Z-axis drive motor questions

[oilyamerican]

I am having trouble with a vintage HAAS 1994 VF-3 z-axis 4-brush type motor.
It had overheated which kicked the machine off.
I inspected the internals, and could not see anything looking or smelling burned or discolored.
I blew all the carbon dust out, polished the commutator, cleaned out the slots between the copper terminals, and inspected the brushes
The questions I have are :
Would I get continuity between the commutator and the steel shaft if the windings are OK , or does continuity mean a short in the windings ?
With the motor wired up, but not installed and the power turned on,but the control not 'powered up' would I be able to turn the motor shaft by hand or not ????
Thanks for your help.

[Al_The_Man]

There normally would not be continuity between comm and shaft, this indicates carbon leakage or other path that should not show leakage.
If power is on but not control, I would expect motor shaft should be free, unless a brake of some kind on that axis.
What about no power at all? Is it free?
Al.

[oilyamerican]

Thanks for replying.
The motor turns freely by hand with or without power.
With the main power on, but without the control powered up, if I turn the shaft ever so slightly, the machine will register an alarm.
If I power up the control, with or without the motor installed , the machine will alarm , warning that there is an error in the z axis.

I am going to switch axis connections to eliminate the possibility that a driver board may be at fault.

[haastec]

Thanks for replying.
The motor turns freely by hand with or without power.
With the main power on, but without the control powered up, if I turn the shaft ever so slightly, the machine will register an alarm.
If I power up the control, with or without the motor installed , the machine will alarm , warning that there is an error in the z axis.

I am going to switch axis connections to eliminate the possibility that a driver board may be at fault.

What alarm are you getting? Depending on the alarm, it could also be encoder related.

[oilyamerican]

Hi,
Here's what I am seeing :
When I go to 'power up' the control, I will get a #105- "Z following error too large".
This is with the motor in place or not.
If I just turn on the power, the motor shaft can be rotated by hand and I will get a #110-" Z-servo overload" when doing so.

Now, I did a little experiment to eliminate the possibility of something else besides the motor causing trouble.
I switched the Y and Z plugs on the cabinet so the machine would think the Z-motor was the Y instead.
Upon power turn on, I noticed that I could NOT turn the Z motor spindle by hand as before.
I could feel the electrical current holding the shaft stationary.
When I went to 'power up' the control, it again responded with a #105 - Z following error etc. NOT a Y, etc. etc.
So...... I'm thinking the Z driver board may be the culprit instead of the motor ????
Now,I noticed my machine is equipped with an 'A' axis driver board and plug outlet; but I have nothing to go to that axis.
This 'A' board looks identical to X,Y,and Z and I got to thinking...... could I swap the A drive for the Z drive ??????
All the wires are marked and go to identical locations on each board.
The only wires not marked are twisted red/black pairs; and these go to all the boards.
It seems simple enough,but I didn't want to go ahead and do that without some input from someone more experienced.
And I just called HAAS parts and they want $1900 for a new motor..OUCH !!!!!
If I can save the day with a board swap, I'm all for it.

And I'm used to swapping boards; as I had an old Bandit CNC that was constantly on the fritz, and I could always limp through a job with a box full of boards

[oilyamerican]

Not wanting to overload anything,I tested my servo motor with a 12V 1a battery charger connected to the motor leads.
It ran, slowly but smoothly in both directions.
It would seem the motor is functioning, but up to par ???
How much voltage/amperage are these things designed to run on ???

[Al_The_Man]

You can test with an automotive battery and also check for ground leakage to case.
I don't see any reason you cannot use the spare card, there may be pots that require adjusting but it should be safe to try.
Al.

[oilyamerican]

Thanks for the reply.
I sent the motor out to a local shop that works on such things and they ran it with various DC voltages, checked the draw, etc. etc.
They said it checked OK.
So, I will be switching the Z and A leads on the control boards and see what transpires.
Hopefully, outside of some adjustments, my problems will be solved.
Then I will send the Z board out to be gone over.
Anyone know if the HAAS will operate with an unused control board removed ????

[Machineit]

Thanks for the reply.
I sent the motor out to a local shop that works on such things and they ran it with various DC voltages, checked the draw, etc. etc.
They said it checked OK.
So, I will be switching the Z and A leads on the control boards and see what transpires.
Hopefully, outside of some adjustments, my problems will be solved.
Then I will send the Z board out to be gone over.
Anyone know if the HAAS will operate with an unused control board removed ????

It will operate with the "A" axis board removed, as long as the axis is disabled, which it should already be.

[oilyamerican]

Machineit,
Thanks for your advice.
Now, you say the machine will operate without the A board; but if I am swapping connections from the Z to the A, can I remove the Z board and still have the machine operate ???
I do not understand if the machine would sense which board is which beyond me switching the connections.
Sorry for being dense about this, I just don't want to make a wrong move and make matters worse.

[Machineit]

Machineit,
Thanks for your advice.
Now, you say the machine will operate without the A board; but if I am swapping connections from the Z to the A, can I remove the Z board and still have the machine operate ???
I do not understand if the machine would sense which board is which beyond me switching the connections.
Sorry for being dense about this, I just don't want to make a wrong move and make matters worse.

As in the picture below, there are four drives. In your machine the drives are probably all the same number. In the picture mine are three of one number (brushless) and one of another (brush or brushless). The "A" axis drive is actually a brush or brushless drive. It actually makes no difference where the boards are located, just what wires are hooked up to them.

When you do your "power-up restart", the machine attempts to home all of the active drives and motors. Normally that is "X" & "Y" & "Z", as you are not using the "A" driver (no four axis hooked up), so the machine does not look for the signals from the "A" axis drive. It can be removed and the wires not hooked up at all. I have done this when a "Z" drive failed and I used the "A" axis drive for the "Z" axis. I did tape the wires that were for the "A" drive so that they could not short to something.

So, unless your machine is different from all the others I have seen, you should be able to put the "Z" axis wires onto the "A" drive and just leave the "A" axis wires off. Then you can see if the "Z" axis will work properly. You do not need to actually move the drive as they are not hooked to anything in back, they are just held to the board by two screws.

Just be sure to look and see that the boards are compatible, IE. the same number.

[oilyamerican]

Hi Machineit,
I double checked that all drive boards were the same part number, which they seemed to be.
But down on the metal mounting bracket, I noticed there was a sticker that stated that the A board was to be for the A drive only.
I looked at the other 3 boards and they had stickers stating for use on X Y or Z axis.
I did the wire switch anyway to see what would happen.
The machine and control powered up like usual without alarms, but the Z seemed...sort of slow.
It was higher than it's home position, so it had to travel down a couple of inches.
Everything homed out OK; and I manually moved the Z without incident.
Where I ran into trouble was when I went to do an empty tool change.
Z had to travel up to do the tool change, and when trying to do so, it alarmed out with a 163- Z axis over current or drive fault.
I reset everything, and hit restart.
Again it alarmed out when trying to ascend to home position.
I got it to reset a couple of times;and moved Z up to close to it's home but now it is a 163 every time I power up the control.
I went in the back and checked fuses,and nothing is blown.
As I stated previously, I had the motor checked by a local motor shop that claimed they work on such items, and they pronounced it OK.
Any ideas what to do next ??? ( besides calling it a day and cracking open a cold one)