Design optimization of a needle holder for in-space 3D printing
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Ημερομηνία
2018-04-28
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The current dissertation thesis documents the design optimization process of a surgical needle holder for in-space 3D printing. 3D printing can provide the means for an autonomous, crew-administered medical care system through an onboard digital catalog of 3D printable files that can be accessed on demand. As space missions become longer and more dangerous the need for on-board surgical capabilities becomes more urgent. The needle holder, used by a surgeon to hold the needle during suturing, is an integral part of a basic surgical kit.
Commercially available needle holders were analysed and a digital model was produced in Solidworks 2016 after an existing stainless-steel instrument. A finite element analysis was run to analyse stress distribution and the model’s geometry was optimized accordingly for the FDM process. Areas like the fulcrum, jaws, handles and locking mechanism were thickened.
To better inform the design process, six thermoplastic filaments were tested to determine their suitability for the needle holder fabrication. Two sets of specimens were printed from ABS, PLA, PETG and Nylon filaments and from composite ABS-Stainless Steel and Nylon-Fiber Glass materials. The first set was tested with their layers in a horizontal direction, as printed and the second with their layers on a vertical position, rotated 90o from printing direction. The materials demonstrated advantageous mechanical properties when the load force was vertical to the parts’ layering. Another observation was the brittle behavior of PLA and PLA-SS which could pose danger in case of a failure during a real medical emergency in zero-g conditions.
Lastly, further simulation studies were conducted on the optimized digital model to examine its structural integrity when fabricated from the aforementioned materials. The vertical values calculated in the testing stage above were used. Inaccuracies of the Solidworks simulation utility in the analysis of 3D printed parts were taken into account. Nonetheless, the maximum exerted stress remained well below each material’s yield strength, making it safe to conclude that all the materials could be used for the fabrication of a functional needle holder. Slight preference could be given to Nylon-FG due to its high yield strength.
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Λέξεις-κλειδιά
3D printing, Space, Optimization, Surgical, Needle holder