October 10, 2006
In the past metal forming in the appliance industry meant giant presses with expensive tooling. Lead-times were forever, and change didn't come easy. Whirlpool Corp. in Fort Smith, Ark., is taking a new approach to metal forming, and flexible technologies are the key.
|Press operator Brandie Watkins wipes down a refrigerator door before conducting a quality check.|
Appliance manufacturing has been due for a makeover for some time. As thousands of U.S. households have rediscovered home entertaining, they have sunk their hard-earned dollars into rehabbing and upgrading their kitchens. In these new "eatertainment" areas, appliances have emerged as status symbols as much as food preservation and cooking tools.
With the heightened focus on refrigerator, range, and washer and dryer products, appliance-makers have had to step forward with new designs that remain true to the promise of functionality and cost efficiency. For example, stainless steel appliances now can be found in modest homes as well as estates, and even some free-standing refrigerators are designed to be flush with counters, providing a built-in look.
To hold consumers' attention, new products have to keep coming. In some instances, design changes may be smaller tweaks, but they provide an opportunity to enamor the consumer and provide the retailer with a new story to tell.
So how do appliance-makers, who have been very successful in mass-producing similar-looking boxes, accommodate the need for flexible manufacturing that can respond to more frequent design changes? They need to think outside that white box and form a new thought when it comes to metal forming. Whirlpool Corporation is doing just that in Fort Smith, Ark.
|A corner of the door is cut away by the laser to accommodate a hinge cap that is applied after painting and provides a finishing touch to the door.|
|When the door is placed on the fixture, a turntable rotates around to deliver the untrimmed blank to the laser cutting head and the trimmed blank back to the cell operator for unloading.|
In a 140-foot by 70-foot wide corner of the factory, Whirlpool is adding to its refrigerator manufacturing knowledge. This is where the company is making refrigerator doors like no one else in the industry. Whirlpool is deep drawing metal blanks to form curvaceous doors that are a new look for the industry, and Fort Smith is using only one draw press to do it.
Deep drawing, of course, is not new to appliance-makers. The tops of washing machines and dryers have been deep-drawn for some time. But Whirlpool Corporation's use of this technology to make refrigerator doors is as new for the company as the look is new for the marketplace.
In early 2004 Whirlpool began discussions with one of its suppliers, Lima, Ohio-based American Trim, about the concept of a refrigerator door forming line that relied less on stamping presses and several dies and more on flexible stamping technology accompanied by laser cutting equipment and automated forming and flanging machines. Based on favorable talks with its long-standing supplier, a decision was made to implement the concept at the Whirlpool Fort Smith Division.
Early on Wayne Trail Technologies Inc., Fort Loramie, Ohio, was selected to provide most of the automation and material handling technology that connected the fabricating processes together in the line. Wayne Trail also called upon their experience with laser trimming technology to help steer the team through some of the early laser processing decisions and provided input concerning the preform oiling and postform washing/drying processes required before laser cutting could take place.
"This door, from our standpoint, was a pretty radical departure from any other door on a typical refrigerator," said Bob Lewinski, Wayne Trail's vice president, marketing and sales. "It's more of an automotive approach—deep drawing to get the shape and detail that you want to achieve and investing in equipment that is extremely flexible when it comes to setup and changeover."
The 1,200-ton hydraulic press from Macrodyne Technologies Inc., Concord, Ont., Canada, arrived in Fort Smith in the summer of 2005. The press, which boasted adjustable hydraulic cushion technology, was accompanied by an automated die storage and retrieval system that included a storage rack capable of holding 20 dies weighing as much as 27,000 pounds each.
"We were very impressed with the die storage and the elevator system. For us, that's something new," said Chuck Burgess, line supervisor, Whirlpool Corporation.
Even before the line was up and running, project planners knew the automated die handling system would save time. A typical die change on a traditional stamping press involved a press operator and a forklift driver and might take 45 minutes to one hour, if everything lined up correctly. Early work with the new press proved that a die changeover could be done in 15 to 20 minutes.
Synergis Technologies Group delivered six dies for forming cold-rolled steel doors around the same time the Macrodyne press was delivered. The six dies are used to form the multiple door styles that Whirlpool makes.
|Upon completion, parts are automatically transferred to a conveyor, which feeds them into the parts washer that removes the stamping lubricants.||The profiles of some deep-drawn refrigerator doors are from 1 in. to 4 in. deep.|
Synergis later delivered the dies used to form stainless steel doors in June 2006.
Before steel blanks are deep-drawn, a lubricant is applied electrostatically to both sides. Wayne Trail's Lewinski said this approach made sense because the much-needed oils are consistently applied, which probably wouldn't be the case if an operator had to apply the lubricants or if older roller or spray applicator processes were used. Additionally, the electrostatic process helps Whirlpool reduce oil consumption.
Even with all the automation in the world, deep drawing a part, especially a large one, is not necessarily an automatic or easy event. Material quality can differ from coil to coil, and a host of other variables can affect forming.
Hydraulic cushion technology is used to tweak the deep-drawing process when a previously stored part program is not delivering a topnotch part. Four sets of cushions located underneath the press bed apply pressure to blanks that are being deep-drawn, and the pressure being applied to a specific section can be adjusted by ±5 tons. For example, if better corner detail is needed, the press operator can increase the pressure applied to that corner and obtain a different result.
|Laser operator Anthony Sheppard uses the parts manipulator to move doors, which can weigh up to 30 lbs. each, onto fixtures that work in conjunction with the laser cutting equipment.||The die storage racks stand four bays tall and five bays across. Eighteen bays are used for die storage, and the two other bays are used for die staging and holding recently removed dies.|
Brandie Watkins, one of two draw press operators at Whirlpool's Fort Smith Division, said the automation has allowed her to become more engaged with quality. Each time a new job is started, she applies a critical eye to the part's flat sections, corners, and the front surface, where she looks for hard spots and other blemishes. After adjusting the hydraulic cushions, she runs another part to see if it meets Whirlpool specs.
Wayne Trail's Lewinski said this one-press approach to fabricating a refrigerator door is not just a big leap in technology, but also one in cost savings.
In the past Whirlpool may have used four dies and presses to replicate the new forming process: one to deep-draw the blank; one to remove the trim from the blank; one to apply flanges; and another to punch out any holes, such as ones for icemakers, door handles, and trim attachments. Today a programmable laser cutter and an automated metal flanging and forming line are taking on most of those responsibilities.
If the automated die handling system "wowed" Whirlpool shop floor personnel, the lasers that were installed to cut the trim off the refrigerator door blanks wooed them. It was neat technology, but it was new technology—and one that called for a big learning curve.
David Taylor, a Whirlpool lead engineer assigned to the formed door project, said the project involved plenty of lessons, including how to program the laser, focus the laser properly at the right point, align the laser for quality cutting, and conduct daily maintenance. Another lesson involved the finicky nature of the cutting process.
For lasers to do their job, the blanks have to be clean, really clean. Needless to say, drawing oils on a blank are not good for laser cutting. That's where FMT, in Findlay, Ohio, assisted. The company provided a parts washing system that provides a hot water wash and rinse to the blanks, which is followed by a hot air dryer section. If not for this step, the deep-drawing process and laser cutting technology couldn't coexist, according to Lewinski.
From the parts washer, the doors are either fed directly into the laser cutting cell or to a "buffer zone," a staging area where the doors can be held while the laser catches up to the speedy drawing.
Wayne Trail suggested the buffer area so that the draw press and subsequent wash/dry section could finish a job rather than be shut down whenever the conveyor became filled with doors waiting to be laser trimmed. This is especially important for parts that otherwise may have been stuck in the washer longer than the prescribed 1-minute process time. Such long exposure to the moisture could have led to problems with white rust or water spotting on the formed doors.
Operators use an overhead part manipulator to take the doors from the conveyor and place them on one of the four holding fixtures, two for each laser. The fixtures are attached to turntables that rotate from the loading area outside the laser and into a Wayne Trail-supplied and -integrated Class 1 laser enclosure, where one of the two five-axis, 2-kW Domino lasers from Prima Laser Tools, Chicopee, Mass., cuts off the trim, ice- maker opening, holes, tabs for forming, and areas for the hinge cap. In some instances, the laser has to elevate as much as 4 in. to accommodate the larger, deeper refrigerator doors. When a door is fully trimmed, the turntable rotates again to present the untrimmed blank to the laser and the ready-to-be-formed part to the operator, who unloads it and loads another untrimmed door.
|The lasers have proven useful in tweaking the geometry of the flanges and corner details without requiring costly die revisions.|
|The deep-drawing process creates the curved features on these stainless steel doors, and the laser pierces the holes where the handles will go and cuts the opening for the icemaker.|
The last piece of equipment installed was the automated flanging and forming line. The equipment from Metal Benders Inc., of Freeport, Ill., provided the automation needed to apply the manufacturing steps needed to complete the various door models.
A Wayne Trail-supplied cross conveyor and pick-and-place system delivers formed and laser-cut doors to the end of the line for final bending. A part locator identifies the door, and the pick-and-place unit loads the part into the forming and flanging operation.
At the time of The FABRICATOR's visit in early summer, the Whirlpool team was getting the line ready to produce stainless steel doors.
"Stainless steel is much more difficult to work with. There are stiffness and springback issues. It's a very different material from the draw quality cold-rolled that we had been working with," said Charles Lawrence, Whirlpool business unit manager.
Whirlpool worked through the issues related to forming the stainless steel doors. Those refrigerators will soon be on retail showroom floors across the country.
Lawrence credited the combined effort of everyone on the project.
"When you have a project of this size, and when you have various vendors, one of the keys to success is having good suppliers of equipment and tooling and having them work together and communicate well," he said.
Burgess added that he was proud to see the shop floor rally around the new technology and pull together to make it work.
"They have done an outstanding job, working by themselves. They don't have design degrees or engineering degrees, but they are the ones telling us what they need," Burgess said. "If it weren't for them, we wouldn't be where we are right now."
Lawrence is confident this new approach to forming makes sense for Whirlpool, specifically, and appliance manufacturing in general.
"It allows us a high level of differentiation among our different brands and allows for updating features with year-to-year model changes without changing the entire process; just update or replace the dies. The rest of the process pretty much remains the same, " Lawrence said.
"There's a big business advantage to us because we don't have to replace an entire process to get a different aesthetic look or some different functional pieces on the door."
This makeover is not yet complete, but the progress looks promising.
STAMPING Journal® is the only industrial publication dedicated solely to serving the needs of the metal stamping market. In 1987 the American Metal Stamping Association broadened its horizons and renamed itself and its publication, known then as Metal Stamping. Print subscriptions are free to qualified stamping professionals in North America.