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Product category: Manufacturing Machinery and Plant Equipment
News Release from: Bosch Rexroth - Linear Motion and Assembly | Subject: Complete drive and automation technologies
Edited by the Engineeringtalk Editorial Team on 05 June 2000

Grainger Machine Tools: a total Rexroth
customer

Grainger Machine Tools chooses a whole range of key components from Mannesmann Rexroth for its machinery, including ball screws, guides, motors, drives and hydraulic cylinders and pumps.

The £1750 million Mannesmann Rexroth motion controls business is able to combine its different drive and automation technologies synergistically and offer machinery manufacturers fully integrated electro-mechanical packages, backed by worldwide after-sales support This single source capability in turn enables OEM's to provide increased lifecycle value for customers and allows them to compete more effectively in a global marketplace

Such an ethos is exemplified by Grainger Machine Tools of Keighley, a specialist UK manufacturer of medium to large CNC milling machines, which places particular emphasis on quality engineering, low maintenance and competitive pricing.

To achieve these criteria, MD Nigel Grainger believes it is essential to use dependable components that will remain in first-class order throughout the life of the machine and that can be supported quickly, in any part of the world.

That's why Grainger chooses a whole range of key components from Mannesmann Rexroth for its machinery, namely Rexroth Star ball screws and linear guides, Rexroth Indramat servo motors and drive electronics, and Rexroth Hydraulics cylinders and pumps.

The synergy between the three suppliers and the compatibility of their components also mean that Grainger is able to adopt the optimum drive solution.

"The 'one stop shop' route means that any technical or service issues can be addressed by just one company," says Nigel Grainger.

"Also, I have purchased and used Mannesmann Rexroth equipment for over twelve years and am completely confident in the quality and reliability of its products." Rexroth linear, electrical and hydraulic components are brought together in the company's latest travelling column, 5-axis milling machine, which is designed and built in-house and priced competitively for worldwide sales.

Indeed, the first model has already been shipped overseas, to a customer that specialises in vehicle production and needed the capacity to machine a complete range of body parts.

Working to an overall accuracy of 0.06mm, at spindle speeds of 0-20,000rpm, the Grainger NGH6 machining centre features a cast iron base, column and ram arm, and has three main vertical/horizontal axes (XYZ), giving 6,000mm, 2,500mm and 1,500mm of travel respectively.

The machining head itself, which incorporates automatic tool clamping and unclamping, is numerically controlled in two further axes (AB), offering 360ø of swivel in one plane and +120ø of tilt in the other, with a positioning accuracy of 0.005ø.

The on-board CNC system controls all five axes concurrently, permitting tremendous flexibility and a wide range of machining profiles.

Rexroth Star provided linear motion, ball rail guideways and ball screw assemblies for the XYZ axes of the machine, as well as bearing blocks on the counterbalance.

The modular rails boast class-leading load capacities in all directions and help to minimise running friction, permitting a smaller drive system; long life lubrication is also incorporated, avoiding the cost and complexity of separate lubrication packs.

Precision-rolled ball screws provide the linear movement and accurate positioning, the tangential lift-off of the balls from the raceway contributing to particularly smooth motion.

Electrical drive and control on each of the main XYZ axes, as well as the AB swivel axes on the machining head, are provided by the Rexroth Indramat ECODRIVE03 system.

Five synchronous 22Nm linear feed AC motors, complete with encoders, are each linked to analogue DKC control units, which are in turn interfaced to the machine's CNC system.

This cost-effective and compact drive solution provides economical automation and highly accurate position measurement, together with straightforward installation and commissioning.

Finally, Rexroth Hydraulics technology, in the form of hydraulic cylinders and pump, is used to counterbalance the swivel head on the vertical axis, causing the 220kg head to drift slightly upwards at rest, and to lock the A and B axes into position when machining.

As with all other Rexroth items fitted to the Grainger milling machine, these components can be readily serviced in any part of the world, via the international Mannesmann Rexroth customer support network.

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