We got far enough on the project CNC mill (built out of mostly salvaged parts) to make test cuts, and evaluate results. I honestly didn't think we would get this far. Back when I first plugged in the salvaged Parker motion control XY table I had only a vague clue where I might go with it, only knowing that I will be learning a lot as I go. Now here's a machine capable of making a decent effort executing G-code programs generated from Autodesk Fusion 360.

There was never a real solid goal for this project, no "North Star" to guide the direction nor a finish line to mark completion. I think I can now articulate the underlying goal for this project: to learn as much as I can about the world of automated machine tools with the smallest possible budget. This is why I didn't worry overly much about imperfections like a bent Z-axis ballscrew or a Z-axis gantry lacking in rigidity: they were good enough to move forward and learn lessons.

At this point the Parker XY table, our old industrial equipment at the heart of everything, has proven to be a solid core. In contrast, our problematic Z-axis has proven to to be the weak point. We could fix those problems, but solutions all cost money. So before I pull out the credit card again, a question: are there things we can learn with excellent XY axis but lackluster Z?

The answer is yes: there exists CNC projects with exacting requirements in XY axis but much less demanding of Z. We've briefly toyed with one category: pen plotters. For a pen holder, it only matters that a pen is put on paper at the appropriate time and lifted otherwise. Factors like precisely square vertical alignment are not important.

Since we've already had some fun with pen plotting, I decided to start exploring the next step up in difficulty: CNC engraving. We will be using a cutting tool in our spindle to remove some minimal material. So while the Z-axis demands are similar to pen plotters, engraving requires a little more rigidity and precision than pen plotting. All the same toolpath generation tasks apply, so as a Hello World to CNC engraving, I engraved "SGVHAK" into the previously prepared surface. With this success, we can look at other projects we can use to learn CNC tasks with the flawed machine we have.