Has anyone had their MX 850 Z axis get pulled down into servo alarm ?

[Leon82]

I'm taking  relatively light cuts with a 3 flute endmill in aluminum. It starts to rumble and you can see the z load increase. Sometimes it pulls the head down into z excess error servo alarm. Its at 70% load just sitting still with no cutting. It looks like the motor is the same size as the 520

[cncappsjames]

Is the A-Axis clamped or unclamped?

[Leon82]

10 hours ago, cncappsjames said:

Is the A-Axis clamped or unclamped?

Both clamped 

[huskermcdoogle]

What does the load look like while it is cutting?  Does it fluctuate greatly?  Maybe the inertia parameter isn't set right and happens to react with that harmonic?  Have you tried faster or slower spindle speeds with success?

[Leon82]

On 10/13/2023 at 6:06 PM, huskermcdoogle said:

What does the load look like while it is cutting?  Does it fluctuate greatly?  Maybe the inertia parameter isn't set right and happens to react with that harmonic?  Have you tried faster or slower spindle speeds with success?

It has spikes in the red when it starts to grumble. Raising the rpm usually helps

[huskermcdoogle]

Sounds to me like you have a tuning issue (low likelihood) or hardware issue in the drive board to me.  If your Z-axis uses the same drive board as X or Y, you could consider swapping it with another axis and see if the problem goes away.  If that's the case then you have a bad drive.  There may be more sophisticated testing you could do.  But I am uninitiated in troubleshooting them by means of anything other than plug and chug.

Do you have more than one of these model machines to compare with?  If you feed it up in z slowly, stopping and starting frequently, is the load dead smooth and repeatable?  Unless you have a right angle head, you can't really easily do a test that would repeat an issue I once had.  But if you side mill while compound feeding that axis with another while it is loaded (Z+) , you would be able to see it clear as day in the finish.

[Leon82]

3 hours ago, huskermcdoogle said:

Sounds to me like you have a tuning issue (low likelihood) or hardware issue in the drive board to me.  If your Z-axis uses the same drive board as X or Y, you could consider swapping it with another axis and see if the problem goes away.  If that's the case then you have a bad drive.  There may be more sophisticated testing you could do.  But I am uninitiated in troubleshooting them by means of anything other than plug and chug.

Do you have more than one of these model machines to compare with?  If you feed it up in z slowly, stopping and starting frequently, is the load dead smooth and repeatable?  Unless you have a right angle head, you can't really easily do a test that would repeat an issue I once had.  But if you side mill while compound feeding that axis with another while it is loaded (Z+) , you would be able to see it clear as day in the finish.

we have two but one is manual guide i and the other is the new ihmi.  but they do the same thing