Y Servo Overheating

[screensnot]

We have a bunch of Fadals in our shop. One is giving us this problem.

If you jog the Y axis all the way to the + limit, after a half hour or so the Y servo has heated up enough for the thermal protection to kick in and shut down all servos.

Our maintenance dept is either too busy to look at it, or we haven't bugged them enough. It's been like this for six months.

We have all gotten pretty used to it, and rarely does someone forget and leave the axis on it's limit. But I did it last week, and I am getting tired of it.

I wonder if someone has seen this before, and know what causes it?

I'd love to be able to walk into the maintenance room and say, "Get off your arse, all you have to do is..."

[Al_The_Man]

From a distance it is almost imposible to point directly to the problem, but in my experience this kind of problem has 95% of the time been due to some mechanical tightness or binding in the area of your + limit, I assume your overtravel limit is working and the drive is not hitting the end of the physical limit?
Al

[screensnot]

Thanks for the reply.

It doesn't appear to hit anything physical.

No matter how fast I jog toward the limit, it stops gracefully (smooth stop, with no clunk or bang) at the same position.

I didn't think it was likely that anyone could say exactly what the problem is. But I figured it couldn't hurt to ask.

Thanks again.

[Al_The_Man]

I would move the axis to the position it faults in and then power down completely and then, if the motor drive end is accessable, try turning it and see how free it turns, compare this to a point in travel where it does'nt fault out.
Just about the only thing usually to cause a motor to heat up without any apparent load is that it has not reached the final position for some reason, but it is still in the range of following error where an error is not detected.
Al

[screensnot]

That sounds like good advice. I'll pass it on to our maintenance guys. The motor drive end is not accessible (without at least removing a cover), so I won't be trying your idea on my own.

[Chris53]

Most of the time one of two things are happening either chips have built up under the saddle leaving the drive under some load at that point or the hard stop whitch on a fadal is a long rod with a stack of belville washers on it has gotten out of adjustment and is in contact with the slide before it hits the end of travel.
One other possibility is that the machine was cold started out of position and the center of travel is now off- Fadals do not have limit switches on the ways and travel is software set by the cold start function, which can be performed anywhere in the range of travel for the machine; IE if you cold start your machine with the head down too close to the table you will have a crash when you attempt a tool change

[alloyspec]

I run a 6030 and sometimes some 4020s and fadal told our maintenence deptartment that if you jog to a limit on a fadal and leave it there it maintains a steady load on the motor and will burn up boards and/or motors.
The simplest way around this is after the last tool runs, cancel the offsets an put in a Y9.0 or Y14.0 move to bring the table out to you with the program.
It must have someting to do with the way the software limits are set up in the controls.You might also check to make sure your cold start position is centered on the table . All it takes is someone to cold start it out of position one time to throw everything off.
This can be related to your other post about c-axis. Sometimes my machine gets an error an an Axis, but it says it is on a different Axis. Maintenence says an error shows up as a stray bit of info somewhere and the control tries to put it someplace.

[Scott_bob]

Sometimes, a guy stumbles onto something in the dark, and it turns out it's what he's been looking for all day. I wonder about your observation, it could be. How could you test your theory? Can you moniter motor or axis drive load when the CNC is on the soft limit?

[Chris53]

yes you can test this theory by either using a clamp on ammeter on the motor lead coming out of the amplifier board- (top left chassis in the CNC cabinet) CAUTION: there is high voltage here -use caution when performing any procedure in this cabinet.
or simply going into the parameters and changing the position read out on the screen from following error to percentage of load.
Do this by entering the (enter next command) screen and typing in (SETP) and hitting (enter) depending on the age & software version of your control you will have 3 to 4 screens of parameters the (P) key will scroll through the pages and using the enter key will scroll through the individual selections.instructions are listed at the bottom of the screen and options are shown in the lower center of the screen for the selected parameter.
find the setting you want and simply choose from the 2 options and hit enter .The manual key will take you out of this screen.
Another Tip; From the (enter next command) screen if you type in (MU) you will have a help screen with all of the commands and options (menu) come up with instructions on how to accomplish most tasks you need.

[alloyspec]

I have had the c-axiz drive fault he describes, usually when I am setting up tools and hand jog the y-axis to the stop to measure the part. I also sometimes get it when I am short on patience and hit the Jog/ pulse encoder dial too fast at the end of the tool . The fault shows up, you think there might be a mechanical problem, shut off the machine,turn it back on ,cold start, and eveything is back to normal.Thats where that theory comes from.

[Chris53]

I intended to mention that it would be normal to see aproximately 1-2 amps max on any axis - not in motion- for a Fadal with DC motors and a little less for an AC motor version. Even when they are at soft limit that should not change; if it did there would be alot more burned up Fadals out there.
These machines have drives that are rated about 25 amperes maximum load and will peak to about 30 momentarily.
axis load (amperage draw) is a product of speed and physical loading on that axis so at 0 speed and no position error there should be little current draw to heat up the drive.

[Chris53]

C axis refers to the spindle drive and usually is related to the inverter having a fault or the orientation prox switch not switching during spindle rotation.
I guess I would have to know what fault number is reported by the control to really have an idea what is happening for sure.
fadals are not too terribly sophisticated and error reporting is not the most in depth or comprehensive part of these controls. The error usually - but not always point you in the direction of the actual failure. In the case of an axis fault the axis reported as having failed could just be where the jog selector switch was set when the failure occured rather than the actual axis at fault and the red light on the amplifier in question is sometimes momentary so you have to catch the actual moment of failure to know which axis went- or see a standing error on the position display to the right of the axis position in question.
With no motion, error values would normally be "0" rolling +/- 1 or 2 counts if everything is normal and the drives up. if the axis is in a bind or "lost" the error value will go up +/- from 0 and will fault the machine when too large a value is seen by thhe control. the only way to recover when this happens is to power down and restart the control.