"Waveguide" Bedside Reading Lamp cnc

thingiverse

I got some 10 mm acrylic glass (PMMA, also known as plexi-glass) from a donor. This material is notoriously difficult to work with on small CNC machines because the chips tend to melt and clog the end mill, resulting in breaking the bit. A solution is to reduce the spindle speed, increase the feed rate, and make fast shallow passes. Adding some drops of water mixed with methylated spirits or washing-up liquid helps cool the cutter, but it increases the mess. Compressed air used to clean out the cutting channel only makes things worse. The sides, especially where light enters and exits, must be sanded smooth and polished clear. The design is based on two principles that give the lamp its unique look: total reflection of light inside a material using waveguides, and bending acrylic glass when heated to a certain degree. To achieve a defined curvature, I created a negative form out of plywood. After putting the acrylic glass in an oven at around 170 °C for 10 minutes (one minute per millimeter thickness), it can be bent with ease. Be sure to wear gloves and note that it will take some time to cool down – during this period, the material is still soft and can lose its shape. For light sources, I used the Ledberg Spotlight from IKEA. I removed all plastics and cut out the diffuser. The base is made of walnut, but any other hardwood would work just as well, even plywood of sufficient thickness. A circle of funky foam gives the lamp a secure stand. I used my desktop CNC machine by Step Craft to do the cutting. Acrylic glass should be cut with a single flute end mill. For hardwood, I used a 3 mm end mill specifically designed for cutting wood. Please keep in mind that the STL file is intended for viewing purposes only and will not print. Visit https://www.zenziwerken.de/en/ for more interesting designs.