BOSS 8 random axis limit error

[rkdygert]

My R2E3 is suddenly "randomly" popping axis limits when it is no where near the limit switches. I say random because it was popping the error at exactly the same spot in a particular program the other day but again, no where near the limits. The program would run fine up until this point and then kick out the axis drives...after re-homing the machine and restarting the program where it left off, the program would finish with no problem.

Today I started the machine up and went to home the axis and the machine popped an axis limit almost immediately, again, no where near the limit switches. After re-enabling the drives and homing, I started running a program...different program than the one that was giving me problems before. I ran the program about halfway through and again it popped the limit.

My maintainance manual says to check the voltage to the FMDC board...this checks out fine. After this, it says to check the FIST monitor. Unfortunately, the manual is less than vague about connecting a computer to the FMDC board...

Any ideas on why it would be causing the limit error or help on how to connect a PC to check the FIST monitor would be great.

Thanks,
Ryan

[UKRobotics]

Could it be a lose connection/broken cable to one of your limit swithes ?

[HillBilly]

Originally Posted by UKRobotics Could it be a lose connection/broken cable to one of your limit swithes ?

That is a good place to start. I would also check the motor overload contact on the spindle contactor. Make sure CR1 is a 12VDC relay. I have seen these replaced with 24VDC relays, causing the exact problem you are talking about.

Darek

[rkdygert]

I wiggled and wacked the limit switches and wires to try to trip the limit myself but I could never get it to do it when I wanted it to. Plus it seems odd that it was always doing it in exactly the same point in the program...

I will check CR1 and make sure it's 12v...thanks. The spindle doesn't stop when the limit trips, it keeps running but the axis drives kick out so I think this rules out the motor overload? (or does the motor overload protect the axis drives as well?)

thanks,
Ryan

[machintek]

Weird. Are you on a phase converter? Is it trying to accel 2 axis to rapid at the same time? If so try seperating the move into each axis on its own line. Just to prove a point. Typically, at the same spot means a cable is flexed a certain way. How about a different program?
Just thinking out loud.

George

[topquark]

Hi Ryan
I'm not sure what the differences between BOSS 8 and 9 are... but I don't think that affects this. I have a R2E3 Series II BOSS 9 Mill and several times have had the Axis Limit problems. In all of them the problem was with the limit switches themselves, sometimes being loose (in vibration heaven) or having corroded contacts or once a loose connection at the terminal block in the back panel. There's a chance that a cable has actually rubbed or worn, too, but that's never happened to mine and it does a LOT of repetitive action.
By the way... to check the FIST, once the machine is on, press the "Help" key. In Boss 9, the selection is "4" and it displays what the problem was very nicely... assuming you know everything there is to know. It is a real help, actually.
Russ Harper
topquark@niia.net

[rkdygert]

I guess the first course of action is to replace the limit switch cables/switches and see if it keeps happening.

Unfortunately, the BOSS 8 doesn't have a CRT so the FIST can't be brought up directly at the machine...it needs a terminal connected to it...just not sure how to do this part yet...

-Ryan

[machintek]

Fist event monitor is described in the maintenance manual using a PC as a dumb terminal and the K3 connector on the FMDC. I run Procomm.

George

[topquark]

Well... I'd try replacing things later. The wiring from the switches all come to the same terminal block in the back and it's pretty easy, with the machine powered down, to use an ohmmeter from one end of the switch chain to the other at that location and look for resistance. The random switch has a good chance of being bad due to arc damaged contacts, or oil, or any other thing that would give it a more than zero ohm reading most of the time. I'm not sure what schematics, etc., might be available to you, but if you have the layout you can see that it's fairly easy to isolate a switch if it DOES measure other than expected.

[HillBilly]

From looking at this schematic (R2E3). It looks like the input in false triggering. K10-7 (circled) should be delivering the limit input to the EAF board. It also supplies the spindle contactors. You would think if this line lost 24v the spindle would stop. Unless it is happening real fast.

Darek

[topquark]

I just found my brain in a pile of chips. After dusting it off I realize I have an R2E4... not R2E3. Sorry about misinformation.
Looking at your schematic, the spindle motor would have to stop if any of the limit switches or overload contacts opened. It would be good to read the FIST and see if it said it got a false ZAP from that line Hillbilly pointed out.
I'll shut up a lot now, since I actually don't have the same machine....
Russ

[machintek]

If you have the R2E4 you have a BOSS event log and a FIST event log available from the front panel.

George