Fadal spindle 'cogging' during tool-change, sounding rough at low speeds.

Hey all!
I noticed a strange behaviour with my Fadal VMC10 today: when it's rotating the spindle to orient for the tool-change it is jerking between positions in roughly 90º increments, rather than rotating slowly and smoothly like it always has in the past...

Also when ramping up to speed after the tool-change the speed is kind of 'revving' (rising and falling) before finally rising to the correct speed. And running at a single low RPM (say 2K rpm) it sounds a little rough, like it is 'cogging' rather than rotating smoothly.

The spindle still feels smooth and normal when rotated by hand.

Anyone had a similar issue with a Fadal, or have any ideas as to what the issue might be?

Thanks in advance!
-Aaron

There isn't a whole lot that it can be...

On the machine control side, you have RPM factor, and orientation factor in the parameters...
You can play with those and see what it does. But the way you describe it "hunting" for its
programmed RPM, tells me you might have a bigger problem..

On the machine side, you have the little hall effect sensor at the top of the spindle, that
coincides with the detent to orient for tool change position..

If I remember right this is an early 90's HS.. I also don't recall if you have rigid tapping or not,
but even if you don't. You might have a spindle encoder that is hooked up to your spindle drive..

There are also a couple of pots on the spindle control 1010 card... But I've never touched those, so
I don't know how they effect things...

Then onto the spindle drive.. All kinds of things could be going on in there.. Also back to the
spindle encoder.. On the drives I've messed with, you can run open loop or closed loop.. IF you
have a spindle encoder, AND the drive is running close loop... I'd try running it open loop. Then
you would know if its the spindle encoder... If you don't have rigid tapping, just keep running it
open loop.


My most recent spindle issue.. When orienting for a tool change, it would overshoot, and correct, overshoot
and correct, overshoot and correct... And would eventually settle and change tools.. Eventually it wouldn't
orient to change tools at all and would error out. Stupid hall effect sensor, they are about $20.

Another thought.. The plugs that go to that hall effect sensor and maybe to your spindle encoder if you have one..
Sometimes they get loose, or dirty (like anything is dirty on your machine ) or they get a chip in them..

Hey Bob!
I had a bet with myself that you'd be the first to answer Thanks as always!

Yeah this machine is an early 90s CNC 88 HS, well remembered! No spindle encoder on this machine, and no rigid tapping...

I will go over the wiring loom for the hall sensors tomorrow to make sure nothing is loose!

Unfortunately just after I posted the machine developed further issues, now it alarms out with:

'SPINDLE DRIVER FAULT - POSITION LIMIT'

If I try to go above about 6,000RPM. Anything below that it's still running but it is still 'revving' and making some odd sounds. It was 'chirping' earlier while trying to ramp up to the commanded speed from standstill.

The spindle load meter looks fairly normal, and the spindle turns freely so I don't think it's a mechanical issue.

Unfortunately this machine has the Mitsubishi Freqrol drive in it, which I know is notorious for blowing up... I'm starting to think the spindle drive is dying... I'm concerned about running it too much more as I don't want it to fail into some state that takes out the spindle motor!

If you have suggestions for which spindle drives you like, please let me know! I know you've had to change a few over the years The glentek one that ITS has looks good...

I've got one machine out here, '93. It HAD a mits Frequol in it.. Which is NOT capable of rigid tapping,
but the machine still had the spindle encoder. I never had the keypad for that one, so I don't know
what it was doing, open or closed loop. Even if I had the keypad, I probably never would have looked..

I've lost one old Baldor, and that old Mits.. If I remember correctly. The Baldor just died, but the Mits
gave me Fits. It was doing stupid stuff for quite some time. Mainly the spindle orient.. You very well might
have one dying on you.. The only good thing... I got $200 on e-bay, plus shipping for a fried spindle drive.

As for new ones.. I don't know.. I bought a new Yasakawa F7 for one machine from FadalCNC... And then for the
the other, I bought the same thing, but not from a machine tool.. I already knew the parameters and all the hook
ups.. $500 for a spindle drive.. It did not have the board for running close loop, I now have that. Its still
in a box in the back of the machine.. But I think the F7 is now discontinued... I did have a board blow in the
drive. $300, and tech support at Yaskawa told me what to check and what was bad.

I'm not sure what I would buy now...

But check all the wires and plugs first.. Hopefully its not the drive, but if its that old Frequol thing,
its going to go someday. That thing is a damn dinosaur.

I've been looking at other VFDs, but I'm concerned that I don't know enough about how the control talks to the VFD to get it integrated quickly... For example: does the control do the wye/delta switching, or is that left up to the VFD?

One additional question: the nameplate HP on the spindle motor is 5HP, but this machine is 'rated' for 15HP peak, and it looks like the replacement VFDs intended for this machine are rated even higher, 20HP but with some configuration. If I was replacing it with a 3rd party VFD would I be looking for a 5HP, or a 15HP?

This is one area that I'm really not very familiar with unfortunately... I am interested in learning more about it, but I don't want the machine to be down for more than a couple of weeks...

The drive does the wye/delta switching.

You want to replace with a drive of similar size...larger doesn't hurt but not large enough and you might be blowing your new too-small drive pretty quick.

I would recommend getting a replacement from one of the speciality Fadal aftermarket companies --- there are at least two now?

Buying from one of them gets you a drive ready to plug and play, and their technical support gives you some peace of mind.

Plus, us Fadal owners need to support these guys when possible, so they will be there in the future when we really need them!

Good luck with it!

ToolCat Greg

Hey Greg!
Yeah I am leaning in that direction, but I figured anything I could do to further my understanding of how the Fadal works under the covers would be a good thing, especially now that I own three of them lol!

I honestly think the drive has finally given way... I've been having intermittent issues with it since I first bought the machine a few years ago. Sometimes I would get 'spindle overload' faults when ramping back up to speed after a tool change, sometimes it would not correctly go to the commanded speed (it would be roughly half speed instead). The issues have been fairly rare (like once every few months) and usually a power cycle fixed them, but it seems they're here to stay now.

I will go over the machine tomorrow and then likely just order a replacement drive if I can't work out the issue!

Thanks!
-Aaron

You mentioned you have 3 Fadals...can you swap a drive in from one of the others to make sure it's the drive?

npolanosky said:

You mentioned you have 3 Fadals...can you swap a drive in from one of the others to make sure it's the drive?

Click to expand...

Fairly certain he has only one machine.

I have 3 Fadals, two bought rather recently... But unfortunately the other two (VMC15s) are in storage at the moment, in a unit that is 3-4 hours drive away and not at all readily accessible! They're waiting until I get a larger shop sometime next year. So for the moment I only have one machine!

Thinking about it further I realized what the failure 'feels like': I would bet that at least one of the windings in the motor is not receiving power properly, hence the 'cogging'... Just about to start tearing the machine down, so we'll see how I go. Hopefully it's just a connector that has shaken loose or something.

Ok! So I've been going through the machine, found a couple of little things. There were a few loose-ish spade connections for the control signals going to the VFD. Those have been cleaned and tightened up.

I also spent some time looking over the contactors. The coil and contact resistances all seem roughly right, but now that I'm trying to fire the machine back up one of the contactors is 'buzzing' loudly, not locking in like it should.

I'm chasing that down now, not sure if it's a control voltage or the contactor itself yet. Any tips for checking over a contactor more extensively on the bench?

Note that the contact buzz is definitely the 'chirp' that I mentioned earlier, sounds different when you're in front of the machine with the spindle running and the cabinet closed.

Seems like this may be my issue!

Quick video showing the issue:

Aaron Gough on Instagram: “Looks like I may have found part of or all of the culprit! After cleaning everything, checking over the spindle, fans, orientation bridge…”

Hmmm. So I pulled and re-seated all the solid state relays on the TB1 board in the control cabinet, which seems to have cleared up the issue with the contactor chatter. However the drive is still misbehaving... I was hoping it was just the contactor as that would have been an easy and cheap fix, however it seems I won't get off that lightly unfortunately!

I was finally able to get a good video of the behaviour that I'm seeing. That chirping noise seems to be coming from the spindle motor. I am not seeing the belt slip or anything though, tension is good and it is clean:

Aaron Gough on Instagram: “Unfortunately, the issue is still happening! I was able to work out the contactor chatter, it seems like the solid state relay that…”

Ah, glad you had the same thought I did. I thought the cogging sounded like a dropped phase. I used to do a lot of RC planes and that was a telltale sign of a bad connection, cooked winding or blown up MOSFET in the speed controller.

To make sure it's the VFD, not the motor, can you check the resistance between phases and from each phase to ground on the motor?

Not sure what to advise on the contactor.
-Nick

npolanosky said:

Ah, glad you had the same thought I did. I thought the cogging sounded like a dropped phase. I used to do a lot of RC planes and that was a telltale sign of a bad connection, cooked winding or blown up MOSFET in the speed controller.

To make sure it's the VFD, not the motor, can you check the resistance between phases and from each phase to ground on the motor?

Not sure what to advise on the contactor.
-Nick

Click to expand...

The contactor seems to be fine now that I re-seated the solid state relay that drives it. I will likely replace that SSR soon just to be sure.

The motor winding resistances all seem fine, however I don't have a mega-ohm meter. Might be worth getting one though as I definitely see more CNC maintenance in my future!

I'm pretty sure the VFD has gone bad on one phase... My multimeter was showing a huge frequency difference between one of the phases. I have been meaning to get an oscilloscope for a while, so it seems like this is a good time to push up that purchase.

I'll report back once I have more info!

For future reference for anyone needing to replace the contactors in their Fadal. Here are the actual third party part numbers for the wye/delta contactors for Fadal VMC10 / VMC15:

Fadal part number: ELE-0745
Description: wye/delta contactor
Actual part number: Deltrol 20241-83
Notes: 900 series relay, 120VAC coil voltage, 30A

Fadal part number: ELE-0746
Description: wye/delta contactor with switch
Actual part number: Deltrol 20246-83
Notes: 900 series relay, 120VAC coil voltage, 30A, with SPDT aux snap switch

There are 3 contactors in the rear cabinet: 2x ELE-0745, 1x ELE-0746.

The wye/delta contactors are controlled by the spindle control card, not by the VFD/Inverter. The snap switch on the second contactor is used to send feedback to the VFD/Inverter and tell it to use a different gain setting in wye versus delta.

Here is the wiring diagram from the fadal maintenance manual:



You can see the wires for energizing the contactor coils go back to the computer cabinet, where they are switched by solid state relays. If you ever have an issue with the contactors chattering or not locking in even though they test 'good' (should be about 100 ohms resistance in the actuation coil) then double check the associated solid state relays and fuses in the computer cabinet!

As a follow up to this:
I bought an oscilloscope and an insulation tester. Tested the motor (tested good) and then watched the output of the spindle drive and noticed that as I supposed the output waveform on one of the phases was malformed:



Having confirmed that I pulled the drive apart to see if there was anything obviously wrong that I could fix. All the caps looked good, there were no obviously charred or otherwise damaged components so the logical suspect is the output IGBTs in the drive. I looked them up and they are very much an obsolete part with replacements seemingly worth their weight in gold, so off to find a new spindle drive.

And here's where the real trouble started... I contacted a vendor who offered an inexpensive option for a drive for my Fadal. I talked with them at some length and they said it should be a drop in replacement that would offer the same or better torque, acceleration and deceleration and so on...

Boy were they full of it! After *lots* of mucking around and one smoked drive (their fault) I got their drive installed and it is totally gutless. Has trouble getting the spindle up to full speed in delta mode (my machine has the wye/delta contactors), takes almost double the time to get up to full speed than my original drive did, tweaking params didn't help either! I had a lot of unahppy back and forth with them about this, once I have the money back for the defective drive I will likely start a proper thread outing them as they really are aiming to pull the wool over on people.

.
.
.

So off I head to ITSCNC and pony up the *real* cash for the 'Universal Fadal Spindle Drive Replacement' that Glentek makes. I get the drive today and 45 minutes later I'm back up and running works perfect on the first try. I'm already making chips!





Big thumbs up from me for the Glentek spindle drive replacement, easy to setup and behaves exactly like the stock drive which is all I was really asking for in the first place! And a big thumbs up for ITSCNC as well, they were very helpful and quick to respond to my questions. From first contact to drive shipped was 1 day, and that's including me asking some hard to answer questions as my Fadal is a bit of an odd duck (VMC10).

All smiles over here right now!

-Aaron

Thanks for always following up on your threads - have learned much from you.

Wagner.

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