Robotic systems form a strong component of coinage production at the San Francisco Mint, including the automatic packaging operations used in assembling sets of coins.

 

Multiple primary packaging lines can be dedicated to specific numismatic products. During Coin World’s May 14 visit, the four-coin 2012-S Presidential $1 Proof set, containing coins depicting Chester A. Arthur, Grover Cleveland (two coins, one for each nonconsecutive term) and Benjamin Harrison, was being packaged.

 

During Coin World’s visit to the San Francisco Mint to document coin production as part of the facility’s 75th anniversary, Don Penning, manager of the packaging division, and packaging industrial supervisor Tonya Jones, served as escorts through the automated packaging operation and helped explain the various processes at play.

 

Packaging operations

 

For the Presidential dollar Proof sets, trays containing struck Proof coins are moved to the first stage of the packaging operation. A tray of coins of one design is inserted to start the process at the first station on the central conveyor system, and then at subsequent stations different coins are introduced. Robotic arms with visual sensors detect the individual coins being introduced into each station along the conveyor system.

For the Robotic Packaging Assembly Process involving the four-coin Presidential Proof set, a plastic one-piece insert, with four thermoformed pockets (one for each coin), is robotically placed onto a pallet (a white polymer plastic template). The same robot, fitted with a visual sensor, then identifies the existence of the insert. If an insert is detected, the first robotic station performs four operations:

 

(1)?The robot will pick up the first coin to be placed.

(2)?The vision system will verify the coin depicts the correct president.

(3)?The vision system will then instruct the robot to rotate the coin so that it is properly oriented within the insert.

(4)?The robot will then place the coin into the insert.

 

These steps are repeated at the next three coin stations for the Presidential Proof dollar program.

 

Once all four coins are present, a bottom, hard plastic lens is robotically loaded onto the pallet. The insert holding the coins is then lifted and placed into the bottom plastic lens. A vision system then scans the four coins for proper alignment within the insert.

 

A top plastic lens is then robotically placed onto the bottom plastic lens containing the insert. The two-piece plastic lens is then pressed together, the final step in lens assembly. The lenses are not heat-sealed, but friction fit.

 

The lensed sets are stacked onto carts and moved to the final assembly stage.

 

The carts are secured inside a caged area, in which two large robotic arms remove the sets one at a time from the carts and evenly space them along a second conveyor, which moves the lensed sets to a station that contains stacks of flattened set boxes bearing the graphics identifying the contents of each set.

 

Automated machinery opens each individual, flattened box, places glue on specific flap areas, pushes one set into each box and closes each box.

 

The boxed sets then move along the conveyor to where they are mechanically pushed into a cardboard shipping container, and the flaps of the shipping box are sealed shut.

 

The shipping box is labeled and moved along to the final station, where each labeled shipping box is palleted robotically for delivery to the U.S. Mint’s contracted order fulfillment center, Pitney-Bowes Government Solutions in Plainfield, Ind.

 

Pitney-Bowes ships numismatic products to U.S. Mint customers to fulfill orders.

 

Mint technicians are stationed throughout the system, at each step of the packaging process, to ensure the operation runs as programmed. If problems arise, the employees can correct problems as quickly as possible to minimize downtime.

 

Assuring quality

 

Hovering behind the scenes of the processes of assembling the sets and then placing them into shipping boxes is a quality assurance team, whose members ensure that the materials used to produce the coins and package them meet contracted specifications.

 

Loretta Dickerson, quality assurance manager with oversight of assay operations; Latonia Johnson, program analyst specialist; and Michael Goggins, supply quality engineer, represented the quality assurance team during the May 14 visit.

 

The facility receives both blanks (unstruck disks of metal without an upset proto-rim) and planchets (pieces with an upset proto-rim). When struck by dies, the blanks and planchets become coins.

 

Certain denominations, for example 90 percent silver, 10 percent copper dimes and quarter dollars, have a slight upset on them when they are received to prevent damage to the surface as they are shipped. The blanks (with no upset proto-rim) and the planchets that arrive at the facility with a slight upset undergo a full upset before they are struck (the double upsetting is what the Mint also calls a “complete upset”). The .900 fine silver commemorative silver dollar blanks, the .999 fine silver bullion dollar blanks, and copper-plated zinc cent blanks are already fully upset and ready to strike when received. 

 

All blanks and planchets that are shipped to the San Francisco Mint are scrutinized by the team for fineness (in the case of precious metals coins), weight, diameter, thickness and surface hardness. Blanks and planchets are tested after being selected from random samples. The Quality Assurance Team examines all shipments of blanks based on incoming acceptance testing guidelines as outlined in the San Francisco Mint’s contracts with its various suppliers. Materials that don’t meet the contracted standards after inspection are rejected.

 

The methods used to test composition and fineness have changed over the years.

 

Dickerson said the San Francisco Mint formerly conducted composition and fineness testing by using radiometry by titration (a method of quantitative chemical analysis), which was labor intensive and required the silver to be recovered from the chemical solution used.

 

Dickerson said the San Francisco Mint currently uses a Glow Discharge Spectrometer unit to determine the metal composition of the blanks. The equipment is calibrated to analyze material over a particular spectral range.

 

The spectrometer does not require reclamation of materials as was required when testing was done by titration. The Glow Discharge Spectrometer unit excites ions and shoots them at a blank in an atmosphere of inert argon gas. The reaction of the ions determines the composite elements in the metal on the blank’s surface and in its successive layers. The sample is not consumed in the nondestructive process. The new process creates savings both in reclamation costs and from the planchets lost during the former assay process. 

 

With Glow Discharge Spectrometry, the four-day process required with radiometry by titration is instead reduced to just 1.5 days, Dickerson said.

 

Visual inspections are also conducted on packaging provided by outside vendors; inspectors look for cracks in plastic lenses, scuffs or other damage and damaged boxes.

 

In addition, random, visual inspections are conducted of coin sets, after preliminary packaging but before the sets are housed in their cardboard holders. Mint employees compare the coins in the set to a color graphic of the coins that are supposed to be in the set, to make sure coins are in the proper location in the set and aligned correctly.

 

When considering packaging vendors, Goggins said he seeks materials that present a good appearance, meet planned color specifications and are functional. Goggins said potential and existing vendors are required to submit prototypes when new packaging options are under consideration.

 

Extensive reviews are made of product returns to determine what defects are in the packaging, and what imperfections, however slight, may be unacceptable.