Help. FANUC OM poor finish in curves

I have a Miyano drill and tap center with a fanuc 0M comtrol. 1994 year.
When I cut a curve it produces a "faceted" finish, showing segments, like the servos are vibrating or not moving fast enough as it moves around the curve.

This machine had the parameters lost and rebooted by a close model machine by the previous owner. Been doing it since.
I have the fanuc parameter book.
Wondering what parameters to look at for things that would cause poor issues in curves.

All mechanicals are good.

Machinist_max said:

I have a Miyano drill and tap center with a fanuc 0M comtrol. 1994 year.
When I cut a curve it produces a "faceted" finish, showing segments, like the servos are vibrating or not moving fast enough as it moves around the curve.

This machine had the parameters lost and rebooted by a close model machine by the previous owner. Been doing it since.
I have the fanuc parameter book.
Wondering what parameters to look at for things that would cause poor issues in curves.

All mechanicals are good.

Click to expand...

You will never be happy with 3d tool paths on that control trust me. But try G08 P1

This was the only option on my SHARP with Fanuc omd

Not trying to do 3d Paths.
Literally just trying to cut a arc or circle using x,y axis.

What's your feedrate and how big is your arc?

Early 90's O series are about as slow as they come. Not suggesting that there isn't something set incorrectly, but it's equally likely that you're just trying to go too fast...

gregormarwick said:

What's your feedrate and how big is your arc?

Early 90's O series are about as slow as they come. Not suggesting that there isn't something set incorrectly, but it's equally likely that you're just trying to go too fast...

Click to expand...

.25" radius, 30 ipm. Doesn't matter on size or speed.
The servos are oscillating. I can hear the hum when the spindle is off.

Since you don't say if the arc is external or internal, I'm hoping it is an external radius. If so, try slowing down the feed rate during the arc. You don't specify spindle speed, tooth count (on end mill), or material. All factors need to be in "Sync".

malcolm rypauf said:

Since you don't say if the arc is external or internal, I'm hoping it is an external radius. If so, try slowing down the feed rate during the arc. You don't specify spindle speed, tooth count (on end mill), or material. All factors need to be in "Sync".

Click to expand...

It doesn't matter internal, external, endmill size, chipload, material, size of the circle being interpolated in x,y.
This is not my first machine, or my first time programing. Its not chatter, the circle has straight lines on it, Its coming out segmented, and the code is not "point to point". Cuts straight lines beautiful.
It has to do with the control and the servos. I am looking for suggestions on servo tuning. I have a feeling the wrong value is in there and causing the servos to oscillate.

Can you call the distributor and ask if they have the original parameters?


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Machinist_max said:

It doesn't matter internal, external, endmill size, chipload, material, size of the circle being interpolated in x,y.
This is not my first machine, or my first time programing. Its not chatter, the circle has straight lines on it, Its coming out segmented, and the code is not "point to point". Cuts straight lines beautiful.
It has to do with the control and the servos. I am looking for suggestions on servo tuning. I have a feeling the wrong value is in there and causing the servos to oscillate.

Click to expand...

The machine you copied the parameters from - does it have exactly the same model amps and servos on every axis as this machine?

94 O is older than I have first hand experience with. I'm assuming it has red cap ac servos and digital drives - does it have a "Servo Tuning" page in the System screen like in the image below?

If the servos are actually oscillating you should see this clearly in the pos error, current, and speed displays on this screen.

It's important to differentiate between segmentation and stepping on your arcs to diagnose what's really happening.

Find yourself a Fanuc Servo Manual that covers the type of servos your machine uses. There will be a page in there somewhere that shows the standard settings of any servo motor designation. Most servo settings on a new install are set automatically by entering a 1 or 2 digit number that Fanuc has assigned to that motor type/size. Make sure that number matches the motor(s) in your machine and what is in your parameters, as well as the 30-40 other motor parameters listed on the page. I can't recall with complete certainty, but I've seldom found anything other then the standard settings in a Fanuc machine. If I have there's only a couple of them and they're different only by small-ish amounts. If you do find some that are different, read what that parameter is about and decide if it's at all possible that a change to this parameter could be part of your problem. They're are a couple servo parameters for quieting down a jittery servo. I had to add some once to a rotary table. Though I'm pretty sure the parameter had to do with quieting when at rest. Anyway... just a place to start to make sure your servo parameters at least resemble the basic off the shelf settings.

Also I'd double check your backlash compensation. At least make sure they're not off by a mile. Who knows what's up along those lines on an older machine.

BTW... if you don't find the parameter page in the Servo Manual, you might try a Connection or Function Manual. I can never remember which.

Thanks,
I have reached out to a few machinery dealers with the same machine on their floor, but have yet to hear back, as in regards to a another set of parameters.
I know they pulled the parameters from the next size up machine.
I cannot find a servo tuning page, so I'm guessing it doesn't exist in the controller, and see if I can find the defaults for those servos.
If you leave you handle on the table you can feel the "jerkiness"

Machinist_max said:

Thanks,
I have reached out to a few machinery dealers with the same machine on their floor, but have yet to hear back, as in regards to a another set of parameters.
I know they pulled the parameters from the next size up machine.
I cannot find a servo tuning page, so I'm guessing it doesn't exist in the controller, and see if I can find the defaults for those servos.
If you leave you handle on the table you can feel the "jerkiness"

Click to expand...

There's a fair chance that the next size up machine also has the next size up servo motors, so your servo parameters are potentially not correct. At least in part. Take a few covers off and read the motor part number off its label and look it up in the servo manual. The bulk of the servo parameters are entered in the same area as all of the non servo related parameters. The servo tuning and monitoring screens can usually be turned on with parameter change. Look in your parameter manual probably in the area concerning your "Dsiplay" and see what you find. If you have a pdf version use the "find" function with key words.

The settings tables I mentioned earlier will have columns for each motor type and also the setting parameter number for each different Fanuc control model. Like I said, I think once you enter the main code number for the motor model, many of the other motor parameters are automatically set. Regardless, it's easy enough to verify whether they are or not.

I had same issues with my SHARP before using G08 P1. This is why I suggested it. Table shook and was jerky in corners, I thought something was wrong.

Worth a shot.

To cover all bases, what does the program look like?
How big are the arc segments?

SteveEx30 said:

I had same issues with my SHARP before using G08 P1. This is why I suggested it. Table shook and was jerky in corners, I thought something was wrong.

Worth a shot.

Click to expand...

My guess is G08 was just hiding crappy servo tuning. A machine should be able to make a nice arc at slow speed without G08, G05.1 or G05

Machinist_max said:

I have a Miyano drill and tap center with a fanuc 0M comtrol. 1994 year.
When I cut a curve it produces a "faceted" finish, showing segments, like the servos are vibrating or not moving fast enough as it moves around the curve.

This machine had the parameters lost and rebooted by a close model machine by the previous owner. Been doing it since.
I have the fanuc parameter book.
Wondering what parameters to look at for things that would cause poor issues in curves.

All mechanicals are good.

Click to expand...

Hello dear Machinist_max
I saw your conversations and explanations about the problem with your cnc machine.

I have a similar problem. My machine is a 3-axis cnc milling machine made by Feeler company with Fanuc O-MD control, made in 2001. When milling a freeform concave surface on a UHMWPE polymer block, the surface finish is not good.
I have also tried various software and hardware solutions but the problem has not been solved. Is your machine problem solved? If it was solved, what was the final solution?

Thanks in advance for your kind advice.