Helical Spring Design Optimization For Endoscopic Devices Using A Design-Of-Experiments And Response Surface Approach

Flexible endoscopes require reliable advancement and steerability of the device tip. Helical spring design is critical to both endoscopic steerability and cable function. To characterize the impact of geometric and material factors on endoscopic function, a parametric helical spring and a cable assembly was modelled using the finite element method and analyzed using a design-of-experiments approach. Individual input parameters (height, modulus (E), force, and width) and two interactions (pitch/width and pitch/height/E/width) were found to significantly impact the radius of curvature (a measure of steerability). The force and pitch/width interaction had negative effects, in contrast to positive effects from height, E, width and the pitch/height/E/width interaction. This information provides critical geometric and material information to guide helical spring design for optimized endoscopic steerability.