Until 1991 or 1992, Lincoln Brass (Waynesboro, Tennessee) turned out valves and fittings primarily on screw machines and a battery of other machines for secondary drilling, milling, threading, finishing and so on. A typical scenario, manufacturing manager David Sharpe says, would be blanking out a part on a screw machine, sending it through two to ten secondary operations for completion, then taking these parts to assembly for valve completion.
"It was pretty difficult to manage," Mr. Sharpe says, "keeping track of what parts were at what stages in a given process, and changing over could take literally days—not that it takes that long to change over a screw machine, but when you factor in all the various secondary machines, you often were looking at days."
Lincoln Brass also has competitive pressure, both domestic and global, that it must deal with. The company uses a long-range strategy that involves investing in the best technology that will consistently address the value side of the value/cost ratio.
"Our strategy," Mr. Sharpe says, "is to buy for the long term. We don't believe in spending money for equipment that's going to need replacement every three or four years, even if that equipment costs significantly less. If we pay $300,000 to $1.3 million for a machine, we expect that machine to run 100 million cycles—or more."
So Mr. Sharpe looked at a variety of companies with these strategies in mind. What he found were Hydromat precision rotary transfer machines and Hydromat technology from Hydromat (St. Louis, Missouri).
Now, with a stable of Hydromats, Mr. Sharpe reports that the tracking difficulty has lessened. Parts that used to take two to ten steps now are down to a single machine setup. The effects on productivity, WIP, inventory, setup and part changeover have been dramatic. "Parts made this afternoon," he says, "will be on a truck bound for the customer by daylight. We've reduced total inventory by more than half, from $8 million to $3 million. By eliminating secondary operations, scrap has, for all practical purposes, disappeared. Setup times have gone from days to 15 minutes or an hour. When you run millions of parts a year, these kind of benefits are not only critical, but can keep you looking back, not ahead, to the competition."
A major strategic priority at Lincoln is the elimination of all secondary operations, says Mr. Sharpe. "An example of how the Hydromats contribute to this is a standard inverting unit. This removes a workpiece from a collet, turns it 180 degrees end--forend and then replaces it precisely back in the same collet. This way we can completely machine the back side of the component, which ordinarily would require a separate, secondary operation, involving another machine and another setup."
Mr. Sharpe suggests that the strength of precision rotary transfer machine technology is in its flexibility to do on a single machine that which traditionally requires several machines, multiple handlings and setups, a great deal of wasted time, loss of quality control and increased scrap.
"Drilling, milling, cross drilling, boring, turning, external and internal recessing, threading, tapping, broaching—these are all normal secondary operations," Mr. Sharpe says. "Doing all these on a single machine gets rid of waste—in time and scrap—and gives us control of our operations."
Further, Mr. Sharpe suggests there are certain operations that would simply be impossible, or at the very least extremely difficult, by any other approach. Drilling a diameter on an angle that must precisely meet with another diameter on the interior of a part, thus becoming an ellipse, is a real challenge using multiple setups, Mr. Sharpe says. "If the angles aren't absolutely precise, the ellipse becomes either too big or too small, and the result is a scrapped out part. However, the table indexing and repeatability are so consistently precise on the Hydromats that this kind of angular drilling isn't a concern."
"We run an average of 45,000 parts a day on some of the Hydromats," Mr. Sharpe says. "They consistently hold 0.0005 inch, day in, day out. We routinely produce surface finishes with an Ra of 6, which is smooth as glass. We annually produce some 12 million valves, and on average there are at least three Hydromat parts in each valve assembly—that's 36 million parts. And for our valves to continue to beat the competition, each of these parts has to be completely within tolerance, each assembly perfectly functional."
A lot has changed at Lincoln Brass in the last six or seven years. The company carries less than half the inventory it did only a short time ago, has dramatically cut work in process and almost entirely eliminated scrap. Product quality has consistently and reliably improved the company's standing in the valve business. MMS