Forging process technology is a universe of its own, consisting of different process steps and shaped by the prerogatives of the forging operators. While every forger has specific production requirements, the engineers and designers of forging and forming technologies are pursuing a consistent line of development with their innovations: higher throughput, increased machine availability, wider availability for automation, and better-quality finished products.
Servo hydraulics for steel forming
Forming technology expert Hatebur is introducing a servo-hydraulic system it designed to increase productivity for the hot-forming systems in which it specializes, systems fed by heated steel bars: by preventing shearing break-outs and scuffing on the workpieces, the new system optimizes bar-surface quality and reduces the need for finish processing on formed parts.
“The servo-hydraulic bar stop optimizes the shear surface and boosts the quality of forged parts. That facilitates and speeds up quality control and can make post-processing obsolete. The technology enhances the productivity of manufacturers,” explained Hatebur CEO Thomas Christoffel.
The new technology resulted from an in-depth research and development program and will be offered for use on a variety of forming machine types, the developer noted. It is focused on “the first step” in metal forming: Before parts proceed through forming stations, the induction-heated steel bars need to be sheared off with very high precision.
The shearing process can induce a slight tilt and an oblique position for the sheared part. “Besides that, the shearing process changes into a tearing process towards the end, resulting in a so-called shearing break-out,” Christoffel added.
Sometimes scuffing is introduced at the sheared surface, which must be removed by sandblasting the finished forged parts.
The Hatebur servo-hydraulic bar stop reduces tilting and oblique positioning, and the effect is that the surfaces are virtually parallel. “Now, scuffing is rarely generated and thus is practically never pressed into folds,” according to Hatebur’s Dr.-Ing. Mihai Vulcan.
Hatebur has been testing the technology since 2017 on a Hatebur HOTmatic HM75 XL hot-forming machine, in partnership with a European automotive supplier. The scuffing on the shearing surface was minimized from 20% of the surface to just 1%.
The new bar stop technology also minimizes or eliminates the shearing break-out, resulting in a considerable quality improvement of the parts.
“If the quality control can be accelerated by only half a second per part,” Christoffel observed, “the technology already brings a real benefit to our customers.”
The shearing process is also quite fast: Depending on the bar diameter and the machine speed, it takes between 60 and 100 milliseconds. Only a servo-hydraulic drive provides the necessary dynamics and power density in a small space.
The Hatebur development team, led by Vulcan, applied an alternating position and force control. Should the bar stop deviate from its target position even by only a few hundredths of a millimeter, the position of the bar stop will be immediately adjusted via the servo valve. “This position control allows us to keep the actual distance between the blade and the bar stop constant during the whole shearing process,” Vulcan emphasized.
After the shearing process starts, the control shifts to force control with position monitoring. Throughout the process, the integrated measuring technology records the process data.
When deviations are recognized, the automatic control adjusts imbalances immediately, ensuring an optimized surface quality.
Open-die press with radial forging option
Servo drive technology has been adopted by forging press developers over recent years to increase process reliability and responsiveness. The coming phase of open-die forging process development may be emphasizing flexibility.
Sichuan Liuhe Forging Co. Ltd., a manufacturer of high-temperature and corrosion-resistant specialty steel alloys and superalloys in Jiangyou, Sichuan, China, ordered a high-speed open-die forging press from SMS group. The two-column, push-down machine with a table shifter and die-shifting mechanism, will incorporate a new radial forging function for open-die presses.
The maximum press force will be 50 MN (5,100 metric tons), and the maximum upsetting force will be 55 MN (5,600 metric tons.) The machine will be capable of forming parts with ± 1-mm tolerances on finished dimensions, including component parts for aerospace and large-scale steam turbines.
Sichuan Liuhe Forging produces semi-finished forgings, reinforcing rings, shafts, parts for turbine blades, and “supercritical” components for gas turbines.
The radial forging capability will be provided by SMS’ 650/50-MN X-Forging Box (XFB), which will convert the movement of the top tool in the open-die forging press into a radial movement of four tools in the X-Forging Box. At the same time, the maximum force of 50 MN will be evenly distributed among the four tools. The maximum initial pass section will be 650 millimeters.
The XFB will be capable of forging a range of quality round products with variable cross-sections. It will allow Sichuan Liuhe Forging to expand its product mix and quickly change between different types of products.
No modifications to the tool chamber or to the hydraulic-electrical connections are required to install the XFB, according to the developer.
“With this investment in the open-die forging press,...we are raising our quality standards to an even higher level,” stated Hong Yuchun, vice-general manager of Sichuan Liuhe Forging. “We are also pleased that the enhanced press control system will mean lower production costs for us.”
Commissioning for both the open-die press and X-Forging Box unit is scheduled for Q4 2019.
Closed-die energy efficiency
SMS group also reported it is supplying a new type of closed-die forging press to Musashi Europe GmbH, producers of multiple types of automotive transmission, differential, engine, and driveline components in carbon, alloy, bearing, and stainless steels. The MT 5000, 5,000-metric ton eccentric forging press will be installed at a plant in Bockenau, Germany, during the fourth quarter of this year. It will produce rotationally symmetric forgings for car and truck manufacturers.
Musashi Europe manufactures automotive parts at six locations in Germany and has production and distribution locations China, Hungary, Spain, and the U.S.
The press developer detailed that the MT 5000 will be designed so that the eccentric shaft and flywheel are directly driven by dynamic torque motors. “This type of drive separates the pure ram motion from the forging energy supply, and combines the advantages of servo presses with those of presses featuring a flywheel and conventional clutch-brake combination,” according to a statement.
The effect is a forging process that is both “energy-efficient and resource-friendly”: energy generated during the deceleration phase can be used to “re-acceleration” the flywheel.
The SMS design incorporates its MEERtorque servo-drive motion control, the effect of which is “precise, reliable, and fully automatic” forging, according to the developers.
In regard to the MT 5000 design, SMS detailed that the reduced number of mechanical components will decrease the maintenance and inspection costs for Musashi Europe. More practically, the press enclosure will open easily for maintenance/inspection access. Power and utility service will be supplied through a central “energy column,” making another maintenance-friendly design attribute.
The press housing will have a “split tie-rod” design developed with finite-element modeling (FEM): Very large press windows will simplify process automation, including die and holder changes. So that individual dies may be replaced, the MT 5000 will have a die-change arm, fitted to the press housing.
An integrated die-spraying system will clean, cool, and dry the dies to maximize die service, process performance, and forging quality.
Factory-scale AM systems
Forgers should remain mindful of the parallel advances in competing technologies — and specifically in additive manufacturing. GE Additive will begin delivering the first M Line Factory laser-based additive manufacturing systems from its Concept Laser subsidiary by midyear, the result of extensive beta testing. General Electric bought Concept Laser AG in late 2016 for a reported $599 million, after which the M Line Factory architecture, system, and software were subjected to review and redesign, as well as testing with selected customers.
The M Line Factory is a modular additive manufacturing platform that addresses the need for production-scale operation, including optimized production-floor space and operator requirements. It automates upstream and downstream stages of the production process and provides interfaces (automation, interlinking, digitization) to conventional manufacturing methods. While standalone machines may allow for economical series production, the M Line Factory’s modular machine architecture offers scalable automation and reliability.
GE noted that its rig and service-life testing identified several improvements that have been incorporated into the new system. This includes improved in-machine architecture and automation; enhanced serviceability, scalable modular system design and ease of service; a larger build platform (500x500 mm); modular onboard software system, with improved exposure strategies; and real-time, in-situ process monitoring; and enhanced process control and thermal stability.
The system also includes a customized material handling function, with pre/post-processing and powder management, with an integrated sieving station. System safety standards were updated too, with full powder and inert-gas containment; contact-free powder handling throughout; no manual handling in the process chamber; and water-flood passivation filters.
“The positive impact the M Line Factory can have on our customers’ operations and their bottom line is huge. It’s important we provide technologically advanced systems that are reliable and add value to our customers,” said Jason Oliver, GE Additive president and CEO.
Forming technology is a critical frontier in manufacturing developments, constantly proving the value of research, testing the limits of component design, and demonstrating the viability of pursuing objectives like higher product quality and customer value.