I bought an overstock optical filter for the lab’s plate reader (Beckman DTX-880). I want to analyze Hoechst dye fluorescence (excitation 350 nm, emission 453 nm). My new filter is the right size for the excitation filter slider, but too small for the emission filter slider. That’s probably because the 450 nm – 480 nm is a  very common excitation size but not a common emission size.

So, I need to either order another emission filter and custom size it to 18 mm diameter ($500) or I need to cut a little filter adapter ($free). I need something that will hold the 12 mm filter securely and block light. I envisioned something like this made from black plastic:

So I drew up 2 layers in Inkskape. The first layer made a partial engrave of a “rim” about 1mm into the 2mm thick plastic. The second layer cut the hole for the filter and then cut the part out of the plastic sheet:

The end result worked out pretty well. The funny thing is that this laser cutter cost ~$300. So it has paid for itself already. Admittedly, it did take some troubleshooting… so maybe the cost benefit was not quite so clean. I had to replace the laser tube (which the company did supply) and I had to replace the power supply ($100). At this point I still call it a win.