Linear guidance systems ensure accuracy and reliability of DMG milling centres

German machine tool manufacturer Deckel Maho Gildemeister (DMG) is working closely with The Schaeffler Group's INA Linear Technology division on a number of new machine tool developments. It currently relies exclusively on Schaeffler's high performance RUE-E linear recirculating roller bearing and guideway assemblies for its large and super sized milling centres.

The linear guidance system is said to provide smooth, uniform running characteristics and high dynamics, ideal for precision linear movement of heavy loads. The range is modular so that customers can select from a range of accessories to suit their application and it also benefits from Schaeffler's patented injection moulding technology, which enables perfect rolling element guidance in the load and return zones, optimised transitions and the best possible running characteristics with very low stroke pulsation.

Schaeffler has reduced the number of components in the design, resulting in more robust, reliable rolling element guidance. Labyrinth seals on the rolling element recirculation system have been implemented to improve protection against contamination. Uniform lubrication is guaranteed due to a completely closed and sealed lubrication duct.

The design of the guides incorporates an efficient sealing concept, comprising standard seals: single lip upper seals, double lip lower sealing strips, as well as double lip end wipers. The end plates fitted as standard in front of the contact end wipers provide extra protection against coarse contaminants, which means the contact end wipers retain their full performance capability even in environments with fine, often aggressive contaminants.

DMG has been working with Schaeffler to develop its DMU/DMC 200 to 340 milling centres, including 5 axis machining centres. Depending on the size of the machine tool and the loads acting on the main axes, linear recirculating roller bearing and guideway assemblies in sizes RUE 35, 45, 55 and 65 are specified. In order to meet specific customer requirements, DMG uses covering strips; double lip wipers and customised sealing kits from Schaeffler's modular KIT system. These are pre assembled at the factory. Load calculations are carried out using BEARINX calculation software, complemented by DMG's own design calculations for further system refinements.

Optimised distribution of lubricant for the RUE-E units ensures minimal flow grease consumption of just one litre per year using machine lubrication intervals of four hours. Additional components are not required.

Due to extremely high axial loads on the milling centres, Schaeffler supplies DMG with selected combinations of guideways and recirculating roller bearing units. These precisely matched pairs are combined to achieve minimal 'waviness' in the guideways and maximum accuracy of the carriages. All key data is recorded in test documents.

The RUE-E units are supplied fully assembled and well protected in special returnable containers, to prevent the risk of damage or product mix ups. Prior to installation, DMG inspects the machine parts on which the linear roller bearing and guideway assemblies are to be installed with extreme accuracy, examining them for compatibility with the linear guides.

Author
Schaeffler

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