How to use toon shader to convert 3D models to patent drawings

Question

USPTO requires patent drawings to be black and white lines images.

I'm using blender to make 3D models. At first I got this:

The problem is it's grayscale with no black lines.There's a answer to suggest using toon shader. Convert 3D models to patent digrams

I checked "Edge" and set "Threshold" to max 255 in "Render" tab, I got:

It's getting better but need more edges to be drawn. I searched and found a tutorial http://www.minimaexpresion.es/?p=1070&lang=en , then I got:

It's too complicated for me and I don't know how to use render layers. So I tried another tutorial http://download.blender.org/documentation/oldsite/oldsite.blender3d.org/80_Blender%20tutorial%20Toon%20Shading.html , which says I should assign different materials with different colors to different objects, so I tried and got this:

It leaves only one way to give a shot: render layers. Is there any simple methods to make it work? I only want this and convert it to indexed colors with black and white palette:

And the "Freestyle" only has one option about line thickness:

Answer 1

You were close in the second image. Instead of using the Edge postprocessor, look in the Render panel check the box labelled "Freestyle".

Then in the Render Layers panel there will be a list of configurable options for Freestyle, including how thick you want the lines and the minimum angle required to render an edge.

The best results are if you use mostly shadeless materials with simple textures (just solid colour).

Answer 2

The PTO rule requirements for drawings in utility patent applications are specified in 37 CFR 1.84, which you can find here: https://www.ecfr.gov/current/title-37/chapter-I/subchapter-A/part-1/subpart-B/subject-group-ECFRc7605aa2d3f3782/section-1.84

Your dark gray background is not compatible with the requirements for numerals and tie lines/arrows identifying the drawing elements, since that would be black characters on an dark background. You need white background, black lines, and black numerals and tie lines.