Mazak SQT10MS - Spindle / Moto r/ Drive alarm - Alarm 32

[mkalavitz]

Hello,

I will try to keep this as short and concise as possible in hopes someone out there can help me locate our problem.

We have (2) identical Mazak SQT10MS machines. These machines have a spindle/motor and are driven my Mitsu FR-SF drives.

The problems that I am having is on Machine 1.

About a week ago, I was setting up a new job on the machine. I adjusted the jaws for the material and was going to run
the front spindle slowly to verify that the jaws were installed correctly and the material is rotating true. The machine
and control was powered up all day. I went to spin the front spindle manually and received a '39 over amperage' alarm on the
control. A moment later it went to a "16 amplifier not equipt" alarm on the control. (A few weeks prior, I received a
'39 over amperage alarm' and after discussing with Mitsu went through the DC-CT adjustments on Channels 40 and 41 and it seemed to
fix the problem.)

So, I go to the back cabinet of the machine and there are no lights/LED's or anything on the power supply (PW-SF) nor on the FR-SF drive.
This can't be good. So, I power the machine down and back up and still nothing on the power supply or drive.

I immediately contacted a CNC drive repair company and they had me check a few things. They had me pull the middle and lower plugs off from the right back side of the SF-CAA board. I then fired up the machine and we have an amber led on the power supply and lights in the drive. Long story short, it seemed possible that
one or more of the output transistors on the SF-CAA board were bad as well as the possibility of other components. There may
even be some IGBT's shot. They wanted me to pull the front hinge panel off and send it to them for replacement. Roughly $2500.
The problem is that if there were IGBT bad, this fix did not replace those as they are a different part of the drive. So, I didn't do this.

Instead, I found a complete used FR-SF drive with the exact SF-CAA board, part number, etc. So, I bought it and had it shipped to me.
I moved the SF-TL stacked card from my old drive to the new drive, moved all jumpers on the new drive to match exactly what was on the old
drive. I installed the drive and fired it up. It came up fine, with no errors. I adjusted the DC-CT channels 40 and 41 as they were slightly
out of range. There are no alarms when the machine is fired up and idle.

Now, when I go and 'start' the spindle manually (as I was originally trying to do), I am getting a '39 over amperage' alarm on the control
and a 'alarm 32' on the drive. Note that the spindle does not even move a fraction or even attempt to move. It is like there is a dead
short. Nothing moves and I get an immediate alarm when I hit start. Something is pulling this down. The power supply lights and SF-CAA board
lights stay on. Just note the alarm 32.

So, after talking to Mitsu and Mazak, I continued to troubleshoot. I disconnected the motor leads from the lower right of the drive and attempted to run the spindle (spindle actually not turning) and it runs fine for about 30 seconds and then alarms out with 'alarm 23'. According to Mitsu this should be expected because it is not getting the expected feedback. Drive running, but no feedback coming back (spindle not actually turning). So, this proved that the drive
seems to be fine.

Now I am trying to determine of there is a problem with the spindle motor, motor contactors, cables, etc. I disconnected the cables from the drive to the KMSDLT contactor. I also removed the 'U,V,W' and 'Z,X,Y' motor cables from the KMSDELT contactor. I followed these cables back through the machine and all 6 seem to terminate to the motor cables which are located in an enclosure just above the motor (same box as the scale). The cable/motor lead connects are a bolt/nut type of connection that are shrink tubed and tie wrapped inside of this junction box just above the motor. They seem very clean and secure. So, I believe that these connections/cables are good and I have reliable U,V,W and Z,X,Y motor contacts in the electrical cabinet.

Per Mitsu. I tested each of the phases with an ohm meter to ground. All 6 came back at 'OL' which is what I understand they should be. I then tested with an ohm meter between each of the phases U,V,W and Z,X,Y. According to Mitsu. and others I have talked to, I should be expecting a very low ohm reading. Instead, I am getting 'OL' for each of the 6. It is acting like there is an 'open'. This does not make a lot of sense to me. I would expect there would not be an open, but rather a small resistance from the motor windings. Also, the control is signaling an 'over amperage alarm', which seems to me like a grounding problem.

Then after talking to Mitsu and others, they recommend that I get a motor guy in there to to a 'Megger' test on the motor. I had a guy come in this morning
and do a Megger test on each of the phases of the motor. He said it all tested out fine. There were no shorts to ground on any of the phases. We tested the motor cables with the Megger inside the cabinet panel (includes cables) and directly inside of the junction box mounted above the motor. All phases test fine.

So, now I am stuck. I am getting an alarm 32 on the drive and the machine alarms out instantly upon pushing the button.

I am wondering the following:
1. There must be a sensing device on the drive to sense this motor current and it is telling the drive to alarm out. What component is it that is sensing this current and telling it to alarm 32? Could it be set to sensitive or be faulty? A dip switch or jumper that is wrong?
2. Why is the ohm reading between the phases of the motor reading 'OL'? It seems there should be a very low resistance on each of the phases and the resistances should be somewhat similar to each other. Instead all of them are 'open'?
3. Is there another contactor or panel mounted to the motor somewhere that could be causing this 'open' or alarm? The windings seem to be fine based on the Megger testing.

FYI...I also changed out the KMSSTAR(left) motor contactor thinking it might be faulty as it is releasing immediately when the start button is pushed. But, now I think the alarm causes this contactor to drop out.

I have not swapped out the KMSDELT (right) motor contactor yet. Could this be the cause of the problem?

Not sure where else to go with this.

Thank you so much for your time to review this and for any advice you may have.

Regards,
Mike

 

[Pipes]

Check pages 30 and 31 of the FRSF Troubleshooting BNPA0801-72 manual. This issue can be caused by input voltage issues/connections. Could also be a defective current detection circuit (see step 8 test).

Can also be a parameter issue with the replacement drive.

 

[cnctoolcat]

My bet is your replacement drive is bad. By far the most common failure point on Mazak's is the spindle and servo drives.
MEAU can evaluate and rebuild your drive. They're the ones to trust, as they built the drive when new, and have the proprietary chips available that are needed for a complete rebuild.
ToolCat

 

[Pipes]

I then tested with an ohm meter between each of the phases U,V,W and Z,X,Y. According to Mitsu. and others I have talked to, I should be expecting a very low ohm reading. Instead, I am getting 'OL' for each of the 6. It is acting like there is an 'open'. This does not make a lot of sense to me. I would expect there would not be an open, but rather a small resistance from the motor windings. Also, the control is signaling an 'over amperage alarm', which seems to me like a grounding problem.

Then after talking to Mitsu and others, they recommend that I get a motor guy in there to to a 'Megger' test on the motor. I had a guy come in this morning
and do a Megger test on each of the phases of the motor. He said it all tested out fine. There were no shorts to ground on any of the phases. We tested the motor cables with the Megger inside the cabinet panel (includes cables) and directly inside of the junction box mounted above the motor. All phases test fine.

So, now I am stuck. I am getting an alarm 32 on the drive and the machine alarms out instantly upon pushing the button.

I am wondering the following:
1. There must be a sensing device on the drive to sense this motor current and it is telling the drive to alarm out. What component is it that is sensing this current and telling it to alarm 32? Could it be set to sensitive or be faulty? A dip switch or jumper that is wrong?
2. Why is the ohm reading between the phases of the motor reading 'OL'? It seems there should be a very low resistance on each of the phases and the resistances should be somewhat similar to each other. Instead all of them are 'open'?
3. Is there another contactor or panel mounted to the motor somewhere that could be causing this 'open' or alarm? The windings seem to be fine based on the Megger testing.

FYI...I also changed out the KMSSTAR(left) motor contactor thinking it might be faulty as it is releasing immediately when the start button is pushed. But, now I think the alarm causes this contactor to drop out.

I have not swapped out the KMSDELT (right) motor contactor yet. Could this be the cause of the problem?

Not sure where else to go with this.

Thank you so much for your time to review this and for any advice you may have.

Regards,
Mike

Sounds like the motor is a Delta/Star motor which is why there are 6 leads. The delta/star contactors you mention, there should be 3 involved in the selection, connect the leads in the appropriate configuration as in the diagram in the link below through the drive's control. You should see the low resistance between the U to X, V to Y and W to Z or some similar pattern, not U to V to W or X to Y to Z.

Yes a bad contact in one of the winding selector contactors or improper selection of them can cause an over current problem.


https://www.google.com/search?q=del...X7IxUAxGM:&usg=__HGBlxtaNNVgR32tRAiIXmjya5lE=

 

[mkalavitz]

Thanks for the help guys.

I had a local motor guy in this weekend. He tested the motor with his Megger tester.

He tested at the motor leads where they connect to the contactors as well at the motor leads in the junction box
mounted above the motor.

Each phase was tested against ground and there was no evident of any internal shorts. He said they all seemed to test out fine.

Per MEAU, this motor looks like a "Y-Delta" motor. He send me a little schematic of the motor. The correct test was from U to X, V to Y, and W to Z.
I removed each of these leads from the motor again and tested. The all tested with a consistent .3 ohm resistance on each. It is what is expected.

I again removed the motor leads from the bottom right of the SF-RF drive. I am able to run the machine (spindle not actually turning) without
an alarm 32. After about 20 seconds of running we get an alarm 23 which is expected. So, the drive actually seems to be OK from that standpoint.

I just don't know if the 'current sensing' (over amperage) part of the drive is functioning OK.

Anyway, I think I need to get MEAU in here to help diagnose further. Unless you have any more ideas, I will post what we find.



Thanks
Mike

 

[cnctoolcat]

The spindle drive's current sensing transducers can go bad. They are little square plastic things that have some of the main power wires passing through. MEAU sells them for about $60 each, and you have to make sure to buy the correct p/n, as each monitors a different amount of current.
If not the transducers, then it's probably your main circuit board, SE-IO1, and/or the big power transistors inside the drive.
Good luck!
ToolCat

 

[SEMmaint]

I was having a VERY similar problem with my 650 (M plus control) last week. I was getting a Spindle Malfunction alarm on the display and the drive showed 32. Which is an overcurrent alarm. We had multiple people in here and they all did their own testing and came back saying it was a bad stator on the spindle motor. Anyways, I wanted to check the resistance coming directly out of the motor so I opened the terminal box on top of the spindle motor and low and behold I found the problem. There was a very small amount of moisture in the box but it was enough to cause two of the six leads (U and V to be exact) to arc together. The wires were melted and there was some damage to the terminal strip. I was able to replace the strip and cut back on the wires to where they weren't melted. And then, the moment of truth came, we fired it all back up and it has been running ever since.

I guess my point is that you should go back and look at some of the more simple things such as bad contactors or even corrosion on terminals before doing anything too expensive. Because I almost pulled a spindle motor about the size of me off a machine because we didn't notice faulty wiring the first time...

 

[mkalavitz]

OK...thanks for the input guys..

Still pulling our hair out here. Still getting an 'alarm 32' instantaneously when the start button is pushed.

I had a motor guy in over the weekend and he Megged the motor (hand crank style). And it all tested out fine.

So, I was at the point to have the local Mitsu. guy in here. He came in yesterday an monkeyed with the machine for 4 hours. $500

He said that the drive looks OK. He also tested the motor i.e. Megger (electronic gadget 500V) and phase-to-phase. It also tests out fine. We called the motor rebuild house that works on these spindle/motor integrated drives. He said based on the Meg test and the phase-to-phase test which showed 105 mA on each phase-to-phase test, the motor looks OK. He said their still may be a problem with the motor, but it is a very very low 1% or less change. It would be very unusual/unlikely. He said that the 105mA across phases was spot on for that motor.

So, now we are talking about sending the old drive into Mitsubishi for a test/rebuilt. From what I gather, it still could be a faulty spindle drive current sensing transducer as toolcat mentions above.

I had the Mitsu tech check the original drive while he was here. He did confirm that it had a bad transistor on the 'V' phase. He said there may be other problems on the board, but he could not tell me and he recommends sending it in to Mitsu. for an evaluation/rebuild.

He said that the replacement drive that is in the machine right now seems to be OK. We can run it fine with the motor leads disconnected. He tried to run it in open loop and this makes no difference (Still alarms out when the motor leads are attached). So, this does not say that the current sensing transistors are bad on this drive. Who knows ?? Arrrr...

I had one of my guys look at all of the cables from the drive back to the motor. There is no evidence of moisture, arching, shorts anywhere. Even the Mitsu. Tech guy said that the cables looked fine as he tested all the resistance back to the motor and was not seeing any grounding.

My tech guy has been doing this for nearly 30 years and he is scratching his head. It either has to be a drive, motor, contactors (which I already swapped out). Which? I certainly don't want to pull the motor/spindle not knowing for sure. Any more ideas? I think I am leaning toward sending the original drive in for repair. Bring it back and try it out. I have another machine exactly like this one, but I do not want to risk swapping its drive out to test. I don't need 2 machines down.

Is there anyway to bypass the drive and spin this motor with an external power source? I need to figure where the problem is coming from...motor/drive, etc...

Any more ideas would be great..

Thanks again for your help..

Mike

 

[SEMmaint]

There IS a way to bypass the spindle drive. However, the drive controls a lot of variables such as speed, etc. Also, if you bypass the drive and try and externally power the motor, and there is something wrong with the motor or anything else you could run into some serious issues. Basically the drive also acts as a safety mechanism. It is constantly monitoring the motor so IF the motor is somehow screwed and you power it up, you could end up tearing the motor up.

 

[wippin' boy]

jumper out the main power cable from the drive to the motor with a big SO cord. I have been all over a machine like this only to find a broken power lead. megger won't show it, a VOM won't always catch it.

and as a rule of thumb, I never replace just a transistor or a top card on those old mits drives. one feeds off the other to much and rarely is the problem in just one of the two

 

[cnctoolcat]

Unless your Mits tech had an oscilloscope, and is very-well versed in the FR-SF drives, he's just guessing as to whether your replacement drive is OK.
MEAU in Chicago are the experts...
Problems like this come back to a faulty drive probably 95% of the time, so play the odds...

 

[mkalavitz]

Hi Guys,

Some updates.

After reviewing the problem more with the Mitsubishi guys, motor guys, and Mike at Spindles Plus, we decided to 'risk' pulling the drive out of our 2nd SQT10MS and put it into our problem machine in order to troubleshoot. Scary...

After swapping the drive and crossing our fingers, the machine fired up FINE! We were able to isolate it to a problem with the drive.

I want to note that Mike from Spindles Plus was extremely helpful. He spent a lot of his time helping me diagnose this problem even when he felt it was
not a spindle/motor problem. I will for sure bring any spindle, VDI tool rebuilds to him! Thanks Mike.

On the bad side, I was quoted a rebuild on my drive from MEAU at nearly $5,000! OUCH!!! It sure is better than pulling an integrated spindle/motor and rebuilding it.

If any of you guys have a good lead on a drive rebuilder, please let me know. Otherwise, I will need to unfortunately bite the bullet and ship it to MEAU for a rebuild.

Yes, CNCToolCat you are right. The guys at MEAU are experts and very very helpful! They also worked with me and gave their best effort before sending anyone in. It is just unfortunately that their products are priced like they are made of gold. Makes it really tough on the small guy

Thanks to everyone again for the help. I will post more after I get the drive repaired and installed.

Mike