (3) The connection and connection of the pulse encoder feedback cable are poor; (4) The pulse encoder is defective; (5) The machine data is correct; (6) ) The servo motor and the tachometer are faulty.
Trouble-shooting: Jinjitong prompts that when the reason for the above analysis is made, the connection and connection of the speed control unit, the main circuit board, the pulse encoder feedback cable are checked, and everything is normal, the machine data is normal, and then the motor is Disengage from the mechanical part, turn the motor by hand, observe the diagnostic status of No. 713, 713 diagnosis content: 713.3 is the X-axis pulse encoder feedback signal, if the line is broken, this bit is 1. 713.2 is the X-axis encoder feedback one turn signal. 713.1 is the B-phase feedback signal of the X-axis pulse encoder. 713.0 is the A-phase feedback signal of the X-axis pulse encoder. 713.2, 713.1, 713.0 Normal motor rotation should be "0", "1" constantly changing, when turning the motor, it is found that the 713.0 signal is only "0" unchanged "1", we use the oscilloscope to detect the pulse encoder A Phase, phase B and one-turn signal, it is found that the phase A signal is not normal. Therefore, the above-mentioned inspection can determine that the shaft-adjusting pulse encoder is defective, and the new encoder is replaced and the fault is solved.
Fault 3: The excitation winding wire of the tachogenerator causes a failure of the control shaft vibration.
Symptom: The IRB2000 robot imported from Finland has failed in 10 cases in 1998. The robot is started. The robot does not run on the guide rail (seventh axis) and has strong vibration. 506 1407 and 509 237 alarms appear on the controller.
Fault analysis: 5006 1407 alarm content is: (1) the robot encounters obstacles when running on the seventh axis; (2) the drive motor is overloaded, the electromagnetic brake is not released; (3) the drive motor passes current, but cannot be reversed correctly; (4) The drive motor does not pass current. The 509 237 alarm content is: the seventh-axis tachometer generator is bad, and the tachometer is open.
Troubleshooting: According to the fault phenomenon and the alarm content, we check the drive system. The drive motor is AC servo motor, the model is NAC093A-O-WS-3-C/110-B-1, and the drive board is DSQC236B. The detection is the speed generator and the pulse encoder to detect and control the speed and position. The gold machine prompts, first we check the connection of each connecting cable, the connector and the driver board are normal, then we check the strong electric circuit and check it. The time relay that controls the electromagnetic brake of the drive motor has a contact disconnection. After soldering, it restarts. Although the time relay works normally, the motor still cannot run, and the alarm is still not eliminated. Then we disconnect the motor from the mechanical part and only connect it. Through the brake power supply, the motor is turned by hand, the motor does not move, and the brake coil is measured, and the coil is burned. After the repaired brake fault is removed, the 506 1407 alarm is eliminated, but the 509 237 alarm is still not eliminated, and the robot still vibrates, so we Measure the excitation winding of the tachogenerator and find that the winding is broken. Because the winding wire is 0.2mm, the wire is too thin and several pieces are broken. Too difficult to repair, repair hopeless, so we orders to ABB, by replacing the tachometer generator, failure to lift.
Fault 4: The pulse encoder is contaminated by oil, causing the shaft to be positioned.
Fault phenomenon: SIEMENS 880 horizontal machining center workbench in October 98 in the process of rotation positioning failure, operation is interrupted, CRT alarm number: 1364 alarm content is 1364 ORD 4B2 measuing System Dirty that the measurement system is contaminated.
Trouble-shooting: According to the content of the fault alarm, the gold machine prompts, we first remove the detection circuit board and the feedback cable connector, clean the dust and oil with alcohol, start the workbench, the fault is not eliminated, then we remove the inspection workbench position. The pulse encoder was found to be filled with a large amount of mechanical oil. Originally, there was a compressed air circuit that passed into the encoder. The compressed air could blow out the dust entering the encoder and clean the encoder. These mechanical oils were made of gas. When the road is ventilated, because the compressed air is unclean, it is brought in by compressed air. We clean the oil with gasoline and improve the quality of the compressed air. After reinstalling the encoder, start the workbench and eliminate the fault.
Fault 5: The closed-loop circuit detects that the signal line is broken, causing the control axis to malfunction.
Fault phenomenon: The SIEMENS 8 system horizontal machining center has a working process, the machine tool suddenly stops running, the CRT has an NC alarm 104, the power is turned off, the alarm is eliminated, and the machine tool returns to normal. However, the above fault occurs after working. Repeatedly.
Fault analysis and solution: Query NC 1O4 alarm, the content is: X-axis measurement closed-loop cable break short circuit, signal loss, incorrect threshold signal, incorrect frequency signal, the machine's X, Y, Z three-axis adopts grating ruler to machine tool Displacement performs position detection and feedback control forms a closed loop system.
According to the fault phenomenon and alarm, we first check the readhead and the scale. The scale is well sealed, the inside is clean, the readhead and the scale are not contaminated by oil and dust, and the readhead and the scale are normal. Then we check the differential amplifier. And the measurement circuit board, after inspection, no bad phenomena were found. After these work, we focused on the feedback cable, measured the feedback terminal, and found that the voltage of line 13 was unstable. After the power failure, the line 13 was measured and it was found that there was a large resistance. After careful inspection, it is found that there is a break in the section of the X-direction moving along with the guide rail, which seems to be disconnected, causing the feedback value to be unstable, deviating from its actual value, causing the motor to lose the step, re-wiring the broken wire, starting Machine tool, fault elimination.
Fault 6: The pulse encoder induces the dimensional error of the workpiece due to the damage of the photoelectric plate.
Fault phenomenon: CNC 862 CNC 20 lathe X-cut parts when the size of the error, reaching 0.30mm / 250mm, CRT no alarm display.
Fault diagnosis: The X and Z axes of the machine tool are driven by the servo unit to control the DC servo motor. The photoelectric pulse encoder is used as the position detection. The reason for the processing size error is generally as follows: (1) X-direction ball screw and silk mother There is a relatively large gap in the pair or the bearing connected to the screw and the screw is damaged, resulting in an error in the execution stroke and the detected size; (2) The measurement circuit is defective.
According to the above analysis, the machine found that the gap between the lead screw and the nut is normal, and the bearing has no bad phenomenon. The cable connection and connector of the measuring circuit are good. Finally, we use the oscilloscope to check the detection signal of the encoder, and the waveform is abnormal. . So we removed the encoder, opened its outer casing, and found that the opaque part of the photoelectric disk had three transparent spots for some reason, which caused the detection signal to be in error. The encoder was replaced and the problem was solved because the self-diagnosis function of the CNC 862 system was not particularly strong. Therefore, in the event of such a fault, the machine does not stop, and there is no NC alarm display:
There are also several equipment failures caused by poor detection components, which are not listed here.
The sensing component is an extremely delicate and easily damaged device. Be sure to pay attention to the following aspects for proper use and maintenance.
1. Can not be subjected to strong vibration and friction to avoid damage to the code board, and can not be contaminated by dust and oil, so as not to affect the output of normal signals.
2. The ambient temperature of the working environment should not exceed the standard, and the rated power supply voltage must be satisfied to facilitate the normal operation of the integrated circuit chip.
3. To ensure the feedback line resistance, the capacitor is normal, to ensure the transmission of normal signals.
4. To prevent external power supply and noise interference, ensure good shielding to avoid affecting the feedback signal.
5. The installation method should be correct. For example, the encoder coupling shaft should be concentrically aligned to prevent the shaft from exceeding the allowable load capacity to ensure its normal performance.
In short, in the failure of the numerical control equipment, the failure ratio of the detection component is relatively high. As long as the correct use and enhanced maintenance, in-depth analysis of the problems, the failure rate can be reduced, and the fault can be quickly solved. The normal operation of the device.
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