Legal, 3D Printed Coins Produced

By on December 8th, 2021 in news, Usage

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A 3D printed, fully legal silver coin [Source: PRINTY]

A Slovakian 3D print service has produced silver coins that are actually legal tender.

3D printing money has long been a fantasy that people wondered would be possible. But now it’s actually been done: PRINTY has 3D printed a silver coin that is legal tender.

Does this mean PRINTY or others can start producing money? Not really, as there are a number of challenges. I spoke to PRINTY’s Radoslav Behul to find out more about this unusual project.

ExOne 160PRO 3D printer used to 3D print silver coins [Source: PRINTY]

The company, which has been around for several years, offers a variety of metal 3D printing services to clients, including use of equipment from Desktop Metal and ExOne. Currently they operate a Desktop Metal Studio System, as well as two ExOne 160Pro systems, with a view to using five units in the future. Their goal is to provide low-cost 3D printing for industries unable to afford the traditional (and expensive) metal 3D printing systems.

This is a good strategy, as there are plenty of general manufacturing operations that require low-volume metal parts that don’t need the high tolerances possible in high-end metal 3D printing.

Recently PRINTY was approached by the Pressburg Mint in Bratislava for a very unusual project: 3D print a silver coin. The geometry of these coins was such that the mint could not produce it using traditional methods, and they contracted with PRINTY for assistance under a public tender.

This is a rendering of the coin design, and as you can see it is rather complex:

Design rendering of a complex silver coin. Note blue positions for diamonds [Source: PRINTY]

I had not heard of the idea of 3D printing in silver, but apparently its quite possible to do with the ExOne equipment. Silver, when properly powdered, can be used as a material in the ExOne binder jet equipment. Apparently ExOne assisted PRINTY in developing the necessary print parameters, which were obviously highly unusual.

A 3D printed silver coin just after printing, this is a green part [Source: PRINTY]

The coins are produced in a multi-stage process. They’re first 3D printed with a binder. Then a sintering process burns out the binder and fuses the silver particles together into a solid object. The then-silver object receives a polish, and finally, in this case, diamonds were affixed to the coin, as you can see at top.

A 3D printed silver coin after sintering, but before polishing [Source: PRINTY]

The coins are for two countries in the South Pacific: Tokelau, a self-governing dependent territory of New Zealand, and Niue, a self-governing island in free association with New Zealand. The 3D printed coins are to be legal tender in these areas, but are not intended for actual circulation. The currency is the New Zealand Dollar.

A 3D printed, polished silver coin, but prior to diamond installation [Source: PRINTY]

How difficult are the legal aspects of this project? Behul explained they must provide quarterly reports to the issuing authority, the New Zealand mint. It’s not as if anyone can just print coins; they must be ordered, tracked and accepted by an actual mint.

I asked Behul about the material, and he explained:

“3D printing the coins with fine 999 silver wasn’t really working with the binder jet process, and we had to change to 925 sterling silver (it’s a mix of silver and seven percent copper). This is a standard material for jewelry. It’s a much harder material, and works better when 3D printing.”

A 3D printed, fully legal silver coin, including diamonds [Source: PRINTY]

I realized there could be a unique issue with this process: powder processes typically require a ratio of fresh powder versus recycled unused powder from previous print jobs. In many cases, polymer powder systems end up trashing some used powder due to these ratios. If this was the case with silver powder, that could be a very expensive throwaway item.

Behul quickly explained that reused silver powder is very expensive, and they’ve managed to have “99% reuse.”

What have we learned here? First, it’s possible to 3D print silver objects, including coins. Secondly, don’t throw out used silver powder! Finally, 3D printing coins is probably not something anyone should undertake unless specifically authorized. Doing so without approval will almost certainly generate a visit from folks in black vans.

Via PRINTY

By Kerry Stevenson

Kerry Stevenson, aka "General Fabb" has written over 8,000 stories on 3D printing at Fabbaloo since he launched the venture in 2007, with an intention to promote and grow the incredible technology of 3D printing across the world. So far, it seems to be working!

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