M39 Bridgeport Mill Will Not Home/All Axis Only Move Negative

[marc3909]

I purchased an M39 Bridgeport Mill, Serial No.: 3276, from a vocational school and it is only moving in a negative direction and is not allowing home to be set.

The table and the head only move in the negative direction (-) no matter what you tell it to do. If you push the X+ button on the JOG pendant it moves to the X- direction. The same is true for the Y and Z. If I keep pressing the button motion will continue to move till it hits the minus limit switch.

For setting home, if I hit ALT-S (cycle start), it jumps for about a half second in the negative direction on all three axis and then a "position error" for the Z-Axis pops up. I tried swapping the servo lines on the X and Z, and still came up with the same error message.

I have minimal experience with mills and CNC technology, but do a lot of electrical/mechanical work in my day job. Any help is greatly appreciated. Let me know if I can provide additional information/photos.

[cncsnw]

On the back of the SERVO1 drive, there is a switching power supply which provides +5VDC, +12VDC, and -12VDC to the logic power header that is low on the left edge of the drive. Check to see if you are getting all three voltages. If not, you will want to replace that switching power supply.

GRY and BLK = COM (0V)
RED = +5V
ORG = +12V
VIO = -12V

If the problem is not with the drive's logic power supply, then it is probably on the drive itself. In that case you will want to get an RMA from Centroid and send the SERVO1 drive in for test and repair.

[marc3909]

I will check after work tomorrow and post what I find.

Thanks!

[marc3909]

I was able to check and this is what i came up with.

Purple 12v
Orange 12v
Red 5.2v

[cncsnw]

When you measured voltage between black/gray and purple, with your red test lead on purple and your black test lead on black/gray, did you get 12V? Or did you get -12V?

Assuming you got -12V -- or that you reversed your test leads and got +12V -- then the logic power supply is probably fine, and you should contact Centroid about getting the servo drive tested and repaired.

[marc3909]

I will double check tomorrow, the last couple days of work have been crazy. There are a few things I would like upgraded or changed could use some advice. I would like to replace the computer and add a vfd if possible. Not sure if I should just upgrade the board now or pursue a repair.

[martyscncgarage]

I will double check tomorrow, the last couple days of work have been crazy. There are a few things I would like upgraded or changed could use some advice. I would like to replace the computer and add a vfd if possible. Not sure if I should just upgrade the board now or pursue a repair.

Do keep us posted....
Marty

[marc3909]

I turned the machine on today and for the first time it is attempting to go home. Y and Z axis are moving, but the X gives a 411 x axis full power without motion. Any thoughts?

[marc3909]

I reversed the z and and x servo leads and the fault is following the lead.

[martyscncgarage]

I reversed the z and and x servo leads and the fault is following the lead.

You mean you swapped the connectors on Z and X and the problem is now on Z and X is moving?