NTN Corporation (hereafter NTN) has developed a ‘New grease (MQGS) lubrication angular contact ball bearing’ for machine tool main spindles. It enables to attain 1.9 million dmn value1) under maintenance free and solid preload2) conditions.
In recent years, main spindle systems for machining center, complex machine center, etc., require grease lubrication to enhance high speed capability for better processing efficiency and surface quality of works as well as for better working environment and reduction of environmental burdens.
In response to those requirements, NTN has been marketing ‘ULTAGE series high speed sealed angular contact ball bearings (BNS type)’. However, extension of grease life and reduction of heat generation are issues to assure even higher speed operations. Also, a system supplying grease from an external unit is a disadvantage to the maintenance and high cost high because it requires piping, additional equipment and energy source for feeding grease.
Hence, NTN has developed a micro amount lubricant supply system that only the base oil separating from the grease due to temperature change during the operation is automatically supplied to the bearing raceway by providing a grease reservoir at the bearing side face. At this time, NTN has been successful in the commercialization. With this system, the world's highest-level operation of angular ball bearing with dmn value of 1.9 million becomes possible under maintenance free and solid preload conditions. NTN names this new grease lubrication system ‘MQGS lubrication [Minimum Quantity base oil of Grease Supply]’ to distinguish it from the conventional grease lubrication.
NTN will exhibit a machining center equipped with a spindle installing this lubrication system and demonstrate its high speed machining at ‘JIMTOF 2008 (Japan International Machine Tool Fair)’, held at the Tokyo Big Site from October 30.
[ Features ]
a. High speed rotation:
Operation with dmn value of 1.9 million under solid preload is possible.
(30% increase, compared with conventional NTN grease lubrication) [Bearing bore dia.: 100mm, speed: 15,000min-1]
b. Maintenance free:
Lubrication piping, additional equipment and drive energy are completely unnecessary.
c. Reduction of environmental burdens:
No oil mist generates, and no external drive unit is required. Improvement of working environment, energy conservation and reduction of environmental burdens are achieved. (in comparison with air-oil lubrication)
d. Total cost reduction:
Additional external equipment and drive energy for lubrication are not needed. Total equipment cost reduction is possible. (In comparison with air-oil lubrication)
[ Application ]
Machine tool main spindles (Machining center, complex machine tool etc.)
[ Contact ]
Machine Tool Group, Application Design Dept., Industrial Product H.Q. Tel 0594-24-3819
1) dmn value = dm (Bearing pitch circle dia. in mm))× n (Rotational speed in min-1)
Example: When a bearing of dm =100mm runs at n = 50000min-1, the dmn value is 100×50,000 = 5 million
2) Solid preload is a preloading method that position change is small at the top end of supported main spindle and the machining accuracy is effectively assured for various general-purpose machine tools.
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