pulling a brushed servo and cleaning it (HAAS vf0)

I am going to be pulling the servo on my has X axis after it started making funky buzzing noises and not moving smoothly.

I have removed the way covers, and found the ball screw/nut moves smoothly by hand.

The servo looks to be secured by 4 large bolts, then 4 smaller bolts further back which look like they hold the case/ encoder on.

A few questions please:

1) do I remove the cables first? I don't want to create more problems by either taking them off and they go funky or leaving them and stretching the cables

2) I assume the encoders is ok to turn on it's back etc as I move it? orientation doesn't mess them up?

3) is the servo output secured to the ball screw somehow? Or does the servo just slide out when the four bolts are released?

I am going to try and video the removal and cleaning process to help others as I can't find much info on it, but understand brushed servos need looking at regularly.

Hope this sorts my issue, if not I will send the servo off for testing, then try and source new cables or a refurbed servo amp... I think they are the three potential fixes.

Any advice would be great (its a 2000 VF0 by the way)

No advice on pulling the servo, but I just want to help confirm if you have brushed or brushless motors. My '97 -2 and '01 -5 are both brushless, and the last post on this thread will help you if there's any question:

What year did Haas switch out to brushless AC drive? 96 or 97?

FWIW, my Z servos are roughly square due to the fins, and around 300mm tall x 150mm square across the fins.

I'd also be surprised if you had brushed servos in a 2000 machine.
If they are though, usually just pulling the brushes out and blowing compressed air in the brush holes to get the carbon dust out is all the service they need.

My 95 VF-1 is Brushless, maybe the VF-0 kept them for awhile longer. Easy to tell by the round motor and four brush caps around the tail of the motor.

As its the X axis motor your in luck as that one is easier then the Y.

Pull table tray off.
Pull back the covers.

Motor and ballscrew connect in that lil box with 4 screws on top....cover comes off and the set screw needs to be loosened to slide the motor shaft out of the coupling. Or disassemble the coupling.

Four bolts hold down the motor...unbolt and slide out.


Pull caps with brushes...some people like to just stick an air hose in there and go to town with plumes of black carbon dust going everywhere...including inside the motor and encoder.
I found a vacuum is your friend. Suck out what you can...then gradually use the blow gun along with vacuum. Clean out armature best you can, replace brushes if needed.

FYI- often times the motor will give a ground fault after this. I verify before locking motor up and installing covers. This way I go back in and clean it again. Sometimes a slow few first moves with the Jog before Axis Zero on get the motor moving a bit cleaning itself up before powering up and homing.

If a brushless...unscrew connections, pack motor up and send out for service.

Yes..motor can be removed and cleaned without pulling cable...just make sure machines powered down.

That's interesting, the servo is square shaped (roughly) with fins on, with a circular enclosure on the backside for the encoder.

I assumed it was brushed due to the age, and that the 4th axis is a 17 pin old style which I thought meant it was brushed, but I could well be wrong.

If it is brushless, would folk still recommend pulling it and trying it off the ball screw to see how it runs?

After that would it be best to try any other tests before sending stuff away to be worked on? I'm on a zero budget (I spent all I had available on the machine and rigging it) so don't want to spend when I don't need to.

I have seen folk suggest swapping out the amp to test on the Y amp for example, but I have also heard that is not a good idea in case the motor/wiring is bad and it blows the 2nd Amp.

Dangle_kt said:

That's interesting, the servo is square shaped (roughly) with fins on, with a circular enclosure on the backside for the encoder.

I assumed it was brushed due to the age, and that the 4th axis is a 17 pin old style which I thought meant it was brushed, but I could well be wrong.

If it is brushless, would folk still recommend pulling it and trying it off the ball screw to see how it runs?

After that would it be best to try any other tests before sending stuff away to be worked on? I'm on a zero budget (I spent all I had available on the machine and rigging it) so don't want to spend when I don't need to.

I have seen folk suggest swapping out the amp to test on the Y amp for example, but I have also heard that is not a good idea in case the motor/wiring is bad and it blows the 2nd Amp.

Click to expand...

I called our HFO with that problem and they told me to switch drives and try it. Plus when you open the back cabinet you'll know what you have, it'll be rectanglur boxes that say Brushless Drive on them or they will be the old style circuit board looking things.

For us it was the drive BTW, the problem followed. We had a 4th axis drive in that machine we weren't using so we used that one.

I have looked, and the Amps do say brushless. Unfortunately it looks like the X has already crapped out once, as the 4th now has X in black marker on it...

Time for a refurb I suppose!

Anyone used Zaritron (on ebay) from Illinois? I can't find a place in the UK that does them.

With these older machine you also have to start thinking of worn out power/signal cables going to the servos, or encoder failures. These can be tough to diagnose, but if you have more time than money I'd start with a review of those elements before pulling motors for rebuilding before you're sure that's the problem.

We need OBD ports on CNC machines...

Dangle_kt said:

Anyone used Zaritron (on ebay) from Illinois? I can't find a place in the UK that does them.

Click to expand...

Everything I mentioned was at my last job, I know my old boss used an eBay seller for his replacement and was very happy.
I'll get the name for you soon as I can.

Dangle_kt said:

Anyone used Zaritron (on ebay) from Illinois? I can't find a place in the UK that does them.

Click to expand...

Yes, it was Zaritron he used back in March and was happy with them.

nice one! thanks guys.
ODB ports give me headaches on cars, let alone on mills

Dangle_kt said:

ODB ports give me headaches on cars, let alone on mills

Click to expand...

That's cause you're trying to plug the OBD scanner into the ODB port. That never works!