Over the weekend, I had a chance to do a fun project in a new medium— a 14" square concrete tile of the Facebook “f” logo.
I’ve heard there’s concrete router bits out there for industrial routers, but definitely didn’t want to try that on an X-Carve. Instead, I decided to make the tile in plywood, cast a polyurethane rubber mold around it, and then pour concrete into the rubber mold.
That turned out to be an expensive, goopy disaster. Polyurethane rubber isn’t cheap, and I made a lot of mistakes my first time working it. Fortunately, the plywood tile came out quite nicely and was still usable:
For the next go, I decided to just make the concrete form out of plywood entirely. I used some scrap 3/4" ply, and a 1/8" carving bit with a slight angle— the idea being that tapered walls would make the plywood form easier to remove.
After cutting the form, we mixed some of this Shapecrete concrete mix. In retrospect, probably any decent concrete mix would have worked for this:
Again, my first attempt with this failed. The problem was in removing the plywood form after the concrete cured. Instead of pulling away the form, I tried to push the concrete tile out of it. This ended it with it cracking around its weak points.
For the second attempt, I just used a circular saw to cut the form down to the point where it was thin enough to just pull away or, in the case of the “f”, pound out:
For anybody trying to do a project like this, I would recommend having your initial plywood form just be a silhouette with thin walls. That way you won’t have to cut it down or carve it out like I did.
Here’s the finished product, which came out quite nicely: