This summer I decided to revamp the staircase going to the garden. They were in bad shape and after some cement work I decided to seal the structure with tiles. The supports for the hand rail were on the way for any large-sized tile, so after searching around I settled for mosaic glass tiles. The glass has a certain internal sparkle that caught my eye. “It has to be easier than usual tiles” I thought. I was wrong.
Cutting these little glass tiles to fit is a painful and time-consuming operation, specially when the needed cut sizes are less than 10mm. I decided to automate that part of the work, and have some fun in the process.
The initial idea consisted in a X-Z axis CNC-like machine that would go back an forth over the tiles, passing over one line at increased depth repeatedly until it’s fully cutted. I started with that first concept, using the Lego EV3 kit.
That first design relied on a vertical push force to move the Dremel up and down. To work, it required that the supporting structure were rigid, and the Lego beams didn’t offer the required level of structural strength. Lesson learned and back to the drawing board.
Talking with my robot-expert colleague made me realize that the Z-axis was not really required. “You are making it too complicated”. He was right! 🙂
Next gen became a simplistic X-axis rail. I still tried to build the Dremel cradle with the Lego Mindstorms kit but didn’t give me a good, strong hold.
I switched to a vintage Meccano set I has found on a thrift store for 2 bucks and had been long waiting in the basement for some creative action.
The next interesting piece was some form of protection to prevent water and glass to spray all around when the machine would be in use. A water supply is necessary to keep the diamond wheel cool. It gives a cleaner cut than dry cutting and the dust is directly transformed in some milky water+glass goo.
For this piece, I cutted the top of a 1.5L plastic soda bottle.
To create the grove that would attach to the top of the Dremel, I sticked 3 “worms” of Sugru to the inner part of the bottle top and carefully screwed it on and off the Dremel. After letting it dry for 24hrs it became a solid screw fit.
Then, I drilled a hole on the top of the plastic to insert the tube that would deliver the water directly to the cutting point. The weight and limited flexibility of the water tube was too much for the plastic cup to hold. Something so close from the moving parts of the Dremel needs a secure installation and therefore I used a crane-like extension to hold the pipe in place.
Back to the Mindstorms
Some Sugru was the key component to bridge hardware-store elements with the Lego Mindstorms pieces. I actually didn’t feel like sacrificing pieces from the original EV3 package, so I bought a small Lego Technic Helicopter to source spare piece to cut, drill and glue without remorse. The chopper kit came with an interesting pipe-like piece that normally would connects two axis together. It provided a good fit for the leadscrew I was using for traction.
The EV3 servo control was quite simplistic: It uses the buttons on the brick to drive the Dremel in one direction or the other and a push button serves of break. The tricky part to sort out with the visual programming environment was “do while (no button is pressed)”. (Note to self: try lejos for more serious programming).
After putting all the pieces together and sorting out the height issues between the rail and the cutting surface, the new contraption was ready to go for field testing.
The results are great. As it can be appreciated in the following image, the machine cut (left) is clean and precise, compared to the classical tile-cutter result on the right.
Short video showing the smooth cutting action.