“We set the standard for how short-run is done.” Asked to explain his company’s motto, Ron Kirscht, president of Donnelly Custom Manufacturing, replied, “We’re a sprinter, not a marathon runner. The two are built differently. A sprinter needs to get out of the blocks fast and get into a rhythm quickly for a world-class time. In our short-run business, moving smoothly from the last good part of the last job to the first good part of the next job is as important as cycle time or part weight.
“You can’t ever recover the excess cost of a bad mold setup. Changing an 18,000-lb mold on our 720-ton press takes 70 to 80 min, and it might run only 30 to 60 min. Smaller presses take 30 to 45 min for mold changes, but our median run time is only 7 hr.”
Based in Alexandria, Minn., Donnelly was started in 1984 by Stan Donnelly (still CEO) with the idea that short-run precision molding was under-served by the big, established molders. This niche became even more important as many long-run jobs in consumer products fell victim to the “offshoring” trend.
Another trend helped confirm the wisdom of Donnelly’s founding idea—mass customization. “That’s when a customer needs a part in three different materials and six colors,” Kirscht explains. “When I started here in 1991, customers ordered a month’s worth of parts, and we molded them all at once. Now, they order, and we produce, weekly or even daily.”
Donnelly has thrived on this short-run philosophy. Today, its 108,000-ft2 plant employs around 220 and operates 33 presses from 20 to 720 tons. Since 1992, its business has grown from $6 million to over $30 million. But it cut its customer base from 300 down to 60 by focusing on those with the most potential for growth. Those customers are scattered over a wide range of industrial markets, from medical to agriculture.
“We define short-run as less than 64 hr per week per mold,” says Kirscht. “Some molds have one cavity, some have up to 64. We ship millions of parts from some molds. But we get uncomfortable when a mold needs to run more than 2000 to 2400 hr a year. “We can be tempted to look at a job that will tie up a press all year, with no mold changes to worry about—it's kind of sweet. But you can’t do both long and short run well. It’s like a decathlete—you can do all those sports pretty well, but you’re not world-class in any of them.”
World-class at Donnelly means running 2800 active molds and 400 materials ranging from PP and ABS to PVDF, PEEK, and Ultem. Some customers order only 300 to 400 parts a year. Donnelly does 285 mold changes a week, 15,000 a year. And it launches 150 to 300 new tools a year—almost one new mold a day.
How do they do it? They have no secret technology for quick mold changes (QMC), Kirscht explains, because of the wide variety of tools that Donnelly must handle. “Almost half our molds are transfer tools that we didn’t build.” So there's no standardization to make mechanized QMCX possible. But Kirscht says trials with magnetic platens show promise for larger presses as a QMC option for some molds.
With no easy technical solution, Donnelly must address mold changes with organization and planning. “We differ from many other molders in that our next mold to run is right there by the press before the current job is done. We pre-stage the mold and the material, which is delivered from a central drying and handling station. Every tool has a Mold Information Manual, and we developed our own setup carts with all the necessary tools at hand. We always use two setup persons per mold, so one can work on each side of the mold, hooking up water lines, etc. We have 12 to 15 setup persons per shift for 33 presses.” And to ensure tne necessary flexibility, Donnelly keeps its press utilization below 70% of the theoretical maximum, vs. 75-80% for a typical longer-run custom molder.
Donnelly also uses small, "just-in-time" hoppers that hold only a couple of shots of material, so there's no waste on short runs. It selects auxiliary equipment like granulators for quick cleanability. Material handlers are trained for quick changeovers, blowing a cloth "sock" through the material lines to clean out residual pellets and fines. And the firm is shifting to non-desiccant compressed-air dryers to facilitate faster material preparation. For secondary operations, Donnelly uses sonic welders, CNC milling machines, and hot stampers that can be wheeled easily from press to press.
And Donnelly is moving steadily to all-electric presses, which now number 25 of its 33 machines. Besides being, quieter, cleaner, cooler, and more energy efficient, Kirscht says they provide better process control, which helps Donnelly achieve a stable process making good parts faster after mold changes.
But the most essential ingredient is employee training. It starts with initial “skill bundles” for new operators, followed by advanced operator training and finally a 13-week Certified Molding Operator (CMO) course for promising candidates nominated by their supervisors. “We find that women have as much aptitude and ability as men,” says Kirscht. “Half of our CMOs are women.” He adds, "Too often companies lose sight of the fact that a failure to train is a fatal error."