--Designed to Accommodate the Increasing Speed and Precision of Large Machine Tools--

NSK Ltd. (NSK; Headquarters: Tokyo, Japan; President and CEO: Norio Otsuka) announced that it has developed a double-nut cooling ball screw that has a cooling mechanism built into preload double nuts, a feature that was designed to accommodate the increasing speed and precision of large machine tools. NSK will launch this product in December 2012. Annual sales of nut cooling ball screws and hollow shaft cooling ball screws are expected to reach one billion yen by 2015.

NSK will display the product at the 26th Japan International Machine Tool Fair (JIMTOF 2012), to be held from Thursday, November 1 to Tuesday, November 6 at Tokyo Big Sight (Koto Ward, Tokyo).



Development background
In recent years, there have been advances in the speed and precision of large machine tools used in the aircraft and energy industries. In response to the need for greater speed and precision, ball screws with hollow shafts for coolant (shaft cooling) have found widespread use. This approach dissipates the heat generated by high-speed operation efficiently through the inside of the shaft. However, with the long double-nut preload ball screws used with large machine tools, length restrictions sometimes make hollow shafts impossible, and where it is possible, the high cost remains an issue.

Now, NSK has applied its proprietary nut cooling configuration to a double-nut preload ball screw to offer a double-nut cooling ball screw that efficiently cools ball screws for large machine tools at low cost.

Product features
1. Cooling capacity equal to shaft cooling
Optimization of the cooling structure inside the nut provides cooling performance equivalent to shaft cooling.
In addition, it is now possible to cool ball screws longer than 10 m, which is impossible with shaft cooling.

2. Preload configuration optimized for nut cooling
When the nuts are cooled, they reach a temperature lower than the shaft, which increases preload.
This product uses a preload system that is optimized for nut cooling, so preload does not increase when the nut performs cooling.
This enables efficient cooling of the ball screw.

3. Improved operability
The ball screw can be cooled easily, simply by connecting the piping component to the feeding and drainage oil hole of the nuts.
The rotary joints and sliding seals required for shaft cooling are not necessary, and since the cooling circuits of each nut are independent, there is no concern about coolant leakage.
In addition, since the outside diameter of the nuts is the same as that of conventional products, there is no need to change the design of the existing housing since it can be used as is with this product.

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