5-Axis Simultaneous Processing in Portal Milling Machines with Transmission Heads from ROMAI
As a development partner for the Chinese mechanical engineering company Shandong Yonghua Machinery, Rottler-Maschinenbau has developed a portal milling machine for major components. It enables 5-axis processing with three transmission heads from ROMAI, one straight transmission head, one 90° angular head and one universal swivel fork head with a motor spindle.
The development and production of portal milling machines is a speciality of Rottler, the machine tool manufacturer from Mudersbach in Rhineland-Palatine. Since 1970, the company has manufactured customer- and workpiece-specific machine tools for different industries all over the world with its highly-qualified construction team and with innovative technology. In China, Rottler cooperates with Shandong Yonghua Machinery and has developed a portal milling machine in gantry design for the Chinese market. With this machine, the machine portfolio’s spectrum of machining major components is extended. It offers movement ranges of 8.5 metres on the X-axis and 4 metres on the Y-axis. The machine concept is designed for demanding CNC processing in tool and mold manufacturing, as well as for general mechanical engineering through to aviation and astronautics. “The complete milling support with RAM and transmission heads for the first machine was built at Rottler and implemented in the portal, which was assembled in China,” says Ulrich Krause, Authorised Signatory at Rottler Werkzeugmaschinen GmbH.
Significant components, which are key for enabling 5-axis processing, are the transmission heads with their impressive dimensions, which were developed and built by ROMAI. Amongst them is a 90° angular head with an overall length of 800 mm, 450 mm of that projecting and a weight of around 600 kg. With a transmission ratio of 1:1, the angular head is designed for milling with up to 4,000 rpm. and an output torque of 1,830 Nm at the HSK-A 100. In addition to that, the portal machine is equipped with a so-called fork milling head. This fork head with a weight of around 1,300 kg and a length of about 1,200 mm has an additional CNC-axis in the fork head housing, which enables pivoting of ±95°. “With the C-axis on the vertical ram and the fifth (A-) axis in the fork head, practically every programmable area is processable,” Krause adds. The fork head offers a maximum of 15,000 rpm with HSK-A 63 and a medium output torque of 89 Nm (at 6,000 rpm). For processing without angular head or fork head, a straight transmission head with about 450 mm length is put in for length compensation of the tool interface. Here, the output speed lies at 6,000 rpm. with an output torque of 2,000 Nm.
The transmission gears of this size are equipped with oil-air or oil-drip feed lubrication due to the high torque in comparison with the size. A precisely measured lubrication amount is fed via a continuous airflow. The fine drips reach the bearing without contact and due to the slight continuous excess pressure, the bearing is protected from contamination.
All transmission heads are automatically exchangeable via pick-up stations, enable automatic tool change for the machining tools and have internal coolant of up to 120 bar. Therefore, the flexible, automated 5-axis processing of major components is possible in the portal milling machine by Rotter/Yonghua in Yanzhou.
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