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Stamping

Feeding the line

By Lynn Stanley

Servo roll feed technology keeps stamping presses moving efficiently

November/December 2011 - Part quality has as much to do with the way someone feels when they use a product as it does with good engineering. Southco Inc., Concordville, Pa., combines both aspects in its development and production of access hardware for a diverse customer base that includes marine, automotive, industrial machinery, medical, telecommunications and computers.

Southco uses the phrase “touchpoint engineering” to describe a practice that has helped the century-old company stay competitive in a fluctuating economy. “Part quality isn’t just about function,” says Dan McCourt, manager of e-business for Southco. “It’s about the experience an individual has when they use one of our customers’ parts. Southco’s engineered access hardware includes key ‘touch points’ such as locks, latches, captive fasteners, hinges, handles and other innovative products to enhance the individual’s interaction with the part, whether it’s through form, touch, sound or appearance.”

The global company offers more than 25,000 standard catalog items with parts production in the millions per month. Southco’s stamping department is a critical component to maintaining part quality and high-volume production output. When the manufacturer began to experience press downtime because of feed-line failure, senior engineer Bill Mitchell began to look at different models on the market. The unique construction of P/A Industries’ servo roll feeds caught his attention. P/A Industries, Bloomfield, Conn., is a global provider of press feed and coil-handling equipment with unique construction features for the metal stamping and fabricating industries.

Eliminating downtime
“I looked at the equipment from an engineering perspective,” says Mitchell. “We wanted to replace two existing feed lines and the construction of these units was very robust with their cast-iron roll feed housing and oversized, chrome-plated rolls.” Southco installed a P/A Industries Advantage servo roll feed on a 60-ton straightside press in March 2011. The manufacturer also chose an Edge servo roll feed for its 32-ton press in August 2011 along with a P/A straightener. The feed lines run cold-rolled and stainless steel as well as aluminum 0.013 in. to 0.188 in. thick in widths from 1⁄2 in. to 41⁄2 in. Prior to installing the P/A Industries servo roll feeds, the thinner, softer materials experienced uneven thinning and marks or scratches.

Uneven thinning is caused by equipment that is unable to maintain uniform roll pressure across the material being processed. If the feed rolls are allowed to go out of parallelism as material is squeezed between the top and bottom pinch rolls, thinning of one edge will occur. This action produces camber, a slight sweeping, bend or curve of the material. Instead of feeding material straight through the tooling, cambered material is crowded to the left or right in the tooling depending on which side is being thinned.

Maintaining parallelism
“Whether the material is on or off-center, we are able to maintain parallelism in our feeds by the way we have designed and constructed the upper pinch roll support mechanism,” says Mark Beiner, regional manager for P/A Industries. “Most feeds on the market offer a double-cylinder construction to raise and lower the top roll in order to apply pressure to the material for a good grip and accurate feed. What we’ve done that’s different is we have designed a torsion box roll support construction, which means that as the top roll squeezes the material against the bottom roll, the feed is able to withstand the resulting twisting forces that are caused by material that is not positioned directly on-center in the feed.

“Because this robust roll support design resists the top roll tilting out of parallelism, consistent tracking of the material through the tooling is maintained. Keeping the material on track is critical because it prevents binding of the tool, which causes material buckling and can contribute to excessive tool wear and die crashes.”

Southco runs progressive dies that are designed and built in-house. If feed lengths, speed and control of deceleration and acceleration are not carefully controlled and consistent, material can buckle or cause a problem that initiates the die protection system and stops the press. “We can’t afford to have our stamping presses stop,” says Mitchell. “The P/A Industries feed lines always maintain parallelism and have eliminated uneven thinning and material buckling.”

P/A Industries’ controls for its feeds primarily use standard Allen Bradley drives. The company has developed and perfected special programming that allows the setup person to adjust speed and accel/decel parameters easily. Job entry and recall is simple and straightforward. “We offer a complete engineering department with mechanical and electrical engineers and programmers,” says Beiner. “The feed length, speed and accel/decel curves can be adjusted at the control panel and saved for future jobs. The controls can be fine-tuned to accommodate surface-sensitive material by eliminating abrupt stopping and starting. These parameters can be saved for a particular job, tool or material type.”

The operator at Southco controls the feed line remotely from the press using a SmartPac controller that uses a servo feed interface. The feed lines also make changing material easy. “They just raise a lever to insert new material,” says Mitchell. “There’s no air pressure to deal with. We pretty much make no adjustments. Changing materials is practically transparent.”

The feed line is made up of three major components: the stock reel, straightener and feeder. Each is important, but Beiner considers the feeder the heart of the feed line. “The feeder controls the accuracy of the parts as they are positioned in the tooling,” he says. “It can also affect the quality of the surface finish.”

Surface finish
For Southco, surface finish is important because a range of jobs have cosmetic requirements from Class A to Class D. Class A is a blemish-free finish often used with bright nickel and zinc plating. Class B calls for minimal marks. “If the feed line marks the material, it’s cause for a part reject,” Mitchell says.

Southco’s stamping equipment is geared for mass production. The presses, which primarily consist of transfer, multislide, straightside and forming machines, are placed in a line for maximum output. Feed lines are located in the center of the press room. Raw material is threaded into the feed line, fed to the press and stamped. Parts coming off the presses move to secondary operations like plating, cleaning or tumbling. “In addition to high-volume production, we’re able to offer customers rapid prototyping,” Mitchell says. “Once we have a concept, we can prototype a new part on a CNC punch press and give the customer a good example of what it will look like before we go into production. Once we verify the press line’s capability to produce the new part, the feed line becomes essential to support the mass production of that component.”

Southco tracks environment, quality, delivery and cost—EQDC—on a daily basis. The stamping department also uses a business system to measure its on-time deliveries internally. “With the installation of the P/A Industries feed lines, we’ve seen significant improvement in on-time deliveries,” says Mitchell. “I experience zero downtime with these feeds. In addition, operators are experiencing faster setup times. Training has also been easy for operators. It’s about a two-minute review with operators and then they are ready to begin making parts. It requires very little of my time to initiate these lines. We’ve noted that the user friendliness of the feed lines has improved overall production efficiency for the operators.” FFJ

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Sources

  • P/A Industries Inc.
    Bloomfield, Conn.
    phone: 860/243-8306 
    fax: 860/242-4870
    www.pa.com
  • Southco Inc.
    Concordville, Pa.
    phone: 610/459-4000
    fax: 610/459-4012
    www.southco.com
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