An ankle-foot orthosis (AFO) is a medical aid that helps individuals with deficient walking patterns achieve a more natural gait. There are various types of AFOs prescribed for different reasons. This thesis specifically focuses on passive dynamic ankle-foot orthoses (PD-AFOs) and even within that branch a very specific type: the carbon dorsal leaf spring orthosis. This type of AFO leverages the body’s biomechanics and gravitational forces to store and release energy at precise phases of the gait pattern, helping to restore some of the ankle function. Furthermore, they address the issue of excessive plantar flexion during the swing phase of gait, which can result in foot drop or an undesirable foot-slamming motion.

To ensure optimal fit and functionality, these orthoses are custom-made to provide the best fit for the lower leg and foot of each individual. Currently, the manufacturing process for these orthoses involves labour-intensive carbon composite layering techniques, which require significant effort and expertise.

An alternative AFO concept was designed, which aims to replicate the behaviour of existing carbon dorsal leaf spring orthoses using SLS-3D printing. This direction was explored as additive manufacturing excels in one-off production and eliminates the need for manual labour, offering cost-effective and efficient production of personalized items. This case is therefore carried out for the companies Parts on Demand, a selective laser sintering (SLS) 3D-printing company, and Livit Ottobock Care, an orthopedics company, to further investigate the feasibility of such an orthosis.

This study involved multiple design iterations, primarily focused on the stiffness behaviour of the AFO to create a novel SLS printable design that exhibits similar stiffness characteristics and gait influence compared to the existing carbon dorsal leaf spring AFOs produced by Livit Ottobock Care, whilst maintaining comparable weight and cost.

A model was created to parametrically refine SLS printable AFOs based on scanned lower leg and foot data for repeatable results using different feet. Subsequently, prototypes were fabricated using this model to validate the quantitative stiffness behaviour and qualitative correction of user gait resulting in an orthosis with a comparable function to the baseline carbon dorsal leaf spring orthosis.

Initial results seem promising for the feasibility of SLS printing PD-AFOs, but requires further validation, as many aspects related to their longevity were excluded from this study. These factors include its fracture resistance over longer periods of time, whether stiffness fatigue will occur, or how the AFO will behave mediolaterally. Nonetheless, producing an SLS-printed orthosis can provide benefits in the long run which for example include not only customized and well-fitting orthoses but also tailored stiffness characteristics for each individual, enhancing the function of the ankle and foot during walking. However, it is important to note that research in this area is currently insufficient.
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This report describes the development of a redesigned haptic glove for SenseGlove, a Delft-based startup specializing in haptic technologies for use in Virtual Reality. Their Nova product line offers force feedback, haptics, and finger tracking to increase immersion in VR and provide intuitive interaction with virtual objects for training purposes. Driven by a desire to implement new features, communicate a new branding direction and increase production rates while maintaining quality, SenseGlove requested a full redesign of Nova’s enclosure with a focus on improving assembly time.

An analysis of Nova’s original assembly process and design was conducted and showed several areas in which it could be improved. Then, three focus points were defined based on principles from Poka Yoke and DFA:

Focus point 1:
Minimize the number of parts needed for subassemblies within the scope of this project.

Focus point 2:
Improve the logic of the assembly steps and make them as self-explanatory as possible.

Focus point 3:
Reduce the loss of progress that can occur from human error during assembly.

Guided by the focus points, a three-phase design process was completed in which Nova was divided into several subproblems that were individually solved, then combined into a configuration model, before finally being integrated with a new aesthetic direction that was co-developed with SenseGlove to create a Nova 2.0 concept with a new assembly process. A proposal for CMF was also provided, along with an evaluation based on assembly, aesthetics reception, manufacturability, and costs.

The Nova 2.0 concept is estimated to take approximately 53% of the original time to assemble, while eliminating the need for several assembly stations and enabling nondestructive disassembly. The new aesthetic direction fits well among other VR devices often used together with Nova but requires some refinement to meet all visual goals set by SenseGlove. The model provided in this report is not yet completely manufacturable, but with minor adjustments and implementation of recommendations should be ready for production. The new production cost is expected to be higher than the original Nova due to the implementation of new features and a redesigned PCBA, though the exact price cannot be determined as some features were beyond the scope of this project.

The Nova 2.0 concept reaches the goals set at the start of this project and SenseGlove is recommended to further develop it but is advised to keep the three focus points in mind when making changes, as design for assembly needs to be applied in all stages of development to bring maximum benefits and reduce the risk of facing issues in the future. ... Read more