November 26, 2006

New MQCJ Oil Jet System For Machine Tool Spindle Angular Ball Bearings

(World's fastest bearing.Use NTN's New Minimum Quantity and Cooling Jet System)

The NTN Corporation (hereafter, NTN) has succeeded in developing a "New MQCJ Oil Jet System For Machine Tool Spindle Angular Ball Bearings". This new commercial use product is designed for machine tools and delivers the world's fastest operating speed. At the Japan International Machine Tool Fair (JIMTOF2006) held on November 1st, actual machine tool cutting was performed using a machining center on display whose spindle was assembled with bearings using this lubrication method. NTN calls this new lubrication method "MQCJ" an abbreviation for "Minimum Quantity and Cooling Jet" to show that this is different from conventional lubrication methods.

In recent years, the main spindle in multipurpose machine tools and machining centers has been required to operate at higher speeds in order to boost machining efficiency and improve the surface quality of the machined piece. The usual method for reaching high speeds is to force-feed lubricating oil to internal bearings in large amounts via jet lubrication and under-race lubrication. However this method has the problem that supplying large quantities of lubricating oil increases the agitation resistance in the oil.

NTN solved this problem by injecting lubricating oil into the inner race, supplying a small but optimal amount to the bearing internally by using most of the remaining oil in the new "MQCJ lubrication method" to cool the inner races. This method also helped attain the world's fastest speed at a fixed pre-pressure load of 5 million dmn and index pre-load of 3.6 million dmn while also reducing moving part wear loss to figures equivalent to air-oil lubrication.

In machine tool spindles, the heat emitted from the motor and the heat from the bearings are usually cooled separately by outer cylinder cooling from a section in the external housing. The lubricating mechanism developed by NTN however jointly cools both the bearing lubricating oil and the outer cylinder cooling oil without requiring separate lubricating oil supply systems. It is effective in reducing costs.

[Features]

(1)	World's fastest rotation speed:
	·Fixed pre-pressure:
		dmn value = 5 million(90% improvement versus air/oil lubrication in prior company equipment) [rotation speed of 55,000min^-1 at a Φ70mm bearing inner diameter]
	·Index pre-pressure:
		dmn value = 3.6 million (40% improvement versus air/oil lubrication in prior company equipment) [rotation speed of 40,000min^-1 at a Φ70mm bearing inner diameter]
(2)	Motions wear loss: Equivalent to air/oil lubrication methods
(3)	Simple oil supply/drainage system: (combines outer cylinder oil cooling with bearing lubrication)

[Applications]

High speed spindles in machine tools
(die-cast and aluminum processing machining centers)

[Sales Target]

Target sales of 500 million yen annually by 2010

Note:dmn value = (dm: Ball pitch diameter (mm) n: Rpm (min^-1))

When a bearing with a dm equal to 100 mm is rotated at a speed of n = 50,000min^-1,
then the dmn value is 100×50,000 or 5,000,000.

[Product Photo]

[Concept View]

Cross section of MQCJ angular ball bearing
Lubricant oil (1 to 2.5 liters per (min-1 bearing)
	Optimal minimum lubricant quantity Jet cooling of inner race
	Drainage of cooling lubricant from inner race and lubricant from bearing

World fastest dmn value! (500×10⁴ at fixed pressure)

World fastest dmn value! (360×10⁴ at fixed pressure)

Minimum Quantity and Cooling Jet
(New Oil Jet System Optimizes Oil Supply For Inner Race Cooling)

[How NTN does it]

(1)	New design optimizes oil supply to insure inner ring protection. Employs an inner race cooling scoop mechanism and custom nozzle
(2)	Combines super-high speed capability along with high-strength Unique NTN internal bearing design
(3)	Durable at high speed and extreme surface pressure operation. Inner races are made of unique custom-made material

[Lubricant oil flow]