BACKGROUND
The U.S. Mint, located in Denver, Colorado is one of only four mints in the United States stamping coins. Approximately 2-1/2 million coins are produced each year at this plant. These un-circulated coins are Special Collectors Edition Coin Sets and are only available at specialty coin shops, home shopping networks, the post office, etc. These coins begin as blanks made from 3-7,000 lbs. of coiled metal. They are then cut and stamped with the appropriate design and date.
PROBLEM
Their cleaning process was terribly laborious. They had several soak tanks with different solutions where an operator would place a basket load of coins in one tank and let them soak. A little while later, the operator would return to shake the basket. Eventually, the basket was transferred to the next tank until finally the basket had made it through 6 different tanks.
 SOLUTION
A sister plant reported that they had a much better solution – a couple of years prior, they bought a Cyclojet 3 from Engineering (see case study 1034) and were saving on labor expenses. They were saving at least 15 man hours a day. The plant in question decided to buy the same system but with four (4) holding tanks instead of two (2) tanks. Today, all their coins are cleaned and dried automatically.
SYSTEM
CJ-3 Cyclojet customized to have four (4) tanks with each holding 150 gallons of solution. The solutions were: 1) alkaline wash 2) rinse for alkaline wash 3) acidic brightener and 4) rinse for the acidic solution. The unit also had fresh rinse and dry stages all controlled by an Allen Bradley PLC.
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