Part I: Lean helps stamper squeeze out automotive 5 percent
October 9, 2007
While other automotive suppliers are struggling or going under, Tier II supplier of ride control components Tennessee Stampings established a lean program that merited a regional manufacturs' award and helped them grow 23 percent per year.
Editor's Note: This is the third article in a three-part series on Tennessee Stampings LLC. Part Iin August explored the company's lean practices. Part IIin September discussed how the company's use of sensors and mistakeproofing led to its growth. Part III examines the company's facility expansion, addition of a transfer press, and installation of an underground conveyor system.
If the mountain won't come to you, you go to the mountain. When your potential client tells you, "Once you get transfer presses, you can start quoting larger jobs and work for us," … you go get a transfer press.
That's what drove Tennessee Stampings of Portland, Tenn., to purchase an 800-ton hybrid transfer press from Eagle Press & Equipment Co., Oldcastle, Ontario, and a transfer system from Linear Transfer Systems, Barrie, Ontario. Tennessee Stampings stamps 100 million automotive ride-control parts annually.
Customers with automotive assembly plants in the Southeast were looking for regional suppliers with transfer presses to contain freight costs incurred from having to ship parts from the North, said Greg Cornett, Tennessee Stampings plant manager.
Tennessee Stampings of Portland, Tenn., purchased an 800-ton hybrid transfer press to stamp large, intricate parts.
"As more automotive is moving Southeast, we saw the need for more transfer-type-work suppliers down here," Cornett said. "We went to several seminars that customers put on—Mercedes, BMW, Kia—foreign customers, mainly. They were looking for metal stampers, and most of them were requiring that you have transfer presses. We had to turn down several jobs because we didn't have a transfer press," he said.
Transfer press technology often allows stampers to form larger, more intricate parts than progressive-die presses, Cornett said. "In a typical prog die, the part stays intact with the web as it travels through the die. A transfer press actually allows you to cut the part loose from the web and manipulate it. If you need to turn it at a 90-degree angle, you can make that happen during the transfer."
Cornett pointed to a large subpanel for a floor plan which is being run as a hand transfer. "This is a left-hand part. There is a right-hand part as well, a mirror image. We stamp out the blanks [left-hand and right-hand] in one die to obtain maximum material utilization. Then we run each blank through two additional dies to finish the component. Having two operators manually transfer parts between the two presses is very inefficient," Cornett said.
Both the left-hand and right-hand parts are blanked in one die to obtain maximize material use.
Typically, if the volume is high enough, the second stamping operation (after blanking) would be run in a transfer press, eliminating the need for two presses and two operators, Cornett said. For the subpanel, 100,000 annually justifies the need for a transfer die.
Because the subpanel is large, the component must be picked up and moved to the next station. "That's where a transfer press comes in," Cornett said. "Using fingers, it picks it up and moves it for you, versus having to have multiple operators and dies.
"If you were to run this floor pan through a progressive die, you'd just have a huge waste in scrap because a progressive die can produce only one part [left or right], which would not maximize material utilization," Cornett said. Because material is a large percentage of costs, scrap spared is money saved, he said.
The 800-ton press the company purchased is a hybrid press, meaning stampers can run a transfer die or a progressive die in it.
"If you want to run a progressive die, you simply back the transfer system up out of the way. If you want to run a transfer die, load the die, lower the transfer system, and install the transfer rails and you're set," Cornett said.
The transfer press is servo-driven, which aids in eliminating jumpy movement, Cornett said. "Many transfer presses operate using mechanical cams that are driven using the energy of the press, but they're very inconsistent, leading to loss of positioning. Anytime you can eliminate variation in the movement of the part, you're going to have a better-quality part," Cornett said.
"Unlike mechanical transfer systems, a servo system allows a smoother and more accurate transition for direction changes. Instead of going into a corner and dropping down, you can round it and make it smoother for part location consistency, which creates a better part," Cornett said.
Every press has the same type of touchscreen press control, so the operator has to learn how to operate only one control system. A real-time control system allows an operator to pull a print, die setup sheet, the FEMA, and the control plan from the press console. In addition, the system lights up and flashes to alert the operator when the next quality check is needed.
Every press has the same type of Helm touchscreen press control, so the operator has to learn how to operate only one control system. "If you can run this press, you can run any of them," Cornett said.
ISO/TS 16949 requires that stampers know the status of all documents, Cornett said. If an engineering change is submitted, all obsolete documents have to be pulled from the floor and replaced with updated ones, and often it's hard to verify that all of them were pulled, he said.
"To aid in this problem, we chose to go with a real-time system. From the press console, the operator can pull up the print, the die setup sheet, the FEMA, and the control plan," Cornett said. In addition, the Helm control lights up and flashes to alert the operator of the next quality check.
"But what impresses everyone is this little feature right here," he continued, as he pointed to another screen. "When I set up this die, I can hit this and it will bring up any incident (Quality Alerts) that has happened over the last three or four years. So the operator knows what problems the die has had every time he sets up," Cornett said.
"Automotive customers know you're going to make mistakes. What they don't like to see is the same mistake over and over. If you do, you obviously haven't done a good root cause analysis," Cornett said.
The tradeoff for the benefits of the transfer press is speed, Cornett said. "You can't run it as fast as a progressive die because you have so much movement of mechanical components such as grippers and fingers," he said.
Cornett said he is expecting a slight learning curve on the new system. "On the transfer press, you've got numerous grippers, fingers, and rotators. Each of these must be properly positioned and sensored for accuracy. We have transfer presses at our sister plants, but we will have our hands full here until we get through the learning curve."
Value stream studies revealed that the 400- and 500-ton presses had to be shut down about 15 minutes of every hour for scrap removal, so the company had a full-length underground scrap conveyor system installed as part of the expansion. Presses no longer need to be shut down for scrap removal.
Going to the mountain sometimes requires a little extra packing.
To accommodate the transfer press, Tennessee Stampings President Mike Haughey decided to expand the facility with a 40,000-sq.-ft. addition—the third expansion since 1998. As is often the case, several factors contributed to the decision.
In addition to needing space for the transfer press, the company needed space for anticipated continued growth. Sales have grown by approximately 23 percent per year for three years.
Furthermore, value stream studies revealed that the 400- and 500-ton presses had to be shut down about 15 minutes of every hour to remove scrap. Haughey and the team concluded that an expansion that would accommodate space for a full-length underground scrap conveyor system and eliminate the need to shut presses down for scrap removal would be a good move (see Figure 2).
"We should never have to shut a press off to dump scrap again—that's an automatic 20 to 25 percent improvement in productivity," Cornett said.
The conveyor is a traversing shuttle-drive system, Cornett explained. "With this shuttle system, there are minimal moving components to replace. The simple system is powered by two drive motors which actuate a shuttle tray running the length of the plant. The tray is supported by torsion bars that help aid the motors in providing the traversing motion. It really is an ingenious method of moving scrap to the traditional incline belt conveyor."
Previously scrap was dumped in a tub. When the tub was full, it was taken outside to be dumped, and a rollback truck then picked up the tubs and hauled them to a recycler.
On the traversing scrap removal system, the scrap is dumped into full-length tractor trailers. The system is fully automated and can run 24 hours a day. "The beauty of the system is, it automatically detects when the trailers are full, switches scrap deposits to another trailer, and automatically contacts the recycler; they'll be here within 45 minutes to pick up the trailer," Cornett said.
"Plus, the scale is in the floor, so we can verify weight before it ever leaves here," Cornett said.
Eight of nine presses have been moved to the new area of the plant to take advantage of the underground scrap conveyor system.
In terms of costs, Cornett said the press cost $1.2 million, and the transfer system cost approximately another half-million, plus the cost of the plant expansion. He is confident the company will continue to expand and obtain enough new work to justify the expense and to keep the transfer presses humming. Tennessee Stampings already has been selected to be the Tier 2 supplier for a large project expected from a Tier 1 supplier.
The stamper is currently bidding on a contract for a project with 12 parts that will put the press at 85 percent capacity. "And once we get to 85 percent, we know we'd better be getting another press," Cornett said.
Tennessee Stampings is looking at other parts to stamp on the transfer press. "Of course, you have to look at the life of the program. Would it be beneficial to run it on a new die instead of continuing to run the part on the existing die? But with any new jobs that we quote, if transfer tooling is justified, that's what we'll choose to do," Cornett said.
Space has been allocated within the building expansion for three other presses up to 1,300-ton transfer lines, Cornett said.
"We don't have the work yet or the presses, but we know it's coming. We're very confident we're poised and capable of getting the work to fill these presses," Cornett said.