Study compares structural integrity of manufacturing processes

LEIPZIG, Germany — There are a variety of ways to fabricate sockets but with any method there are pros and cons. According to Lonnie Nolt, research engineer, Ohio Willow Wood, the traditional plastic casting method is widely accepted even though the process is time consuming and destroys the original shape data. CAD/CAM improved upon the plastic casting procedure by documenting the residual limb’s original shape as well as any new modifications. Still, CAD/CAM has its detractors.

  Lonnie Nolt
  Lonnie Nolt

“A potential alternative to conventional fabrication is direct manufacturing,” Holt said at the ORTHOPÄDIE + REHA-TECHNIK 2012 International Trade Show and World Congress. “Direct manufacturing is the process that directly converts the CAD model to the product without the use of external processes or manual labor.”

Direct manufacturing provides an automated use of fabrication and has the ability to implement additional features that are not attainable by traditional methods, according to Nolt.

Nolt compared the structural integrity and feasibility of two direct manufacturing technologies — Fused Deposition Modeling (FDM) and Selective Laser Sintering (SLS). The average strength of the SLS sockets was approximately 7,800 N compared with FDM ,which was 3,350 N.

“The SLS sockets were shown to be a viable option for prosthetic sockets in terms of mechanical strength and fatigue resistance,” Nolt said. “The study indicated that the SLS sockets as fabricated produced higher static strengths and minimum variation compared to carbon sockets.”


Nolt L. Comparison of direct manufacturing technologies for the application of prosthetic sockets. Presented at ORTHOPÄDIE + REHA-TECHNIK 2012 International Trade Show and World Congress. May 15-18. Leipzig, Germany.

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