Early Collaborative Key to Designing for Medical Applications

Cleveland, OH - June 6, 2009


Advanced medical device designs are evolving rapidly and demand higher standards for medical liability. Applying linear motion components to these medical applications yield the best results when collaboration begins at the early stages of the design. Modification to current parts or a custom design may offer the optimum solution; therefore, an emphasis must be placed on collaboration during the early stages of design with medical device manufacturers.

Nook Industries offers a wide variety of standard modular actuators and ball screws for medical applications in their extensive catalog. As a leading linear systems and components manufacturer, Nook Industries (Cleveland, OH) recognizes that medical application specifications often exceed the capabilities of standard, cataloged products. Nook leverages its decades of expertise when modifying standard parts or creating custom designs for medical applications. Nook utilizes vigorous quality systems, a vertically integrated manufacturing model and implements a disciplined product realization process that reflects the Food and Drug Administration's Quality System Regulation 21 CFR-Part 280.

According to Nook Industries' CEO, Christopher Nook, "We often start with the customer's performance specifications focused on the product's expected life, environmental conditions, material selection and physical size. We then incorporate enhancements to the product's design that address the rigors of most medical applications. This process has allowed us to sell modified standard products to the Medical industry very successfully."

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The following disciplined realization process is executed for Nook medical device applications.

Priorities for 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:

Design 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 can't be consistently and efficiently produced. Nook leverages SolidWorks® COSMOS software at this stage to provide a full range of integrated modeling and simulation that medical product manufacturers need to design better products, faster - and at lower cost.

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Medical Device Trends/ Products:


With the growing worldwide shift toward smaller packaged applications - typically requires lower load capacity and higher precisions. Nook's Precision Screw Group has recently introduced its Small Diameter Ball Screw Assemblies (SD Ball Screw) designed for smaller footprint applications to meet the needs of these medical applications. In addition to medical equipment, these screws are used in robots, guided missiles, unmanned vehicles and aerospace applications.

The small diameter ball screw line was developed as an extension to its Power-Trac™ offering to provide design engineers 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 40-100lbs., and a high precision (lead accuracy measured in microns; 10ths of 1,000s of inches).

  • Lead accuracy of: ± 100μm/300mm - Standard Rolled (Carry, MRT)/ ± 25μm/300mm - Precision Rolled (PMT)
  • Standard diameters from 6mm to 12mm
  • Standard leads from 1mm to 6mm

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According to Nook Industries CEO, Christopher Nook, "The Small Diameter (SD) Ball Screw's 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 6mm diameter to 12mm diameter.


To meet the high duty cycles and sterile requirements of pharmaceutical, medical, and clean room applications, Nook also offers an extreme-duty solution with its new Stainless Steel Modular Linear Actuator Series (QLZE / QSZE / QST-KE) Positioning System. Developed by Nook's Precision Actuator Group, 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 requires no bellows to cover the extrusion which typically wears out over time.

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.

Nook's Stainless Steel Modular Linear Actuator Series meets the corrosive challenges created by harsh chemical environments for food/beverage, packaging and petrochemical industries.

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The challenge of expanding product range miniaturization goes beyond materials and tools. After intensive development and recent discoveries in metallurgy, production, and assembly technique, Nook has mastered its 4 × 1 (diameter × lead in mm) which fulfills all test characteristics for rolled screws as a series-produced rolled part. The diminutiveness, or fineness, of the delicate part is achieved not only for the ball screw, but even more for the nut and for the assembly.

This "micro range" line transcends the "traditional" Ø 6 mm, through the 5-mm ball screw, to a diameter of just 4 mm. Key to design engineers at the outset is that instead of the outer diameter of 10 mm (of the cylindrical nut), previously standard on the market, this is now just 8 mm. Achieved by implementing a brand new ball return, and its sophisticated assembly, the diameter reduction of 2 mm corresponds to an impressive 25 percent.

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This reduction represents an alternative to the customary costs for rolled screws as the 4 × 1 ball screw from Nook opens up a competitive price dimension. The equation is simple; the smaller the screw, naturally the lower the cost proportion of the material. This development offers an affordable option not only for "normal" applications, but also as a replacement for ground versions.

The 4 × 1 type ball screws are already being used in medical technology in applications for removing tissue (biopsy) for laboratory tests, amongst others. Also in use in optical devices, the miniature ball screw will doubtless conquer further fields of application; primarily due to its diminutiveness, robustness and reliability, paired with a significant price advantage.

Nook's 4 × 1 line includes the PowerTrac™ Carry™ metric rolled ball screws and Speedy™ metric screws.

Speedy™ metric screws are designed to move light loads at high travel rates and have lead-to-diameter ratios of up to 6:1 - enabling efficient conversion of linear to rotary movements (sliding friction). Extremely efficient and cost effective when compared to other methods of high-speed actuation, they are available with durable wear resistant plastic nuts. For higher loads, bronze nuts are available. Special plastic materials can be ordered for demanding applications.

  • Standard diameters from 5mm to 65mm
  • Standard leads from 3mm to 200mm
  • Alloy and Stainless Steel Screws
  • Bronze and Plastic Nuts

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Market Trends / Conclusion:

The footprint for medical device applications is reflecting a trend toward diminutiveness worldwide. Until 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. Ever smaller dimensions are also the aim 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.

The standard, rolled sizes available from most suppliers extended as far as a diameter of around 6 mm. If a smaller diameter was required for design reasons, recourse was taken to the ground ball screw - but at a very steep price.

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

Corporate Profile:

For over 40 years, Nook Industries, Inc. has been a leading manufacturer of linear motion components and linear motion control systems. Manufacturing one of the most comprehensive selections of integrated linear motion systems in the world, Nook's progressive growth has been achieved through its commitment to quality, continuous improvement, defect prevention, and the use of statistical methods and consistent training to ensure the quality of its products.

Headquartered in Cleveland, Ohio, Nook Industries is an ISO 9001-2008 Registered company that provides controlled motion solutions in a wide range of industries including; transportation, medical/diagnostics, paper, chemical, food/beverage, solar/aerospace, entertainment and communications markets. Clients in these markets rely on the company's products for tooling, product design and engineering flexibility to provide modified standard products to meet their respective application requirements.

Whether the application requires an off-the-shelf linear motion component or an engineered solution tailored to fit your application - Nook provides comprehensive engineering, design and analysis in providing the highest quality linear motion manufacturing solutions on the market today.

For more detailed information, visit the Nook web site at: or call: 1-800-321-7800.

©2009 Nook Industries

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Editorial Contact:

Agency Contact: Rachel Kerstetter 216.242.0415