I want darkfield and oblique stops with my low and medium magnification objective lenses on my compound microscope. I want them to be repeatable in case they break or I find another needy scope. I want them easy to make and use so I can share them with the world. They need to fit in the filter tray. I also don't really know what sizes I need so I want a way to generate a laser cuttable geometry that can sweep a variable over whatever range.
First I made a few patterns in solidworks but I wanted to be able to change things like arm spar geometry and swept range really fast and painlessly. That is not solidworks. I wanted to change one thing and have it carry through the entire swept set. And kerf compensation because the laser at HSL doesn't automatically apply it. Yikes... Onward towards a better solution...
OpenSCAD is a dream. I wrote the following script which even includes kerf compensation. It auto generates and even neatly tiles the two pattern sets. Then I can export right to DXF. This is my first openSCAD project. I think I am hooked...
There is a kerf bug. Technically the kerf is the entire width of a cut, not the difference between expected and actual edge coordinates. The script is actually looking for 1/2 of the kerf. So if your cut is 0.3mm wide then you need to put in 0.15mm as your kerf. Oops. I'll fix that someday.
Here is the openSCAD script. 
And here is what it spits out (DXF) 
And here is a pdf file you can use to laser your own set but really you should just load the openSCAD script and customize it yourself! CMON LAZY BONES! File:Microscope stops 0kerf15mm.pdf
Using 1mm thick cardstock at a power of 20 Watts and a travel speed of 10mm/sec I was able to produce the following. I assumed the same 0.15mm halfkerf. The results are amazing! The spars and ring are thick and sturdy and they fit perfectly in my filter tray!