Newer techniques

Up until quite recently, the two production methods for slide-rule scales have been either to prepare them in printable form or to make an animated software version of the slide rule.

Laser engraving and cutting

Lately, I have seen at least a couple of examples of slide rules that are using laser engraved acrylic. The laser cuts the parts (e.g., discs: the examples I'm thinking about are circular models) and engraves the scales. Ink is wiped into the engraving an excess removed with a cloth, a very old-school technique.

Unluckily (or perhaps - fortunately), the sort of hobbyist laser engraver I might be able to afford for home use is outright scary and dangerous, and I suspect illegal to import. Most of the "safe "laser engravers (e.g., won't kill you with fumes or allow you to blind yourself) seem to be priced for the small business market, so not quite in the budget of the hobbyist maker.

I will at some point see if I can't perhaps find a local shop that does laser engraving and cutting on demand and find out whether they can engrave scales I've done. I expect any scales I have developed so far would need some tweaking; line thicknesses and fonts might need to be heavier for successful laser engraving than needed for printing.

For now, though, I have a small collection of 1/8 inch laser-cut wooden disks. I'm using them for some of the more fancy models for which I'm making replica scales; I guess that makes at least some of my projects partly laser engraved.

CNC Machine engraving

Another technology is machine engraving, which is to say, cutting and engraving by means of rotating bits, and following a computer program. There is an emerging market for hobbyist-scaled CNC equipment. It is still quite expensive and requires, in my estimation, a fair amount of expertise to operate and I mean: operate safely.

CNC machining seems to me to be the home-brew answer for reproducing one of those fancy brass calculating instruments found only in museums, though the home instrument might be using a softer metal, like aluminum.

Because the engraving is done by a rotating bit, I suppose CNC might have difficulty engraving really fine lines. I have seen examples of standard linear rulers made with this technology (also by laser engraving), so a CNC engraved slide rule may not be entirely unlikely

3D FDM printing

I reckon the FDM (Fused Deposition Modeling) approach to 3D printing (the 'hot-glue gun on a gantry' style) is probably the most popular of the technologies mentioned on this page, for hobbyists.

However, the one really key thing you cannot do with this kind of printer is to actually print scales. In FDM printing, surfaces are made by depositing molten plastic; the material flows when heated. Any "engraved" areas would largely fill in with melted plastic.

However, it's probably a good tool to build the mechanical parts for slide rules: 3D printed cursors or cursor frames, gears, end pieces, slides, stators or disks, threaded parts, various mechanisms for alignment. I'm sure that it could be used to print plastic frames or disks as well. You would have to add the scales afterward, either by stamping them or gluing a paper/plastic scale to the surfaces.

I'm very new at this technology, and I am not yet sufficiently skilled at 3D modeling to get good results, but I will certainly be using my printers in my future projects.

3D printing happens to also big good for printing tools that aid construction. One of my first prints was a device to locate the center of a circle, very handy during builds. Models for such aids are readily available on free sites...you download the model and 3D print it at home.