How to go outside soft travel limits?

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ashesman
Posts: 395
Joined: Thu Dec 03, 2020 4:54 am
Acorn CNC Controller: No
Allin1DC CNC Controller: No
Oak CNC controller: Yes
CNC Control System Serial Number: none
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CNC12: Yes
CNC11: No
CPU10 or CPU7: No

How to go outside soft travel limits?

Post by ashesman »

I need to my spindle to travel outside the soft limits of my machine during tool change. I cant see a ways to do this. My old controller had an M code that disabled soft limits during tool change.

Normally I don't want the spindle to be able to travel out of the green area. During tool change it needs to travel into the blue area. Only the Y+ soft limit needs to be disabled or changed. If I was to just set the Y plus limit to include the green and blue areas, it is easy to crash into the red areas which is where the tool racks live when they are hidden away.

Any ideas?
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cncsnw
Posts: 3763
Joined: Wed Mar 24, 2010 5:48 pm

Re: How to go outside soft travel limits?

Post by cncsnw »

You can modify the software travel limits through CNC system variables #23501-#23508 and #23601-#23608.

I would set it up so that the Y axis homes in the plus direction, to a home switch that is separate from the Y+ limit switch, so that Y home is where you have "+Y Limit" marked on your diagram.

In normal operation (outside of a tool change) you would then have a non-zero Y minus travel limit; and zero for the Y plus travel limit (prohibiting movement to the plus side of Y home).

You could then have your M6 macro set #23602 to a positive value when it needs to move Y into the tool-change zone; and set #23602 back to zero when it is done.

The only problem with this is that, if you interrupt the tool change before it finishes running, you will be left with the extended travel limit in place. You can partly work around that by also setting #23602 to zero in your cncm.hom macro, so that it at least gets reset on startup. If you wanted additional insurance, you could also set #23602 to zero in an M3 macro, so it gets run in nearly every program cycle.
ashesman
Posts: 395
Joined: Thu Dec 03, 2020 4:54 am
Acorn CNC Controller: No
Allin1DC CNC Controller: No
Oak CNC controller: Yes
CNC Control System Serial Number: none
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No

Re: How to go outside soft travel limits?

Post by ashesman »

Thanks for the explanation. I did look at those variables but thought they were read only. I just rechecked the manual and they are actually read/write so that solves that problem. I have to stop doing this stuff late at night!

If interrupted mid tool change, the old controller would run with no limits on any axis so this is not quite as bad!
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