There are a lot of CNC machines sitting around in basements and garages, but we haven’t seen anything like this. It’s making lenses using a standard CNC machine and a lot of elbow grease.
The process of making a lens with a CNC machine begins by surfacing a waste board and taping an 8mm sheet of cast acrylic down with double-stick tape. The lens is then cut out with an 8mm endmill, removed from the stock material, and wet sanded to remove the tool marks. Wet sanding begins at 400 grit and progresses to 2000 grit, after which the lens is polished with a polishing compound meant for high-gloss car finishes. This was done by hand, but in this instance there’s no shame in using a real buffing wheel.
Several other lenses are demonstrated, including a cylindrical convex lens, but these are only planoconvex lenses, or lenses that are flat on one side. Biconvex lenses can be constructed by gluing two planoconvex lenses back to back, which is done with an acrylic glue, in this case Acrifix adhesive. The result is remarkable: with a lot — and we mean a lot — of sanding and polishing, you can make an acrylic lens on a cheap hobby CNC machine. The trick is just a very small stepover on your CNC path.
There are a few more videos planned in this series, including one on using Fusion 360 on defining the shape of the lens to have the right focal length. We can’t wait to see that.