[duane999]

I have an 89 4020. I had to replace the x axis ball screw right away when I got it. It was very noisy and ruff. I had to replace the x axis servo motor soon afterwards. The y axis runs very smooth and quiet. Even with the new ball screw and motor I can't get this machine to produce a nice finish when the x and y axis are running together. I have set the feedrate clock, x,y,z loop gain. (set to 595 on monitor) I have noticed that the feedrate # that is displayed on the monitor after the x, y, & z coordinates jumps eraticly on the x axis. Y & z axis display fairly steady readouts. When I was setting the loop gains this was also the case. I could get y & z axis dialed in to the 595 + or - 3 but the x axis fluctuates about 15 so I set it so it was anywhere from 587 to 603. I have switched the x axis amplifier with the z and I have the same results so the problem is not the amplifier card. I removed the x axis motor and turned the ballscrew by hand. It turns nice and smooth. I don't know what else to check. Any Ideas?

Thanks
Duane999

[Delw]

You know this is going to sound really stupid but.. If everything is good including the gibbs being adjusted right and the table being square and level. check your belts.
Told you it sounded stupid

The face on my parts were not the nice finish they should be.
I had some belts go out. Changed the belts and everything ran fine. after 1-2 days of running I noticed my RPM meter wasnt fluctuating anymore. so just out of curiosity I checked the rpm on the spindle( in the back) it was also steady. it used to run 200-600 RPM fluctuation. Its been ) fluctuation since I replaced the belts.

Like I said It sounds dumb and I am thinking its more coincendce than anything else in my case as I don't think change belts would steady RPMS.

[duane999]

I have a brand new set of belts in the shop so I'll try that tomarrow. I'll let you know what happens

[Delw]

Duane.

I would wait until you check everything else. unless of coare you are getting RPM fluctuation. I am betting its your gibbs or your table has slop in it.

[Neal]

If you are moving multiple axes and have a bad wall finish, the Servo Loop Gain maybe out of sync. If you call the Tech Support guys at Maintenance Technologies (Fadal Service) they can instruct you as to how to make this adjustment.

Neal

[JR1050]

All of the above suggestions are very good and should be explored thouroghly.I would check the resolver bearings,tach connections,and the coax single plug that goes in the axis card itself.Bad connections are the root of 50% of the problems you'll encounter.You can try swapping the Z and X axis card(you already did the amps) and see what happens-make sure the jumpers are set right-and tight.It does sound like the loop gain is off.You have DC amps and motors and all the wiring runs thru a single sealtite conduit-which breaks,the wires rub against each other and you can get noise,which will cause all kinds of problems.Id check for excessive ripple on the motor leads-Good luck.

[Javy]

Did you resolve your problem ?
I'm having same problem only while machining "arcs",not straight cuts.
Is this what you meant by "both x and y in motion" ?
How did you fix machine ?
Thanks

[marko893]

same problem here,please come back if you fix it.

Thanks

[Javy]

Replaced x axis encoder.
This took care of the problem.

[JoBwan]

To anyone that has had this problem, and fixed it. I have heard that you can't change the encoder without the motor. This is on a 1998 Fadal 4020 with an 88hs contoller.
Model# is 906-1 and the serial# is 9808550. It looks like they are A/C servo motors. Is there anyone that can give me any other insight on this. I would appreciate all the help I can get. Thanks,

[iess525]

To anyone that has had this problem, and fixed it. I have heard that you can't change the encoder without the motor. This is on a 1998 Fadal 4020 with an 88hs contoller.
Model# is 906-1 and the serial# is 9808550. It looks like they are A/C servo motors. Is there anyone that can give me any other insight on this. I would appreciate all the help I can get. Thanks,

You are correct, you cannot change the encoder alone. If you need a new motor, let me know...I can walk you through install over the phone.

[Drassk]

What's it about the setup that matches the encoders to the motors like that?

It's odd that a new encoder wouldn't work with a motor that previously had the same encoder on it.

[Neal]

Just for clearification, you can change a resolver in a DC servo motor BUT you CAN NOT change the encoder in an AC servo motor. Unfortunately the terms encoder and resolver are frequently used interchangeably. The AC motor Encoder must be phased to the individual motor and few if any machine owner will have the correct equipment to adjust the Encoder.
The DC resolver is NOT phased to the motor and is simply adjusted by manual rotation to set the Cold start position.
I hope that this helps clear away the fog!!

Neal

[Drassk]

Ahh, gotcha: it's an encoder with commutation tracks on it. It's not just an encoder, it's also some fake Halls!

That those can't be replaced easily has nothing to do with it being an encoder VS a resolver; regular encoders can be switched just as easily as a resolver. If the encoder's being used for commutation then it would be a hassle to line up a new one, but locking it in one phase and lining up the commutation track manually is probably worth the $1000 savings to a shop that has some electronics background.

I think I'm going to code in a phase search when I get around to making that controller, I've always thought avoiding the problem is the easiest solution

[Neal]

Avoid a Problem??? Where is the fun in that?????

Neal