Abstract
Rapid prototyping describes techniques that designers employ in order to fabricate models of a physical product using computer aided design in three dimensions. . Rapid prototyping allows the designer to bind one layer of material to another layer using computer aided design on three dimensional frame. This report describes rapid prototyping techniques as applied in a case study. The report will pay attention to the prototyping technology used, the materials used in producing a prototype and the accuracy of the models that are produced using the rapid prototyping technology in question. One of the most prominent of these techniques is stereolithography. Since the stereolithography was introduced in 1987 as the first rapid prototype system, subsequent rapid prototyping techniques were introduced. Stereolithography uses additive manufacturing, also known as three dimensional printing technologies to produce prototypes, models patters and production parts. This is done a layer at a time by curing photo reactive resin using ultraviolet laser. Other sources with ultraviolet power can also be used in place of the laser. For every layer of the liquid photopolymer that is curable using ultraviolet laser, the laser beam from the power source traces out a cross-section made from the prototype or pattern onto the surface of the photoreactive resin. It is important to note that supporting structures are required in stereolithography. These supporting structures are meant to fasten the parts to the platform of the stereolithography elevator. Any loss in accuracy in stereolithography can be traced back to the data preparation stage of the entire process. Tessellation is used in the design stage to come up with prototypes. Additionally, loss of accuracy can occur due to the quality of the surfaces of the rapid prototypes. This case study explores the use of stereolithography in Materialise, a company that specializes in three dimensional printing and additive manufacturing. This company has used the stereolithography technique to revolutionize the automotive industry. In future, the tessellation process of stereolithography will be used to prepare three-dimensional models for the medical industry to better understand the anatomy. With increasing globalization and evolution in technology, the applications of stereolithography will only become more varied.
Introduction
Rapid prototyping is a technology that has been around since the last decade of the last millennium. Rapid prototyping describes techniques that designers employ in order to fabricate models of a physical product using computer aided design in three dimensions. Although this technology has only become available in the recent past, it has a variety of applications. Since its inception in the late 1980s where it was employed to create prototypes and models, rapid prototyping as a technology has undergone a metamorphosis. As such, this technology has helped designers to conceptualize designs of prospective products by allowing the designer by building the desired component one layer at a time. Rapid prototyping allows the designer to bind one layer of material to another layer using computer aided design on three dimensional frame (Kamrani & Nasr, 2010, Pp. 7).
Rapid prototyping is widely embraced in the engineering realm because of the benefits that designers enjoy courtesy of this technology. The technology allows designers to communicate design ideas in a fast and effective manner. Additionally, the function, design fit and forms of the designs can be effectively validated before the production starts. Designers also value this technology because it offers a lot of flexibility during the design process because of the option of running through iterations of multiple designs with ease and the fact that there are better end products and lesser design flows during production. This report describes rapid prototyping techniques as applied in a case study. The report will pay attention to the prototyping technology used, the materials used in producing a prototype and the accuracy of the models that are produced using the rapid prototyping technology in question.
Stereolithography
There are many techniques used for rapid prototyping. One of the most prominent of these techniques is stereolithography. Since the stereolithography was introduced in 1987 as the first rapid prototype system, subsequent rapid prototyping techniques were introduced. These include selective laser sintering, fused deposition modeling and laminated object manufacturing. Nonetheless, stereolithography has been to most widely used rapid prototyping technique in design and production since its introduction in 1987. Stereolithography uses additive manufacturing, also known as three dimensional printing technologies to produce prototypes, models patterns and production parts.
Materials Used
This is done a layer at a time by curing photo reactive resin using ultraviolet laser. Other sources with ultraviolet power can also be used in place of the laser. For every layer of the liquid photopolymer that is curable using ultraviolet laser, the laser beam from the power source traces out a cross-section made from the prototype or pattern onto the surface of the photoreactive resin. As the name suggests, the resin is photosensitive and van be cured using beams of ultraviolet energy. As such, when the photoreactive resin is exposed to the beams of ultraviolet energy, it cures and solidifies. The pattern that is traced is similar to that of the prototype used. Additionally the beams of ultraviolet light join the resin to the layer below. Once the intended pattern has been traced in the resin, the stereolithography elevator platform comes down by distances that are similar to the thickness of one layer (Chua, Leong & Lim, 2010, Pp. 56).
More often than not, one layer is between 0.05 millimeters and 0.15 millimeters in thickness. Once the patterns are completed on one layer, another layer is added onto the previous one, and the pattern is traced on the new layer. This is done by the use of a blade that is filled with resin. The blade that is filled with resin is swept across the crossectional of the pattern. This coats the cured resin with fresh material. When this process is repeated for the number of layers that the designer desires, a three dimensional part is formed. The complete three dimensional parts are then engrossed in a chemical bath. This is done so that the excess resin can be cleaned of the complete parts. Finally, the complete parts are cured in an oven that is heated by ultraviolet energy.
It is important to note that supporting structures are required in stereolithography. These supporting structures are meant to fasten the parts to the platform of the stereolithography elevator. The supporting structures also prevent deflection of parts as a result of gravity. Additionally, the support structures fasten the cross-sections in place. This enables them to oppose lateral pressure that results from the horizontal movements of the re-coater blade. When the three-dimensional Computer Aided Design models are being prepared, the support structures are generated automatically prepared to be used in the stereolithography machine. The support structures can also be manipulated manually before the stereolithography is started. When the process is done, the support structures ought to be removed manually from the complete product. This requirement is different from other rapid prototyping techniques that are also cheaper compared to stereolithography.
Accuracy in Stereolithography
Any loss in accuracy in stereolithography can be traced back to the data preparation stage of the entire process. Tessellation is used in the design stage to come up with prototypes. During this process, the designer uses triangles to prepare the computer aided design model. The designer can reduce the size of these geometric shapes in order to suit different desires. The reduction in size can result in differences between the surfaces approximated in the design and the actual surfaces after production. It is also of note that triangles that have no topological information, when used in preparing the computer Aided Design models tend to induce errors. These errors emanate from the gaps, overlaps and mixed normals. The redundancy in the fact that the sharedordinates in the individually recorded triangles are duplicated can also introduce errors into the model. This can happen especially when the initial triangle has errors in the dimensions. Such errors are propagated in other triangles, and by extension the complete prototype. Additionally, loss of accuracy can occur due to the quality of the surfaces of the rapid prototypes. If these parts are of poor quality, the errors are transmitted into the finished products. Some designers have sought to improve the quality of these prototypes before they are used in the production. Such attempts should be done with care, so that one does not alter the geometric shapes, and by extension the size and shapes of the prototypes (Gibson, Rosen & Stucker, 2010, Pp. 28).
This case study explores the use of stereolithography in Materialise, a company that specializes in three dimensional printing and additive manufacturing. This company has used the stereolithography technique to revolutionize the automotive industry. The use of stereolithography in this company is not limited to parts of any size. Materialise has used its extensive knowledge in stereolithography to produce large prototypes when needed. For instance, the company produces car parts that are large, like car bumpers all in one piece. The company has devised a twelve mammoth stereolithography machine that has a building platform that is longer than two meters. This means that the company can make car parts that are more than two meters in length, or shorter.
The image above shows a car anterior bumper that is prepared using stereolithography technique by Materialise. The anterior bumper is prepared all in one piece using additive manufacturing, a technique that is embodied in stereolithography. The company also provides custom made part, irrespective of the complexity or the level of detail required in preparing them. This is due to their top of the range technology and stereolithography machines.
Future applications
As noted earlier, stereolithography has evolved to influence many applications. Of late, the technique is used to prepare three-dimensional physical models that are used by surgeons in their daily routines. Additionally, stereolithography is used in combination with magnetic resonance imaging to make models in grounding of complex surgeries. In future, the tessellation process of stereolithography will be used to prepare three-dimensional models for the medical industry to better understand the anatomy.
Conclusion
Stereolithography has a wide range of applications in our contemporary society. The ability of this technique to produce results with speed makes it very applicable. Additionally, the ability of this technique to produce large parts in one piece suits the needs of different industries, like the automotive and aerospace industries. The applications of this technique also help service delivery in the medical industry through the use of medical models. With increasing globalization and evolution in technology, the applications of stereolithography will only become more varied.
References
Chua, C. K., Leong, K. F., & Lim, C. S. (2010). Rapid prototyping: Principles and applications. Singapore: World Scientific.
Gibson, I., Rosen, D. W., & Stucker, B. (2010). Additive manufacturing technologies: Rapid prototyping to direct digital manufacturing. New York: Springer.
Kamrani, A. K., & Nasr, E. A. (2010). Engineering design and rapid prototyping. New York: Springer.
