Grating fault and maintenance 1 fault phenomenon: a cam (milling) grinder of ATEK AG5200 CNC system in Switzerland suddenly lost control of the V-axis after starting, and the positioning was inaccurate, and the system did not give an alarm display.
Analysis and treatment process: Due to the high-speed rotation of grinding wheel during the machining process of this machine tool, the cutting fluid is foggy, which is easy to enter the inner cavity of Heidenham grating ruler and pollute the grating. Similar faults have occurred several times before the fault occurred, and the fault can be eliminated by cleaning the grating moving ruler and static ruler with compressed air. However, after this cleaning, the fault still cannot be eliminated, and it is initially suspected that the fault may be in the grating ruler or its pulse shaping circuit.
On this machine tool, the sine signal output by grating ruler is amplified and shaped by EXE pulse shaping circuit to form a square wave, which is sent to the control part through J3. By measuring Ua 1 and U a2, *U a 1 and *U a2 square wave signals in J3 plug-in, it is found that U a 1 and U a2, *U a 1 signals are normal, with an amplitude of about 2.5V; But the square amplitude of *U a2 is less than1v.
Further examination of the grating input ie 1 and ie2 signals of J 1 plug-in shows that the sine wave of ie 1 is normal, with an amplitude of about 1V, while the amplitude of ie2 sine wave is only 60mV, which is very messy. Check whether the connection between the grating and J 1 is normal, indicating that the grating is bad.
Considering that the grating ruler is composed of reading unit and signal output, the reading unit is composed of light source, condenser, moving ruler and static ruler. The signal output consists of a photocell and an amplifier circuit. After in-depth analysis of the measurement results, it will be found that the ie 1 signal is always normal, but ie2 is abnormal, indicating that the reading unit is not damaged.
According to the above analysis, the failure of photovoltaic cells as photoelectric conversion devices can be preliminarily judged. The voltage across the photovoltaic cells was measured, and it was found that one group was about 2.5V, and the other group was only about1V.. It shows that this group of photovoltaic cells has been damaged. After replacing the photocell, the fault was eliminated and it worked normally.
Grating fault and maintenance 2 fault phenomenon: after a horizontal machining center using Heidenham grating ruler is turned on, the X axis moves slowly in the forward direction and the system has no alarm display.
Analysis and treatment process: the machine tool adopts Heidenham grating ruler as position detection device. Because the servo system is a fully closed-loop structure, there is no alarm after the system is started, and the X axis moves slowly forward. It can be preliminarily considered that the speed control loop of the servo system works normally and the fault is caused by the bad position loop.
Check the position following error of the numerical control system, and find that the position following error of the system does not change when the X axis moves slowly, and preliminarily judge that the fault is caused by bad position feedback signal.
Check the connection cable of the position detection system, and after confirming the correct connection, use the oscilloscope to detect the output pulse of EXE60 1, and find that Ua 1, Ua2, *U a 1, *U a2 have no output. According to the schematic diagram, the grating input ie 1 and ie2 signals are further examined, and it is found that the sine wave signals of ie 1 and ie2 are normal. The signal of the preamplifier EXE60 1 was measured step by step, and it was found that EXE60 1 Long Line Driver 75 1 14 was defective. After replacement, the machine tool returned to normal.
Grating fault and maintenance 3 fault phenomenon: a horizontal machining center equipped with HEIDENHAIN grating ruler, after starting up, the X axis moves normally forward and backward, but the machine tool can not run back to the reference point.
Analysis and treatment process: the forward and backward movement of the X axis of the machine tool is normal, which proves that the CNC system and servo drive work normally. In this case, the bad return reference point is generally caused by the improper setting of the deceleration signal, zero pulse and return reference point parameters.
Using the diagnostic function of the system, check whether the deceleration signal returning to the reference point is normal, check whether the parameter setting of returning to the reference point is correct, and preliminarily judge that the fault is caused by poor zero pulse.
Check the connection cable of the position detection system, and after confirming the correct connection, use the oscilloscope to detect the output pulse of EXE60 1, and find that Uao and *Uao have no output. According to the schematic diagram, the ie0 signal input by the grating is further examined, and it is found that the ie0 sine wave signal is normal. The signal of the preamplifier EXE60 1 was measured step by step, and it was found that EXE60 1 Long Line Driver 75 1 14 was defective. After replacement, the machine tool returned to normal.