This is not quite a fourth axis question, it’s more about trading out one of the length axes for a rotation one. (eg imagine the X axis was fixed/removed and post running from +Y to -Y was rotated under it, instead)
What I’m aiming for:
B(rotation Y), Y(translation), Z(translation)
X(translation), A(rotation X), Z(translation)
I’m assuming with the motor wiring shouldn’t be an issue, since I’m still only using 3 axes at a time. But what I don’t know is if GRBL can be reconfigured (or recompiled) this way, or if it will even parse A/B (rotation) commands at all. Looking at the references has been unhelpful since they only really cover the G/M commands.
Is this even possible to do via modification of the (current) stock x-controller? if not what are my options for achieving this behavior? I’m trying to avoid faking it.
for reference I’m looking at either Fusion 360 or V-Carve for my CAM ware, both of which can handle wrapped toolpaths.
Angus beat me to it!
It might be more of a pain than just upgraded to a MACH3 system would be simply due to the Gcode translations/wrapping and such.
that thread is one of several I read through… unfortunately all the ones I’ve found (including that one) fall into 2 categories; either they just went for a different controller (and/or custom software), or they used an indexing system (AKA “Faking it”) which limited the function of axis as below.
RE: Just wiring with no reconfiguration of the GRBL software.
as I understand it GRBL treats X/Y/Z as Distance measures, rather than Degree, which I believe is what the CAM’s output… so would require an additional post processor to convert those (might not need a post processor with unwraps?) I can’t imagine it’d properly set the feedrates when doing rotational movement that way (since they are inversely radius dependent). The feed rate issue could be overcome by limiting it to an indexing mode for rotation so it only makes length cuts at depth but it’d require even smaller than normal stepover per index on contour work (which is my main goal)
if I’ve mucked something up in that let me know… I’ve been doing a lot of reading on specs and capabilities but I’m short on practice, so I may have jumbled things up.
From the sound of it I’m guessing the Indexing hack is the only option under GRBL right now? Is anyone aware of an alternative firmware that would work on the stock X-controller? If not, are there any recommendations of alternate controllers / firmwares that fully support rotational axes?