Servo press technology can help fabricators capture additional work

March 2012 - Waukesha Metal Products and Industry Products Co. have slipped the bonds of the traditional fixed stroke in favor of the programmability of mechanical servo press technology to gain profit-boosting efficiencies and pioneer new methods for parts production. To achieve their goals, both companies invested in mechanical press equipment from Komatsu America Industries LLC, Rolling Meadows, Ill.

“In 2009, Waukesha acquired the assets of another stamper and doubled its business,” says Rob Bauer, engineering manager for Sussex, Wis.-based Waukesha. “We needed to expand our capacity but we wanted the latest technology to support that growth. As a fabricator that makes a broad range of parts for a diverse customer base, the ability to control ram speed and stroke made the servo press a natural fit.”

The international metalforming supplier works with materials as varied as its parts and its customers. Waukesha uses low-carbon and high-strength low-alloy steel, stainless steel, cold-roll steel, spring steel, tin plate, copper, bronze, aluminum, brass and exotic coated and painted materials to support metal stamping, sheet metal fabrication and tool design and build services for industries ranging from solar, aerospace and military to dental equipment, agriculture and automotive.

“Although the servo technology was new to us, we had an existing relationship with Komatsu and had experience with the quality of their machines,” says Bauer. “The ability to access local service support was also a key factor for us.”

Komatsu designs and manufactures gap frame, straightside and servo mechanical presses. Waukesha installed the 330-ton servo press in 2009 and found the flexibility of the machine’s programmable stroke supported existing work but also allowed the metalformer to take on new jobs and solve customer challenges.

One such part, a 3-in.-by-8-in. brushed steel cassette case for holding dental instruments, required the customer to fabricate it using a seven-step hand process. Scratches and burrs had to be removed manually and a PVC coating had to be applied to prevent scratching.

“We convinced the customer that we could stamp this part in a progressive die on our servo press, eliminate secondary operations and meet their cosmetic finish requirements,” says Bauer. “Our engineering team designed and built certain features into a new tool. The new tooling coupled with our ability to adjust ram speed on the servo press allowed us to reduce a seven-step fabrication process to one step with excellent results. The combination lowered our customer’s piece-part price by 70 percent, which immediately made the part competitive for export to the Asian market.”

Available energy
Since ram speed controls metal flow, the ability to control or adjust ram speed means a stamper can hold part dimensions and metal thickness more accurately to produce a near-net-shape part. “Changing the state of steel takes so many foot pounds of torque or energy,” says Jim Landowski, general manager of Komatsu. “When we talk about energy, we aren’t talking about motor horsepower. We’re talking about energy available to do the work in the working part of the stroke. With high-strength materials in particular, you may have to slow the velocity of the stroke in order to let the material flow to the desired angle or specification needed. A standard mechanical press powered by a flywheel loses energy if it’s slowed too much through the working portion of the stroke. With the servo press, energy is constant regardless of slide velocity.”

Waukesha discovered another advantage to being able to adjust ram speed when a customer changed its material requirements for a round dust shield component. The part was drawn originally from mild steel. When the customer switched to stainless steel, operators encountered a tooling problem. “We designed and built the tool around mild steel,” says Bauer. “The new material choice was causing issues with the draw, so we shifted the tool out of the mechanical press and into the servo. We found that by reducing the ram speed during the draw process we were able to use the original die with the new material and actually produce a more consistent part with fewer issues.”

Piqua, Ohio-based Industry Products Co. also sees its business heading in new directions and chose Komatsu’s servo press technology primarily for its parallelism and dwell capabilities. Industry Products combines material knowledge with research and development to provide automobile manufacturers with tooling, fabrication and assembly of cargo and trunk systems, acoustic and water shield solutions and protective in-transit materials.

The fabricator installed a 300-ton servo press in October 2010 and a second 200-ton servo press in November 2011. Industry Products is using its steel rule die cutting expertise in an innovative fabrication approach that depends on a high degree of press accuracy and parallelism. The dies, which resemble cookie cutters, are formed from 1-in.-by-0.028-in. steel strips into the part’s profile. “Parallelism and flat conditions are very critical,” says Tom Craft, tool and die coordinator for Industry Products. “When the two press platens meet, they must be within 0.002 in. across the entire length of the platen. Any deviation is detrimental to us achieving consistent, accurate die cutting.”

Controlling variables
Lateral movement of the press can be equally destructive. “If the die bottoms out or the slide shifts laterally, the die could be destroyed,” says Landowski. “We equip our servo press with plunger guides to control lateral movement of the slide. The days of using a press as a hammer are gone. Repeatable accuracy and the ability to control all variables in the stamping process are important. The servo press is able to guarantee variables like die height changes, because unlike a conventional mechanical press, the servo automatically makes periodic adjustments to account for variations caused by conditions like thermal expansion.” The servo’s repeatability to 10 microns guarantees part accuracy stroke after stroke.

Dwell time also is a critical factor for Industry Products, which is using its steel rule die cutting expertise in the servo press to die cut and thermal form sound-deadening materials for automotive applications. Once the punch and die close, the material is cut and held in the die in a fixed position, allowing heat to form the part and giving the operator time to perform any secondary processes. Certain non-ferrous material has a tendency to condense, and if the die strikes too quickly, the operator may not achieve material shear.

“Dwell is the cessation of motion controllable by the operator,” says Landowski. “By controlling velocity (speed) and movement (position), the operator is able to dwell as necessary to achieve a clean shear.” The result is predictable, consistent parts.

“We can load the tooling, push the start button and produce good parts the first time,” says Craft. “There are very few companies able to support this type of application. The servo press has allowed us to pioneer a new way of fabricating parts for this application and given us a true market advantage. We’ve performed setup for a handful of these new parts, which we’re developing to go into production. We see this as an expanding area of business. This development gives us the opportunity to provide a better product for our customers, and we expect capacity to increase.”

According to Craft, the servo press also eliminates the guesswork associated with conventional mechanical press production. “We get real-time data on what is happening with the press, from how much thermal expansion, deflection and press stretch we are getting to feedback on distances between the slide and bolster. This digital data takes the place of a lot of educated guessing that we had to do in the past,” he says.

As Waukesha and Industry Products continue to navigate unknown business spaces, the flexibility and programmability of the servo press supports exploration of new opportunities with its ability to reduce costs and improve stamping and manufacturing processes. FFJ

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