Design and build a CNC machine

Building the Base:

In the past two weeks I was designing and building the CNC's base and the X carriage.

I started from designing the entire CNC machine with SketchUp (you can find the 3D model in the downloads section of the blog), then I went to a local metal shop to buy some iron flat bars, after that I started to punch every hole onto the bars, according to the 3D model, with a center punch and finally I've drilled and tapped each hole.

Here the photos of the iron flat bars:

Iron flat section bars before tracing

The stepper holder after tracing and punching (I've used a black marker to enhance the visibility of the traces)

With this kind of construction the bars haven't to be perfectly cut to lenght (for example if the bars are roughly cut with a band saw), in fact the distance from the holes will not be affected from that, moreover the nuts and bolts construction allow you to achieve the maximum precision and squareness possible when assembling the machine, even without ultra precision tools.
For the nuts I suggest the nylon lock ones as they prevents misalignment over time.
The tools needed are:

• A drill press (even a cheapy chinese one, the important is to tune it up correctly);
• Some drill bits;
• Some metal taps (preferably a three pieces set);
• A metal vise;
• A center punch;
• A metal scriber;
• Some lub oil (I suggest WD-40);

Here some photos of my workbench and tools:

My drill press, note the threaded rod, it prevents the drill's table from twisting under load

Drilling the base's holes, I've clamped multiple bars at once to quicken the process

After the drilling process I've cleaned up the bars with some kitchen degreaser and then I've painted black each bar to prevent rust, here the final result:

I've noticed that this kind of coupler creates tons of backlash, so later on it will be replaced with something else

When I was designing the CNC I decided to make every hole 1mm bigger to allow some adjustment when assembling, and this works great, especially if you haven't been much accurate at tracing/punching.
For the rails I've used C40 steel round bars, note that painting the rails isn't a good idea, in fact the paint will not last very long due to the continous rubbing of the bearing over the bar, so to prevent rust you should keep the bars always oiled, WD-40 works great.

Building the X Carriage:

For the X carriage I've used the same approach that I've used to build the base, here the result:

When assembling make sure to be ultra accurate at squaring up everything, especially the base's bars, the X carriage's bars and the rails. Remeber that if two pieces are dead on square and you place them in front of a light source you shouldn't be able to see the light between the pieces and the square.