NSK shows its competency in ultra-fine positioning

As an expert in motion control, NSK frequently supplies customers with manipulators and positioners that meet micrometre and even nanometre accuracy requirements. Such solutions perform fine positioning operations under a microscope field of view, demanding the application of skilled engineering and know-how. A case in point is NSK’s nanopositioner, which exemplifies the company’s expertise in integrated mechatronics and precision positioning drive technology. This knowledge is the result of many decades spent pioneering the development of related technologies such as bearings, linear-motion products and image-processing solutions.

The market demand for positioning mechanisms with nanometre accuracy continues to expand across sectors that include semiconductor manufacturing equipment, biotechnology, optical communications devices and micro electro mechanical systems (MEMS), to list but a few. Fine positioning stages intended to meet these requirements have been available for some time, typically comprising a ball screw, stepper motor and piezoelectric element. However, these solutions generally lack stiffness and fall short of the ultra-high resolution needed at high speeds.

NSK’s nanopositioner overcomes these challenges. Featuring a proprietary ball-screw fixed-end bearing unit with piezoelectric element, the device provides fine positioning at nanometre accuracy and high speeds without compromising mechanical rigidity. Maximum speed is 72 mm/s, while resolution is 5 nm and positioning accuracy is ±15 nm.

Among the major differentiating features of the nanopositioner is its configuration and system structure. Conventional fine positioning stages use a stacked piezoelectric element as a form of piezoelectric actuator, but this design is vulnerable to tension, moment and radial forces. The deployment of compression springs can counter this effect, but they lack adequate rigidity and can hamper high-speed operation.

Instead, the NSK nanopositioner incorporates a piezoelectric element in a ball screw fixed-end bearing unit. Mounting the piezoelectric element on the same shaft as the preloaded bearings means unwanted moment or radial forces do not occur. In addition, the provision of bearing preload as compression force on the piezoelectric element avoids tension, while rigidity is uncompromised.

The nanopositioner offers easy application in XYZ positioning stages. By way of example, the device is at the heart of a proven NSK micro-manipulation system for fine positioning. With the ability to manipulate items as small as a single cell, the system is ideal for a variety of medical science and biotechnology applications, while nanotechnologists find the system useful in assembling microscopic tools.

Driven by a rotary motor, the nanopositioner provides the required fine-motion positioning control of various set-ups and micro-manipulators, ensuring ease of operation and the highly accurate movement of various stage attachments.

Two types of NSK nanopositioner are available: the M series featuring a compact single-axis stage; and the CD series with dual-axis XY table.

1) The structure of NSK’s nanopositioner avoids the application of radial, moment and tension forces found in many conventional counterparts

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