Now that it is built, it’s time for the MPCNC first test.
They say that you should walk before you run. I needed to accomplish two things. First, to create a design or model that could be milled with my Mostly Printed CNC machine. Second, to get an idea of how well the machine would work.
So, the “baby steps” would include creating a simple engraving using a pen. Thus, the MPCNC first test would involve some 2D plotting on a piece of graph paper. The model was a series of concentric circles (“bull’s-eye”) and some text. The tool was a cheap pen, mounted in my universal tool holder.
It turned out pretty well. The circles were not perfectly concentric, but close. The outlined letters were clear but a bit shaky. Some of this might be due to the pen not being entirely rigid in the holder.
The model was created in a program called Estlcam, a German-created piece of software for computer aided manufacturing. The two dimensional drawing of circles was obtained from a web site as an image or picture. Estlcam imports drawings in one of two formats. These are DXF or SVG format files. DXF is a drawing exchange format standard made popular by AutoCAD. SVG, or Scalable Vector Image files are a popular standard using XML.
Once I loaded the image into Estlcam, I was able to add some text. Then, I created a milling tool that would mimic my pen, and used it to create the “tool path” in G-Code. This G-Code is like a small computer program which, when run, tells the CNC machine what to do.
MPCNC First Test – So what do I do with this G-Code?
When you use a CAM program to design a tool path, you also have to set up your machine. The most basic of the set-up work is to make sure that your G-Code and the CNC machine have the same origin. So, I placed the notepad on the surface of the CNC and manually moved the pen over the spot that would be my origin. Then, I homed the machine by manually entering the G-Code “M92 X0 Y0 Z0”. This told the Arduino controller that the MPCNC was at point zero on all three axis X, Y and Z.
Previously, I had instructed the CAM program to “engrave” to a depth of 1 mm with the tool head – in my case, the pen. So, when I did the setup, I carefully made sure that the pen was 1 mm above the paper. My measuring tool was a small piece of cardboard of the right thickness. Also, the G-Code was instructed to raise the pen by 2 mm above the paper when it was moving to a new position. This prevented movement lines from being drawn between engravings.
Having completed the prep work, I crossed my fingers and pressed “run”. The MPCNC first test sprang to life, moving the pen to the right places and engraving the drawing on the paper. The engraving took about a minute and, when complete, the tool head returned to the point of origin. Much more to learn, but at least I am on the right track.