[diss] Perustieteiden korkeakoulu / SCI

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Browsing [diss] Perustieteiden korkeakoulu / SCI by Subject "3D printing"

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  • Direct digital manufacturing: projection stereolithography and incremental sheet forming
    (2017) Lehtinen, Pekka
     School of Science | Doctoral dissertation (article-based)
    The drastic development of advanced manufacturing technologies coupled with consumer demands for more customized products are causing the manufacturing industry to move from mass production to small volume and a wide range of products. These kinds of requirements are met by direct digital manufacturing (DDM) techniques that seamlessly produce three-dimensional objects directly from digital data in a single step regardless of the complexity of the products to be built. DDM techniques include additive manufacturing and forming techniques where highly specified products are fabricated in layers. Due to the high versatility of DDM systems and low tooling costs, DDM is outstanding in one-off production. However, DDM is still an immature technology that will make a real impact across a large range of industries as it is developed further. This thesis aims to develop two DDM techniques: (i) projection stereolithography and (ii) incremental sheet forming. While the first one is an additive manufacturing technique where a plastic part is fabricated by selectively curing liquid polymer in layers, the second one is a metal forming technique where the desired shape is created through a series of small incremental deformations. First, a projection microstereolithogarphy apparatus that can produce high quality miniature objects with a resolution of a few micrometers was built and some specific issues related to the printing process were solved. The research involved increasing the manufacturing speed, developing suitable polymer solutions (resolution, conductivity, biocompatibility, penetration depth control), and providing new insight and methods to control the curing mechanisms of liquid polymers. Secondly, the effect of local heating on the formability of metal sheets in incremental sheet forming was investigated. In this research, metal sheets were formed by a round tipped tool that was attached to a 3-axis positioning system and the investigated materials were aluminum, copper and steel. To increase the formability of metal sheets, a laser light source was used to irradiate the bottom side of the sheet. With this method it was possible to produce shapes that were impossible to form without heating.
  • Imaging and digital design for medical applications of additive manufacturing
    (2019) Huotilainen, Eero
     School of Science | Doctoral dissertation (article-based)
    Since their inception in the late 80s, additive manufacturing (AM) technologies have contributed largely in the paradigm change of production engineering. A focal area where these processes offer exceptional contemporary applications and future potential is the medical milieu; low production volumes, high degree of customization, and complexity of required shapes are strong drivers leading towards digital fabrication.  Medical applications of additive manufacturing are classified to span five distinct categories: medical models, external prostheses and guides, surgical tools, inert implants, and biomanufacturing. The primary aim for this dissertation is to develop the five-step process for medical applications of AM: medical imaging, digital design, fabrication, post-processing, and clinical application.  In the center of a successful clinical AM application lies the digital design phase. The results of this dissertation present optimization framework for medical imaging in order to ensure quality of source material for the designs. Subsequently, the design step is enhanced by developing and presenting practical and computational methods for design automation and conversion techniques into efficient clinical applications.  The research focusing on the critical steps of the process is complemented with a holistic view on the complete process. Apart from the technical solutions offered, the collaborative needs, and information and communication flows within the process are essential for successful medical application of additive manufacturing. Critical future research topics required in the research area include novel material and software development as well as more efficient utilization of existing technologies.