SO3 XXL: Homing switches AND Z-axis touch plate?


Just ordered a SO3 XXL. I’m a crabby old engineer that’s owned several CNC routers and mills, but downsized to a smaller home and needed a smaller router to fit a basement workshop.

My primary question is: Can I use both homing switches and a Z-axis touch plate with the SO3? Are there enough GPIO pins and does the shipping software have support for it?

I’m a little nervous about starting over with a new motion control package after using Mach 3 and MultiCam-style controllers for years, but I’m going to give it a try.


Hi @audioguy - Yes, the board has discrete inputs for your limit switches as well as for a touch probe/plate.

I hear you about being nervous on “downsizing.” I’m actually heading in the opposite direction as I’ll likely be modding my XXL to use a Pokeys57CNC and Mach4 in the nearish future. You should be able to find much, if not all, of the capabilities for the new system using the various open-source utilities which are readily available.

I’d be curious to hear what you are nervous about losing, or is it more of a learning curve kind of thing?

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Hi John,
Thanks for the reply.

Yes and yes.
After working with heavy routers, I’m not quite sure what to expect. If I can get 20 IPM and 1/16" DOC in 6061 aluminum with a couple of thousandths of flex I’ll be happy enough. More flex and I’ll be progressively less happy. I’m not expecting 200 IPM @ 1/4" DOC and .001" worst-case deflection in that 6061 with the SO3. I gave that up for a more sustainable lifestyle in my dotage. :slight_smile:

And the 2nd yes - I worked as a motion control engineer with Forth-based industrial controllers for larger routers and mills, and used Mach 3 on a few of my own retrofit machines. I’m not sure what to expect from grbl - a couple of months ago I would have thought someone forgot a few letters and left the cage door open.

I did NOT spend $200K on this machine and don’t expect it to work like I did. I do hope I’ll get some useful prototyping done with it without too much cussing, however.


I believe you may find some of the tools listed at: of interest.

If you had an SO3, rather than an XXL, I’d strongly advocate that you get the threaded metal bed — as it is, even w/ the XXL, I believe that you’ll be happier if you can work out some way to replace the MDF — it’s fine for basic work, esp. in wood or plastic, but as a base for metalwork, it leaves a bit to be desired. The problem of course, is that’s a rather large expanse of area to cover, and even using aluminum extrusion, that’s going to be a fair chunk of change.

I’ve been looking at t slot tables. I can get a 600x400 mm cast iron table ground to .002" / 8" for $750 or so plus shipping, or an aluminum table ground to .005" for $250 that I can surface myself if I’m slow and careful and keep the ambient temp within bounds.

Before I do any of that, though I need to get a “feel” for the machine and whether it would be worth going to those routes. If not, something bolt-together than maybe TIG welded and surfaced might be in order.

I guess we’ll have to see. Waiting. :slight_smile:


Oh and sorry, thanks for the links. I have CAD and CAM software, but that doesn’t mean I shouldn’t look around and see what’s available.