Doosan 2000sy B axis locked up

Machine: 2006 Doosan 2000sy with Fanuc 18i-TB control

I was running a bar feed program all day using the sub spindle as a bar puller, all was running perfect no strange sounds at all. Then the machine alarmed out and went into an E stop type mode. When I tried to move the B axis away from the part, the machine kicks off into an E stop type alarm.
I Have tried moving the B axis several times, it would only move + and - .004 then alarms out again. Then all of a sudden the B axis moves almost all the way back home while i'm using the mpg, then alarms out again. ( the axis movement sounded normal at this point ) We have removed some of the sheet metal to expose the ball screw and all looks clean and straight. When we tried to rotate the ball screw by hand it seems locked in position. I am thinking it could be a servo brake but it dose not look like there is a brake on this servo. All the other axis move smoothly at this point, it's only the B axis locking up.

Has anyone seen this type of problem?

This sure sounds to me like a feed back issue. + - .004" this amount is probably the following error in the parameter. Then it running away while your on the wheel.
sure sounds like the feed back is gone. What are the alarms? The brake may be inside the motor, A quick way to tell is remove the cannon plug for the motor supply power,
Look at the pins should be 4 large pins (3 power one ground) if there are additional pins there could be a brake. I will check my 18I book and I believe i have the drawings for this machine as well at the shop. I do believe that most sub spindles do have a brake. Do you have a scope to check the encoder? I made a jumper cable that I install and hook my scope to check the 3 signals and the marker pulse. If you want a picture of the cable let me know.

I will keep this thread updated in the hopes that it will help someone in the future.

At closer inspection I have found the end of the ball screw has an 8 mm hex key slot, when I turned the ball screw with the hex key it rotated tightly but became much looser. We oiled the ball screw with way lube and all seemed fine for 15-20 mins then the B axis locked up again. My thoughts are, one of the bearings have been contaminated with chips or the bearing cage has come apart. possibly grit lodged in the gibbs.

Quote:

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Originally Posted by CNCRebuilder

This sure sounds to me like a feed back issue. + - .004" this amount is probably the following error in the parameter. Then it running away while your on the wheel.
sure sounds like the feed back is gone. What are the alarms? The brake may be inside the motor, A quick way to tell is remove the cannon plug for the motor supply power,
Look at the pins should be 4 large pins (3 power one ground) if there are additional pins there could be a brake. I will check my 18I book and I believe i have the drawings for this machine as well at the shop. I do believe that most sub spindles do have a brake. Do you have a scope to check the encoder? I made a jumper cable that I install and hook my scope to check the 3 signals and the marker pulse. If you want a picture of the cable let me know.

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Thank you for the reply CNCRebuilder
I took a look at the cannon plug and found it only has 4 large lugs, the other plug is much smaller, its plugged into the pulse coder. The alarm is over torque B axis. The machine only has 1500 hrs run time.

409 alarm? you may be on the rite track with a mechanical bind. I'm still confused as to why it would run away when you were moving it with the pulse handle.
Please let me know what you find on this,
Thanks

This is what I have found.

The gibbs on the B axis had the adjustment screws back out causing the gibbs to drive deeper into there seats. I have cleaned, lubed and adjusted everything. All seems to be working. I will update after running the machine for a few hrs. Sorry for the confusion CNCRebuilder about the run away axis, I was controlling the axis at all times with the mpg.

Attachment 238256

Ok. This is what I found, one of the adjustment screws for the bottom gibb broke off causing the gibb to drive deeper into the seat. I have attached afew photos of the tiny 6 mm adjustment screw with a large undercut.
I'm sure doosan could have used larger screws in this area. Hope this helps somebody else in the future.

Mike Roy in Canada