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Linear Motion Control - 03/10/2021

NSK's miniature ball screws

Human beings provide the measure: the drives of surgical robots, blood pumps, and MRI and CT equipment (for example), must offer a design that ensures they perform their tasks very precisely and smoothly without emitting any contamination. Specifically for facilitating movement in medical technology, NSK provides a continuously expanding range of linear guides and ball screws to suit the smallest installation spaces. Among the many notable features of this product range is a special surface treatment on the raceways of NSK ball screws.

It is not surprising that miniaturisation plays a central role in this intricate area of application. Surgical robots perform small-scale movements with extremely high positioning accuracy, but low torque in comparison with most industrial applications. Maximum running smoothness is a further prerequisite. Even for blood pumps or cardiac support systems, it is not a question of delivering high performance, but rather a constantly fail-safe operation with excellent running smoothness.

NSK meets these requirements by developing linear technology components and systems with medical technology applications in mind. The company’s offer includes a wide range of miniature ball screws (4-15 mm diameter) and miniature linear guides (size 05-15).

Many of these components are equipped with the optional K1 lubrication unit, which enables long-term, maintenance-free and thus uninterrupted operation. This minimum-quantity lubrication system also keeps the ball screws and linear guides permanently clean and functional. Specially developed greases are available for short-stroke applications.

NSK’s miniature ball screws also use a special surface treatment on the running surfaces of the ball raceway. A special texture produced by superfinishing creates the conditions for retaining the lubricant within the raceway and for generating only a very low friction torque. In addition, this effect ensures exceptionally quiet smooth running of the linear components. To suit certain applications, NSK can also manufacture the components with other types of surface coating.

A ball screw that NSK developed for a manufacturer of mobile cardiac support systems demonstrates the extreme requirements that linear drives need to meet. In such systems, the patient's blood circulation connects via a cannula to a compressed-air diaphragm pump. A miniature ball screw from NSK performs a stroke of up to 55.5 mm, 60 to 130 times per minute. This repeated action forces a defined amount of air against the diaphragm, on the other side of which is the cannula conveying the patient’s circulating blood. Here, the ball screw fulfils a highly sensitive, life-saving task.

When selecting the drive system, the service life of the NSK solution was the decisive criterion. In comparative tests involving various other linear actuators, the NSK product achieved by far the best value: around 120 million cycles.

As well as human body applications and surgical robots, NSK linear actuators are also prevalent in laboratory instruments, blood analysis equipment and medical imaging devices such as microscopes and CT/MRI systems, among others. This applies to individual linear components as well as complete assemblies (ball screw plus linear guide, for example) and NSK Monocarrier actuator systems with an integrated servo or stepping motor.


Picture 1): Among a wide variety of applications, NSK's miniature ball screws are used in cardiac support systems

NSK miniature linear guides of the PU/PE series

Picture 2): The NSK range for medical equipment includes miniature linear guides of the PU/PE series

NSK Monocarrier actuator

Picture 3): Manufacturers of medical laboratory analysers take advantage of the NSK Monocarrier actuator for demanding handling tasks

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