All,
I have now spent the last 6 months refurbishing and fixing the sheet metal and other mechanical parts of my Maho MH600E. The decision to do so was based on the fact that I was able to get everything with drives, spindles and controller up and running after spending years fixing them.
Then, last night when trying to fit on some of the last parts it started to happen
..
First it was next to impossible to get the door safety relays to work. Not still sure what happened to them, but at some point I was able to get them to work as they should, and was able to get the controller to start.
So for homing axes. This is when one after the other of the axis drives started to act strange. First time I tried to home the axis it started moving, but after about 100 mm it failed with Y09, I05 error. After restarting the machine I decided to home just one axis at a time. I wasn't sure if the z axis was on its limit switch so I decided to manually move the axis out so I was sure it wasn't tripping the limit switches. Then I made a new attempt to home the z axis. And again I got error: Y 09, I05. As far as I know this is an error that means the drive isn't able to move the servo, or the servo isn't moving as expected. I know the axis is moving freely as I just turned it by hand. So it's not something mechanically stopping it from moving.
So I restarted the machine once more, and started the controller and was able to engage the drives. Then I tried to move the axis by hand while the drive was engaged, which should make it "fight back" and try to make it stay where it was. But to my surprise it wasn't hard to turn it, and I was able to move it. This again made it fail with Y 07, I05, idle position fail (not exactly sure if the translation, my manual is in German).
I did check the tachometer by turning the axis by hand and watching the LED's on the drive flash as expected.
Then I started expecting driver failures and tried to find out what drives had failed. One clue I noticed is that the motor had stopped "singing" like they normally do. I know the motors starts to "sing" a rather unpleasant ~2.5kHz tone when the drives are engaged. Having looked at the signals going to the servos that arent surprising. At one point I thought it was something wrong, so I found my scope and started to look at the signals at the output. But I soon realized this is square wave BLDC servos, and that this singing was a result of this. Like this photo (0.1 ms/div 50V/div):
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Anyway, the servos on the axes who had failed had stopped singing. But at this point I was beyond curious on what had just happened, and needed to know if the last axis (the X-axis) was able to move at all as well. So I restarted the machine and was able to get the drives engaged again. And I checked that the x-axis servo was singing and started to home it. But also this axis halted and gave me X 09, I05. So by now all my servo drives were "dead", although no errors were shown on them and all the expected LED's on them were on. I was still able to get them engaged, and I checked turning the axis again by hand to check if it was trying to control it or not. And I found it was holding it vaguely, only enough to give it a feeling of sticking a bit more than when the drives are off. After pulling it past the set threshold for failing it let it go and gave me X07, I05 as expected.
Not sure what to do I decided to pull out the scope again and see what the drives were putting out. And I was surprised to see that they were now putting out a more or less triangular wave about 100V p2p.
The voltage at normal is about +/- 200V (400V p2p), and is more like a square wave with very rough top and bottom as can be seen on the first photo. Not sure about the frequency, but I think it is approx. the same as previously (about 2-2.5 kHz). I took a picture of the waveform with my iPhone (not sure about time/div, but it is still 50V/div).
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At this time I started looking in to other causes for this. After all it's strange for 3 drives to fail like this unless there is something common that is causing this. I measured the voltage on the 300V DC buss. And it was ~326V DC. A bit high yes, but it is as low as I'm able to get it since the voltages are higher now than when these drives were made. On the 220V input on the KDV I measured 236V AC (within the allowed +/- 15%).
Anyway, by now I was even more frustrated and started to look for other causes of the fault, and ways to fix it. So when looking at the drives I noticed they all had a reset button. I assumed this could be a way to try to get the drives back in to working as expected. So I tried pushing it (X-axis first). This was while the drives were engaged (which might be a bad idea?, not sure, but I was rather desperate by this time). This tripped the e-stop immediately.
The sad result of this was that now I'm no longer able to get the machine out of e-stop. The cause of this seems to be the KDV2.1 power supply. It's no longer closing the relay Bb to verify its working, so I'm beginning to expect something is wrong with this. I checked the +24V and the +/-15V and they are ok.
Now only the Aux voltage LED is on, not the Power OK. But I expect this to be correct as it's not receiving power on the main input.
When I refer to the manual in regards to Bb not closing it says: Cause 1: There is a fault in one of the drives. The other option is a fault in the ribbon cable, but I dont expect this. But I will check it to verify.
I'm surprised that this fails now and not when the drives started to behave strangely. It was only after I tried to press reset on the drives that this happened.
I don't remember the exact details anymore, but I do remember it sounded like a small relay inside the Y-axis was tripped when I pressed the reset button on it (which was after pressing reset on the X-axis that caused the e-stop). And from what I read in the manual it should be possible to press the reset button when signal power is on. But I wasn't able to figure out if it's bad to press it while main power is on and the drive is engaged.
I'm reading the manual now (I don't have access to the machine now since I'm at work), and as far as I understand the Bb on the KDV is taking the Bb signal from all the drives and adding it to its own. And when I take a look at the pictures I took of the drives before I pressed the reset button they had all Bb LED on, meaning there was no errors in the drives (as far as the internal diagnostic goes anyway). I don't have pictures of the drives from after this so I don't know if they are on still. But this will be the first ting to check when I get back home. Its just that I have to make it close the Bb relay to power it
.. I just hope its not all the drives that have failed and needs to be fixed/replaced.
When reading further I also noticed that the RF LED should be on. On the picture I have it's not lighting up on any of the drives, which is indicating that the drive isn't getting a signal to RF. I have to investigate this as well.... This is all starting to get really messy. Of course I didn't note whether these LED's were on or off before the failures started to appear. And now I'm not able to get them to turn on because the Bb won't close....
This is so frustrating! I have spent months and months putting all the time I have available (since before Christmas) in to refurbishing this machine believing the electrical parts of it was finally fixed (which took me even longer!). And now when I'm just about to make my first proper tests on the machine this happens..... AAAARRRGH! :bawling:
Does anybody have a clue about what is happening to my machine and why? Any help would be greatly appreciated.
Anders
