Switzerland, January 9 2019: Hatebur has introduced their servo hydraulic bar stop in order to make metal forming manufacturers more productive.
“The servo hydraulic bar stop optimizes the shear surface and boosts the quality of forged parts. That facilitates and speeds up the quality control and can make post processing obsolete. The technology enhances the productivity of manufacturers,” explains Thomas Christoffel, CEO, Hatebur. The Swiss enterprise, a global leader in high-quality forming machines and tools, will offer the new technology on a variety of machine types.
The innovation targets the first step of the metal forming process. Before the parts are formed in the various forming stations, the inductively heated steel bars need to be sheared off with highest precision. In the past, the shearing process led to a slight tilting and an oblique position of the sheared part. “Besides that, the shearing process changed into a tearing process towards the end, resulting in a so-called shearing break-out,” informs Christoffel. Sometimes scuffing was generated at the sheared surface, which needed to be removed from the finished forged parts by sandblasting. If these scuffing were pressed onto each other during the forming process, the producers needed to post process the parts by metal cutting.
Due to the servo hydraulic bar stop, the tilting and oblique positioning can be drastically reduced, and the surfaces are now virtually parallel. “Now, scuffing is rarely generated, and thus, is practically never pressed into folds,” explains Dr. Ing Mihai Vulcan, an employee of Strategic Projects at Hatebur. Since 2017, Hatebur has been testing the technology thoroughly in a development partnership with a leading European automotive supplier. It was tested on a Hatebur HOTmatic HM75 XL. The scuffing on the shearing surface was able to be minimised from 20 per cent of the surface to just 1 per cent. The new bar stop technology also minimised or eliminated the shearing break-out. This resulted in a considerable quality improvement of the parts, facilitating and speeding up the visual control after the sandblasting. “If the quality control can be accelerated by only half a second per part, the technology already brings a real benefit to our customers,” informed Christoffel.
The shearing process is incredibly fast; depending on the bar diameter and the machine speed, it takes between 60 and 100 milliseconds. Only a servo hydraulic drive can offer the necessary dynamics and power density in a small space. The inter-divisional project team of Hatebur, led by Mihai Vulcan, applied an alternating position and force control. Should at the end of the in-feed movement 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,” explains Vulcan.
After the shearing process starts, the control shifts to a force control with position monitoring. Throughout the process, the integrated measuring technology records the process data. When deviations are recognised, the automatic control adjusts imbalances immediately, ensuring an optimised surface quality.