The Art of Electroplating: How Progalvano Barrels Solved the “Coin Problem”
Introduction: The Challenge of Small, Flat Components
In the field of precision electroplating, treating flat, thin, and lightweight surfaces has always been one of the most complex challenges. When it comes to coins, medals, or tokens, aesthetic and wear-resistance requirements are at the highest levels: the deposit thickness must be perfectly uniform and the surface entirely free of any imperfections.
Everyone knows the enemy number one in this particularly field: the suction-cup effect.
Progalvano sought to find the most efficient solution to solve this specific issue.
Why Are Coins So Difficult to Process?
Processing coins inside a standard rotary plating barrel presents two main obstacles:
Sticking (“Suction-Cup Effect”): Being flat, coins tend to overlap during rotation. The thin film of plating solution between them creates an adhesive effect that keeps them stuck together. The result? The contacting faces do not get plated, leading to rejects and uneven deposit thickness.
Impact Damage: Coins must not suffer dents or scratches during tumbling, requiring a fluid and at the same time delicate movement.
The Challenge: How can we guarantee continuous, constant, and individual tumbling of every single coin, without compromising the gentle nature of the treatment?
To overcome these limitations, Progalvano’s R&D team designed and manufactured a special high-performance barrel, equipped with unique features specifically engineered for handling flat components.
1. Anti-Sticking Internal Grooves and Profiles
The heart of the innovation lies in the internal structure of the cylinder. We integrated special geometric grooves and ribs on the internal walls.
How it works: These grooves break up the flatness of the barrel’s surface and prevent the coins from sliding and stacking together. Instead, they force them to “hop” and flip over with every rotation, constantly breaking the suction-cup effect.
2. Optimized Perforation
The barrel’s perforation has been calibrated to the millimeter to ensure maximum current flow and rapid recirculation of the chemical solution, while simultaneously preventing the thin edges of the coins from getting caught in the holes. The 8mm hole diameter and custom pitch allow for optimal current flow while preventing the dreaded suction-cup effect mentioned above.
3. Controlled Rotation
The importance of a constant rotation while treating coins is a key aspect, mostly linked to the nickel treatment.
Progalvano always includes a device for controlling the continuous rotation of the barrel inside the tanks: in case of a stop during the revolution, the system immediately release a sign that prevent a customer from loosing a non-conforming output as a result of a process without rotation.
The Results
Total Uniformity and Zero Rejects
The introduction of this special barrel into production cycles has brought immediate and quantifiable benefits to our partners:
Zero Suction-Cup Effect:
Total elimination of “stuck” coins and, consequently, of unplated areas.
Homogeneous Thickness:
A metal deposit (whether nickel, copper, bronze, gold, or silver) perfectly distributed over the entire surface of the coin, meeting the extremely strict standards required by mints and medal manufacturers.
Time Optimization:
Reduced cycle times thanks to constant electrical conductivity and improved internal fluid dynamics.
This case study demonstrates Progalvano’s commitment to adapting its products to new market needs, which are becoming increasingly diverse.