Problem- 1988 fadal A axis motor overheating

[smts]

working on an 4020, machine runs fine for about 2 hours. it has a A fourth axis. when the A axis is running it draws about 6.7 amps. When it stops the current goes to 15 amps and begins heating up the motor, then the thermal will trip. Have gone through extensive troubleshooting with Fadal, which has been helpful, but are still having this problem. Any Ideas ? I've swapped drives, motors, clock card.....Thanks

[Al_The_Man]

Does the A axis have a brake when at position?
If so either the brake is coming on prematurely before final position is reached or the drive is not being set to disable when in position.
If it does not have a brake, it may be have a hard time keeping position for some mechanical reason, or even tuning.
Can you measure the initial current when a move is commanded?
Al.

[scadvice]

... check the worm and worm gear for lubrication. Then check the same for backlash adjustment, the worm and worm gear could be to tight. A long shot are the bearings.
Steve.

[smts]

Thanks guys, we just went through this axis and replaced bearings, reset backlash to factory specs. .0005. The brake has been disabled, as it was totally rusted. I think it may have been a tuning problem, as today I was finally able to get the thing to settle down some. Adjusting the signal gain and tweeking on the balance, back and forth, the current started to come down, but still sometimes peaks at 8 amps in some postions, but never the same position twice. Go figure....I also adjusted the backlash in the control from 0 to 10 and that helped also. So they will run it next week and let me know. I will keep you posted. The inrush current was about 10 amps and then would settle to 6 after it was running.....thanks again

[Al_The_Man]

If this is a rotary axis, there are generally two types, positioning only, this type uses a brake when in position, and the motor MUST be disabled.
The second, is an interpolated axis, and the motor is always active, no brake.
Do you know which this is meant to be? Although if it had a brake, it sounds like the former.
Al.

[smts]

Hi Al, Well the motor had a brake and limit switches, all which have been disconnected. Using M60, M61 used to enable and disable the brake. So do you think that the programs should enable these commands to disable the motor? In other words, is that what these commands do also? They have never used the brake, as they didn't even know about these commands until we came in to work on this axis, and yes it is a rotary axis, as far as what brand, I don't know as the nameplate is missing, the book they have is sketchy at best.....Thanks

[Al_The_Man]

M codes are made up at the discretion of the MTB, but if the rotary table had a brake, it should definitely have had a drive-disable command whenever the brake was applied.
This may be part of the problem.
Al.

[smts]

Thanks Al, I will be getting back there this week and check that out and let you know....Brent

[smts]

We tried the M60, M61 commands, the brake solenoid does fire but since the limit switch for the brake on is disconnected, I will " assume " that the control doesn't know the brake is on. so the drive will not disable, as is the case here. When we tried the M60, the drive remained enabled drawing 10 amps just sitting there...so not really sure what to do next....except tear down the axis again and repair the brake and make the switches operational.

Brent

[Al_The_Man]

Either the motor is disabled unconditionally when the brake is energized, or it requires confirmation feedback from a limit switch etc, I would think.
Al.

[smts]

yep, I agree with you. I think I will simulate the limit switch for the brake on and input it to the control and see if the drive disables, if it does, then we have to look at getting the brake fixed....Brent

[dango]

here is some clue to check about A axis brarke
in the software from 97 and up there is a parameter for set it
you can check the amplifier if you make M60 the light if it is AMC
turn from green to be light green
you can check the connection on the amplifier
if no' 6 have 2 wires and no' 9 conected with 2 wires one is bridge to no' 7
then you got a disable for the amplifier
there is no limit switch for that