AXYZ router cutting error

I uploaded a picture to show what I am experiencing.
When my CNC is cutting, it will shudder a little bit (most times, not all), and all of a sudden it's out of alignment. It is cutting .5" to the left of where it should be. This is happening in the X and the Y direction.
I have already contacted AXYZ tech support, but tech support told us we are running too fast (@75IPM). They recommended slowing it down. That doesn’t seem to make sense.
Help!
Thanks,
Jon

Its because its open loop positioning with steppers?

GENERALDISARRAY said:

Its because its open loop positioning with steppers?

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Has to be. This is the main problem with hobby grade machines that use open loop steppers; when their torque limit is exceeded they skip steps and don't notice.

Jonkovach, I believe your options are to slow it down as recommended, or replace the steppers with larger, more powerful ones, or even better with Clearpath servos; they have models that are plug-and-play replacements for steppers. Figure about $250 - $300 per axis, but your performance will greatly improve.

jonkovach said:

...........and all of a sudden it's out of alignment. It is cutting .5" to the left of where it should be.

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I can do better than that with a chainsaw zip-tied to a backhoe shovel........

Wait a minute... I am using Kollmorgen H31NRHT-LNF-NS-00 on a 25 year old router... with stepper drives... you are telling me that I can put servos in... plug and play??

GENERALDISARRAY said:

Its because its open loop positioning with steppers?

Click to expand...

That sounds like the problem. But I doubt AXYZ will tell you that. Different tooling may help, until the feed pressure causes another servo stall. AXYZ makes large format machines that are light weight. Even if you can keep the servos in step you will have a hard time being accurate with the frame flexing from heavy feeding.

So this is NOT a hobby grade machine. It's an AXYZ 6000 series machine. It's 25 years old, but it's solid steel. Movement/flexing is definitely NOT a problem.

I am starting to think that the stepper doesn't have enough torque to get through it all. Is this a possibility? Do steppers lose torque over time?

These are stepper motors. Does anyone know anything about Clearpath servo replacements? They are plug and play, I am told. I am intrigued.

Thanks,
Jon

jonkovach said:

So this is NOT a hobby grade machine. It's an AXYZ 6000 series machine. It's 25 years old, but it's solid steel. Movement/flexing is definitely NOT a problem.

I am starting to think that the stepper doesn't have enough torque to get through it all. Is this a possibility? Do steppers lose torque over time?

These are stepper motors. Does anyone know anything about Clearpath servo replacements? They are plug and play, I am told. I am intrigued.

...

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Stepper motor torque decreases as speed increases. That is likely why AXYZ tech support is telling you to slow down. If it's an older machine, there may be some new mechanical binding in the motion that is now too much for the steppers to overcome and are stalling.

kinetiq said:

...there may be some new mechanical binding in the motion that is now too much for the steppers to overcome and are stalling.

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I'm completely with you on this.
I just can't figure out what exactly that is!!!!!

Jon

jonkovach said:

I'm completely with you on this.
I just can't figure out what exactly that is!!!!!

Jon

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If you slow it down does it still cut off?

When it shudders, does the drive show some sort of overcurrent error? If the drive has tripped out but the controller's still sending pulses you'd get what you're looking at. Is it a combined drive or individual drives?

Steppers can demagnetize if they're overheated. Steppers are pretty cheap.

If it was me, I'd write a program that moved at increasing speeds back and forth over and over again just in the X axis over the whole travel, until you find the speed that trips it. Then the same thing in the Y axis.

Once you can reliably make it trip in one axis or the other, try to narrow down where it's tripping. If it's usually in the same area, then there's probably a mechanical problem binding it up. If it's random, try replacing the motor or motors on that axis.

AXYZ isn't a hobby machine, they're more of a sign shop machine. Not sophisticated, but they'll do the business. A decent chunk of the CNC router market is still steppers, for whatever reason. CNC routers are a weird market onto themselves.

Man, for a router, I can't imagine 75ipm being too fast. I feel like my Laguna is pretty much a POS (bought it used for the right price and it's super useful to me for what it is) and that'll hold 300ipm in cut all day long with appropriate deceleration in the corners.

jonkovach said:

So this is NOT a hobby grade machine. It's an AXYZ 6000 series machine. It's 25 years old, but it's solid steel. Movement/flexing is definitely NOT a problem.

I am starting to think that the stepper doesn't have enough torque to get through it all. Is this a possibility? Do steppers lose torque over time?

These are stepper motors. Does anyone know anything about Clearpath servo replacements? They are plug and play, I am told. I am intrigued.

Thanks,
Jon

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For the most part it is a tube frame machine. Most routers are but the tube size and wall thickness make a difference. My 5' x 12' machine weighs 25,000 pounds+. Your machine is not rated for processing phenolic. Hard nasty stuff. I can do 1" phenolic in a single pass. Not knocking your machine, but heavy cutting is beyond its limits. I have friends with AXYZ machines and they can produce a lot of parts. But if you ask for heavy ACCURATE Z axis cuts in the middle of the table you will be disappointed.