To cut a long story short: tol-protractor-drawing-assembled-height-04.stl is most likely what you need. The rest is written for advanced users.

This model is for drawing. There is also The SMALLEST Protractor for CAD modelling.

I found several protractor models in internet, but I didn’t like that they were too large for my needs and most of them were not optimized for transparency. I decided to make the smallest transparent protractor that can be still usable after being printed with 0.4 mm nozzle.

I used FreeCAD to find the smallest radius of the protractor that keeps 180 marks with 0.4 mm width and 0.4 mm spaces between them. I found that 5 cm radius seems to be the lowest limit. Of course, if you have 0.2 mm nozzle, you can try to make it smaller, but I don’t have it, so I made it as small as I could print.

I made some tests to find out how many layers of transparent (“natural”) PETG can still remain transparent enough to be able to read the text under it. Evidently the less layers you have the better, but I found that 4-5 layers are also transparent enough. Anyway I decided to print only 2 layers because 1 layer is not reliable and 2 layers seem to be quite good. It’s worth noticing that PETG is highly transparent if you print it one line above another like “IIII” or “----”, but it becomes rather blurry if you use a cross-pattern that fills like “XXXX”. It’s up to you to decide how to fill it but if you use only 2 layers, I think the cross-pattern is more reliable (the thing becomes more durable).

Another problem that I bumped into is that the font that I initially used was too small and the 0.4 nozzle blurred lots of the digits. This is most likely because I have a cheap printer Ender 3 V2 with the cheapest PETG that I could find in local shops :-) I had to redesign the model to use a larger font. The disadvantage of the larger font is that the numbers 170 160 150… are printed very close to each other, but I think it is better than blurred unreadable small symbols.

If you still experience problems with printing even these large digits, try reducing the flow (I used 85% flow for the digits and the scale in the final version but it still looks over-extruded) or replace PETG with PLA which is much less leakable and supports better resolution (I just don’t have black PLA so I used PETG anyway). There are surly some settings in the slicer that can improve the result or make it worse. I'm amateur in 3D-printing so I'm not sure, it feels like the first prototype on the left is even cleaner and sharper than the final version on the right I don't know why… You see the 1-degree marks are separate on the left and they are “glued” on the right, although they should be separate in both prints… I also tried to slice it with 0.2 line width but it just stops extrusion in places and skips some small parts. If anyone knows “perfect” settings for this kind of print with 0.4 mm nozzle, share them in comments please.

As this model is on the verge of 0.4 resolution, make sure your slicer slices it correctly before printing! I found that CURA slices it perfectly with default settings but PrusaSlicer removes a lot of the scale (maybe it can be fixed somehow in the settings but I didn’t try).

I attached 2 prepared assembled models, they are ready for printing right away with 0.4 nozzle and 0.2 layer height:

tol-protractor-drawing-assembled-height-04.stl - 0.4 mm base height + 0.2 mm scale height.

tol-protractor-drawing-assembled-height-10.stl - 1.0 mm base height + 0.2 mm scale height.

THE FOLLOWING IS FOR GEEKS ONLY!

I also attached 2 parts to be used as a constructor. To print them correctly, make sure both are aligned on the same place (check correct rotation and use “Center Selected” in CURA if needed).

One part pt1-tol-protractor-drawing-base.stl is 0.2 mm layer of the base. Suppose you need to print a solid non-flexible protractor with the height of 2 mm. Load the base in CURA , select it and use Scale feature. You can also scale X and Y, for example, if you need double radius size, set 200%. As for the height, set 1800%! Note that there is some bug in CURA 4.13.1 for Linux with resizing params. If you set 1000% it really shows 2 mm height but it slices only 6 layers of 0.2 height, so the real height will be 1.2mm!!! This bug may be fixed anytime, so always check the number of layers sliced, because the real height of the thing = number of layers * layer height.

The second part pt2-tol-protractor-drawing-labels.stl is the scale. I separated it in case you will print it with a different color the way I did. My printer only supports one color, so I print the base, keep it on the table, replace the filament and print the scale above the base. There is “Z offset” plugin for CURA to make it easy. I know that there are other ways of switching filament during the print, but I like this one more because you can clean the nozzle and print something useless in the corner to make sure that the nozzle is completely ready, and only then start to print the scale (it gives more “clean” starting of a new layer without any sh!t leaking from the nozzle by itself that may eventually spoil the initial part of the scale).

Warning: if you print in 2 colors the way I described, make sure that the second .gcode file does not operate on Z lower than the final Z of first .gcode, otherwise you will just break the thing that was printed with the first .gcode file! CURA automatically adds a code to clean the nozzle by printing 2 lines at Z=0.3, you should remove or modify it if you print something over what was already printed and glued to the table! The good thing is that you don’t need to modify anything in the .gcode if you print something with a low height (like this protractor) and if you clean the nozzle somewhere near X=0 ! Anyway, you should learn how to print with 2 colors before complaining! It was the first time I printed a thing with 2 colors and I’ve spoiled 4 prototypes of this protractor before I’ve got a model that satisfies me :)

This model is for drawing purposes. I think later I will make a different non-flexible version with an angle-finder-helper to measure angles of various things for duplicating purposes.

If you manage to print a usable copy of this protractor, I would appreciate it if you share a photo of it here with a comment what filaments were used.

Solution for PrusaSlicer (and maybe some other slicers) to slice the scale correctly.

The marks in this protractor have only 0.42mm width and PrusaSlicer thinks that this tiny part of the model is unimportant and should not be printed. This model was designed for 0.4 mm line width that is default for 0.2 mm nozzle, so the marks have only 0.42 mm line width to be sliced properly, But PrusaSlicer has default setting of 0.45 mm width!!! I found 2 solutions:

1) Check "Detect thin walls" in the print settings, it will slice all the scale marks but also make "4" look strange :)

2) Go to Print Settings/Advanced/Extrusion width and change everything there from 0.45 to 0.4. It will make acceptable slicing but still it is worse than the one Cura makes.

I recommend using Cura to slice this print (there are Linux, Apple and Windows versions and they are free). It slices everything well with default settings. It also has a setting called "slicing tolerance" that can include even smaller things to be sliced! Middle (default) and Inclusive slice the scale well while Exclusive will slice it without the scale the way PrusaSlicer does. Besides, it has several useful settings to noticeably improve the quality of this print that PrusaSlicer doesn't.