The machining of bearing seats, for example in hydraulic pumps or crankcases, ranks amongst the most demanding tasks of machining. This often has to ensue deep inside the component and allows only very low tolerances.
ROMAI offers especially produced (double) angular heads for such machining tasks, for example in order to mill or finish-bore crankshaft passage in engine blocks or bearing seats of axial piston pumps.
Heavy-duty machining poses special challenges for processing machines in terms of stiffness, robustness and usually also in terms of the size of machines. The recently built large-scale portal milling machines by Rottler-Maschinenbau are an impressive example for this, utilising large-scale angular heads by ROMAI for certain machining tasks.
ROMAI in Vaihingen/Enz has been developing transmission gears in the form of driven tools, angular heads and multi-spindle heads for 60 years. One of the special strengths of the family business is the production of application-specific special solutions. “Since the tried-and-tested KÜMA product range has been produced and further developed by us, this also includes more and more machining heads for large-scale processing machines - stiff, angular, or with added integrated NC axes,“ explains Mathias Maier, General Manager at ROMAI. The heads with swivel axis which we have recently delivered for the large-scale portal milling machines of Rottler Werkzeugmaschinen GmbH are an impressive example for the huge dimensions.
The large-scale portal milling machines from Rottler are designed specifically for the customer for heavy-duty machining. Ulrich Krause, Authorised Signatory at Rottler Maschinenbau explains the gigantic dimensions: “The portal milling machines have a portal of 3,700 mm and the portal, driven by four engines overall, covers its 21 metres of travel on the X-axis on hydrostatic guides.” Rottler-Maschinenbau relies on complex technology, which does not exploit the machine bed as an oil return channel. Therefore, there cannot be any contamination of the hydrostatics oil with cooling lubricant. Another speciality is that the classic gantry design has been perfected and built with the X-axis at the bottom, which improves the accessibility of the floor plate. The two supports on a fixed crossbeam, which is the Y-axis, stand out with this individually-customized design and enable simultaneous processing. “Feed forces are at 150 kN here, and maximum torque is at 9,500 Nm with a possible 110 kW at every spindle,” Krause explains the utilisation in heavy-duty machining.
As additional components for certain processes, the portal machines are equipped with transmission heads from ROMAI, which can be put into the vertical ram fully-automatically. With a weight of around 1,600 kg and a length of 750 mm overall, its dimensions are also impressive. The housing of the angular head has an additional pivoting spindle housing on the output side, which has a 90° angle. This is interlocking and indexable every 2.5° via axial clamping through Hirth joints or alternatively adjustable with axial clamping in every position. Adapted to designated processes, the transmission heads have a transmission ratio of 1:1.5 at 2,000 rpm.
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.
KÜMA Werkzeugmaschinen GmbH’s especially constructed and built machine components for machining have been established in the industry since the 70s. The company’s multi-spindle, drill, milling and turret heads, as well as the spindle and slide units constitute ideal components for machine tools. Known for precision and thanks to their constructive know-how, they are especially valued in the automobile industry. Specialities of KÜMA are machining heads for large-scale processing machines with rigidly driven, or pivoting i.e. positionable tools.