I’ve been thinking about building a CNC mill or a router for several years. These are some of my thoughts:
-Main goal is learning about CNC in general and being able to machine plastics, wood and soft metals like aluminum.
-I don’t have much space nor budget, so that has to be taken into account. I’m happy with a 200x200mm work area.
-Cost must be kept low.
-I don’t have particular tolerance requirements. I think I’ll be happy with +- 0.1 mm for most things I do.
-I have a small lathe, drill press, angle grinder and stick welder.
I was thinking of making an L-shapped reinforced concrete base, from which threaded rod would protrude on four places on the base and on other four on the column. Those would be used to attach 20 mm thick aluminum plates, making their position slightly adjustable so they can be aligned, particularly if concrete shrinks or what not. Those and other necessary plates I would have cut to size, and do the drilling and tapping myself.
On those plates I would mount some SBR20 rails and RM1605 ballscrews as shown on the pictures below. Three nema 23 steppers would run the show, and the spindle could be something like the ubiquitous RT0700C makita router which seems a good compromise for my situation
I would be buying one of those kits on ebay providing both the rails and ballscrews for three axis, and cutting those to length. Seems to be the most cost-effective option. For shortening the ballscrews, I think the easiest method would be to cut them with an angle grinder, drill and bore a hole on the lathe (as they are case hardened and the inside is soft), loctite a cilindrical piece in place and machine it concentric.
Regarding electronics, I would be using and arduino and GRBL for starters, as that’s what I’m most familiar with.
I still have quite a bit of work to do on the design, but I’ll be glad to receive any feedback regarding this approach.