> how long is it before you can't print a replacement part for something you bought because it looks too similar to an OEM part and the manufacturer doesn't think you should be able to do that so they throw a little money to the right politician

At least 25 years. That's the time passed since the first introduction of Eurion marks on banknotes. As far as I know, noone has used it to block reproduction of anything other than money.

When I was in college I wrote a computer program (yes, involving yellow text) that couldn't be photocopied because I put the "o"s in the right place to trigger the eurion-finding algorithm. People thought it was neat.

That isn't true though, coupons, boarding passes, and even confidential documents use Eurion marks. It's not everywhere because it isn't worthwhile going through the hassle of getting printers that can print them; while 3D printing OEM parts would be much more valuable.

Lots non-currency of documents around the world with EURion marks. If you're a secure printing shop and your business model primarily revolves around impressing your clients with long lists of document security features, it'd be malpractice to not implement this kind of padding.

EURion marks are a feature you must include on your banknote for it to even be considered real. And it's _one_ feature. It's relatively trivial to make a chip which can detect their presence.

On the other hand, if I need a replacement part for something, it's unlikely I will find the manufacturer giving me models for it. And if a manufacturer is giving me models for it, they probably do so with the explicit expectation that I might end up using them to manufacture a replacement.

In most cases either me or some other volunteer will need to measure the existing part, write down all the critical measurements, and then design a new part from scratch in CAD.

Even if somehow you are able to fingerprint on those critical measurements, that's just _one_ part.

The only way this kind of nonsense law could work is if you mandate that 3D printers must not accept commands from an untrusted source (signature verification) and then you must have software which uses a database to check for such critical measurements, ideally _before_ slicing.

Except that still doesn't work because I can always post-process a part to fit.

And it doesn't work even more because the software will need to contain a signing key. Unless the signing key is on a remote server somewhere to which you must send your model for validation.

This is never going to work, or scale.

There are even more hurdles... I can design and build a 3D printer from scratch and manufacture it using non-CNC machined parts at home. A working, high quality 3D printer.

Where are you going to force me to put the locks? Are you going to require me to show my ID when buying stepper motors and stepper motor drivers?

What about other kinds of manufacturing (that these laws, at least the Washington State ones, also cover)?

Will you ban old hardware?

What about a milling machine? Are you going to ban non-CNC mills?

These are the most ignorant laws made by the most ignorant people. The easiest way to ban people from manufacturing their own guns is to ban manufacture of your own guns. But again, this is a complete non-issue in the US where you can probably get a gun illegally more easily than you can 3D print something half as reliable.

Actually I tried to use it just for fun on some vouchers, but it didn't work on the copy machines I tried. They just happily photocopied the vouchers.

Is this true? Couldn't I put the mark on a page of my book and photocopiers would still detect and refuse to copy that page?

No idea why this comment is getting downvoted so hard. This was exactly what I thought of too, and it provides a concrete answer to the question.

There’s valid concern with these types of laws and scope creep. But there’s also precedent which shows they can work and be applied reasonably.