< > [Additive Manufacturing](../) > SLA
## Stereolithography
#### [the first 3D printing technique (the importance of filing a patent)](https://www.sculpteo.com/blog/2016/12/14/the-history-of-3d-printing-3d-printing-technologies-from-the-80s-to-today/)
<div><a href="https://www.thehenryford.org/collections-and-research/digital-collections/artifact/242212/#slide=gs-249773"><img src="http://www.cadimensions.com/wp-content/uploads/2018/01/slavpolyjet1.jpg" alt="" width="500" /></a></div>
#### Right side up/ Top Down Photopolymerisation
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<div><span style="color: #999999;">The build platform is lowered from the top of the resin vat downwards by the layer thickness.</span></div>
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<div><span style="color: #999999;">A UV light cures the resin layer by layer. The platform continues to move downwards and additional layers are built on top of the previous.</span></div>
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<div><span style="color: #999999;">Some machines use a blade which moves between layers in order to provide a smooth resin base to build the next layer on.</span></div>
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<div><span style="color: #999999;">After completion, the vat is drained of resin and the object removed.</span></div>
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#### Reversed/ Bottom Up
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#### <span style="text-decoration: underline;"><strong><a href="https://formlabs.com/blog/ultimate-guide-to-stereolithography-sla-3d-printing/#materials">Polymerization</a></strong></span>
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<div><img src="https://formlabs.com/media/upload/_thumbs/graphic-3-01.png.895x0_q80_crop-smart.png" alt="" width="895" height="356" /></div>
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<div><span style="color: #333333;"><strong>Resin Component</strong></span></div>
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<div><span style="color: #333333;"><em><u>Monomers</u></em><u> </u><em><u>and Oligomers </u></em>The core of the resin; carbon chains that will make up the solid parts.</span> <span style="color: #999999;">(<strong>Decides mechanical and thermal properties:</strong> Since photoreactice resins undergo a chemical change on the point of hardening, they can be tuned to produce different result<strong> )</strong></span></div>
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<div><span style="color: #333333;"><em><u>Photoinitiator </u></em> Molecules that react when exposed to UV light, initiating the reaction.</span></div>
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<div><span style="color: #333333;"><em><u>Additives </u></em> Visual and functional supplements, such as pigments or dyes. (apearance)</span></div>
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<div><span style="text-decoration: underline; color: #333333;"><strong><a style="color: #333333; text-decoration: underline;" href="https://formlabs.com/media/upload/XL-DataSheet.pdf\">Material</a></strong></span></div>
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<div><span style="text-decoration: underline; color: #333333;"><a style="color: #333333; text-decoration: underline;" href="https://formlabs.com/blog/how-to-choose-the-right-3D-printing-material/">(evaluation)</a></span></div>
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<div><span style="text-decoration: underline; color: #333333;"><a style="color: #333333; text-decoration: underline;" href="https://formlabs.com/media/upload/Clear-SDS_u324bsC.pdf">clear</a></span></div>
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<div><span style="text-decoration: underline; color: #333333;"><a style="color: #333333; text-decoration: underline;" href="https://formlabs.com/media/upload/Tough-SDS.pdf">tough</a></span> <span style="color: #999999;">different types of monomers change material property to tough</span></div>
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<div><span style="text-decoration: underline; color: #333333;"><a style="color: #333333; text-decoration: underline;" href="https://formlabs.com/media/upload/Castable-SDS_yzC8bun.pdf">castable</a></span></div>
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<div><span style="text-decoration: underline; color: #333333;"><a style="color: #333333; text-decoration: underline;" href="https://formlabs.com/media/upload/Flexible-SDS_eSMv2T6.pdf">flexible</a></span> <span style="color: #999999;">early version have similar material property. black pigment added in the newest version</span></div>
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<div><span style="text-decoration: underline; color: #333333;"><strong><a style="color: #333333; text-decoration: underline;" href="https://formlabs.com/media/upload/A-Guide-to-Post-Curing-Formlabs-Resins.pdf?mkt_tok=eyJpIjoiT1dKaE9UUTNNR1JqTkRBMiIsInQiOiJyMFVMNnVCT0NOSlJKQWJRZGFET1VwdVI1dHZSQzFTUzhRQVB0V0k3ZXBRbXdqZmhseU1VMWFjQTdPNHRYWVNaOHVJZEVvWGZGVEhhNFFqVWdta0tnQUpqXC96YWxxQUpaS2xUODlpTkhwVDRkNGNwRWdncWJ3QzZrdmppaXlUT2UifQ%3D%3D">Post Curing</a></strong></span></div>
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<div><span style="color: #333333;"><strong>Green States</strong></span></div>
<div><span style="color: #999999;">While they’ve reached their final shape and form, the polymerization reaction is not yet driven to completion, so are not fully set.</span></div>
<div><span style="color: #999999;">During the SLA 3D printing process, the components of the resin form covalent bonds. This provides high degrees of lateral strength, but the polymerization reaction is not driven to completion. Rather, the print process is modulated in a way that keeps the layer in a semi-reacted state called the “green state.” This green state differs from the completely cured state in one very important way: there are still polymerizable groups on the surface that subsequent layers can form covalent bonds with.</span></div>
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####<u><span style="color: #ff6600;">Fun</span> <span style="color: #333333;">Things to do with Desktop SLA</span></u>
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<div><span style="color: #333333;"><strong>(smoothness, watertightness, UV exposure)</strong></span></div>
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<div><span style="color: #333333;">Lens, <span style="text-decoration: underline;"><a style="color: #333333; text-decoration: underline;" href="http://amosdudley.com/weblog/SLO-Camera">100% 3D printed Camera</a></span> (<a style="color: #333333;" href=" https://formlabs.com/blog/photos-from-a-3d-printed-camera/ ">Photos</a>)</span></div>
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<div><span style="color: #333333;"><a style="color: #333333;" href="https://formlabs.com/blog/3d-printing-transparent-parts-techniques-for-finishing-clear-resin/"><span style="text-decoration: underline;">shiny transparent objects</span> </a></span>(clear coating, soak in epoxy, soak in resin. <span style="color: #999999;">Designers like me waste same amount hour of the printing trying to make them clear</span>, <span style="color: #ff0000;">Not Fun </span>experiments)</div>
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<div><span style="color: #333333;"><span style="text-decoration: underline;"><a style="color: #333333; text-decoration: underline;" href="https://support.formlabs.com/hc/en-us/articles/115000018024-Using-Castable-Resin">Jewelry</a></span> <span style="text-decoration: underline;">(<a style="color: #333333; text-decoration: underline;" href="https://youtu.be/BX8w-GUPz1w?t=8m">investment casting</a>) </span></span></div>
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<div><span style="color: #333333;">fluid channel (drainage problem)</span></div>
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<div><span style="color: #333333;"><span style="text-decoration: underline;"><a href = "printedOptics.pdf"> light channel</a></span> </span></div>
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<div><span style="color: #333333;"><span style="text-decoration: underline;"><a style="color: #333333; text-decoration: underline;" href="https://formlabs.com/media/upload/Formlabs_OpenFL.pdf">open FL</a></span> <span style="text-decoration: underline;">(<a style="color: #333333; text-decoration: underline;" href="https://github.com/formlabs/openfl">gitHub</a>)</span></span></div>
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<div><span style="color: #333333;">single-line lithopane</span> <span style="color: #999999;">black resin 1 layer on acrylic board</span></div>
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<div><span style="text-decoration: underline;"><a href="https://info.pcboard.ca/uv-led-pcb-exposure-build/"><span style="color: #333333; text-decoration: underline;">Expose pre sensitize pcb</span> </a></span>(<span style="color: #999999;">if you want to live longer don't try it: Chemical Lamination that will resolve in water after UV exposure, rest of the lamination act like protective film during etching process. Soak it in Ferric Chloride and uncovered part will be etched. Ingestion of <strong>ferric chloridecan result in serious morbidity and mortality.</strong></span> )</div>
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<div><span style="text-decoration: underline; color: #333333;"><a style="color: #333333; text-decoration: underline;" href="https://docs.google.com/spreadsheets/d/1GOB0cCpFdja8ZRXWzOQFaYb6GP7ySc3FDqEgjmnik8M/edit#gid=85404480">save money</a></span></div>
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#### Formlabs
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<div><span style="text-decoration: underline; color: #333333;"><a style="color: #333333; text-decoration: underline;" href="https://formlabs.com/blog/interactive-tour-form-1-3d-printer/">Form 1</a></span></div>
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<div><span style="text-decoration: underline; color: #333333;"><strong><a style="color: #333333; text-decoration: underline;" href="https://support.formlabs.com/hc/en-us/articles/115000307950">Form 2</a></strong></span></div>
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<div><span style="color: #333333;">Curing</span></div>
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<div><span style="color: #333333;"> Violet Laser (<span style="text-decoration: underline;"><a style="color: #333333; text-decoration: underline;" href="http://slac.stanford.edu/pubs/slacpubs/15250/slac-pub-15357.pdf">405nm</a></span>, Max Output: 250 mW <strong><u><a style="color: #333333;" href="http://www.lasersafetyfacts.com/resources/Spreadsheet---laser-classes.pdf">Class</a> <a style="color: #333333;" href="https://en.wikipedia.org/wiki/Laser_safety#Class_1">1 Laser Product</a></u></strong><u> </u> ) <strong> </strong></span><span style="color: #999999;">class 2: laser pointer class 4: LaserCutters without full enclosure</span></div>
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<div><span style="color: #333333;">Optical Path </span></div>
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<div><span style="color: #333333;"> galvo, mirrors, Optical Window</span></div>
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<div><span style="color: #333333;"> Wiper </span></div>
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<div><span style="color: #333333;">for optics eliminate unwanted refraction, semi-solid green state in tank mix the resin and remove any small parts of the print that stick to the bottom of the tank.</span></div>
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<div><span style="color: #333333;">aerate the silicone layer for more successful peeling process</span></div>
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<div><span style="color: #333333;">Peeling </span></div>
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<div><span style="color: #333333;">elastic silicon layer on resin tank ( clouding from peeling chemical or mechanical worn? Can I tear it down and poor smoothon and reuse it)</span></div>
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<div><span style="color: #333333;">peel motor (Verticle tilting form1, sliding for form2)</span></div>
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<div><span style="color: #333333;">tank carrier</span></div>
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<div><span style="color: #333333;">Refill</span>
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<div><span style="color: #333333;">level sensor</span></div>
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<div><span style="color: #333333;">thermopile</span></div>
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####<span style="text-decoration: underline;"><strong><a href="https://www.3dhubs.com/knowledge-base/3d-printing-geometry-restrictions">Desktop Printer Limitation </a></strong></span>
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<div><span style="color: #333333;">Build Volume</span></div>
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<div><span style="color: #333333;">Material Flexibility</span></div>
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<div><span style="color: #999999;">Inverted SLA comes with its own set of limitations. Due to the peel forces affecting the print when it’s separated from the surface of the tank, the build volume is limited, and larger support structures are required to keep the part attached to the build platform. Peel forces also limit the use of more flexible materials—Shore hardness below ~70A, because the support structures become flexible as well.</span></div>
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<div><span style="color: #333333;">Print Orientation</span><span style="color: #999999;"> (show and tell)</span></div>
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<div><span style="color: #333333;">Maintenance</span></div>
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<div><span style="color: #333333;">resolution ( x,y 140 microns <span style="text-decoration: underline;"><a style="color: #333333; text-decoration: underline;" href="https://en.wikipedia.org/wiki/Angular_resolution">Rayleigh criterion</a></span>, z 25 microns)</span></div>
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#### Other SLA laser/DLP/LCD Machines:
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<div><span style="color: #333333;"><em><u>Desktop:</u></em></span></div>
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<div><span style="color: #333333;"><em>Laser:</em></span></div>
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<div><span style="color: #999999;">The Projet 1200</span></div>
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<div><span style="color: #999999;">Ember</span></div>
<div><span style="text-decoration: underline; color: #999999;"><a style="color: #999999; text-decoration: underline;" href="https://www.uniz.com/">Uniz Slash OL (Uni-Direction-Peeling)</a></span></div>
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<div><span style="color: #333333;"><em>DLP (usually near-UV projector):</em></span></div>
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<div><span style="text-decoration: underline; color: #999999;"><a style="color: #999999; text-decoration: underline;" href="https://www.3dsystems.com/fabpro">FabPro 1000</a></span></div>
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<div><span style="color: #999999;"><span style="text-decoration: underline;"><a style="color: #999999; text-decoration: underline;" href="https://www.kudo3d.com/titan2-and-titan2-hr/">Kudo3D</a></span> (<span style="text-decoration: underline;"><a style="color: #999999; text-decoration: underline;" href="https://www.kudo3d.com/understanding-kudo3d-psp-resin-container/">Passive Peeling</a></span>)</span></div>
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<div><span style="color: #999999;"><span style="text-decoration: underline;"><a style="color: #999999; text-decoration: underline;" href="https://www.gizmo3dprinters.com.au/3d-printers">GIZMO3D</a> </span>(405nm Violet Projector)</span><a href="https://www.gizmo3dprinters.com.au/3d-printers"><br /></a></div>
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<div><span style="color: #333333;"><em>LCD:</em></span></div>
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<div><span style="color: #333333;">UV light Source + LCD <a style="color: #333333;" href="https://hackaday.io/project/21461-low-cost-open-source-lcd-based-sla-3d-printer">(<span style="text-decoration: underline;">DIY</span>)</a></span></div>
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<div><span style="text-decoration: underline; color: #999999;"><a style="color: #999999; text-decoration: underline;" href="https://youtu.be/5YrUQOYLoK0?t=3m44s">Anycubic Photon</a></span></div>
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<div><span style="color: #333333;">Daylight-Sensitive Resin Required (Hard to work with):</span></div>
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<div><span style="text-decoration: underline; color: #999999;"><a style="color: #999999; text-decoration: underline;" href="https://makezine.com/2017/10/26/ono-3d-printer-in-action-at-maker-faire-new-york/">ONO 3D</a></span></div>
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<div><span style="text-decoration: underline; color: #999999;"><a style="color: #999999; text-decoration: underline;" href="https://photocentricgroup.com/lchr/?v=7516fd43adaa">The Liquid Crystal</a></span></div>
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<div><span style="color: #333333;"><em><u>Industrial: </u></em></span></div>
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<div><span style="text-decoration: underline;"><span style="color: #999999; text-decoration: underline;"><a style="color: #999999; text-decoration: underline;" href="https://www.3dsystems.com/3d-printers/prox-950">proX 950</a> </span></span><span style="color: #333333;">right side up </span></div>
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<div><span style="color: #999999;"><span style="text-decoration: underline;"><a style="color: #999999; text-decoration: underline;" href="https://www.prodways.com/en/industrial-3D-printers/">Prodways</a></span> </span><span style="color: #333333;">DLP</span></div>
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#### Why not SLA
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<div><span style="color: #333333;">Why <span style="text-decoration: underline;"><strong><a href ="../dlp/index.html">DLP/LCD</strong></span>: shorter curing time per layer. Smooth Surface finish sacrificed. resolution not necessarily</span></div>
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<div><span style="color: #333333;">Why <span style="text-decoration: underline;"><strong><a href ="../clip.pdf"> CLIP </a> </strong></span>: No more peeling </span></div>
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<div><span style="color: #333333;">Why <span style="text-decoration: underline;"><strong><a href ="../multiphoton/index.html">Multi-Photon</strong></span>: Overcome the limit of <span style="text-decoration: underline;"><a style="color: #333333; text-decoration: underline;" href="https://en.wikipedia.org/wiki/Angular_resolution">Rayleigh criterion</a></span>.</span> <span style="color: #999999;">Based on the limitation of optical diffraction, generation of Airy Pattern. IR have larger wavelength so less diffraction, Multi-photon technique require much higher photon density to triger TPA(two-photon absorption) to achieve polymerization</span></div>
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