Advanced Coil Feeding at
Maytag Herrin Plant
Increases Efficiency of
Progressive and Deep-Draw
Die Stamping Operations

Faster speeds, with reduced die maintenance resulting from improved material feeding accuracy, combine to yield a 25% increase in press throughput

Wringing out every drop of part-producing productivity from metal forming capital equipment has long been a hallmark of the appliance industry. Today's household washers, such as the top-selling Maytag Performa, are an amazing value for the rugged machine that they are. At Maytag's Major Appliance Division in Herrin, Illinois, selection of both stamping presses and related material handling automation are carefully planned to ensure cost effectiveness.

The recent addition of a highly-flexible and productive coil-fed press for stamping internal washer components (such as motor brackets and cabinet braces) is a case in point. The system is typically set up for high-speed, short-stroke progressive die stamping. However, both its speed and versatility have recently been further verified, based on running a deep-drawn tub support part at double the speed (18 strokes per minute) of the press that has traditionally run it.

The cell consists of a new Brown-Boggs (Ancaster, Ontario) 400-ton eccentric gear press, fed by a coil handling and feeding line designed and built by Coe Press Equipment (Sterling Heights, Michigan). Bogart Machinery (Wentzville, Missouri) supplied all of the equipment in the cell.

John Boker, the Senior Tool Engineer who was responsible for selecting and implementing the new cell, outlines the objective: "We were looking for a 25% increase in throughput from this stamping press, compared to other similar stamping presses. This would allow us to meet our production volumes, on various parts, without the cost of any significant amount of overtime. We are meeting this goal, due in large part to two factors: one is the speed of the press and the coil feed. The second is the reduced die maintenance we're experiencing because of the accuracy and reliability of the servo-controlled coil feeding equipment."

The programmable, servo-driven Coe ServoMaster roll feed is an important factor. Roll speed is 340 feet per minute, with feed accuracy of +/- .003". This is more than enough coil-feeding speed for press strokes of 35 to 40 per minute, with feeds up to 18" (3 to 5" is more commonplace for the prog dies).

Accuracy Results in Reduced Die Maintenance

"At these speeds, the accuracy of the servo feed is even better than the specs, and this reduces die wear because the pilots and the punches are lined up perfectly, every time," says Tom Stephenson, Senior Tool Engineer. "Air feeders cannot deliver this type of accuracy. You also don't get the miss-feeds you can get with air feeders, where you lose your tooling edges because you're trying to punch through misaligned material that isn't prepped or pre-cut, for instance." John Boker adds: "We're able to complete our longer production runs without stopping for die maintenance, and that adds to the uptime improvement."

On the press, Wintriss DiPro Die Protection supplements the Smart PAC® press automation control, which is integrated in a single control console with the Coe ServoMaster controls.

Coe's MRS5 pull-through straightener efficiently removes the "coil set" from the incoming steel, ensuring that flat material is sent through the feed and arrives at the first die. Currently, the press operation is running widths under 10 inches, with the heaviest being .078" gauge. The system is designed for material thicknesses up to .082" (up to 22" width), and up to .080" at the maximum width capability of 30 inches. On the front end, a 10,000 lb.- capacity Coe motorized coil reel supports and unwinds the coil stock, assisted during coil changes by a 30" x 120" threading table.

Simpler, Faster Changeover

Simplifying and speeding up die changeover, involving coil width changes, is a high priority. Tom Stephenson explains the improvements gained from the Coe servo-controlled coil feeding system: "We are moving toward our eventual goal of a 10 minute die changeover… hit-to-hit… on this press. From the coil feed standpoint, you can't get there if you've got 5 or 6 trial-and-error, manual length adjustments. That's why the Coe servo-driven feed, with its stored programs, gives us an advantage. Length adjustments are automatic. It's easier to change the location and the clamping, and get the proper angle. Adjustments on the straightener are fast, too. When the first part you stamp is a good part, you've saved yourself a lot of time."

Currently, dies are removed and loaded into the press via a fork truck, but the use of subplates (for standardized die location), ¼ -turn die clamps, and automatic press adjustments (for shut height, for instance) have sped up the process. Additional die change assists such as die lifters and bolster extensions, which are used on many light presses in the plant, may be added later.

Boker and Stephenson, representing the tool/manufacturing engineering and the production engineering functions respectively, have worked as a team for a number of years. During John Boker's long tenure, there is hardly a category of appliance metal forming tooling that he has not been involved in. Since 1984, he has been a prominent champion for automating processes at Maytag, where it makes sense. "I've found that it's best to automate at the start of a new model program. But they don't happen every year…so we're always looking to make incremental improvements throughout the product cycle. " Specifically, concerning coil feeding, he adds, "my intention is to standardize on the more advanced technology…Coe's servo-driven equipment…for virtually all prog die processes here in the plant. The advantages are clear, and the technical support and service response is very good, given that the team includes both Coe Press Equipment and Bogart Machinery."

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