Exacting industry standards are driving medical-device manufacturers to specify linear actuators and ball screws with capabilities that exceed those of standard components. Nook Precision Screw Group, Cleveland, (nookindustries.com) addresses this problem by practicing early and disciplined collaboration with customers incorporating linear-motion components into medical devices such as syringe pumps, prosthetics, or injectors.

Nook first works closely with customers to establish design parameters. These might include load capacity, lead accuracy in microns, size of the working envelope, material constraints such as magnetism or radioactivity, and operating conditions such as whether the device will directly interact with humans.

As designs progress, the company evaluates them to target potential problems by making extensive use of CAD and FEA software. Together the programs provide modeling, simulation, visualization, communication, and compliance capabilities. The company also validates designs with real-world testing equipment such as durometers.

An example of a customizable ball screw that Nook recently developed comes from its SD Ball Screw, intended to provide precise, efficient movement in a compact package. The small diameter (under 10 mm) ball screws have a load capacity of 40 to 100 lb and come with standard leads from 1 to 3 mm.

A more complex example is the customizable Stainless Steel Modular Linear Actuator Series (QLZE / QSZE / QST-KE) Positioning System. The series is engineered with a stainless steel cover that wraps over the square aluminum profile to eliminate damage from caustic wash-downs. The 0.37-mm thick housing also protects the aluminum from clogging and pitting. The standard, single-carriage version carries loads up to 1,600 lb.