Product category:
Bearings
News Release from: NSK UK | Subject: Robust Series angular contact bearings
Edited by the Engineeringtalk Editorial
Team on 21 May 2001
Bearings meet need for higher spindle
speeds
NSK's new Robust Series precision angular contact bearings are designed to satisfy the exacting demands of motorised machine tool spindles for smooth running
NSK's new Robust Series precision angular contact bearings are designed to satisfy the exacting demands of motorised machine tool spindles for smooth running - even during rapid acceleration, higher levels of temperature tolerance, low heat generation, higher speeds and longer life A synergy of optimised internal design, materials and lubrication technology, the Robust Series bearings can achieve previously unattainable operating speeds, up to 3.55 x 10(6)dmN, in their ultimate EX hybrid configuration
This article was originally published on Engineeringtalk on 12 May 2000 at 8.00am (UK)
Related stories
Ballscrews and linear guides with non-contact ball
Non-contact balls enable ballscrews and linear guides to run smoother and quieter with reduced vibration.
Comprehensive bearing selection guide from NSK-RHP
The precision bearing specification and selection guide from NSK-RHP is one of the most comprehensive available.
The Robust Series meets the requirements of the machine tool industry for ever higher spindle speeds to enable a wider range of machining operations - from rough machining to finishing - to be performed on a single machine tool.
For machines to provide this flexibility it is essential that their spindles are able to supply high speed performance and short start-stop times (i.e high acceleration and deceleration).
If a belt drive or a gear drive is used for a spindle with such capabilities, the result is usually excessive heating, sliding and wear.
If a direct drive motor and coupling are used, this gives rise to additional design demands, such as alignment between the motor and the spindle, the selection of a suitable coupling and the method of holding the tools in place.
Furthermore, the overall length of the spindle has to be longer, resulting in space restrictions and greater inertia.
Further reading
Farm Force presses rely on Self-Lube bearings
RHP's Self-Lube bearings are providing the high degrees of reliability and life demanded by Farm Force on its range of cultivator presses.
Power transmission components for demanding users
Spacea bearings, ball screws and linear guides provide performance and reliability even in super-clean, vacuum, nonmagnetic, corrosive, high/low temperature, nuclear and high speed uses.
NSK-RHP keeps F1 snowmobiles at the top
Jacques Villeneuve, three times winner of the F1 Snowmobile Championship relies on NSK-RHP's well proven Self-Lube bearings in every race as part of his Bombardier snowmobile
To avoid these disadvantages, the latest generations of machine tools are increasingly being equipped with motorised spindles, i.e spindles with their own built-in motors.
The only problem with this development is that motorised spindles suffer greater exposure to changes in their surrounding environment - notably motor heating and sleeve cooling, particularly during sharp changes in rotating speeds.
This has profound implications for spindle bearings.
Latest job opportunities
Maintenance Engineer, Multi-skilled Engineer.
Maintenance Engineer (Distribution)
Job Title: Maintenance Engineer, Multi-skilled Engineer.
Area: Hertfordshire, Bedfordshire, Middlesex, Buckinghamshire, Essex, London, Northern Home Counties, South East
Salary: £37,000 - £38,000 + generous...
Electrical, Mechanical, Maintenance Engineer
Mechanical Fitter, Diesel Fitter, Mechanical Technician
Job Title: Electrical, Mechanical, Maintenance Engineer
Area: Bedfordshire, Hertfordshire, Buckinghamshire, London, Berkshire, Middlesex, Surrey, Essex, Home Counties, South...
Maintenance Engineer, Multi-skilled Engineer, Shift Engineer, Production engineer
Maintenance Fitter, Technicians X 5
Job Title: Maintenance Engineer, Multi-skilled Engineer, Shift Engineer, Production engineer
Area: Essex, Middlesex, Hertfordshire, Bedfordshire, Buckinghamshire, London, Home Counties, Surrey, South...
It is well known that abrupt changes in spindle speeds produce a temperature difference between the outer and inner rings of spindle bearings.
This causes the reduction of bearing clearances and, if the bearing is pre-loaded in a fixed position, tighter pre-load, which in turn increases heat generation and increases greatly the possibility of bearing seizure.
Because of these factors, bearings for motorised spindles are required to be robust enough to resist seizure and to maintain running stability while generating reduced levels of heat under severe thermal conditions.
These are exactly the qualities possessed by NSK's new Robust Series precision angular contact bearings.
Designed to achieve higher operating speeds than conventional precision bearings, with minimal levels of thermal deformation, the new Robust Series bearings meet the widest range of operational demands with a graduated construction which, in its ultimate form, combines optimised internal geometry with the high resistance to seizure and wear of new SHX steel technology, and the operating speed of hybrid silicon nitride ball material.
The Robust Series is available in four types: S, H, X and EX, all of which are suitable for operation with grease or oil/air lubrication.
The base bearings in the Series are the "S" type bearings, with steel balls and rings, and the hybrid "H" type, with silicon nitride balls and steel rings.
Both of these bearing types are designed for use in motorised and non-motorised spindles, and are capable of speeds 20% higher than conventional precision angular contact ball bearings The effectiveness of their design can be judged from the fact that the H type can be lubricated with grease at speeds where conventional bearings require oil / air lubrication (1.3 x 10(6) dmN).
Moving further up the performance scale, the X type hybrid ceramic bearings have the same design as the S and H types.
However, they are equipped with special high strength polyamide resin cages and have rings made of SHX material, a new steel developed by NSK.
SHX steel is highly suited for use in machine tool spindles which must run at high speeds with a minimum supply of lubricant.
Importantly, its heat resistance is nearly equal to that of M50 steel, a material which is used widely in bearings for jet engines, while its wear resistance, resistance to seizure and durability are all superior.
In user terms, this means that the X type bearings can be used at even higher speeds than the H type, up to 1.7 x 106 dmN) with grease lubrication Offering the highest performance of all within the Robust range is the hybrid EX series.
Like the X type bearings these units have silicon nitride balls, polyimide cages and rings manufactured from SHX steel.
The design of the EX bearings is, however, a synergy of materials and lubrication technology, the latter being NSK's exclusive Spinshot lubrication system.
While previously oil jet lubrication has only been possible at speeds exceeding 2 x 106 dmN, the Spinshot lubrication system enables the EX series to sustain such speeds with a mixture of air and oil.
The use of oil/air instead of oil jets reduces overall costs by allowing the structure of the spindle to be simplified.
It also cuts down on the consumption of oil, an added environmental benefit.
With the Spinshot lubrication system in place the limiting speed of the EX series is greatly increased.
The operation of the system creates centrifugal force which increments the oil flow into the bearing as its speed increases, enabling ultra-high limiting speeds up to 3.55 x 106 dmN to be achieved under conditions of constant pressure pre-load. Request a free brochure from NSK UK ...
• NSK UK: contact details and other news
• Email this article to a colleague
• Register for the free Engineeringtalk email newsletter
• Engineeringtalk Home Page
Search the Pro-Talk network of sites
