2012

Mechanical Components for Demanding Applications

Small-diameter ball screws and stainless steel linear actuators deliver performance and durability for compact, portable, and lightweight applications.

Advanced medical device designs are evolving rapidly and demand higher standards for medical equipment reliability. Applying linear motion components to these medical applications yields the best results when collaboration begins at the early stages of the design. Beginning with specification requirements provided by the medical device manufacturer, definition of design priorities must be incorporated for finished devices intended for human use, including:

• Performance: load capacity and length/range of travel requirements
• Efficiency: high-precision/low-precision
• Accuracy: lead accuracy measured in microns; 10ths of 1,000s of inches
• Envelope: compact
• Material Constraints: stainless steel, magnetism/non-magnetism, radioactive elements, etc.
• Operating Environment: non-direct exposure with patients or attached to the human body, etc.

Design Reviews

altDesign reviews are conducted at various stages involving comprehensive, systematic, and documented examinations of a design that will evaluate the adequacy of the design requirements and evaluate the capability of the design to meet these requirements.

Designing a ball screw is not practical if it cannot be consistently and efficiently produced. Nook leverages Solid - Works® COSMOS software at this stage to provide a full range of integrated modeling and simulation that medical product manufacturers need to design better products, more quickly, and at lower cost.

Small-Diameter Ball Screws

With the growing worldwide shift toward smaller packaged applications typically requires lower load capacity and higher precisions. Small-diameter ball screw assemblies (SD Ball Screw) are designed for smaller-footprint medical applications, as well as for us in robots, guided missiles, unmanned vehicles, and aerospace applications.

The small-diameter ball screw line was developed as an extension to the Power- Trac™ offering, to provide design engineers with a globally accepted metric product for compact, portable, and lightweight applications requiring high accuracy, repeatability, and durability.

The small-diameter (below 10mm) ball screws are designed with a load capacity of 40–100 lbs., and a high-precision (lead accuracy measured in microns; 10ths of 1,000s of inches).

• Lead accuracy of: ±50μm/300mm - Standard Rolled, ±25μm/300mm - Precision Rolled
• Standard diameters from 6 mm to 12 mm
• Standard leads from 1 mm to 6 mm

The small size and customizable design offer precise, efficient movement in a compact package for medical device applications. Designed in metric dimensions to meet universal industry performance standards, Nook catalogs SD Ball Screw sizes from 6–12 mm in diameter.

Stainless Steel Linear Actuators

To meet the high duty cycles and sterile requirements of pharmaceutical, medical, and clean room applications, an extreme-duty solution is offered with the new Stainless Steel Modular Linear Actuator Series (QLZE / QSZE / QSTKE) Positioning System. These products are designed with a stainless steel cover band that wraps over the square aluminum profiles. The stainless steel cover helps protect the actuator when it is exposed to caustic cleaning solutions. The stainless steel design does not require bellows to cover the extrusion.

The standard single-carriage linear actuators offer push-pull type directional loading that can handle loads up to 1,600 lbs. of force and maximum thrust loads up to 1,100 lbs. of force. Higher load capacities can be achieved with modified carriages configured with additional rollers or bearings added to the specification.

This series meets the corrosive challenges created by harsh chemical environments for food/beverage, packaging, and petrochemical industries.

Market Trends

The footprint for medical device applications is reflecting a trend toward diminutiveness worldwide. Prior to recent developments in medical device miniaturization, a heavy, permanently fitted installation was necessary for a doctor to measure a diabetic’s blood sugar level. Today, this is achieved using a portable device no larger than that of a matchbox. In creasingly smaller dimensions are also desirable in machine elements. In the past, “micro dimensions” (diameter 6 mm and less) in ball screws were reserved for the production technique of “grinding.”

Inverse to this trend; precision and performance requirements are growing higher, as are liability and compliance standards. The end result, however, remains steady — custom solutions that are ready for production, meet stringent performance and compliance standards, and ultimately provide a better product. Since higher liability factors and higher performance standards are the norm, involving medical device manufacturers at the inception of design is paramount to meeting all industry protocols and compliances when linear motion components are involved.

Because of the pressure for miniaturization, the medical technology industry (as well as optics, etc.) is increasingly demanding smaller ball screws. This has motivated most manufacturers to tackle and solve production problems associated with rolling micro diameters.

This technology was done by Nook Industries, Cleveland, OH. For more information, visit http://info.hotims.com/40430-191 or call: 1-800-321-7800.

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