Trying to build a CNC machine

[markusb2]

Hi all of you.

I'm new to this forum (reged a long time ago, but was never active) and come here to seek help from all experienced people when I try to build my own CNC machine!

I have very little knowledge about CNC machines. Electronics has been my former hobby but never building machines, just so you know, Im a rookie here.

Got a X-Y table from a friend about 2 years ago. Two stepper motors fitted, and it looked like a strong base to build on.
Tried to read up on the CNC subject on different forums but I felt it was to much at the moment. Project was put aside.

Now I've picked up this project again and intend to make something out of it. I need a mill..
I hope to be able to mill aluminium when its done.

First let me show you what I have to start with.











This is how I got it. No electronics or anything. And no Z axis... my biggest headache.

When I got the table the top aluminium plate was full of glue, so I guess that is what its been used for.
The whole assembly feels very rigid. No play that I can feel anywhere.
Feels like a good base for this project?

This is what I know about it.
The markings on the ballscrews says FHPC 20.
The screws are 20mm diam and 5mm/turn.
Rods are 20mm diameter.
Linear bearings say "W.Germany, STAR, 067-20"
Steppers. Superior electric, M093-FD11 6-wire

I have built 3 stepper controllers using Allegros A3979 stepper IC with built-in translator. This was also done 2 years ago.
The controllers are rated max 2.5A and the two steppers on the table are rated 5.5A.
A guy on our swedish electronics forum designed the controller.
Last week I finally finished building the motherboard for the controllers. No optocouplers yet, but there will be when I build a new version of the motherboard.

I will probably have lots of questions while Im building this, and my first question is, how do I best design the Z axis?
This is a big problem for me because Im not really sure how to begin working on the machine.
I need it to be stable enough to mill aluminium.
I have access to MIG welder, angle grinder, drill press and simple tools like that in our workshop.

I am trying to build this on a low budget but I am aware I will have to spend some cash to get precision.

The stepper for Z will be a NEMA 23 which I allready have.

Please help me get started!

[markusb2]

I just tried google sketchup.
Would this be a good start? Or will it be unstable and ruin my machine?
Welding this to the bottom of the table frame.





Imagine the X-Y table sitting on the bottom bars in the Z-frame in the sketchup image.