Very cool!! @wild.bill I really appreciate you sharing your thoughts. As I research I'm finding a wealth of information out there. I have decided to go with my own design, but am using ideas from many of the kits and custom builds I see documented on the web. Right now I'm focusing on the frame and motion systems. I am trying to use sketchup to document and validate the design, but I have a lot to learn in that area. For me that is really the fun of building the thing, all the learning. I may try my hand at TIG welding some aluminum brackets, possibly anodizing, and of course all that needs to be learned about CNC routing. Right now I have settled on approximately 1000mm x 1000mm platform. Here is what I have so far:
For the Y-axis sides I will use two 30-6060mm aluminum extrusions (one for each side). On top of them will be SBR20 linear motion ball slides. These will support the gantry. I went with the 3030 based extrusions as the mounting holes for the SBR20 are 30mm side-to-side. The 30-6060's heft together with the SBR20s should provide good stability. I will use 30-3060s for the cross members. I also plan to fabricate some 250mm cross braces from 3060 aluminum.
The motion will be driven by some 0.9 degree NEMA 23 76mm steppers with 1.9Nm of peak torque. These will drive SFU1605 1000mm Ball Screw.
For the gantry I am going with two 20-4040s configured as a truss beam. I will create the cross members out of 1/4in aluminum plate. On the 4040s there will be two SBR12 linear motion ball slides to mount the carriage. The carriage will hold a ball screw and smooth rod linear module, which will of course hold the router mounting hardware. The module will have 300mm of motion. That may sounds like a lot, but I would like the flexibility regarding material and bit hights.
I was looking into the complexity and cost associated with making a closed-loop control system. It would not be crazy more expensive to do (maybe another $300), but for now, I am going open-loop. I plan on homing each Y-axis rail before starting a cut, so any missed steps will be nulled. I guess it all depends on what materials I end up routing. I may get the steppers with the rotary encoders (about $30 more per a stepper), giving me the option later if I want.
For control, I am thinking of going with Smoothie. I am using it now for the FT5 3D printer, and find it works very well. I am not sure the CNC branch is as well supported, but it appears many are using it. The controller board's stepper controllers will not be powerful enough for the three main NEMA 23s, so I will use external controllers. I have not decided which just yet. I may go with one of the inexpensive Chinese stepper controllers and see how it works.
Well, that is it for now. I would love to know more about your software tool chain. There looks to be a lot of options out there.
Oh, I love the water cooled spindle motor too. I assume that has its own PSU and control hardware. Did you find the air cooled router was underpowered, or just liked the no blow of the water cooled spindle motor? Have you thought of adding a vacuum rind to trap and remove the waste? I know that would block your view of all the fun, but...