From linear guidance to Hexapod struts

A Schaeffler (UK) product story
Edited by the Engineeringtalk editorial team May 11, 2000

In anticipation of the demands from designers of future generations of machine tools, the INA Bearing Company has developed a range of innovative products.

In anticipation of the demands from designers of future generations of machine tools, the INA Bearing Company has developed a range of innovative products to fulfill every increasing performance requirement.

As well as introducing a series of high quality bearings - for which INA is internationally renowned - this time specifically designed for screw drives, the company has exploited its expertise in rolling bearing technology to come up with a range of telescopic struts and joints for hexapod operation, linear guidance systems, braking and clamping elements for linear motors, and measuring systems for rotary table bearings.

The screw-drive ball bearing range embraces both Series ZKLF axial angular-contact types with two rows of balls, and Series DKLFA which has a third row of balls for heavy loads at high speeds.

Both types have holes machined through the outer casing for bolting to a flat surface, thereby enabling the screw drive to be bolted directly to its location in the machine tool frame and enhancing the design at a lower cost.

The telescopic struts and joints have been designed by INA to meet the demands of so-called 'parallel kinematics technology' which is having a big influence on the development of machine tools towards tripod and hexapod systems.

Three different joint designs have been incorporated in the components to provide two or three degrees of movement.

For ball joints, INA makes use of a traditional ball-and-cup arrangement.

In this case, however, hundreds of small balls are interposed between the surfaces, giving excellent friction behaviour while maintaining a low Hertzian pressure between the surfaces of the ball and cup.

Despite point contact, high rigidity is achieved because of the favourable load distribution.

The company has also designed universal joints which employ either one or two arrangements of angular contact needle bearings to allow two or three degrees of movement.

These devices are ideal for use on structures subjected to high speeds and accelerations, while a series of cardanic joints have been developed to transmit torque and to offset shaft misalignment.

In the latter case, axial radial needle bearings are used for the rotating elements.

The use of INA RUES and BKE spring-loaded braking and clamping elements in place of dedicated braking systems eliminates costly preparation time as well as saving valuable installation space and reducing the number of components employed.

They can be retrofitted to existing guidance systems where they are used directly on the guideway and can be used as emergency braking systems.

The braking force is applied by the mechanical energy stored in three disc-springs and released by the action of a small hydraulic unit delivering about 55 bar.

Precision and cost-effectiveness are also among the prime features built into the KUVE four row ball guidance monorail systems that INA has developed for advanced machine tools.

These recirculating guidance systems incorporate an integral lubricant reservoir adjacent to the raceways, giving maintenance-free operation for up to 40,000 kilometres in many cases, and can be fitted with double lip seals and additional long-term lubricant units for more demanding applications.

In addition to the purely mechanical components for machine tool design, INA has introduced the new YRTM Series of contact-free measuring systems for bearings used in rotary tables.

Based on a pair of magnetoresistive sensing heads, the systems are integrally fitted to the axial radial bearings used on the rotary table to measure the angle of movement in steps down to 0.0001ř.

Further details of these innovative components for advanced machine tool design are contained in an INA publication, PWZ, entitled: 'The future of machine tools - with INA'.

Find out more about this article. Request a brochure, download technical specifications and request samples here.

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