2015-16

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Browsing 2015-16 by Author "Aaron, Ralston"

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    Design and Manufacture of 3D Digital Light Processing Stereo Lithography Apparatus Printer
    (2016-07-21T06:49:44Z) Aaron, Ralston; Avinash J, Singh; Bobby Seban, John; Chethan, K
    Stereo lithography or SLA is an additive manufacturing process using a container of liquid UV/light-curable photopolymer "resin" and a UV light source to build parts one layer at a time. On each layer, the UV beam traces a cross-section pattern of the part onto the surface of the liquid resin. Exposure to the UV light cures, solidifies the pattern traced on the resin and adheres it to the layer above. Photo Lithography is very simple, light illuminates the resin and the resin hardens. To be more exact a quantity of light falls/shines onto the resin, if the energy quantity of that light is high enough it will induce photo polymerization of the resin. While 3-D printers are already out in the market and doing well, there is still a need for a smaller and more cost effective design. This is what we achieve to do with our project. In a conventional DLP SLA printer the print base going into the resin container which limits the size of the product being printed to the maximum depth of the container itself! Where as in our case there is no such limit as the Z-axis is scalable as the base rises up with a bottoms up approach! The aim of the project is to design an SLA printer which works "bottom up" by using a vat with a somewhat flexible, transparent bottom, and focusing the UV light, upward through the bottom of the vat. The stereolithography machine starts a print by lowering the build platform to touch the bottom of the resin-filled vat, then withdrawing upward one layer thickness (which can be as small as 10 microns). The light source we are using is a DLP projector. This light is reflected off a first surface mirror before touching the resin. This is done to reduce the height of the printer. The UV light from the projector then writes the bottom-most layer of the desired part upward through the transparent vat bottom, and the photopolymer hardens selectively where the light strikes. An advantage of this bottom-up mode is that the build volume can be much bigger than the vat itself, and only enough photopolymer is needed to keep the bottom of the build vat continuously full of photopolymer. Often a depth of only a centimeter or two of liquid photopolymer is adequate to print tall, thin structures 10 cm tall. Thus, bottom-up printing exposes far less photopolymer resin to atmospheric oxygen and room light which can degrade or prematurely harden the photopolymer and so decreases waste of the expensive photopolymer.