Seven Degree of Freedom Curvilinear Toolpath Generation for FDM 3D Printing with Applications in Patient-Specific Medical Device Prototyping

University of Minnesota Ph.D. dissertation. December 2019. Major: Mechanical Engineering. Advisor: Arthur Erdman. 1 computer file (PDF); xvi, 161 pages.Additive manufacturing, or 3D printing has changed engineering, prototyping, and design by giving users unprecedented ability to realize designs they could have previously only dreamed of. However, these technologies have limitations. 3D printing is traditionally a layer-by-layer process of depositing material to gradually build a 3D object from 2D slices. Layer direction, part orientation, and overhang angles are all interlinked printing considerations, which may require engineers to make compromises while designing objects for 3D printing. This thesis offers a solution to many of these limitations in the form of a seven axis 3D printing system. Seven axes of motion, three linear and four rotational, allow for standard 3D movement of a printing system with added rotation of both the nozzle and the build plate. Increasing the degrees of freedom of a 3D printing system makes it possible to improve part strength, reduce support material usage and print time, and create objects that are impossible to print otherwise. These extra axes unlock potential to manufacture anatomical models and perform patient specific device development due to the irregular and complex shapes involved. Custom algorithms provides the user with complete control over the seven axis toolpath. This thesis documents the applications of seven axis toolpath generation, presented as a series of case studies, as well as design and development of the aforementioned 3D printing system. The first study examines how tool approach angles and bed angles affect the quality of sample parts containing high angle overhangs. The strength of parts printed while utilizing extra axes is maintained for a given toolpath, while surface quality and overall dimensional accuracy is improved. The second study documents the design, construction, and testing of an oropharyngeal airway, a device that has difficult geometry. Layers that follow the device profile improve strength and eliminate the need for support material. The last case study showcases a workflow for creating patient specific airway stents from patient scan data. These techniques may be useful for many other applications including patient specific anatomy creation, bioprinting, and reworking previously 3D printed objects