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Stereolithography (SLA)
- 1. 3/31/2021 1 K J SOMAIYA COLLEGE OF ENGINEERING, MUMBAI-77 (CONSTITUENT COLLEGE OF SOMAIYA VIDYAVIHAR UNIVERSITY) Production Engineering - II Internal Assessment – 2 Presented by: Smit Doshi- 1915123 Somrick Das Biswas – 1915124 Yashika Tank – 1915126 Siddharth Upadhyay - 1915127
- 3. INTRODUCTION •Additive manufacturing is a specific 3D printing process. This process builds parts layer by layer by depositing material according to digital 3D design data. For example, instead of milling a work-piece from a solid block, additive manufacturing builds the part up layer by layer from material supplied as a fine powder. •Rapid prototyping is the fast fabrication of a physical part, model or assembly using 3D computer aided design (CAD). The creation of the part, model or assembly is usually completed using additive manufacturing, or more commonly known as 3D printing. There are different types of Rapid prototyping (RP) available. •It includes a variety of manufacturing technologies, although most utilize layered additive manufacturing. However, other technologies used for RP include high-speed machining, casting, molding and extruding. In this presentation we will take a deeper look at Stereolithography or SLA. •Stereolithography (SLA or SL; also known as stereolithography apparatus, optical fabrication, photo-solidification, or resin printing) is a form of 3D printing technology used for creating models, prototypes, patterns, and production parts in a layer by
- 4. HISTORY •Stereolithography or "SLA" printing is an early and widely used 3D printing technology. In the early 1980s, Japanese researcher Hideo Kodama first invented the modern layered approach to stereolithography by using ultraviolet light to cure photosensitive polymers. •However, the term “stereolithography” (Greek: stereo-solid and lithography) was coined in 1984 by Chuck Hull when he filed his patent for the process. Chuck Hull patented stereolithography as a method of creating 3D objects by successively "printing" thin layers of an object using a medium curable by ultraviolet light, starting from the bottom layer to the top layer. •Hull's patent described a concentrated beam of ultraviolet light focused onto the surface of a vat filled with a liquid photopolymer. The beam is focused onto the surface of the liquid photopolymer, creating each layer of the desired 3D object by means of crosslinking (generation of intermolecular bonds in polymers). It was invented with the intent of allowing engineers to create prototypes of their designs in a more time effective manner. •After the patent was granted in 1986, Hull co-founded the world's first 3D printing company, 3D Systems, to commercialize it. •Stereo lithography's success in the automotive industry allowed 3D printing to achieve industry status and the technology continues to find innovative uses in many fields of study. Attempts have been made to construct mathematical models of stereolithography processes and to design algorithms to determine whether a proposed object may be constructed using 3D printing.
- 5. METHODOLGY •Stereolithography is an additive manufacturing process that, basically works by focusing a UV laser on to a vat of photopolymer resin. •With the help of computer aided manufacturing or computer-aided design (CAM/CAD) software, the UV laser is used to draw a pre- programmed design or shape on to the surface of the photopolymer vat. Photopolymers are sensitive to ultraviolet light, so the resin is photo-chemically solidified and forms a single layer of the desired 3D object. •Then, the build platform lowers one layer and a blade recoats the top of the tank with resin. •This process is repeated for each layer (of a certain thickness raised by the machine) of the design until the 3D object is complete. •Completed parts must be washed with a solvent to clean wet resin from their surfaces. Schematic representation of Stereolithography: a light-emitting device (a) (a laser or DLP) selectively illuminates the transparent bottom (c) of a tank (b) filled with a liquid photo-polymerizing resin. The solidified resin (d) is progressively dragged up by a lifting platform (e).
- 7. MATERIALS The liquid materials used for SLA printing are commonly referred to as "resins" and are thermoset polymers. A wide variety of resins are commercially available and it is also possible to use homemade resins to test different compositions for example. Material properties vary according to formulation configurations: "materials can be soft or hard, heavily filled with secondary materials like glass and ceramic, or imbued with mechanical properties like high heat deflection temperature or impact resistance". It is possible to classify the resins in the following categories: •Standard resins, for general prototyping oRelatively brittle •Engineering resins, for specific mechanical properties oABS-like or PP-like mechanical properties oLow thermal resistance •Dental and medical resins, for use in living beings oBiocompatible oHigh abrasion resistance oHigh cost •Castable resins oUsed for creating mold patterns oLow ash percentage after burnout
- 8. SOFTWARES The first step of SLA manufacturing consists of designing a 3D model through CAD [Computer Aided Designing] software. A lot of such software's are available in the market. Some of these are AutoCAD, SolidWorks, Fusion360, etc. The resulting CAD file is a digitalized representation of the desired object. It must be drawn according to scale, and then saved in an STL file format. The STL file format allows the SLA printer to read the CAD file. One must always recheck the STL format and select the most optimum orientation of the object to be printed. The user has the freedom to either manually add support for overhanging portions of the item to be printed, or the software can also automatically do so for the user. A common practice is to build with the biggest surface area set as the reference plane. This ensure that less material is wasted on printing supports and other auxiliary structures, that are not required in the finished product and are removed. AUTODESK MESHMAKER, FREECAD, SketchUp are various other software’s that also facilitate repairing, editing and reading of STL files.
- 9. POST PROCESSING •After finishing the layer by layer material polymerization, the platform rises out of the tank and the excess resin is drained. •A solvent (usually isopropyl alcohol also called isopropanol), is necessary in order to remove the excess non-solidified resin. •Often times, a lot of the resin is trapped within the structure. In such cases, proper arrangements such as drainage channels need to be designed beforehand. •Alternatively, the model is removed from the platform, washed of excess resin, and then placed in a UV oven for final curing. •Post-print curing enables objects to reach the highest possible strength and become more stable. •Post final curing the, object printed is cleaned properly. The support structures and other attachments that are not desired in the final product are removed. Precautions must be taken that this process of removal doesn’t damage the finished product. •Finally, sandpaper or other abrasives are used for a better surface finish.
- 10. APPLICATIONS •Product designers use this process for rapid manufacturing of representative prototype parts. This can aid visualisation, design and development of the manufacturing process ahead of mass production. •Stereolithographic models have been used in medicine since the 1990s, for creating accurate 3D models of various anatomical regions of a patient, based on data from computer scans. •Production volumes in the aerospace industry are generally large (more than 70,000 parts per year) & hence 3D printing has predominantly been used in the past as a prototyping solution rather than the manufacturing of end parts. •3D printers can produce a range of high-quality custom products and appliances at low unit costs with superior fit and repeatable results. •Jewelry professionals use CAD and 3D printing to rapidly prototype designs, fit clients, and produce large batches of ready-to-cast pieces. •3D printers are multifunctional tools for immersive learning and advanced research. They can encourage creativity and thus can be used in education. •3D printed parts have starred in stop-motion films, video games, bespoke costumes, and even special effects for blockbuster movies. And therefore, can be used in entertainment Industry.
- 11. Stereolithographic model of a denture. The structures will need to be removed in post processing Finely printed and finished SLA print SLA printing allows to print intricate objects that other processes can’t Versatility of SLA printing allows one to print a vast multitude of objects for various applications
- 12. ADVANTAGES It’s quick: A major advantage of stereolithography is that the part can be built in a relatively short period of time since curing is fast. Parts can take anywhere from a few short hours to a day or more. It’s cheap: The feedstock used in stereolithography are generally quite cheap to produce in bulk, so the powders and photopolymer resin contribute very little to the cost of the process. Therefore it is only the cost of energy for the laser and automatic platform, that is incurred during manufacturing. This cost is negligible. It aids prototyping: By creating a low-cost yet accurate model, the process can help one find potentially costly mistakes by detecting design flaws before the manufacturing process even starts. It can be a cost- effective option for low-volume production of parts and provides quick lead times for making these. It’s a multi-material process: Since its initial introduction, SLA has undergone refinement in terms of its standard processing capability, and in the range of materials that can be used with the process. In recent years there have been advances in making it a standard process for joining metal and even ceramic powders prior to them being solidified via the sintering process. This means that almost any component can now be initially formed using SLA. This means that highly complex component parts required for high temperature or highly abrasive applications can be formed without having to use expensive machining techniques. Surface Finish: While the surface finish on parts is a function of the particle size used to create it, SLA parts are renowned for having very good surface finish. High Precision: The use of a liquid starting material results in a particularly smooth surface in the case of SLA-printed 3D objects, generally making subsequent processing superfluous. The object’s precision is limited only by the quality of the system. The finer the laser’s beam diameter, the greater the precision of