A strategic approach to modernizing hydraulics significantly improved extrusion-press performance without breaking the bank.
The extrusion press is arguably one of the most valuable and hardworking systems used in any industrial setting. Productive and long-lasting, many presses operate for decades with proper maintenance and lifecycle management.
For hydraulically driven extrusion presses, the pumps, spool valves and other elements operate under challenging conditions. One U.S. aluminum extrusion company, after assessing the performance of the drive and control of their aluminum extrusion press, undertook a carefully planned, phased process of upgrading key hydraulic and electronic control components. The goal: Ensure that the machine continues to reliably supply high-quality aluminum extrusions to a wide range of customers.
General Extrusions Inc. of Youngstown, Ohio, is a third-generation, family-owned manufacturer of aluminum extrusions, supplying products to machine builders and users across the automotive, transportation, consumer durables and many other industry segments.
The seven-inch, 1,675-ton unit at GEI’s Youngstown plant is the company’s primary aluminum extrusion press. It has been in operation since 1967 and runs three shifts to ensure uninterrupted and on-time parts delivery.
“This press is at the heart of our manufacturing process,” said Jason Andre, general manager at GEI. “We generally produce between 12 and 15 million pounds of product a year, so keeping the press healthy and operating at peak efficiency and productivity is crucial to our business and keeping customers satisfied.”
In recent years, the leadership at GEI began an organized assessment of the performance of the press hydraulics and controls. This strategic planning and management review evaluated the risks associated with maintenance downtime on the press, as well as reduced extruding efficiency and output due to the aging of the legacy hydraulics.
“The wear and tear on older hydraulic components led to an increase in fluid leaks,” said Andre. The system’s existing spool valves were based on dated technology, making it difficult to find replacement parts for repairs. In addition, the system’s original design meant that there was a higher level of inherent shock in operating the press, forcing GEI to deal with fluid leaks on a weekly, and sometimes daily, basis.
“Once these factors started adding up, we made the decision that it was in the best interest to move forward with newer, modern hydraulic systems,” said Andre.
The company recognized the need to carefully plan the upgrade process. The goal was to modernize the extrusion press over time to better manage capital expenditures and make it easier for the company to “pay as you go,” instead of being saddled with one large and expensive project. Equally important, GEI wanted to identify how to sequence the upgrades during regularly scheduled outages, instead of taking the press out of production for a multi-week shutdown.
After considering the product offerings and capabilities of several industrial hydraulic technology suppliers, GEI chose the drive and control experts at Bosch Rexroth as their partners. According to Andre, Bosch Rexroth supported a step-by-step upgrade program, and its engineers helped GEI define the key elements of each phase.
“One of the things that Bosch Rexroth brought to the table, besides their hydraulic technology, was the concept of doing this project in stages,” he said. “Their ability to come in, work through with our team so that we could lay out the project in a manner that was more doable in a shorter time frame was a real positive.”
Michael Kramer, press application engineer at Bosch Rexroth, was the lead point of contact for the upgrade project. According to Kramer, after assessing the legacy hydraulics at GEI and understanding their goals, Bosch Rexroth assisted with or worked on the following project phases:
- Upgrade the hydraulic fluid conditioning system.
- Replace the line-mounted spool valves with a hydraulic manifold system.
- Replace key piping elements.
- Install new state-of-the-art hydraulic pumps.
- Modernize the control system.
To-date, several of these phases are complete or are ongoing, while others are being planned.
Bosch Rexroth recommended the hydraulic fluid conditioning system upgrade as a first step to ensure that the new hydraulic pumps and other equipment would operate with peak efficiency and quality. GEI has replaced their cleanliness system’s pumps, filters and heat exchangers to meet ISO cleanliness targets and ensure trouble-free startup as new components are introduced.
One of the major elements of the upgrade project was to replace the line-mounted spool valves controlling hydraulic fluid flow throughout the press with a state-of-the-art manifold system. The existing, decades-old spool valves were obsolete, difficult to replace or repair, and inefficient — wasting energy through excessive leakage.
According to Kramer, a manifold system reduces the number of potential leak points in a hydraulic system. The modern logic valves that are part of the manifold system can be independently tuned to reduce hydraulic shock while speeding up machine cycle times. This can help improve productivity due to faster actuation times, and their leak-free design also offers greater pressurization rates of the main ram.
Bosch Rexroth supplies hydraulic manifolds for a wide range of industrial applications. Using proprietary software and an advanced production facility, the manifolds are designed, manufactured, assembled, and tested to ensure reliable, efficient performance that satisfies specific press requirements.
According to GEI’s Andre, Kramer and his Rexroth team provided a detailed explanation why a custom-engineered manifold solution would provide a dramatic improvement for the press.
“Initially, we were mainly interested in how using manifolds to replace the spool valves would reduce our leakage issues and some of the issues related to shock,” he said. “A real bonus was how the manifolds helped improve our dead cycle time. We have documented roughly a three-second reduction, and that translates into approximately 200 additional production hours on an annual basis, giving us increased capacity to fill customer orders.”
The manifolds incorporate Rexroth LC-LFA cartridge control valves. These valves can be independently controlled to open in sequences that maximize efficiency and help minimize system shock — capabilities that the spool valves could not support. And because they are readily available off the shelf from Rexroth, the risk associated with obsolete spool valves is eliminated.
The manifold system helped significantly reduce hydraulic shock, which is a huge benefit to the entire press, according to Andre, resulting in fewer failures and problems with mechanical elements such as tie rods and other press components.
The installation of the manifolds also gave GEI the opportunity to upgrade piping in the system, going from a welded network of pipes to a weldless system. This can better absorb shock and reduce potential leak points, compared to the older piping.
Once the manifold installation and piping upgrade were complete, upgrading the two hydraulic pumps powering the press was next.
The legacy pumps were difficult and expensive to repair and were significantly less efficient than modern pumps. They also required approximately 30 to 40% more energy to operate compared with current designs. The antiquated pumps also generated a lot of heat which had to be removed.
“Not only would new pumps be easier and less costly to operate and maintain,” Kramer said, “pump replacement offered us the opportunity to increase the hydraulic flow rate and power input to the press to increase productivity.”
The team selected the Rexroth AA4VSO 355 axial-piston variable pump, which is designed for high-pressure industrial applications. The AA4VSO 355 is a 355-cc pump that can operate at 1,800 rpm. According to Andre, the existing pumps delivered approximately 108 gpm, whereas the new AA4VSO pumps will increase pump output by 30%.
“In hydraulics, volume is directly related to the speed you can run your press at,” he said. “By going to a higher volume, the new pumps will help reduce dead cycle time on top of the improvements we’ve seen with the new manifold, once the new pumps are installed.”
By performing the manifold upgrade first, the legacy pumps, originally designed and installed with two pressure ports requiring a complex valve arrangement, were converted to “one-way” operation. The manifold design completely changed the hydraulic circuit, setting the system up for easier installation of the new pumps.
When the time came for the pump upgrade, it was virtually a “drop-in” operation performed over a weekend shutdown. In addition, planning the project in this way allowed GEI to replace one pump at a time, spreading their capital investments out and improving their cash-flow position.
The new pumps also provide significant space savings, as the old pumps and their motors were mounted horizontally on top of the press, with suction lines feeding the pump. The new Rexroth pumps are vertically mounted and submerged in the tank, providing major space savings, as well as making it easier to install and service the system.
“That space savings lets us open up 20%, 25% of that space, and from a maintenance standpoint everything is housed in a very compact, localized space,” he said. “Plus, installation time is very short —it takes about four hours to remove the legacy pump and install the new Rexroth pumps, keeping our downtime to a minimum.”
He added that the new pumps also provide Industry 4.0 performance information that they did not have with the older pumps, giving GEI more predictability and insight into their hydraulic system.
Upon completion of the pump upgrades, GEI’s next major step will be to upgrade the press controls platform. Bosch Rexroth is proposing an upgrade that leverages the company’s extensive experience with extrusion-press hydraulic controls. Rexroth’s platform is capable of highly dynamic control of press force and velocity and can perform power-limiting, to ensure the press uses all available power to maximize production.
The velocity control function provides extremely accurate speed control during extrusion, including during the critical breakthrough period, helping improve product quality and reduce scrap rates. The pressure control function is always active, limiting maximum tonnage even during breakthrough, which offers the added benefits of reducing stress on the press and extending die life.
In addition, a new control system offers the opportunity to improve press availability and maintainability through fast and flexible Ethernet I/P communications, I4.0 data collection and analysis (including predictive maintenance), and custom diagnostics to assist in troubleshooting. GEI is currently assessing the potential costs and timeframe for this project.
Throughout the project, the teamwork between GEI and Bosch Rexroth has helped ensure that the right technology and engineering design decisions provide the best solutions. From the beginning, GEI was confident that Bosch Rexroth had the right combination of drive and control technology and extrusion press expertise for this project.
“Mike and his team were able to come in and show us how this project could be split into phases that would minimize any downtime we might have to face,” said Andre. “That, combined with the history of the company within the aluminum extrusion business, their reputation within the industry, their size and ability to meet our needs — so we could continue to meet our customers’ needs — really gave us the confidence that this would be a success.”
Filed Under: Pumps & Motors, Valves & Manifolds