Setting up soft limits in UCCNC .. "Logic"

[John11668]

So are we saying that the ONLY reason for softlimits is to prevent the machine traversing beyond the home switches and crashing into endstops ( and I guess killing the traverse if we try to go beyond the positive limit, regardless of whether switches are fitted there) . in which case it seems to make sense to have a soft limit of zero and maybe an arbitrary back-off of say 5 , (and I guess that wound be +5 to bring it back within the working area)

So then I guess that I choose an offset in my G code routine to bring the tool to a new start position on my workpiece , Is that so ?

[ngwagwa]

So are we saying that the ONLY reason for softlimits is to prevent the machine traversing beyond the home switches and crashing into endstops ( and I guess killing the traverse if we try to go beyond the positive limit, regardless of whether switches are fitted there) . in which case it seems to make sense to have a soft limit of zero and maybe an arbitrary back-off of say 5 , (and I guess that wound be +5 to bring it back within the working area)

So then I guess that I choose an offset in my G code routine to bring the tool to a new start position on my workpiece , Is that so ?

Correct re purpose of softlimits ie prevents crashes at end of travel.

Whatever back off you set you don't need to alter the gcode as Zero is still zero. So to clarify on my machine with a back off of minus 5mm after machine has been homed the DRO will display -5mm when displaying machine co-ordinates.

[John11668]

Correct re purpose of softlimits ie prevents crashes at end of travel.

Whatever back off you set you don't need to alter the gcode as Zero is still zero. So to clarify on my machine with a back off of minus 5mm after machine has been homed the DRO will display -5mm when displaying machine co-ordinates.

But doesnt a backoff of -5 take you beyond the home limit presuming you are homing in negative direction from an x positive position on the table .??

[ngwagwa]

But doesnt a backoff of -5 take you beyond the home limit presuming you are homing in negative direction from an x positive position on the table .??

As I said earlier make sure you have the right direction for the back off - my home is far right so moves postive in X to get home, therefore I back off negative.Big noise and you got it wrong!

[JAZZCNC]

So to clarify on my machine with a back off of minus 5mm after machine has been homed the DRO will display -5mm when displaying machine co-ordinates.

I'm not sure that it works quite like that. It's been a few months since I set up a UCCNC machine but I think it Backoff works like most other controllers.? Which is that it looks for the Home switch then after hitting the switch Zero's the DRO, then backs off the set amount and Re-Zero's DRO again. When finished the MACHINE coordinates will show Zero.

It does this so you can have your HOME position or MACHINE ZERO at any point on the machine ie: Centre of travel, away from where the switch is physically located.

SOFT LIMITS are ALWAYS taken from MACHINE ZERO and limit the travel in the + & - directions. So in my Centre of travel example above with 1000mm of total travel, you would have Min soft limit = -500 and Max soft limit =+500.

If MACHINE ZERO was at the switch then soft MIN =0 Softmax =1000

Hope that helps clear a little of the confusion.!
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