A solid piece of platinum that weighs about 50 lbs and is the size of a 16-ounce beverage can is worth more than $1 million, and a small pile of chips cut from that piece of precious metal could be worth thousands of dollars. Becasue of that, shops, such as Johnson Matthey, that work with platinum have to practice stringent material-control procedures.
On entering and leaving Johnson Matthey's ultra-secure Medical Products Group shop, employees pass through a security check point. That check point has metal detectors and screeners more sensitive than those that are found in airports and many public buildings. As a result, most of the shop's 120 employees wear metal-free clothing to speed the security process.
"We are like the Fort Knox of medical shops," says Jyrki Larjanko, engineering manager at Johnson Matthey. "Everything is controlled, and we know what is coming and going, even scrap tooling, which is reclaimed in special containers that are sealed by security
personnel prior to leaving the shop." Johnson Matthey uses several methods for tracking every milligram of platinum through its shop, but — because of security issues — the only one Larjanko is permitted to mention is barcoding.
Every machine in the shop is equipped with a safe that is used to lock material and parts overnight. At the start of a job, the machinist receives a specific amount of platinum. That platinum workpiece is weighed carefully and, when the job is finished, the parts and the scrap and the chips are weighed carefully again. Employees filter out the machine's cutting fluid and remove scrap residue from the machining envelope, even on the shop's EDMs.
Cleaning machines completely is necessary for scrap reclamation and to fulfill the requirements for medical jobs. Medical parts customers are extremely picky about the materials and chemicals that come in contact with their parts, so Johnson Matthey adheres to strict procedures dictated by an ISO standard for cleaning its machines. Each machine is given a thorough cleaning and tooling change between every job, even when the jobs are for the same customer. In fact, the shop cannot allow the smallest amount of residue — including chips, cutting fluids and remains on tooling — from one job to mix with the next.
According to Larjanko, this meticulous cleaning does not necessarily increase job leadtimes because shop personnel have done it so often that they are quite fast at it. In addition, the shop uses special, custom-designed pump-out equipment that quickly drains fluid out of machines, filters it and pumps it back in. Chips and residue are then moved to a room where they are cleaned and processed for the shop's recycling system.
