A method for image-guided positioning of cochlear specimens in insertion test benches using 3D printed stands

Cochlear implants include an electrode array (EA) which needs to be inserted into the cochlea. Insertion tests using artificial cochlear models (ACM) or ex vivo specimens are widely used methods during EA development to characterize EA design properties, including insertion forces. Measured forces are directly linked to the orientation of the cochlear lumen with respect to the insertion axis of the test bench. While desired insertion directions in ACM experiments can be predefined by design, specimens are individually shaped and the cochlear lumen is embedded invisibly. Therefore, a new method for accurate, individual specimen positioning is required. A key element of the proposed method is a customizable pose setting adapter (PSA) used to adjust the specimen’s fine positioning. After rigid fixation of the specimen to a holder featuring spherical registration markers and subsequent cone beam computed tomography the desired insertion direction is planned. The planned data is used to calculate the individual shape of the PSA. Finally, the PSA is 3D printed and mounted between force sensor and specimen holder to correctly align the specimen to the test bench’s insertion axis. All necessary hard- and software have been developed including the specimen holder, a software for registration and trajectory planning, and a custom Matlab script whose output drives a parametric CAD file of the PSA. Positioning accuracy was determined in a first trial using 10 virtual trajectories and was found to be 0.23 ± 0.12 mm and 0.38 ± 0.17°. The presented stereotactic positioning procedure enables high repeatability in future ex vivo insertion experiments due to accurate, image-guided control of the insertion direction.

VPP Coupling High-Fidelity Analyses and Analytical Formulations for Multihulls Sails and Appendages Optimization

A procedure for the optimization of a catamaran’s sail plan able to provide a preliminary optimal appendages configuration is described. The method integrates a sail parametric CAD model, an automatic computational domain generator and a Velocity Prediction Program (VPP) based on a combination of sail RANS computations and analytical models. The sailing speed and course angle are obtained, with an iterative process, solving the forces and moment equilibrium system of equations. Analytical formulations for the hull forces were developed and tuned against a matrix of CFD solutions. The appendages aerodynamic polars are estimated by applying preliminary design criteria from aerospace literature. The procedure permits us to find the combination of appendages configuration, rudders setting, sail planform, shape and trim that maximise the VMG (Velocity Made Good). Two versions of the sail analysis module were implemented: one adopting commercial software and one based on the use of only Open-Source codes. The solutions of the two modules were compared to evaluate advantages and limitations of the two approaches.

Generative Design for Additively Manufactured Textiles in Orthopaedic Applications

The aim of this work is to implement a new process for the design and production of orthopaedic devices to realize entirely by Additive Manufacturing (AM). In particular, a generative algorithm for parametric modelling of flexible structures to use in orthopaedic devices has been developed. The developed modelling algorithm has been applied to a case study based on the design and production of a customized elbow orthosis made by Selective Laser Sintering. The results obtained have demonstrated that the developed algorithm overcomes many drawbacks typical of traditional CAD modelling approaches. FEM simulations have been also performed to validate the design of the orthosis. The new modelling algorithm allows designers to model flexible structures with no deformations or mismatches and to create parametric CAD models to use for the production of orthopaedic devices through AM technologies.

Solving structural design challenges with generative solutions

Topology optimization is one of the main engineering problems, that should be addressed from the conceptual stage. An existing design is developed through traditional means and attempts to optimize it through an algorithmic postprocess, regarding various criteria. Physical systems that determine fixtures or contact in the assembly relate to design constraints, while the outcome material, optimal distributed, responds to criteria like minimal mass or maximum stiffness. The paper presents the principles and criteria used in shape design. Using a case study in Fusion 360 Generative Design workspace, the preserves and obstacles in generative design are identified at components and equipment level, along with main parametric CAD geometric definitions. The results in the generative solutions proposed for a given fixture are graphically presented and explained, also, analyzed from the manufacturing point of view.