Hi Leonardo, > > Just to clarify because sometimes it confuses me too. And please someone > correct me if I'm wrong: > > Positive and negative soft limits are always with respect to the 0 home > position. No matter where the home switch is located or if that 0 position > is aligned with the switch. In fact, your 0 position could be > (theoretically) anywhere in your joint's travel as long as you're inside > your hard limits of course (I didn't experiment with sharing both home and > limit switches so I don't know the behaviour with that setup) the only > thing changing will be the min and max limit that will allow you to > establish the safe distance before hitting the hard limits. >
That's the way I understand it too. The Home switch position (if not required in the INI/HAL files) becomes whatever the position is. Theoretically I guess on start-up the G53 locations are initialized to 0. However if the carriage is way over to the left rather than the center a soft limit of -10" would run into the chuck if there's only 1" of movement left. I know on the mill when the G-Code is loaded I'm often told that the movements will exceed my machine dimensions. But that's because I've set a physical home switch and my work envelope is configured in the [JOINT] sections of the INI file. MIN_LIMIT = -0.04 MAX_LIMIT = 13.5 Now if I've set G54.x == 0 at machine world coordinate 2.0" I'm within MIN and MAX LIMITs. But if the G-Code I load wants to do a X-3.5 it won't let me. The fault is move will exceed limit. So then if I move the X axis over by 2" so in G53 it's now at 4.0" and reset the G54.x = 0 with the Touch Off button, now the G-Code will work. And in AXIS the trace of the tool motion is now inside that red line 3D envelope. Attached is a low res photo of limit switches set up on a Harrison lathe. The Z axis are U shaped pieces holding the switch with a thumb screw to tighten into place. Needless to say the smart thing to do is to set the switch locations so the carriage can't run into either the chuck on the left or the tailstock on the right. The X axis is interesting in how it's set up. The switches appear to be in series with the NO switch on the X all the way out point and the NC switch at the X all the way in point. The rod moves and opens the circuit at either end. Very clever. John
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