Mini cnc build log #1

About a year ago I participated in a CNC group buy on a slovenian electronics forum (part of members split and formed another forum). Up to a few weeks ago I had all the elements packed up, but now I finally started to put it together.

The machine is designed by the author of Planet CNC. He is producing and selling great CNC controllers and accompanying software. Actually on the group buy I only ordered the mechanical parts of the machine. I plan to add and upgrade the controller and motors on my own 🙂

The machines frame is made of bent steel sheet and some parts are made from machined aluminium blocks. This is how the collection of the parts looked like before assembly:

Well, actually the frame originally came unpainted and I used some red metal paint to protect it from rust and to make it look pretty 🙂 I brush painted it, but the result came out quite nice. I don’t seem to find any photos of the paint process which probably means I didn’t take any. I used nails and some wood pieces to support the frame while drying. Minimising the contact points or hanging the piece while drying will also minimise the blemishes on the finish.

The first thing was to install the extendable legs to the lower steel frame and to level the assembly.

Then I assembled the first axis. The axis is supported on the two round precision rails. Linear ball bearings of standard type are used and are pressed directly into aluminium block and fixed with seeger rings. As the steel frame is bent it can not have absolutely accurate dimensions, so aluminium guide blocks are used to hold the round rails exactly in the right place. Their exact position will be “tuned” later as I “calibrate” the axis.

Assembly itself is a bit tricky as all the elements of the axis have to be introduced through the hole in the front of the bent steel frame (hole in the front right corner in the lower picture). I would prefer a more open design, but that would probably mean a little less strudy frame.

The front and rear aluminium guide blocks are also used to hold the bearings for the ball screw in place. They are held between the aluminium guide block and the steel frame. Normal bearings are used – no axial ones unfortunately.

Finally with the axis bearings and ball screw in place I could now attach the aluminium work bed which comes over the axis. It also closes up the frame making it stronger.

Painting took me a two afternoons and also the aseembly took one. There were also some additional tasks to do like boring the holes in steel frame to their correct sizes and tapping them which I didn’t document here as they are not too interesting.

I actually own another small CNC that I intirely bulit myself, but it’s frame is not very rigid (it’s made of wood), so it can only be used for engraving soft materials like wood / plastics / PCB and for drilling. It also has a 100mW blue laser attachment which can be used for marking wood. Well, actually its most problematic issue is low speed (probably due to high friction in diy nylon bearings and low power of its motors). Nevertheless it has been used in quite a few fun projects.

When I complete the machine, I will probably first try to run it with a parallel port interface that is currently used on my other CNC (Mach3 / LinuxCNC), however I plan to transit to Arduino CNC / RAMPS and later probably a Planet CNC controller…