From rLab

When our old laser tube finally died after 5 years of faithful service it seemed a shame to simply throw it out so instead we made a display piece out of it! The back board was made from a lump of scrap MDF that used to be a storage shelf downstairs before the last re-organization. We cleaned the tube from all the soot and tar that had built up on it over the years, and then flushed the coolant passages with a strong solution made up from 1L of water and a dishwasher tablet in order to remove the biofilm that had built up in there. An approximate paper template was produced using the large printer which was glued onto the MDF and then cut around using the band-saw. After the wood has been approximately shaped, a bit of left over polystyrene was cut into a template of the curved ends of the display board using the laser cutter, this template was screwed onto the board and then cut around using the router with an edge-follower bit.

Once the timber was approximately shaped the edges were formed into a nice molded shape using the router again and an ogee cutter. The holes in the MDF were filled using a paste of wood glue and sawdust and once set the entire piece was sanded down. An angled rail was formed from some more bits of scrap timber and screwed to the display board in order to hold 2 strips of UV LEDs pointed at the laser tube and shielded so that people looking at the display wouldn't be able to see the LEDs directly. The wood was all sealed with MDF sealer and sanded again before being painted with dark-grey matt-finish paint. In order to mount the display board to the wall above the laser it was attached to a french cleat made using the table saw.

Some mounting clips to hold the laser tube were designed in OpenSCAD and produced using the 3D printer, they were screwed to the mounting board to hold the laser tube where the UV LEDs would be pointing as directly as possible at it.

After a phone call to the tech support line at FastColours, we bought some samples of Fluorescein and Rhodamine-B fluorescent dyes and mixed them up to make a water-based solution that glows bright orange/red under UV light. FastColours were very helpful with advise on suitable dyes to select and how to use them to get the best results, they also warned us that the dyes were incredibly concentrated. This proved to be very accurate as the 20 gram samples we got would probably have been enough to make up over 1000L of final solution! The UV dye was poured into the cooling channels of the old laser tube and the hoses capped with nylon plugs made on the metal lathe. The tube was installed into the clips, secured with cable-ties as a backup in case the clips failed and then mounted above the laser cutter.

A small brass plaque listing some relevant information about the tube was made using the CNC milling machine in single-point engraving mode and polished up using the buffing wheel.

The OpenSCAD file for the design is available here.