Bedside-Reading-Lamp "Waveguide"

I got some 10 mm acrylic glass (PMMA, a.k.a. plexi glass) from a donor. This material is not super easy to work with on a small cnc, as the chips tend to melt and clog the end mill resulting in breaking the bit. A solution is to reduce the spindle speed, ramp up the feed and make fast shallow passes. Some drops of water mixed with methylated spirits or washing-up liquid help to cool the cutter. However it increases the mess. Especially if you use some compressed air to clean out the cutting channel. The sides but in particular the edges where the light enters and exits should be sanded smooth and polished clear.

The design is based on two principles giving the lamp it's unusual look:

• first the waveguide based on total reflection of light inside a material
• the possibility to bend acrylic glass if it's heated to a certain degree

In order to get a defined curvature, I made a (negative)-form out of plywood. After putting the acrylic glass into an oven at approx 170 °C for 10 minutes (according to the thickness: 1 min per 1 mm thickness) it can be bend with ease. Be sure to carry gloves and mind the fact, that it will take some time to cool down. In this time the material is still soft and can lose the shape.

As a light source, I used the Ledberg Spotlight from IKEA. I stripped the all the plastics and cut out the little diffuser. The base is made from walnut, but any other hardwood would do, even plywood of sufficient thickness. A circle of funky foam gives the lamp a secure stand.

The cutting was done using my desktop cnc-machine by Stepcraft. Acrylic glass should be cut with a single flute endmill. For the hardwood, I used a 3 mm end mill specially intended for cutting wood.