Above: With the Multipress hydraulic press and Delta Computer Systems’ RMC75 motion controller system, fabricators can produce repeatable parts and eliminate setup time.

The marriage of custom hydraulic press and electronic control unlocks productivity for difficult forming operations

April 2013 - Fabricators covet deep drawing for its ability to economically form complex and asymmetrical shapes in high volumes. The process also is ideal for products that require superior strength and minimal weight, but mastering the technique has proved challenging and limiting.

Deep drawing shapes metal blanks through pressure applied by the die, creating parts with a depth that conventional metal stamping solutions can’t achieve. Deep draw processes also are subject to radial drawing and tangential compressive stresses that can cause wrinkling or cracking. Attempts to tame the technique have seen the emergence of some unconventional solutions. One company has crossbred several technologies to engineer a hydraulic press system with a different approach.

New systems approach

Multipress Inc., headquartered in Columbus, Ohio, and New Providence, N.J.-based distributor Schilling Sons are designing custom hydraulic presses and integrating electronic control technology from Delta Computer Systems Inc., Battle Ground, Wash. The marriage of hydraulics with electronic multi-axis motion control gives fabricators the ability to cut costs and reduce scrap from deep draw processes, as well as eliminate processing steps from operations that involve exotic materials formed to tight tolerances.

Effective sheet metal deep drawing is characterized by smooth sheet metal flow. Metal flow is affected by material type, thickness, tool surface finish, lubrication, punching speed and improper blank holding pressure. In a deep drawing process, a pressure pad or blank holder cushion holds the material while a punch pushes the sheet metal blank into a die cavity. The radii of the punch and die cavity edges control metal flow into the die cavity. With conventional equipment, the pressure pad or blank holder cushion remains fixed throughout the drawing action. To avoid tearing or wrinkling the material, fabricators struggle to find a happy medium with the fixed pressure exerted during the drawing process.

“We knew we needed a systems approach to this problem that could equip customers to vary pressure during the draw process,” says Barney Raye, president of Multipress. “Wrinkling and fracturing are common issues with a fixed pressure, deep draw operation, especially if the customer is dealing with temperamental material. Scrap also is a problem. With the jobs that were coming in the door we began to look for technology that could help us solve these problems.”

Raye says analog hydraulic controls have been in the field for about 30 year, but the electronics were always a few steps behind. Technological advances empowered these controls with more sophisticated capabilities. But a full-blown analog control was price prohibitive according to Raye. Today, cost is no longer the predominant factor it once was, primarily because analog controls lack the flexibility of digital control platforms. Multipress is one of the pioneers in the field of hydraulic power, offering a full line of bench, floor model, four-post and custom-engineered presses.

Hydraulic press meets motion control

The press builder found a solution to its motion control problem in technology first developed for the forest products market. “The forest products market is a very technical segment,” says Delta motion products marketing manager Bill Savela, P.E. “It requires companies to move large masses quickly and with precision.” Fabricators also want to move fast, accurately and precisely, and they don’t want to have downtime. “We leveraged our multi-axis motion controller technology to introduce the one- and two-axis controller in the mid-2000s,” Savela says. “The control is intuitive, easy-to-use and cost-effective. We had been offering press controls but Multipress really expanded our press control application.”

The motion controller and its software use an Ethernet connection to communicate with the machine’s PLC, allowing the fabricator to monitor various performance parameters on the fly. Delta designs, manufactures and markets single- and multi-axis motion control and accessory products for industrial hydraulic, pneumatic and electric closed loop position, velocity and pressure applications.

Multipress has been using the RMC75 for nearly six years. “We read about Delta’s RMC75 one- or two-axis motion controller,” says Lee Schilling, president of Schilling Sons. The machine and tooling distributor provides engineering services for companies like Multipress. “Delta’s ability to transfer its technology to a new, unrelated market led to the introduction of the one- and two-axis RMC75, which gives us the capability of their multi-axis controller at a more cost-effective price point.”

Coordinating components

On a Multipress machine, the motion controller profiles pressure levels along with the position of the ram or tool. “With our system approach we use the RMC75 to control cushion or pad pressure during a draw progression,” says Raye. “The control, a closed loop system, provides real-time feedback on position and pressure, allowing the operator to apply higher pad pressure initially. Once material begins to flow, pad pressure can be lightened or varied while the punch is moving to prevent fractures or tearing.” 

Because the motion controller coordinates the main ram, pressure sleeve and cushion, the hydraulic press and control combination also is suited for odd-shaped components and exotic materials. The more nontraditional, the better the fit, Raye says. Several factors have fueled the press builder’s dozen or so installations of its motion-controlled, custom-engineered hydraulic press over the last few years. 

Change among fabricators has been one challenge. Understanding what operational problems a fabricator is encountering and what enhancements could help remains a first step for Multipress and Schilling Sons. “Change in this market is slow,” says Schilling. “A lot of fabricators don’t realize this solution is out there and that it can be a real problem solver.” Raye adds that as a press builder, it’s important to understand both the requirements of the application and how they impact the design of the press. “We don’t treat the press cylinder like a cylinder,” he explains. “We treat the press cylinder as an actuator or hydraulic device that controls the flow of material or power. We consider factors like stability, but getting the hydraulics right is just part of the equation. It’s also about defining the opportunity and then marrying the right components for the application.”

Saving money

“In today’s market, when you build a press you also have to take into account the electronic components,” Schilling says. “Engineering and integrating a workable system that also is user friendly and accomplishes advantages in production is a bit of an art form. We’re now marrying this ability, via the control, to coordinate the pressure pad force with the position of the draw stroke. It’s not expensive to implement but the cost savings can be very dramatic.”

The closed loop control gives fabricators flexibility by allowing them to connect, control and optimize their forming operations. “As fabricators become more familiar with the control they begin to see visually and numerically where they can make additional tweaks,” says Savela. Fabricators working with exotic materials often have to add annealing operations to part forming. The more a part is worked the more costs are added to the overall unit price. The ability to make consistent, repeatable parts while cutting setup time and minimizing the steps to make a component can yield substantial savings. “Just being able to walk up to the press and dial in a job is huge because you aren’t spending production time in setup,” says Schilling. “And the operator can reset the press exactly the same each time for difficult operations.” 

“We’re not a large company,” says Raye, “but our small company culture was a fit for Delta and Schilling Sons because part of providing the right solution is the one-on-one contact with customers and the field support. Being able to mesh the technology resources of three companies yet provide one face to the fabricator is a real one-two punch when it comes to pushing fabricators to new levels of productivity.” FFJ

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