World Money Fair Technical Forum Review: Part 2

In last month’s issue of Coin & Mint News, we covered five of the presentations made in the first session of the World Money Fair Technical Forum 2023, which took place on 2 February in Berlin and was hosted by Dieter Merkle of Schuler and Thomas Hogenkamp of Spaleck.

In this issue, we cover the five presentations made in the second session, which focused on PVD coating and toolmaking.

The remaining presentations from the third session will be covered in the next issue.

Improvement of PVD Coating Adhesion on Laser Engraved Dies

Teer Coatings

Dr Halin Sun, Technical Director of Teer Coatings, introduced his topic by thanking the Royal Canadian Mint for their cooperation in developing PVD coatings for the mint industry from as far back as 2002. He listed the six PVD coatings currently used in the numismatic industry, the latest of which is a carbon, or more specifically, a graphite coating.

However, the main topic of the presentation was the resolution of adhesion of the coatings based on issues raised by customers. These were:

Poor coating adhesion caused by unintentional die surface contamination
Poor coating adhesion caused by a water-based solvent cleaning line
Coating adhesion issues after introducing the laser engraving/frosting techniques.

A solution was the introduction of a Linear Ion Source (LIS) as a precleaning process, and this system is now available in new PVD machines from Teer Coatings.

Alternatively, testing proved that LIS cleaning can be achieved successfully using a separate LIS cleaning chamber prior to PVD coating with chromium nitride.

In conclusion, Dr Sun said that PVD coating has been proven to be very successful and is now referred to as the ‘Green Coating Process’. It should replace traditional electrolytic hard-chromium plating techniques. The LIS pre-cleaning processes provide reliable removal of the top layers at low temperatures, thereby dramatically improving PVD coating adhesion.

PVD Coating in a Modern Mint Environment

Croatian Mint/Inorcoat

Goran Paladin, the then Director of the Croatian Mint, related his experience of producing Croatia’s euro coins in a short period, aided by the Mint’s decision to use PVD coating. Romain Waidelich, CEO of Inorcoat, provided the supplier’s aspects of the achievement.

The Mint planned to produce the required amount (420 million) of euro coins in a period of four months. It chose in advance to introduce PVD coatings for its dies for employee health, sustainability and productivity reasons – increased die life, clean technology, stable and easy to manage. The Mint operated its new die production facility ‘according to the book’ benefiting from the experience of others and specifically Inorcoat, its supplier.

When the dies failed it was from chips or cracks, not surface wear, so the dies were allowed to continue producing coins until their relief became unacceptable. The average die life achieved was above 1 million for €1 and €2 coins; for lower denomination coins, die lives of several million were achieved, the highest 6.5 million. Currently one non-euro coin die produced 11.57 million coins, and two dies have exceeded 12 million since.

The PVD machine installed at the Croatian Mint is the Inorcoat MS-700, which has a small footprint, is integrated, and can be installed and operational in 2-3 days.

Inorcoat has also developed various PVD coatings and is currently working on selective PVD coatings with Teca-Print (pad printing) to create completely new coin designs and surfaces with new visual and haptic experiences.

Direct Laser Engraving – Flexible and Faster Workflow Leading to High Productivity

ACSYS Lasertechnik

Alexander Aminidis of ACSYS reviewed the recent history of producing dies for coin production using the hobbing process. The whole process takes weeks before a production die is available. Some processes involving more master dies can take months before a die for striking is available. Today the industry requires that fewer dies are produced but in shorter times.

Laser engraving is not new, but today the technology has progressed so that ACSYS’s Premium Performance Laser Scan Head can speed up 3D engraving by as much as 70%.

The second development is the introduction of the ACSYS Femtosecond laser with pulse forging, the latter allowing a shiny silver finish to be created, similar to a polished finish.

Another advantage of direct laser engraving is that dies can be produced and stored, and then accessed for production when repeat orders arrive. Research has shown that on average only 25 working dies are required. Other advantages include their high durability and lifetime, high consistency and true to shape to the original data, and that difficult designs can be better managed and manufactured.

Specific examples of the time to engrave dies with pulse forging were:

5 euro cent = 17 minutes
2 euro = 42 minutes
1 Australian dollar = 39 minutes
For commemoratives, a 30mm x 0.4mm medal design = 2 hours and a 40 mm x 2mm high relief design = 12 hours.

Advantages of Laser Engraving with Dual Wavelength Femtolaser Based on Grayscale Bitmaps

GF Machining Solutions

Manuel Gómez-Marzoa, Technical Product Manager, Lasers at GF Machining Solutions, described the company’s three main technologies.

The first, the core technology, is texturing – 3D texturing, 3D structuring and 3D engraving. The second is laser micromachining for micro engraving, micro cutting, micro drilling and micro turning, which is the main technology for the coin industry. The third is additive manufacturing.

The Laser P 400 U is the one best suited for the coin industry and features two lasers, the Nanosecond 50W FlexPulse infrared and the GF Femtosecond Flex/Pulse infrared (20W or 40W). The two are interchangeable as the light comes out from the same hole.

The latest Femtosecond laser, the GM Femto FlexiPulse™ 40W IR-Green Laser source, can work in two wavelengths – the 22W Femto Green and 40W Femto Infrared. The benefit of the 22W Femto Green is that it has half the spot size of the 40W IR laser, and it is possible to switch from one to the other instantaneously. Other benefits are that a wider range of materials are suitable for use with this two-laser machine and additionally, using its FlexiBurst function, the laser engraved surface can be cleaned.

The GF machine should be regarded as a machine tool with laser engraving, its proprietary CAM suites providing ‘limitless freedom of design with unmatched performance and productivity for 3D texturing and engraving’, said Marzoa.

Preparing Your Coin Designs for Manufacture

CarveCo

Robert Newman, a founder of CarvoCo, a major supplier of software for coin design, started where he left off in the previous year (online) when he talked about higher resolution (see CMN December 2022).

He announced that, just prior to the Technical Forum, CarveCo had succeeded in increasing the resolution of its software from 4,000 x 4,000 to 8,000 x 8,000 – which is equivalent to 64,000 triangles, described by Robert as ‘pretty insane’!

The presentation covered the two key aspects, design and production. The new high-resolution capability of the software should be used selectively, ie. only when beneficial. The point of the new software is that choice and/or options have been greatly expanded.

The new software tools have been thoroughly tested and in all cases the time taken for tasks was less – in some cases 50% or more – than with the previous software.

The sculpting capability of the new software was shown to have greatly improved, and to have much greater flexibility and capability. Equally important is exporting the detailed information for tooling – to convince any sceptics the new software’s capability in this respect was both explained and demonstrated.