[sparsrus]

I have a 1987 Bridgeport Interact 1 MkII with a Heidenhain 151 controller. The machine has been running well until it slowly would indicate that the machine has hit the limit switch when it was not near the switch. The envelope that the machine could run in without showing the switch warning grew smaller through time. The last time it was run, it booted up fine, homed as usual, but as soon as I tried to jog it off the limits, it showed the limit switch warning and would not go farther. I am able to jog all axis back and forth about 1/4", but that is all. I I jog any of the axis, it shows up as the limit switch that was hit. I have driven the y axis off manually and it moved back to the Y limit with the jog control, but would not reverse.
The machine will boot up, but will not home. I can manually move the axis the 1/4" it allows and it will pass over home in all axis. The control then displays the manual mode, as usual. I can not move it farther than about 1/4".
I have checked voltage and continuity through all of the limit switches, check lube oil level and checked voltage and they are OK. All of the ready LEDS on the drive cards are lit, and as I mentioned I can drive all axis a very small amount with the jog control. I have also checked the 24V controller voltage. The controller was checked and updated by Heidenhain a year and one half ago. I can not drive the table off the limit switches with the power enable button depressed.
Any ideas of where else to check?

Thank you very much for your help.

[machintek]

In theory you say you checked the switch limit switches for open circuits. Have you checked the machine travel limits (parameters)?

George

[sparsrus]

Thanks for the reply. I have checked the limits and they have not changed from when the machine ran . I disabled the software limits using the code and booted the machine. it went through the homing fine, but as soon as the table gets off the reference switch for the axis that I am jogging, the limit switch warning comes up on the control and I can move no further. This happens in all of the axis. I mistakenly said in my first message that the machine won't home by itself, it does, in fact move over the reference switches and homes correctly.

Thanks again for your help.

[machintek]

another stupid question. There are soft limits where the drives do not drop out and hard limits where they do. Your cables are old and stiff (like me), and it sounds like a broken cable that is degrading. Can moving a cable create the same error?

George

[gus]

If it is hard limits [flashing error]it is probably a bad switch or cable. as for soft limits, ther are 2 limits in the 151, the user accessable and the machine limits. Are the user acc. ones messed up? press the mod key, they should all be set to like + or - 500

If those are ok write down the parameter settings for the machine limits and you can change them 'on the fly' and see if the machine will move. IOW, increase the x minus limit by 20mm and see if it gives you 20 mm more travel.

[machintek]

A hard limit will drop out the drives.
A flashing error is fatal and requires a reboot of the machine to clear.
It has been a while but I believe this is correct.

George

[sparsrus]

Thank you all for your help. I appreciate your time. The only warning that comes up is "Limit Switch X +" when the table is jogged X+ direction after homing. The warning does not flash, nor do the drives drop out. The happens on all axis and in both directions on all axis (X+-, Y+-, Z+-). Drives stay on and I am able to jog a small amount in both directions in all axis.
I'll recheck the soft limits and I will recheck all the cables and switches to try to see if that could be causing it.
Thanks again for your efforts.

[gus]

With this error message, it is almost certainly the software limts have been misprogrammed. It is possible that the + limit is set to a negative number and thus has no travel, and that the small motion is all negative to the encoder pulse

[sparsrus]

Gus and George..

Thanks again for your input. I rechecked the software limits and you were right, the limits were set incorrectly. It was up and running happily until I noticed smoke from the spindle drive cabinet. One of the line chokes (37A, 200uH AC choke) was giving up the ghost. Any ideas on where to find a replacement?
I really appreciate the time that you have spent on this silly (as it turns out now) problem. If you ever get out in the Santa Cruz, CA area, I owe you dinner.

[machintek]

Apply my dinner to a new choke. I do appreciate the offer!
Try DIGIKEY or such for a choke. Or google it.

George

[gus]

The big ones[10 lbs]? might have one, check when I get to work

Why would it die is my question.....

[gus]

Yeah, I 've got three of the little monsters holding the floor down

[machintek]

Chokes have windings made of enameled wire. They do get hot thus they are subjected to expansion and contraction. This makes the wires rub against each other. Eventually the insulation fails. Just one theory for a method of failure. Another would be just too much current.

George

[gus]

well, my point is that they don't; so something is amiss