Fabricators niche revolves around spinning sheet and plate
April 10, 2007
Glenn Metalcraft Inc. started out as a tool and die shop in Minneapolis in 1947. Today it is an $8-million-a-year contract manufacturer that has created a niche in spin-forming circular and conical components up to 0.750 in. thick. Glenn has found a high-volume niche, producing wheels, brakes, and other components, using a process that traditionally was used almost exclusively for prototype and low-volume work.
If you traveled all over Minnesota looking for a spinning shop, you'd likely overlook Glenn Metalcraft Inc., a fabricator located in out-of-the-way Princeton. If you thought that spinning was good only for prototype and low-volume work, you'd likely overlook this shop, which has carved out a niche in high-volume production. If you thought spinning was limited to 54-inch-diameter, 1/2-in.-thick plate, you'd likely overlook the fabricator that sets the standard in dimensions for metal spinning.
If you needed to subcontract a circular or conical component made from sheet or plate, overlooking Glenn Metalcraft would be unfortunate indeed. Although spinning is useful for low-volume production and prototyping, Glenn has found it suitable for the high-volume manufacture of agricultural, construction, and military vehicle components. And while spinning commonly is used for fabricating large parts, Glenn pushes the envelope with its custom-made lathe that can handle parts up to 78 in. in diameter and 13/8 in. thick.
"My grandfather started this company as a tool and die shop in 1947," said President Joe Glenn. The company dabbled in various pursuits, including powered lawn mowers. Adding spinning to the company's repertoire wasn't part of any particular plan, but it turned out to be a good move.
"A neighbor had a hand-spinning lathe in his basement and a couple of accounts. Because of a roadway expansion, he was being displaced, so he approached my father and my grandfather. He asked if they would be interested in the lathe and the accounts, and he would teach them how to spin," Glenn said.
"They didn't do a lot with it in the 1960s, but in the 1970s the tool and die industry experienced a major downturn. They decided to put more energy into the spinning side of the business to keep the company afloat during hard times," he said.
Before long Glenn had 30 hand-spinning lathes. They required the operator to control the tooling manually by manipulating a lever and roller. It was labor-intensive and demanding work.
"Shortly thereafter we invested in our first CNC machine and we have purchased a new machine every couple of years since then," Glenn said. "Typically when we buy a new one, it is a little bit bigger and a little bit stronger than the previous one. Our philosophy has been to build up each new work center and watch closely to determine the needs we have not been able to satisfy. The opportunities usually are in the form of bigger and heavier workpieces."
Manufacturing has changed in other ways over the decades. Before CNCs, setups were time-consuming and therefore expensive. At the same time, material and storage space were relatively cheap. Technology turned this relationship on its head. After an operator programs a part with a CNC machine, he stores the setup for later retrieval, so subsequent setups take little time and cost next to nothing. Material and space are now relatively expensive, so manufacturers work tirelessly to reduce the amount of material on hand—whether it's raw feedstock or work-in-process (WIP)—and conserve space.
Likewise, spinning's position has undergone a sea change, Glenn said. Once used only for low-volume or prototype work, spinning traditionally was used for proving a part. After the part was considered successful, manufacturers developed a high-speed, high-volume process, one that conventionally was based on stamping, according to Glenn.
"A part might go through three stamping processes, then go to a machining center, then go to another machine to cut the holes," Glenn said. Every additional setup requires time; the handling between machines requires labor and time; and using several machines means that part tolerances stack up. Also, this type of operation eats up quite a bit of real estate.
Spinning is a completely different animal. The process relies on a high-strength lathe, a tool, and a roller. The tool has the shape of the finished part, and as it rotates with the workpiece on the lathe, the roller puts pressure on the workpiece and forces it to conform to the shape of the tool.
Forming a typical part by this process requires just a few steps. After loading the blank into the lathe, the operator forms the blank to the required shape. He then can use another tool to machine it while it's still in the lathe. If it's a simple part, he removes it from the lathe and crates it for shipment. If it requires more processes, the operator moves it to another workcell for punching or welding. Even with these other steps thrown in, Glenn is confident that spinning reduces process steps.
Lathe operator Lee Pettit mounts a blank onto Glenn Metalcraft's newest lathe, which can handle parts up to 78 inches in diameter and up to 1.375 in. thick. Many of the blanks are too heavy to be loaded and unloaded manually, so the operator uses a crane to do the lifting.
He cited one component that formerly required 27 process steps. No longer. Glenn's service center supplies a value-added blank, and Glenn does the rest in three steps. Only two of those steps involve manufacturing the part; the third is shipping.
Although all the parts aren't that simple, many of Glenn's parts are, so its manufacturing processes are straightforward and streamlined. This shows up in the amount of inventory it has on hand. Glenn keeps its WIP to less than 30 days, and for most orders, the throughput is less than seven days. Glenn's operation is an accountant's dream come true, regarding raw materials.
"We don't have any," Glenn said. He is fortunate—his customers are predictable, and the orders are consistent, so he has been able to eliminate raw material inventory.
Traditional spinning requires several passes with the tooling and a lubricant applied with a brush. Glenn uses shear spinning, which requires just one pass with the tooling. The process reduces the part's thickness and cold-works the part.
"We have done tests and found that the cold working increases the tensile strength and yield strength by 50 percent. In other words, you get a lighter, stronger part," Glenn said. "We also flood the part with coolant. When using a brush, we found a 5/8-inch part would heat up to 600 degrees, and the movement at that temperature is phenomenal," he said. The resulting dimensional changes were unacceptable, so Glenn switched to a flood system.
"Flooding also removes particles and results in a better finish," Glenn said. "It's less likely to embed small particles of metal into the surface of the part. And the lubricant is water-soluble, so our customers are much less likely to encounter painting problems. When we used an oil-based lubricant, we'd get frequent calls from customers asking what sort of lubricant we used, because they couldn't remove all of it before painting."
CNCs swept through the manufacturing industry and changed machine tools forever. Before CNC, Glenn's operators used two joysticks to control the forming tool. Running this type of lathe required a little experience and a lot of coordination and dexterity.
The machines weren't entirely manual. They were equipped with a controller, and as the operator formed the part, the machine recorded the joystick's motions and could repeat these motions for subsequent parts. The problem was that the controller relied on a perfectly duplicate setup to repeat the part.
"On the old machines, the bed doesn't have a fixed position," Glenn explained. "It has to be changed to accommodate different parts. We have to deal with other variables too. The forming tools, the mandrels, and the workpiece thicknesse—if any of these vary, the old program is junk. We used the old programs about 80 percent of the time, but the other 20 percent cost us a lot of time."
Glenn upgraded one of the old machines with a controller manufactured by MJC Engineering & Technology Inc. This boosted the recall rate to nearly 100 percent. It also gave Glenn the confidence to move forward with another project—working with MJC to develop a new lathe.
The new machine, the result of two years of planning and collaboration between Glenn and MJC, is model SP-78200-3. The model number tells part of the story. It can handle parts up to 78 in. in diameter, has a 200-horsepower spindle, and is equipped with a three-station turret. It uses a 100-HP hydraulic system and is rated to handle parts up to 1.375 in. thick.
The three-station turret helps to remove some of the steps from an already simple operation.
"With three stations, we have fewer tooling changeovers," said Glenn.
The thickness capacity is probably a little more than Glenn really needs, at least for now.
"So far we have made parts up to 3/4 of an inch thick on this machine," Glenn said. "We have quoted parts up to 1 inch." Spinning projects that exceed 1 in. in thickness are not too common, so Glenn isn't likely to run the machine at the limits of its rated capacity. "One inch is probably the maximum that we'll quote," he said. Still, the extra capacity is there if he needs it.
"It's unique in that it's a two-roller machine. It was designed typically to manufacture wheels. Most wheel machines have two rollers, but they're not as big or this heavy. This machine allows us to manufacture large and heavy wheel centers for agricultural and military vehicles."
While Glenn hasn't stepped out of the hand-spinning market completely, the company has intentionally reduced the hand-spinning portion of its business. Joe Glenn found that the manufacturing environment changed over the decades, and his business model became a classic case of the 80/20 rule: Approximately 80 percent of the company's revenue came from just 20 percent of the customers. The other 80 percent of the company's customers mainly were the ones that placed small, infrequent orders for products made on the old hand lathes. In many cases, they had been Glenn customers for decades.
Fabricators everywhere find themselves in a similar quandary. One on hand, the cutthroat forces of global competition force a fab shop to make tough decisions in terms of letting go some of its less profitable customers. On the other hand, a fabricator can't take customer relationships lightly. Most fab shops don't advertise, but instead rely on word-of-mouth referrals for bringing in new customers and good service for keeping them. So how does a fabricator bring himself to shed customer relationships, especially since many of them were started by his grandfather and built up by his father?
Glenn knew what he had to do, but he didn't want to leave any of his customers out in the Minnesota cold. Many other fabricators in the area spin metals, so Glenn was able to guide a lot of them to other shops that were more than happy to take on new business. For those long-term customers who haven't left the Glenn fold, he still keeps several hand lathes and a skilled operator onboard.
Will the day come when those parts are no longer required? Undoubtedly. Products come and go. But as Glenn has shown in its willingness to adapt, fabricators can continue to thrive in a climate that is continuously changing.