Marvel of Engineering, Part 2

In Part 1, the U.S. Mint finally bridged the issue of power with the steam press, allowing the mint to free itself from the need for human-powered presses. This allowed far greater consistency than had previously been possible and also improved output, going from 20-30 coins per minute to upwards of 100. (Modern presses are capable of churning out 800 coins per minute.) 

However, the steam press was loud, clunky, and limited by the laws of physics and metallurgical allowances, mainly pertaining to the die strength. To overcome this, the minting process would have to fight its greatest battle yet—against the laws of nature. The modern minting system stands as a testament to the ingenuity and perseverance of engineers, metallurgists, and visionaries who would not accept “fast enough” as an answer.

The Introduction of Electricity

Not long after the United States transitioned to steam-powered presses, electricity was added to the equation. The electric motor was invented in 1821, and over the next several decades it saw widespread use for industrial purposes. During the late 1800s, the U.S. Mint in Philadelphia slowly transitioned to electricity and began using automatic blank weighing machines. 

One of the biggest changes revolved around the forest of belts and pulleys that was a key distinguishing feature of the steam process. The steam-powered process required boilers, which turned water into energy. The energy would then have to be moved from the boiler to the press. During this process, up to 50 percent of the energy could have been lost. The belts frequently needed replacing and could often jam, which would have caused the entire process to grind to a halt, whereas the electric motor allowed individualized power, meaning each press was powered by its own motor, improving both efficiency and safety.

The introduction of full electrification in the minting process in 1901 allowed even greater speeds. Presses became capable of producing more than 120 coins per minute. The main victory of the electric minting process was sustained consistency. 

New Materials

In the early to mid 1900s, the mint continued tweaking details to further streamline the process. By the 1960s, the price of silver and copper was surging, and the United States was facing an economic crisis. People began to hoard silver coinage, and the mint searched for cheaper materials to cut the costs of coins. To save the economy from its severe lack of change, the government issued the Coinage Act of 1965, which mandated the removal of silver from dimes and quarters. 

Engineers and metallurgists went straight to work. The end result was the creation of clad coinage. Metallurgists developed a way to efficiently sandwich metals, allowing the core to be made of pure copper between cupro-nickel (75 percent copper, 25 percent nickel) layers. One of the best examples of the ingenuity behind this switch occurred with the vending machine. Vending machines at the time used electromagnetic sensors to detect whether a coin contained 90-percent silver. To bypass this, mint engineers calibrated the specific ratios and thicknesses of the layers so precisely that the final coin was able to trick the vending machine. 

Speeding It Up

With disaster averted, the mint returned to finding ways to speed up the process. A major breakthrough was made in the 1980s with the introduction of the horizontal Schuler presses. Prior to this, older presses all depended on gravity to assist the process, but during later periods, this sometimes caused the coins to bottleneck. On vertical presses (dies on top and bottom), feeder fingers were used to place the planchet on the die for striking and for moving it from the die after striking. 

The horizontal Schuler press eliminated the need for gravity. On the standard vertical press, after the coin is struck, it is wedged tightly inside the die collar. Next, a cam pushes the lower die upwards, forcing the struck coin out of the collar. Afterward, the feeder fingers then slide forward, pushing out the struck coin and depositing a new planchet. However, gravity is used for dropping the new planchet in and removing the struck coin. 

For the most part, gravity was considered useful. But as technology continued to rapidly develop, gravity became a bottleneck that slowed down the process, allowing only around 120 coins per minute. Schuler (now Andritz), a large metal-press making company, developed a new method. Instead of using gravity to assist the process, horizontal Schuler presses use a rotary-dial styled mechanism. The dies are positioned side by side. Each time the dial rotates, the dies strike the coin. After striking, the dial rotates again. The rotation can be performed at speeds much higher than what gravity can provide. The introduction of this method allowed the striking of more than 750 coins per minute, making the invention of the horizontal press one of the most influential machines in the modern minting process. 

The Digital Element

By the turn of the 21st century, the mint made another major transition. One of the key design phases of the mint process was the creation of galvanos, which were used to craft the final design of the coin and later create dies. Now, everything has transitioned to a digital platform, as the mint now uses CAD and digital imaging technology. 

Today, the entire minting process is seamless, creating nearly perfect coins at quantities that would have been unimaginable a mere 70 years ago. This process took thousands of years to develop and refine. We use coins daily, passing them on without a second glance. Yet, each piece is a testament to those centuries of struggle and innovation.