Project CNC

I’m an unlikely soul to be writing about understanding CNC. But I’m the perfect candidate to break it down for you because it was such a struggle for me. The explanations I got just weren’t adequate. “It” begins in your head with an idea. You have come up with an idea for a part of a specific size and shape. As an example we will use a cube with a round pocket in it.

Next you must make a “mechanical” drawing with all the correct dimensions. That must be done in a CAD (Computer Aided Drawing) or a CAD-like program. There are several available on the Internet free. The one I use is SketchUp Pro. I paid $500 for mine. Shortly after that Google bought them and put out an abbreviated version free for the taking. Your SketchUp drawing will look like this:

Our next step is to the world of CAM (Computer Aided Machining). CAM can’t recognize SketchUp files. Cam looks for DXF files. So we must export our SketchUp drawing as a DXF file. So make a folder somewhere in your computer and call the folder “My DXF files”.

Just as CAD, CAM can be had free. The one I use is SheetCAM. Go to SheetCAM.com and find the downloads section. Then look for SheetCAM TNG. This is a form of SheetCAM that’s under development. You can use it free. After a certain number of days it will expire. When this happens simply go back and download it again. You will not lose your files and it’s not annoying though it seems like it would be. After you get SheetCAM installed you will import your cube DXF. It will look something like this:

As you can see there is an image of you cube. You can now use the options in SheetCAM to tell your machine what you want done. In this case we want the machine to cut out the square shape and then cut a flat-bottomed round pocket. Amazing! Now that you’ve given it orders you click on the green P. When you do that it spits out a G-code. G-code looks like this:

As you can see G-code is nothing but text. From here we go to the CONTROLLER. The one I use is Mach3. As usual, a free version is available. Go to www.artsoftcontrols.com and download it. The only catch is that it only allows 500 lines of code. But you can make quite a few projects with that amount of code. And you can certainly use those lines to see whether or not you love it enough to pay the $159 to get unlimited lines. Mach3 reads G-code and tells your CNC machine what to cut. Mach3 not only tells your machine what to do, it also shows a path that the tool will follow. In this image you can see our cube (the tool path for it) on the right. You can see the G-code on the left.

The next step is to take your cube off the table and marvel at it.

I have not gone into detail with the operation of the various forms of software. It would just slow down the reading of this section of my site. But I will gladly provide step-by-step instructions (to the extent that I’m qualified) to get you through the worst part of the learning curve of each. Brilliant people have created these miraculous programs and they’re all initially free, and as an option, can be purchased dirt cheap (in my view). Enjoy!