3D Printable Ronchi Ruling Plate

That's right. You can 3D print a working Ronchi ruler. 

About the Model

This model is a Ronchi plate designed to work with the Stellafane Foucault-Ronchi Testing Stand slide holder developed by user Hack_n_Splice. The grating consists of 0.2mm lines spaced 0.2mm apart, going from the top of the slide to the bottom, printed directly onto the print bed. This results in a 5 lp/mm (63.5 line per inch) Ronchi grating, almost identical to the commonly used 5 lp/mm gratings available commercially. 

Ordinarily, the dimensional accuracy of a 3D printer is good. However, by limiting movement to a single axis while printing a line, the accuracy is extraordinary, matching the accuracy of laser printers that have long produced DIY Ronchi gratings. 

How to Print

Printing this model is a test of your 3D printing skill- with my Ender 3 V2, I struggled to align the bed and nozzle properly, as evidence in my own print. There are several strict requirements. 

• Your bed must be flat. No textures permitted; only attempt this if you have a glass bed. 
• Your bed must be perfectly level. Any dips or rises in the bed must be < 0.02 mm, or the print will fail to have distinguishable lines. Some printers can model imperfections in the bed- they may be able to shine while printing this model. 
• Your bed adhesion must be good, but not perfect. If your filament is too well adhered to the bed, the ruling will rip as you lift it off of the bed. 
• Your nozzle must be clean as a whistle. In fact, you should only really attempt this with new nozzles, before they are schmooed up with old filament. 

Print this model with a 0.2 mm nozzle, and set your slicer to 0.08 mm layer height. Use your filament of choice. PLA is recommended, because it is extremely strong. If you use a filament bulb in your tester, however, you may want to use a more heat-resistant filament. I had good results with PETG. No supports are required, and bed adhesion methods should not be used. Seriously, if you struggle to remove this from the print bed, it WILL break. 

Limitations

Obviously, this is an imperfect ruling. Each line is separate, meaning that they can change shape and position over time. Wind and breezes can blow them around. Heat from a lamp can warm them. And of course, touching them can absolutely destroy them. That said, if you already have a 3D printer, give this a shot. Perhaps this model could be printed directly onto a glass slide. See how far down the 3D printing astronomy rabbit hole you dare to go.