From linear guidance to Hexapod struts

Bearings

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 futuregenerations of machine tools, the INA Bearing Company hasdeveloped a range of innovative products to fulfill everyincreasing performance requirement.

As well as introducing aseries of high quality bearings - for which INA isinternationally renowned - this time specifically designed forscrew drives, the company has exploited its expertise in rollingbearing technology to come up with a range of telescopic strutsand joints for hexapod operation, linear guidance systems,braking and clamping elements for linear motors, and measuringsystems for rotary table bearings.

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

Both types have holesmachined through the outer casing for bolting to a flat surface,thereby enabling the screw drive to be bolted directly to itslocation in the machine tool frame and enhancing the design at alower cost.

The telescopic struts and joints have been designedby INA to meet the demands of so-called 'parallel kinematicstechnology' which is having a big influence on thedevelopment of machine tools towards tripod and hexapod systems.Three different joint designs have been incorporated in thecomponents to provide two or three degrees of movement.

For balljoints, INA makes use of a traditional ball-and-cup arrangement.In this case, however, hundreds of small balls are interposedbetween the surfaces, giving excellent friction behaviour whilemaintaining a low Hertzian pressure between the surfaces of theball and cup.

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

The company has alsodesigned universal joints which employ either one or twoarrangements of angular contact needle bearings to allow two orthree degrees of movement.

These devices are ideal for use onstructures subjected to high speeds and accelerations, while aseries of cardanic joints have been developed to transmit torqueand to offset shaft misalignment.

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

Theuse of INA RUES and BKE spring-loaded braking and clampingelements in place of dedicated braking systems eliminates costlypreparation time as well as saving valuable installation spaceand reducing the number of components employed.

They can beretrofitted to existing guidance systems where they are useddirectly on the guideway and can be used as emergency brakingsystems.

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

Precision andcost-effectiveness are also among the prime features built intothe KUVE four row ball guidance monorail systems that INA hasdeveloped for advanced machine tools.

These recirculatingguidance systems incorporate an integral lubricant reservoiradjacent to the raceways, giving maintenance-free operation forup to 40,000 kilometres in many cases, and can be fitted withdouble lip seals and additional long-term lubricant units formore demanding applications.

In addition to the purely mechanicalcomponents for machine tool design, INA has introduced the newYRTM Series of contact-free measuring systems for bearings usedin rotary tables.

Based on a pair of magnetoresistive sensingheads, the systems are integrally fitted to the axial radialbearings used on the rotary table to measure the angle ofmovement in steps down to 0.0001ø.

Further details of theseinnovative components for advanced machine tool design arecontained in an INA publication, PWZ, entitled: 'The futureof machine tools - with INA'.

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