Bad spindle encoder

HS-1RP with 20Haaspower Haas vector drive.

While orienting the spindle, after it oriented i noticed the spindle was vibrating back and forth a tiny bit and made a loud audible vibration noise from the transmission like gear lash. The RPM meter showed it bouncing around from 0~10 RPM trying to maintain 0 speed. If i grab the spindle nose by hand and put a little load on it while oriented it will push back a little and stop vibrating and hold its position. Ive been chasing a severe spindle noise and i think i may have eliminated the bearings which left me to the tranny or motor. But im starting to think the problem might be a bad spindle encoder. With the tranny running only in high gear the tranny noise is worse at lower RPM's, once you get over about 2500RPM it still makes a lot of noise but it smooths out a bit. I know from past experiences with bad axis encodes on most CNC's they will usually start to vibrate when they hit a bad spot or just make a lot of growling noise as the axis moves as the motor oscillates at high frequency.

Does this sound like an ecoder issue or more like a problem on the spindle drive itself?

Two things. They all vibrate to a certain extent when the spindle is oriented, but I'm not sure if that's an indication of your problem. Mine doesn't make any real noise when it's doing that, but it's a direct drive spindle.

Second thing:

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If i grab the spindle nose by hand and put a little load on it while oriented it will push back a little and stop vibrating and hold its position.

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Do NOT do that!!! If you happen to push too far, the spindle will turn one revolution as fast as it can to get back to it's commanded position, breaking anything of yours that is in the way in the process. I've seen mine go 3 revs a couple times when hitting the spindle orient button.

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Originally Posted by GITRDUN

HS-1RP with 20Haaspower Haas vector drive.

While orienting the spindle, after it oriented i noticed the spindle was vibrating back and forth a tiny bit and made a loud audible vibration noise from the transmission like gear lash. The RPM meter showed it bouncing around from 0~10 RPM trying to maintain 0 speed. If i grab the spindle nose by hand and put a little load on it while oriented it will push back a little and stop vibrating and hold its position. Ive been chasing a severe spindle noise and i think i may have eliminated the bearings which left me to the tranny or motor. But im starting to think the problem might be a bad spindle encoder. With the tranny running only in high gear the tranny noise is worse at lower RPM's, once you get over about 2500RPM it still makes a lot of noise but it smooths out a bit. I know from past experiences with bad axis encodes on most CNC's they will usually start to vibrate when they hit a bad spot or just make a lot of growling noise as the axis moves as the motor oscillates at high frequency.

Does this sound like an ecoder issue or more like a problem on the spindle drive itself?

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Like Matt said, most Haas machines will vibrate some when orientated; some worse than others.
It's possible that your spindle noise and your orientation vibration may be unrelated.

This won't be easy because it is a HS1RP, but I would check the spindle encoder belt and pulleys first. Make sure the belt is in good shape and not saturated with oil. If it's been on there a long time, no harm in changing it out anyhow. Inspect the pulleys for distortion of the drive teeth. If they are aluminum they are prone to becoming distorted which can cause improper RPM and even orientation issues due to belt slipping.

Good luck!

The encoder is actually easy to get to on this one. Ill pull the belt and pulley off and inspect or replace. When i say its vibrating while oriented i mean its violently vibrating. It sounds like a hammer drill. I know enough not to grab a firm hold on the spindle nose just in case, i wouldnt recommend any one doing that either but thought i would share it. The harder you push on a servo motor the harder it pushes back.

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Originally Posted by GITRDUN

The encoder is actually easy to get to on this one. Ill pull the belt and pulley off and inspect or replace. When i say its vibrating while oriented i mean its violently vibrating. It sounds like a hammer drill. I know enough not to grab a firm hold on the spindle nose just in case, i wouldnt recommend any one doing that either but thought i would share it. The harder you push on a servo motor the harder it pushes back.

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That's a better description of your issue and definitely not a good thing.

For what you are describing now, I would doubt that the belt will be the root cause as I have never witnessed a belt do something like that. A worn belt/pulley will not help things granted, but it's quite possible that the encoder is bad as you suspect.

When the machine is at a commanded rpm, does it hold the commanded speed well or does it make big jumps; a few jumps in rpm is fairly normal? Any issues with orientation changing?

Have you unplugged everything and then reconnected? The encoder signals are logic level current and voltage and the connections are just as prone to developing bad contact due to oxidation as any logic level connection.

It will run close to commanded RPM, fluctuates within +/- 7 RPM i would say but the load meter bounces pretty heavy. No issues with orientation, it hits spot on every time but as i noted it vibrates. I have disconnected and reconnected the plugs at the encoder and on the board. I hadnt thought to clean the contacts on the board which i will certainly try. Ive seen bad connections cause weird motor problems many times especially on old machines.

Problem is definately not the spindle drive itself. We switched vector drives with another of our machines. Still had the same issues, no change at all. And the drive from the HS-1 works flawlessly in the other machine. So I think i will replace the encoder and see what happens. I didnt want to spend $400 until i had the drive eliminated.

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Originally Posted by GITRDUN

Problem is definately not the spindle drive itself. We switched vector drives with another of our machines. Still had the same issues, no change at all. And the drive from the HS-1 works flawlessly in the other machine. So I think i will replace the encoder and see what happens. I didnt want to spend $400 until i had the drive eliminated.

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Good call and good luck with the new encoder.

GITRDUN

It sounds like your encoder is working as it should, but with a very slight chance it could have a problem, when trying to hold position,I would say there are some setting's ( Filter's ) that are not set correct, like Haas has filters for the axes drives that also need to be set correct, or you will get the same problem that you are having with the spindle

Had a similar problem years ago on a cnc where the encoder was slightly loose. Not sure what the mount is on yours, but it would hunt for position. The more it vibrated the more it would vibrate the loose encoder and this would make it worse.
John