I have wanted a CNC milling machine for some years now....at first I built my own CNC router out wood, which turned out fine but it could not work on anything harder than wood. Therefore, after a lot of research, I decided to buy myself a manual mill and convert it to a CNC mill. Let me start by saying that this conversion process is still ongoing, as I keep improving little things to get more performance out of the machine, but up to this point I spent at least 300 hours working on it. Here is are some details about the machine:
1) Closed loop driver motors on all axis
2) SFU1605 ball screws, C7 accuracy grade. Currently these are the weakest point of the machine as they have tons of backlasch (about 0.13 mm). Fortunatly I can compensate the backlash via software, which helps a bit but doesn't solve the problem completely
3) PlanetCNC 4 axis board
4) Vertex rotary table with a self-centering 4 jaw chuck
5) Self-machined aluminum mounts for motors and screws on all axis
6) Wood and plexiglass enclosure, to keep the chips inside and the workshop clean
Here are some changes that I am planning to do in the future:
1) Changing the single nuts to double nuts on all axis, to eliminate the backlash completely and improve the machining quality
2) Design and build a circuit that acts as a link between the CNC controller board and the milling machine spindle controller. It will manage program start, pause and emergency stop. It will also monitor the enclosure safety, making sure that the door is closed before the machine can start.
3) Add compressed air to the machine to have better chip evacuation and part cooling
4) Add a venturi vaccum pump to be able to build vaccum fixtures to build parts
5) More ideas will come up for sure....