I have had this 2×4 cnc machine for 4 years now, and have outgrown it. Made of MDF with aluminum rails and skate bearings it won’t go down in history as a super sturdy machine. That said it served me well and together we made some awesome things. I have been volunteering at the high school robotics team, and having a machine that can mill aluminum with a reasonable amount of accuracy was my design goal.
Doing the slow troll on craiglist and facebook marketplace I came across this guy. Stout steel frame, and nice linear bearings. The z-axis on it was some sort of ink sprayer – not sure what exactly it’s previous life was but good bones for my build. Now I just needed a table, z-axis, electronics, mill.. the little things.
One thing that was interesting/concerning was this used belts instead of ball/lead screws to move the x/y axis. There is an included gearbox with a 2.5:1 ratio off the stepper motors, and my concern was if I could get and maintain the accuracy needed. Overall these rail systems were very well built, and even the belt-tightening mechanism was well done.