Sprinting the last .010" ??

[nelZ]

Hi all,

I've got a Shizuoka AN-S and have torn off the Bandit (thank Grid) and reused the servo motors, put quality encoders on it and have Camsoft Plus driving a Gallil card (new from Camsoft). It's the 3 Axis card with the ICM2900.

The symptoms are.

1. When doing the job I have a CNC spin indexer turning a part. When it indexes, a slitting saw does an X into the part, then a slower Y to finish the cut, then reposition and index for the next cut. When it does the Y it goes fine then lurches on the last 5 or 10 thou...(like a sprint to the finish line)

2. This axis has me tweaking the AMC drives all the time because occasionally the Y will jitter rapidly, oscillating around the finish line by about 2 to 4 thou....I adjust the feedback and current limit to fix but it has always come back. When running a program and it does this the program will stop after timing out not having reached the target position. I have No problems with the X or Z which are wired the same way (cable routing, etc.) and the same idiot (ME) did the servo tuning.

I'm running the machine since I have to make parts and have to live with it until the backorders are controlled.

Any thoughts?
Thanks,

[nelZ]

ADDENDUM
If the move was made in G0 (rapid) it has no problems with jittering

[Karl_T]

What I'd try:

I suspect this may be coming from the TOLERANCE, BLEND, or <one other command that I forget right now> in Camsoft.

To verify, I'd go native Galil and command some low speed moves. If the problem is still present, its in the servo tuning most likely. If not, look to the above issues.

Karl

[nelZ]

Hey, Karl,

Did you think of the other command which coould do it?

BLEND I don't use and TOLERANCE has no effect.

Keep 'em Flying
Nelson

[Karl_T]

Hey, Karl,

Did you think of the other command which coould do it?

BLEND I don't use and TOLERANCE has no effect.

Keep 'em Flying
Nelson

SMOOTH

But, its time for you to contact the wizards at Camsoft on this one.


Karl

[nelZ]

Well, Karl I haven't had much success with that route so I changed the startup.fil POSERROR parameter and - with crossed fingers - I may have gotten it.

Damn strange though, I changed the value from .003 to .0001 for squats and giggles, and it stopped....I had been observing a test routing I did and it literally jumped .020 to the target position (no sense)

I have a pile of broken .012 carbide slitting saws in my trash can...$60 a pop.

I hope I got it.

BTW what do you do? automation machinery?

Thanks again, (and again)
Nelson

[HuFlungDung]

NelZ
What kind of gearing is in the spin indexer? I've never seen one but had the idea that they were just notched plates with a dog? What you described maybe sounds a little like mechanical backlash between the encoder and the motor, which makes it tough to do a really tight tuning job.

[nelZ]

Hey Hu,

It's a Haas 5-C spinner (CNC).

A loose encoder shaft was my first thought. I checked everything - tight and fast.

Strange thing is that X and Z axes were happily panting like my dog while the Y was goofy. I tuned it up fine (Y has more mass on a vertical mill) and the PID numbers looked logical.

Why did the POSERROR only affect the Y?

Perhaps Camsoft can postulate why my symptoms occurred.

Nelson

[camsoft]

We're going to start by sending you the current version. You're 2 versions behind. Then once you get this installed we'll have you do some test and make us a History file with the same version we're using.

Tech Support
CamSoft Corp.
support@camsoftcorp.com
PH 951-674-8100
Fax 951-674-3110
www.cnccontrols.com

[nelZ]

Thank you Camsoft folks,

I got 6.6 today and installed it. On Friday I changed the POSERROR in startup.fil to .0001 and this, thus far, has solved the lurching and oscillating. I had tuned the Y axis by the book as with the other axes. When this problem was seen, it was largely intermittent, between 10 and 50% of the time it occurred. I jotted down the tuning settings as well as the pot settings on the drives and experimented with them trying to solve it a couple months ago. Having the P too high would be a prob, as with the I, the D had less effect on the symptom. On the AMC drives, lowering the loop gain helped fora while then it came back.
Very odd that only the Y is affected in that the wiring is the same (shielding, etc).
I will try to make the problem happen again for your research benefit. I assume you want a history file in the same manner as before?

Thanks,
Nelson

[camsoft]

nelZ,

Good to hear. If the problem does happen again. Yes, we would like to a history file.


Tech Support
CamSoft Corp.
support@camsoftcorp.com
PH 951-674-8100
Fax 951-674-3110
www.cnccontrols.com

[Karl_T]

Thank you Camsoft folks,

I got 6.6 today and installed it. On Friday I changed the POSERROR in startup.fil to .0001 and this, thus far, has solved the lurching and oscillating.... ,
Nelson

I don't see how this can help you. POSERROR kicks out the drive when the limit is exceeded. AFAIK, that's its only function.

Karl