US Coins

San Francisco Mint triples Proof set assembly with robots

The San Francisco Mint has completed installation of a robotic loop assembly system that triples the speed of packaging Proof coins into plastic lenses for special collector sets.

The system, developed by the Mint’s engineering team in conjunction with the manufacturer, Farason Corp., Coatsville, Pa., gives the San Francisco Mint the ability to fill coin lenses at the rate of 1,800 lenses per hour, versus the previous 600 per hour, a Mint official said.

The system replaces a labor-intensive system installed in 1999 that required significant manual inspection of coins and plastic lenses, checking for damage that would prompt removing the coins or lens from the assembly system.

The new robotically controlled digital inspection assembly inspects each coin and lens at each phase of the assembly operation. Coins and lenses can be rejected if they fail to meet quality control specifications. If defects are found, the system will shut off for the defective item’s removal, and then restart.

(Each lens is composed of a top and bottom plastic enclosure and a cardboard insert with openings sized for the respective coins, which are robotically placed into them.)

Once the multistep operation is complete, the finished lenses are moved by automated trolleys to the next station where they are loaded for placement into the full-color cardboard storage boxes before final shipment in delivery boxes.

Don Penning, the San Francisco Mint’s industrial manager for packaging, said the digital visual detection equipment will, at every entry interval, inspect the coins and lenses for defects. A final quality control inspection is conducted at the end of the line when the finished lenses exit the assembly loop.

Where the previous assembly system required three full-time operators, the new system requires only two workers to keep the system stocked with sufficient top and bottom plastic lenses, cardboard inserts, and coins. The system will shut down if any station from which coins or lenses are fed runs out.

Penning said the system has eight feed points that operators must stock with coins, lenses or inserts. Five feed points are for coins, two are for lenses, and one is for inserts.

The cardboard inserts are first in line on the conveyor. The insert is robotically selected and robotic arms are programmed to retrieve the proper coins from the correct coin trays and place them into their proper positions in the cardboard inserts. The inserts with the coins are then placed into the bottom lens.

What the Mint calls “reverse suction” at the tip of the robotic arm is used to pick up each coin without leaving marks or causing damage.

The trays of coins to be loaded into the robotic loop assembly have different coin counts per tray based on denomination:

??Lincoln cents, 132 coins per tray.

??Jefferson 5-cent coins, 110 coins per tray.

??Roosevelt dimes, 144 per tray.

??America the Beautiful quarter dollars, 80 per tray.

??Kennedy half dollars, 56 per tray.

??Presidential and Native American dollars, 72 per tray.

After the proper coins are robotically moved from their respective trays and deposited into their proper locations in the insert, the insert is placed in the bottom lens, and the assemblage moves along the conveyor for positioning and securing of the top lens. It then moves to a final inspection station and on to packaging.

San Francisco Mint Plant Manager David Jacobs said the cost of the new assembly system is $2 million, and with digital visual inspection at each stage, it is considerably less expensive than the cost of outfitting each coin press with the same inspection system. Each inspection system would cost between $400,000 and $500,000 per coinage press, Jacobs said.

Jacobs said only one of the facility’s 18 coinage presses has a visual detection system for inspecting and identifying defective coins.

With automation initiated 15 years ago to date, the San Francisco Mint’s workforce has shrunk from just over 600 workers to just over 200, with the reduction accomplished through retirements and attrition. Most of the production employees are cross-trained in multiple disciplines to allow them to be used in different operations when needed, Jacobs notes.

The robotic loop assembly will be used beginning in mid-September for the 2016-S America the Beautiful Quarters Proof set, 2016-S America the Beautiful Quarters Silver Proof set, and 2016-S Presidential $1 Coin Proof set to be stockpiled for 2016 release. 


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