Stereolithography is often used for prototyping parts. For a relatively low price, Stereolithography can produce accurate prototypes, even of irregular shapes. One of the advantages of stereolithography is its speed; functional parts can be manufactured within a day.
Printing time can last anywhere from hours to more than a day. Although stereolithography can be used to produce virtually any synthetic design,  it is often costly, though the price is coming down. Resolutions of. Another disadvantage is that the photopolymers are sticky, messy, and need to be handled. Newly-made parts need to be washed, further cured, and dried. From Wikipedia, the free encyclopedia. Retrieved Formlabs, Inc. Retrieved 26 December National De La Propriete Industrielle.
Primante 3D. Savla Associates.
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- History of stereolithographic processes.
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Archived from the original on 14 February Retrieved 10 August Virtual and Physical Prototyping. Asberg, G. Blanco, P. Bose , J.
stereolithography: مواد عمليات ، و التطبيقات: Paulo Jorge da Silva Bartolo: dinachstithecoun.ml: Amazon US
Garcia-Lopez, M. Overmars , G. Toussaint , G. Wilfong and B. Moon, Jimmy Hai, and Carlo Paventi. Retrieved 3 August More specifically, as the print platform lowers itself into the resin glass tank, an ultraviolet laser light, from underneath the see-through tank, shines on it. For this reason, SLA is sometimes called the laser 3D-printing technology. Exposed to the laser light, the resin cures, solidifies and sticks to the platform. As more resin is exposed to the laser light, the pattern is created and joins the layer above.
As more and more layers are being created, the build platform slowly -- very slowly -- moves upward, finally pulling the entire object out of the tank as the print process is finished. Acta Oto-Rhino-Laryngologica Belgica. Reproduction accuracy". Medical Modelling: the application of advanced design and development technologies in medicine. Cambridge: Woodhead Publishing Ltd. Journal of Oral and Maxillofacial Surgery. Retrieved 7 October British Journal of Plastic Surgery. October Pediatric Radiology.
Live Science. Purch Group. Proto Inc. Retrieved 22 June Luma 3D Print. Infospace LLC.
Retrieved 17 December Digital Trends. Each sliced layer is saved as a digital mask image, which is then projected usually by a digital micromirror device DMD to cure a thin layer of liquid resin [ 10 — 15 ]. A good property of the top—down projection approach is that top surface of the cured layers is free, making it always feasible to recoat a new layer of liquid resin on top of the cured layer.
However, when the needed new layer of liquid resin becomes thin, the recoating process becomes more challenging and sometimes even impossible, because of the liquid viscosity and surface tension. A resin recoating process based on a sweeper is usually required to flatten the top surface.
For low-viscosity resins, a deep-dip recoating approach with a long waiting time can also be used to replace the surface sweeping process. As a cured layer is constrained by the tank surface, it is found that the separation of the cured part is a critical issue, especially when it has microfeatures. The fabricated microstructure can be broken easily during the layer separation process. Hence, the adoption of such bottom—up projection approach in microstructure fabrication is greatly limited due to the layer separation.
We tried to minimize the resin refreshing time by utilizing the bottom—up projection configuration and a single-layer movement separation approach. It is found that a large separation force may occur and bubbles will be generated during the separation process, especially when a small layer thickness and a fast separating speed are used. Therefore, a 2-mm thick flexible layer of polydimethylsiloxane PDMS, Sylgard from Dow Corning, Midland, MI is coated on the bottom surface of the liquid vat to assist the separation [ 16 , 17 ].
After projecting a mask image through the bottom surface of the liquid vat for a certain time and curing a layer of resin, the platform is moved up with a proper velocity along the Z direction by a certain distance. Enough waiting time is necessary to ensure the complete filling of liquid resin in the gap with no bubbles existing. Therefore, to achieve a fast building process, the process parameters that determine resin recoating are critical, which are investigated in the paper including the moving-up distance and the delay time for complete filling of liquid resin. A long waiting time and a big moving distance would guarantee a complete filling of liquid resin in the gap; however, the building time will be longer.
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Hence, it is desired to identify the shortest waiting time and smallest moving distance in order to achieve a fast fabrication speed. To identify the minimum waiting time needed to guarantee a complete filling of liquid resin, a prototype has been developed, as discussed in Sec. Cubes with various sizes are built by using different waiting times and moving distances for a commercial resin SI from EnvisionTec with a viscosity of cP.
For example, Fig. If the built parts have holes or deep shadows under a microscope, the waiting time is considered insufficient. Accordingly, a longer waiting time will be used to rebuild the parts. A critical waiting time for void-free curing is identified for different gap sizes. Figure 3 plots the relation between the critical waiting time, the cube size, and the Z movement distance. In all the tests, the same Z movement speed 0.
It can be observed that:. The minimum waiting time increases with the dimensional size for the same gap height, and bigger gap height results in a smaller minimum waiting time. According to the calibration tests for the preselected liquid resin, a single-layer separation and resin recoating process is developed by setting one-layer-thickness gap height and the minimum waiting time based on Eq.
Figure 4 presents the build time of a layer using the proposed single-layer movement approach. T curing is dependent on the light source, such as light intensity and wavelength, and the photo-sensitivities of the resin. The rest of the build time is used for separating the cured layer from the constrained surface and recoating a new layer of liquid resin for the next-layer curing.
As discussed before, the bottleneck for achieving a fast building speed is the resin recoating process [ 8 , 9 , 11 , 17 , 18 ]. In this study, the following methods are used:. We utilized a bottom—up projection configuration, which is widely adopted in macroscale stereolithography systems but not in micro-stereolithography systems. The platform is moved up by only a layer thickness to separate the newly cured layer and to allow resin fill in the gap, instead of using the conventional method of moving up a certain distance and then moving down to form a layer gap.
An additional waiting time after the platform movement is added to complete the resin recoating process. According to the experimental calibration in Sec. As shown in Fig. A DMD-based projection device was developed by modifying a commercial projector from Acer. In particular, optical system settings, such as the projection image focus, light contrast, and light intensity, have been adjusted or modified to project a well-focused image on the liquid resin curing plane.
A blue filter and a black mask are used to filter the light. The envelope size is 9. Note that by selecting different optics, e. It integrates the slicing, image loading, projection, and motion controlling, as shown in Fig. To calibrate the micro-manufacturing capability of the developed process, cylinders with varied diameters, and channels with varied sizes have been printed and characterized by measuring the fabricated microstructures using a precision measurement equipment from Micro-Vu Windsor, CA and comparing with the CAD model.
A contour elite 3D optical microscope from Bruker Billerica, MA was used to measure the surface roughness. The top surface of the printed cube in Fig. Other postprocess techniques such as chemical etching, post-curing, and meniscus approach can improve the precision and surface finish of fabricated objects. To verify the capability of the system on building complex microstructures or mesoscale parts with microfeatures based on the fast printing method, various tests have been carried out for different geometries.
CAD models, built parts, and the related microscopic images are shown in Figs.
Rapid Prototyping: Process and Applications
If the calculated waiting time is 0, a 0. For models as shown in Figs. Therefore, a 0. Figure 8 shows a turbofan test case.
Related Stereolithography: Materials, Processes and Applications
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