Computer Numerical Control Machine

 (2020-21) My gantry 3D printer fascinates me. Three small stepper motors, some extruded aluminum, a printer head, and a controller box has amazing versatility in what one can produce. And after watching This Old Tony (https://www.youtube.com/c/ThisOldTony/videos) explain the basics of computer numerical control, I caught the bug and wanted to try to learn more. When I saw a kit on Amazon for less than $100, I purchased it and other parts I’d need to build a three-axis CNC machine.

I spent many weekends in my shop, cutting up and filing metal parts. I laid out designs for plastic pieces in FreeCAD and printed them on my 3D printer. As I was nearing completion of the parts and ready for assembly, I did some work with our latest small form factor HSM. A handheld device with a touch screen, I realized that I had a perfect opportunity to see if I could automate interaction with the HSM via my CNC machine. The toughest challenge was the capacitance touch screen. I had to experiment with different techniques to press buttons on the LCD display. I eventually settled on a 10mm diameter nail that I shaped, letting the weight of the “stylus” and gravity work in my favour. (I also had to ground the stylus to the printer bed to create enough capacitance to activate the buttons.)

I added a relay switch to the mix to enter and remove PIN secrets to and from the HSM. After writing a small Python script to move the touch head on command, I had a simple, precision, open-loop transducer or SPOT as I nicknamed my device. I created a video of SPOT to share with my colleagues at work: https://youtu.be/GqS2l-SkrI4. Once satisfied with SPOT’s reliability and reputability, I sped up movement five-fold.

SPOT sits on a desk beside my 3D printer, gathering dust. But I have plans to repurpose the parts for another project. And I enjoyed my introduction to computer numerical control.