[nzben]

This arrow 500 I have is going to be the death of me, if it's not one problem its another.

I've just got a good handle on operating it, managed to machine up a good few parts. However now the spindle is going a bit crazy - any thoughts or comments on how the system works would be greatly appreciated.

The spindle will bang backwards and forwards violently, it sometimes runs smoothly for a few seconds, however not running at preset speed, mostly violently hunting for speed and reversing it will then just alarm out.

Another alarm it will have is when aligning it will error with Datum search error but it's turning fine several revolutions.

The controller is a CT FNC, The spindle drive has recently been replaced with a second hand unit that has worked well for a couple of weeks. Spindax spindle controller.

The machine is setup for rigid tapping, I havent quite figured out how the computer gets its signal yet - frm looking at cabling diagrams etc it looks like the resolver is going into the spindle drive which it commutates off, then interpolates an encoder output for the FNC?

I've continuity tested the cabling/plugs from the resolver to the spindle drive and from the spindle drive to the FNC - all appears good.

Has anyone seen this before? Any ideas? Does it sound like the resolver is gone?

[uli12us]

It sounds, like the spindle encoder don't works correctly. Or you have a bad cable between encoder and control.

[sudip]

Look it may be a mechanical problem. you should check the spindle bearing, inner and outer spacer. Also if the preload of the check nut is less from its rated loading, Then your problem will happen.

you should try this link.
Spindle Run Out Problem In HMT VMC 500 Machine, angular contact bearing fault.

[nzben]

I had no idea it could be a mechanical issue - so I didnt bother to mention the current mechanical status of the machine. I'm sure the spindle bearings need replacing. Although parts machine to size and the spindle turns freely by hand it's as noisy as can be, I've only been running it upto 2k to try and keep noise levels reasonable.

One other thing I forgot to mention after my long and frustrating day... About half an hour before coming up with the fault, the tone of the machine changed, a few seconds later it tripped out with error "spindle stall" I lifted the Z up, reset the machine, spun the spindle by hand - it seemed to spin freely so started it up and it was back to it's noisy normal self again.

I also noticed while snooping around under the covers, the belts seem looser than I would expect. I cant see a method for tightening them, is it worthwhile replacing them now as well? Are they just generic belts that I'll find at my local bearing and belt shop or r they a specialist belt for this machine?

If I remove the belts, then try run the motor will it run ok or likely trip out on an error? I figure this will remove any mechanical 'issues' from the motion. This should also tell me if it's the spindle bearings at fault or motor bearings. If it still has the same problem with belts disconnected I guess I'll hunt around for a suitable resolver? I guess I can put an Oscope on by resolver output and spin the motor to see if it's putting out a clean signal first?

thanks again for all input

[uli12us]

I think you have a belt driven spindle, If you remove the motor and it runs without speed fluctuation, than your spindlebearings need replacement. If you can feel no stops in the spindle, the fault is in your Motor, Resolver/encoder, cable or VFD/AMP.

[nzben]

I need help - desperately! I've replaced spindle bearings, the problem is still there - maybe not as bad as before, but maybe I'm getting use to it, so just doesnt seem as bad.

I'm going to get myself into a veritable financial pickle if I dont resolve my problem soon, I've got orders waiting - the machine at this point has been down two weeks and is going to suck me down the plug hole.

So any thoughts on what to check and how to test it would be very much appreciated.

I'll go over what it's doing, and what I've tried.

As mentioned above I've replaced spindle bearings, tried with belt tight, loose and in between. I thought I had that eureka moment when I pulled top of resolver and found the resolver was only held on by one screw as the top of the motor had stripped, the rotor was rubbing on the outer. I retapped the motor and made up some nice spacers to hold it flush. Pulled the resolver apart and found some small gouge marks in the housing where it had been rubbing, I rubbed them down to make it all smooth and delicious again, no wires seem to have touched and the iron rotor didnt have any scrape marks on it.

One thing the machine does which I think is odd, is when aligning, as soon as the align button is held the spindle starts jittering and slowly hunting. I find this odd because I didnt think the spindle got it's command to move anywhere till all axis were homed. It will jump around and find home after axis have aligned. From here it will obviously be very jittery when givin the M3 S200 command. I guess when given the S200 command speed will range from 0 to 350 in short sharp bursts.

I tried to put an Oscilloscope on the excitation of the Resolver but spindle drive tripped out immediately. I have the scope running through an isolation transformer and floating earth to prevent grounding out a signal.

So as mentioned earlier by a poster, the fault could be in the motor, the resolver, the cabling, the spindle drive, etc. How do I isolate and test each one? Ideally I'd just buy a replacement motor, spindle drive etc and just swap them out, however my budget it not gonna cope with that.

If I knew a little more about the operation it might make things easier, does the NC controller tell the motor drive how much to correct by or is this all controlled in the spindle drive? Does the NC controller tell the spindle drive "I want 500RPM" and the spindle drive takes care of the rest? If this is the case I can isolate my search between the spindle drive and the motor, else I'll have to look at the NC side also.

Again - any thoughts, similar experiences testing methods would be greatly appreciated.

Thx

[nzben]

Forgot to mention, rotor withing resolver is running slightly eccentrically - are they tolerant to this?

[sudip]

I can tell you to check the motor load that means the current taken by the motor. If it varies with the rotation of spindle then it may be a GREASING problem. I dont know what kind of grease are you using, If it is very high viscosity grease then there may be a hunting problem in spindle rotation. I recommend you to use Isoflex white grease and dont use excess quantity of grease.
May this help you
Greases Used In Bearings.

[greg b]

I dont know much about that control,I think most 500 Arrows have the Acramatic A2100 control.I know my hawke 150 had some weird things going on some time ago with the spindel and it worked out to be the spindel drive which just about commands everything the spindel does.But they run a kolmorgen drive and with the right diagnosis you can get a good idea whats going on but as I said my knowledge on that control is zero both my hawke and arrow have A2100 controls with Kolmorgon drives,but it still sounds very much like a drive wig out unless of coarse theres wires loose or shorting out could it be a limit switch stickiing and not letting the machine home correctly.Man it stinks when your that buisy and a machine goes down,I have been there to many times all I can say is I hope you get it running soon,Theres a guy on this forum called Mike Kilroy who repairs spindel drives but im not sure if he works with the one you have,you may be able to give him a call to point you in the right direction if you cant find any other probs.Best of luck.

[nzben]

Just wondering, does the drive use the resolver for commutation or is it just used for feedback? The rotor of the resolver is not keyed so can slip - because it has hit the outer of the resolver, I figure if it uses resolver to commutate the out of alignment will cause significant issue?

[uli12us]

I think, the resolver is only for feedback. Normally for spindledriving the machines use asynchron motors like any normal 3~Motor. I suspect the resolver. Eventually if you have a motor with the same power and tension, you can try to assemble the resolver on it and look, how this works. If you can turn your motoraxis with your hand, its probable that the bearings are defective, but you can change it anyway, because these parts are really cheap.

[nzben]

I think we've narrowed it down to the resolver. I put a clock on output of back of motor, it ran near perfect, tho a little louder than I think it should when spun by hand.

The moment when I figured it should be the resolver was I ran the spindle real slow, 5rpm. I noticed the jitter would happen at the same four places during each revolution. Four places on the spindle mean twice per rev or 180deg on the motor shaft. To then check it wasnt a motor fault I loosened the resolver stator and turned it by hand, the error then followed. I figure if it was a motor/winding/drive issue the fault zones would have remained stationary? - sound plausible???

Soo..... does anyone know anybody who has a Spare CT resolver they want to sell??

[uli12us]

In another thread a short time before another Cincinnati user searched a resolver as well. It seems, that these parts are not easy to acquire. I don't know if it works, but evenually you can adapt a resolver from another motor. Maybe it helps, if you write the complete number of the motor, than every1 can look, if (s)he have a good part.

[nzben]

Well I was wrong, it wasnt the resolver. I bought one from a guy in the UK, put it on and it seemed to behave worse. Was a little annoyed - I was sold the resolver as "good" however it looks like its been smashed with a hammer a couple of times then shoved down a kitchen waste disposal unit. I had to machine the rotor face back to being true since it wouldnt sit on the shaft properly after its abuse.

Prior to fitting the resolver I'd replaced the spindle bearings, the motor bearings sounded a bit loud, so pulled them out and replaced them too $$$$!! I stuffed up with the replacement of spindle bearings - however I think I'll start a new thread on that.

I pulled the spindle drive out, opened it up and went over every solder joint I could that potentially might have some weight on it. Put spindle drive back in, hooked it up and it appears to work - fingers crossed it stays that way. Hopefully this thread can be of help to someone else. I was sure it was resolver due to issues mentioned prior - jst shows u never can tell.

[mallardfizz]

lo interested to know who you bought the resolver from and approx cost.
as to your other thread i think you might have trouble getting to the bottom bearing to remove excess grease. i have replaced about 10 sets so far (2 sets this week) and i find that the bearings cannot be removed without destroying them. the bearings i buy are allready greased and come in a matched set of three. what bearings did you use?
regards
mallardfizz
ps i should add i have a customer over here looking for the same resolver and i dont want to use your supplier

[nzben]

Hi Mallard,

Steve from SEC services sold me the resolver, It was cheap enough at 100 pound but I wasnt aware the rotor had been given some abuse. Unfortunately I spoke too soon about fixing the hunting issue - next day it was back to old tricks. Had a good play with it, jst trying to get a definate diagnosis, after running and hunting, turned spindle off, walked away and was looking through manuals - after about five mins there was a loud bag and bright flash of light from electrical cabinet. Forensic investigation shows the spindle drive had blown a high voltage capacitor, not sure if that cap was on its way out and what had been causing my problem, but unfortunately I have a much bigger problem now! Anyone know of any SA1100 CT drives around going cheap?