Rapid prototyping is a set of various techniques that is usually used for fabricating a model or a sample using 3D computer aided design. The rapid prototyping allows prompt and effective collection of data necessary to produce a sample or a particular detail. Historically, the method was used to convert drawings into fabricated samples and details. However, the entire group of techniques is comparatively recent, as the first available options became available with the advancement and penetration of digital machines. The development in rapid prototyping is a result of progressing technological advancement and a high demand in machine tool manufacturing.
The most popular technique that is currently used in high demand is Stereo-Lithography, also known as SLA. The main principle of its function is to perform prototyping “based on selective polymerization of a photosensitive resin using ultraviolet light” (“Services/Rapid Prototyping” n.d.). The method utilizes an ultraviolet laser beam that is concentrated over “the top layer of photosensitive resin contained in a vat” (“Services/Rapid Prototyping” n.d.). The beam changes its position and, as it moves, it takes the coordinates of the sample in axes X and Y. It helps polymerize the sample within the established boundaries of a specific section. In the end, the cured layer of polymer goes down backed by a platform that is assigned to it. It helps a new layer of resin cover the cured layer.
The key advantage of the method is that it allows achieving high accuracy in samples production. Therefore, it helps industries to produce more efficiently and flawlessly. It also stimulates the increase in industry presence and market share. The method has an excellent surface finish and is capable of fabricating thin walls and high detail. However, the method has some disadvantages as well. It requires post-curing and uses materials that can be scarce (photo polymers). Some support structures are required. The process is almost impossible to perform with support structures removed. It is possible that some curl, shrinkage and war page may appear as a result of the phase change. The method is quite cost-consuming though pretty efficient in time. Under careful observation of safety rules, the method does not represent any significant threat to the health of people and the state of the environment.
Another well-known method is called Selective Laser Sintering (SLS). The main feature of the method is in melting and fusing of the powdered material by a special high power laser beam on the selective basis. The powder is collected by a counter-rotating roller and placed to the designated areas on the table in certain amounts. Then, a laser beam fuses the powder and places it in the required section using a cross-hatching motion. A special table is adjusted according to the necessary thickness of the layer. Later, the roller performs same operation while building the second layer. Some powder remains unsintered and is used as the support for overhanging portions. Any subsequent layers may need it.
The key advantage is that the prototypes, fabricated using this method, are completely porous (normally they have 60% density compared to model samples. Thus, they impair their surface finish and strength. The method may be used for fabricating samples of various materials. It is also more progressive than SLA as it needs no post curing. It is pretty efficient in costs and time and does not require support structures as an obligatory part of the process. However, it has some limitations. Surface finish is rough compared to the previous method. Complex operation and many variables make the process difficult. Material changeover is complicated compared to any other methods. It requires post processing and finishing preparations.
The third most used method is called Fused Deposition Modeling (FDM). This technique is mostly based on melting and selective disposition of “a thin filament of thermoplastic polymer (ABS – engineering and medical grade – plastic, Polycarbonade and investment casting wax)” (“Services/Rapid Prototyping” n.d.). Each layer is made in a cross-hatching fashion. The selected material is being provided in a wire form which is supplied in sealed spools. This wire is placed in the FDM head. This head moves in the axes X and Y in zigzag movements and produces each layer one by one. The support materials are needed and usually it is a table that moves down after the completion of each layer. However, the powder may be a serious concern for health issues.
The method has many advantages. It does not require post curing and is environmentally friendly. It is available for the wide range of materials and allows free material changeover. It is very economical that makes it very cost-effective. However, it is not recommended for using by fabricating small features and details with thin walls. Its surface finish is as rough as in the previous method. The FDM requires support materials and some support design, removal or integration is very complicated. Z-axis is weak and the method is very time-consuming while working on large, dense parts. However, it does not have any serious concerns about health risks.
The 3D printing process is a very recent but extremely perspective method . It is extremely cost effective and very fast. However, the equipment may seem expensive, the cost analysis of the entire process shows that it is very effective. Moreover, the promptness of the production can cover expenses. It is also capable of providing colorful parts. The idea is in ‘printing’ sections using powder. It is placed in layers that appear to one another. Using the special inkjet print head, the printer sprays a binding solution of the powder. Within seconds the layer is ready, and starts from the beginning. Therefore, 3D printing function is based on a few steps, including spreading powder, spraying binder, built completing and removal of the excess powder. It is absolutely safe for human health and is environmentally friendly. 3D printing has a number of advantages that makes it number one choice in the rapid prototyping (“Services/Rapid Prototyping/3D Printing Process” n.d.).
In conclusion, it is worth to mention that rapid prototyping technologies are on the rise. One changes another and becomes more effective, efficient and time-saving. A design engineer currently may use a wide variety of methods which he or she can select based on his or her own expectations about the results. SLA, SLS and FDM methods all have their own advantages and disadvantages and a design engineer should select them based on the characteristics of the prototyped product. The first one may be a threat to people as it works with a powder that can be spilled. Other methods are more advanced and definitely have more pros than cons.
Among them all, the most striking and commonly used method of rapid prototyping is 3D printing that has recently received its popularity. 3D printing offers the fastest, the easiest and the most effective way of fabricating details and samples of high quality of various materials. It also may allow changing color. 3D printing has already been used in various industries, including medicine, so that its usage in engineering is almost inevitable. Engineers can build their samples with less effort, but much more detailed and significant results.
References
Services/Rapid Prototyping. (n.d.). Protosys Technologies. Retrieved from http://www.protosystech.com/rapid-prototyping.htm
Services/Rapid Prototyping/3D Printing Process. (n.d.). Protosys Technologies. Retrieved from http://www.protosystech.com/rapid-prototyping-3d-printing.htm
