Module - DP234 Technology Author of Assignment Derek Covill. Assignment Title Rapid Prototyping

Transcription

1 Module - DP234 Technology Author of Assignment Derek Covill Assignment Title Rapid Prototyping Name Cindy Wei Ying Chen Student Number Date of Submitting - 23 April

2 Abstract This report is about to review how much do I understand about the rapid prototyping technology. From the basic question like what is rapid prototyping, how does it work to some further consideration, such as how rapid prototyping system can reduce cost, accelerate time to market, and improve the product quality. In this book, I am going to share out my experience I had by using rapid prototyping methodology on my real project. This real experience gives me a deeper understanding at many recent innovations achieved by rapid prototyping technology, including: - Advances in materials, hardware, software, part accuracy, and surface finish - Time saving in rapid prototyping - Development in rapid tooling 2

3 Introduction In the word of Michael Schrage of the MIT Sloan School of Management, For companies that genuinely care about incremental and breakthrough innovations, organizational redesign and core process re-engineering are not enough. Companies that want build better products must learn how to build better physical prototypes. Physical models and prototypes are the fundamental to improve product development and production, even though the rising interest in computer stimulation of 3-dimentional objects, and virtual reality. Next to technical properties such as security equipment, safety consideration, handling and styling are key factors for consumer to make the purchase decision. The thing is these properties can only be evaluated by physical prototypes. For this reason, to be able to create a high quality functional prototypes will remain an important element of product development cannot be replaced by digital models and analysis. This report is about the process for me understanding what rapid prototype is, and the process will include: - The research in rapid prototype - My personal experience - Critical discussion - The conclusion of the whole report Rapid prototyping is a methodology of physical objects using additive manufacturing technology. It generally refers to techniques that produce shaped part by gradual creation or addition of solid material, and it is different to fundamentally forming and material removal manufacturing techniques. The use of additive manufacturing is the machine will read from the CAD drawing that we input into the computer and then it will lays down the layers of liquid, powder or sheet material by creating the model from a series of cross sections. 3

4 Literature review History of Rapid Prototyping Industrial application of rapid prototyping as material additive manufacturing process started a decade ago. During that first decade of industrialization, additive manufacturing process has been one of the most important technique on electro physical and chemical process. Table 1: Examples of physical and chemical appearance in material removal and material addition manufacturing. Phenomena Materlal removal processes Material addition processes Chemical processes Chemical machining Electro-chemical machining Stereo-lithography (photo-pdymerisation) Laser-induced CVO Thermophysical processes Laser beam machining Plasma beam machining Electron beam machining Electro discharge machining Selective laser sintering Plasma spraying Electron beam sintering Electro-discharge depositio Liquid jet processes Water jet machinin 3D ink jet printing Solid jet processes Abrasive jet machining Powder jet laser cladding Ultrasonic processes Ultrasonic machining N/A Although most rapid prototyping processes in use today were already know in 1991, most of them were still in a development stage. In fact, we were to wait until about 1993 to see 3D systems stereo lithography process as first one, to become very successful on the market. In 1997, 1057 rapid prototyping machine were sold, which bought the total installed RP machines to some 3289 units. The processes are classified according to the type of material used, such as liquid, powder, solid layers or gas. Gas based systems are not yet available, but they are mentioned to completely together with few academic process. Even though the actual production speed of rapid prototyping process is quite slow as compared to conventional manufacturing process, like forming or cutting, the first decade of rapid prototyping development already allowed cutting down machining times by some technology. The production time could be reduced from half an hour to 3 hours only. Further development that may reduced production times even further and speed increases as those achieved in two decades of development on wiring cutting EDM. There are few examples of such developments are: application 4

5 of a rotating mirror to increase the laser scanning speed, scanning speed, multi fibre illumination in stereo lithography, and multi printing head for ink jet or 3D printing. Some attention also goes to time reduction elimination of post-processing activities. The high degree of automation makes additive manufacturing process ideally suited when aiming for short throughout time. Recent developments make it possible today to reduce the total throughput time for one off parts to one day (24hours). Such a one-day production service is offered since the end of 1997 by Belgian rapid prototyping service bureau. Today this one-day manufacturing concept allows production of concept models. Functional prototypes and functional parts cannot yet to be produced because the part s properties are subject to the limitations of the stereo lithography process used here, and because part finishing is reduced to a minimum too. However, this concept could be easily extended in the future to other rapid prototype manufacturing process able to produce high strength polymer, metal or ceramic parts and it may change basically the way production process are organised and operated. One of the success reasons of additive manufacturing in the future could well be its ability to produce complex shaped parts in materials that are hard to machine conventionally, like hard metals, ceramics, and composites. For example, the production of complex shaped plastic products without need for expansive and time-consuming special tool is injection moulding. During the past few years, excellent process has been achieved in developing new or better materials for additive manufacturing. Today, one or another additive manufacturing process can produce parts in any materials, like polymers, metals, ceramics, wood-like parts, and composites. Besides composites, many additive manufacturing processes also allow production of multi materials parts such as soft core and hard skin. Few current technologies that are popular for people to use, such as selective laser sintering (SLS), direct metal laser sintering (DMLS), stereo lithography (SLA), 3D printing (3DP) and (EDM). Selective laser sintering (SLS) Selective laser sintering (SLS) is in a fast-developing trend because of its many advantages compared with the other RP processes. Faster building speeds, wide range of materials, and simple post treatment have made SLS extension application. Selective laser sintering produces parts by fusing or sintering together successive layers of powder material. One of the strongest features of SLS is that it is able to process a very wide range of materials in a direct way, such as standard polymers, metals and ceramics, while yielding excellent material properties. However, some researchers found out the biggest problem of the metallic parts manufactured directly with SLS is that the performance and accuracy are very bad because of steps 5

6 in Z- direction producing, decrease of metal powder and high viscidity in the parts. Therefore, methods have been found and shown to be feasible for actual application through the combination of SLS and precise casting. The case study using SLS rapid prototyping - University library in Berlin The picture on the right hand side is a 3D model of the new library for the Faculty of Philology at the Free University, Berlin. The brief was to produce a stylistic model which highlighted the roof support structure of the building which would be used for exhibition display. This model was not actually used as a tool within the design process, as the building had already been built. There is a range of application can be put in the laser sintering process. This model demonstrates the major concept of technology, it is an architectural model and it weights virtually nothing. Figure1 the rapid prototype of It has very incredible strength that can be library in Berlin. generated through expert engineering design and this is designed by Foster and Partners. This is a very stiff model and it has a very complex structure, it will take weeks or months for people to make this model by hand and it will be very hard to make it accurate and precise in every aspect as a very clean model as this one. This is a very interesting example that people can do in laser sintering, and for this particular model, most range of work is architectural work. There are some artistic works that are SLS in polymers or in plastic, but also some casting work as well. Direct metal laser sintering (DMLS) Comparing the RP technologies, the direct metal laser sintering (DMLS) shows the great promise for direct production of functional prototypes and tools. The DMLS process can be performed by two different methods, powder deposition and powder bed, which differ in the way each layer of powder is applied. In the powder deposition method, the metal powder is contained in a hopper that melts the powder and deposits a thin layer onto the create platform. The powder deposition method offers the advantage of using more than one material, each in its own hopper. The powder bed method is limited to only one material but offers faster build speeds. On the other hand, the possibility of successfully sintering metal powders in CAD data will lead to a major reduction in time for the tool making. However, regarding the performance of tools it is necessary to expand the range of usable raw materials depending on the application. So far, two powder systems based on bronze and steel compositions have been developed for DMLS, which are 6

7 commercially available. Many people have been dealing with the material investigation, e.g. Klocke et al. have studied laser sintering of a mixture of copper and tin powder to create bronze parts, Greulich et al. have developed a blend that consists of a mixture of steel and bronze powders for direct laser sintering, Laoui et al. have studied laser sintering of WC Co hard metal powder, Niu and Chang have been studied DMLS of high-speed steel powders and Petzoldt et al. have introduced a hard metal base powder mixture for rapid tooling. Apart from these, some other publications have been concentrated on the fundamentals of the laser sintering process, for instance, Bunnell et al. described two metallurgical mechanisms taking loose metal powder beds and sintering it to nearly full density using a scanning laser beam. Lewis and Schlienger illustrated practical considerations and capabilities for laser assisted direct metal deposition. Stereolithography (SLA) The steoeolithography process begins with the generation of a CAD model of the desired object. Solid CAD models make the process easier, but surface CAD models that are watertight have also been used successfully. Afterwards, the boundary surface of the CAD description are formed as a connected triangles which are arrange in orders. This step is performed using as interface specification developed by 3D Systems Corporation, Valencia, California, the company that pioneered the rapid prototyping and manufacturing industry. The triangles may be as large or as small as desired. Smaller triangles result in finer resolution of curved surface and improved part accuracy through reduced inaccuracy, while larger triangles minimise the system storage requirements, at the expense of accuracy. In the general SLA prototyping, laser scanning a new layer of resin follows over the solidified layers after the elevator is lowered into the bath. After the photopolymer surface is coated, the UV laser scans the input 2D sliced data. The following processes are repeated in the same manner, resulting in the building of a 3D free form. 3D printing (3DP) 3D printing technology works by importing 3D CAD and other 3D source data into its proprietary ZPrint software. ZPrint then digitally slices the solid object into horizontal layers, or cross-sections, creating a 2D image for each layer. When ready, the user sends the cross-sections to the 3D printer via a standard network, just like an ordinary document is sent to a desktop 2D printer. This simple set-up generally typically takes less then 10 minutes. Using standard inkjet printing technology, Z Corp. 3D printers create models layer-by-layer, depositing a liquid binder into thin layers of powder. After 7

8 cross-sections are printed, excess powder is shifted away for reuse on the next model. This recycle feature helps makes Z Corp 3DP technology even more affordable. And the entire process is extremely fast - Z Corp 3D printers typically build at a vertical rate of 25mm-50mm (1" - 2") per hour. The case study using 3D printing 3D printing prototypes of toys made by a Japanese company called BanDai. Figure 2 on the right hand side shows the finished products by the BanDai company. Figure 3 indicates the CAD Work that will be input in the 3D printing machine after this drawing process. Figure 4 is the photo of machine they use to print 3D prototypes. Figure 5 shows the 3D prototype that completed by the 3D printing machine. Figure 6 and 7 (at the bottom) presents are the models that already fabricate by people. 8

9 Electro-discharge machining (EDM) Electro Discharge Machining (EDM) is an electro-thermal non-traditional machining process, where electrical energy is used to generate electrical spark and material removal mainly occurs due to thermal energy of the spark. EDM is mainly used to machine difficult-to-machine materials and high strength temperature resistant alloys. EDM can be used to machine difficult geometries in small batches. Work material to be machined by EDM has to be electrically conductive. In EDM, a potential difference is applied between the tool and the actual work piece. Both the tool and the work material are to be conductors of electricity. The tool and the work material are soaked in a dielectric medium. Generally, kerosene or deionised water is used as the dielectric medium. A gap is maintained between the tool and the work piece. Depending upon the applied potential difference and the gap between the tool and work piece, an electric field would be established. Universally, the tool is connected to the negative terminal of the generator and the work piece is connected to positive terminal. As the electric field is established between the tool and the job, the free electrons on the tool are subjected to electrostatic forces. This is how the EDM process worked. This process can be used to machine any work material if it is electrically conductive and material removal depends on mainly thermal properties of the work material rather than its strength, hardness etc. EDM electrode production can be used in rapid prototyping techniques. Any material demonstrating good electrical conductivity can be used as an electrode for EDM. In practice those materials that can be machined easily, exhibit low wear rates during EDM, and combine low resistivity with good thermal conductivity are used. Traditionally, electrodes have been manufactured from metallic materials including various forms of copper, tungsten, brass, and steel, also nonmetallic material. The conventional methods of producing the electrode profiles include stamping, coining, grinding, extrusion/drawing and, more commonly, turning/milling. The possible production techniques using RP models may be classified as either direct or indirect. For indirect manufacture a negative or inverse of the desired electrode geometry is modeled and into this a shell is generated. This shell is produced by material deposition or sheet deformation. The shell may be either backed up before or after removal from its master with a suitable resin or low melt alloy. The direct manufacturing route begins with a model, which may need to be offset or sized to allow for the applied coating thickness. This model can be coated by deposition or sheet formed, the SL model being used directly as the electrode. 9

10 Personal experience in the design process At the beginning of the whole design process, I wasn t sure what I was going to make for my rapid prototyping lectures, so I started with designed some random stuff that I might use for the actual prototyping process. I know it was a good chance that we can make our own prototypes in the university, because normally the 3D printing is very expensive in the market today. I chat with few of my course mates and asking them if they have any idea of their prototyping experiment. One of my course mates suggested me to create a more complex design, because this is a good chance to test how far this machine can do. After all the opinions from the others, I began with a jewellery stand design with complicated details. I used many square cubes to build up this jewellery stand, hope this can successfully worked in the rapid prototyping machine. What I mean worked is hopefully it is strong enough to take it out from the machine without break it when finished printing. Two days later, I found out maybe I could get the CAD Figure 8 is my jewellery drawings that I did from the previous years and see if stand design. I can use anything else rather than jewellery stand for my rapid prototyping experiment. Unfortunately, I didn t find anything that is good enough to put into the 3D printing process. Finally, I decided to make a prototype which is also the project on my dealing with now, even though I know this product is not going to be a very complex design, but at least there is a good reason for me to do this as it is what I am working on at the moment. My plan for this 3D printing experiment was sketched down my design idea, drew it on the soildworks, talked to friends about my design to see what they think and then talked to lecturer to see if the product is in good condition in order to print it out through the 3D printer. From my personal experience, I found out the benefits of rapid prototyping are the completely manufacturing process is faster, the production costs less, and the quality is improved. For my own product which is size around 100mmx100mmx100mm, it only took one night to do it or maybe even shorter. Normally, if I would like to make it by myself, it might take me two to three days to make it and it won t be as pretty as the rapid prototype. Quality Role I personally think the quality is improved through the use f rapid prototyping and manufacturing. There are certainly a number of reasons to explain why quality should be advance. First, more time is available to make and test prototypes. This allows the designers to find weakness and failure modes early enough to address them in the final design. Second, more time can be spent in exploring alternate 10

11 designs that improve reliability, ease of operation, and overall customer satisfaction. Third, designs can be finalised much later in the process, ensuring that the latest advances in technology can be applied to the product. And fourth, designers enjoy a continuity process, including rapid feedback on design concepts. This enhances designers ability to dwell on identifying problems and finding solutions, while still remaining on schedule and within budget. Recently, a hot topic in many business publications has been rapid time to market. It has been determined that being six months late to the market relative to your competitor can sacrifice as much as 30% of the available profit from a given product life cycle. By speeding up the product development process, RP contributes to faster product launch and potentially higher profits. Another profitable is that potential customers can test the products being developed at an early stage of product evolution. It is a good advantage to be assured that the product being introduced truly meets customer needs, preference, and expectations. This is why rapid prototyping and manufacturing is so important to the market today. Product Cost Rapid prototyping and manufacturing contributes to reduced manufacturing costs. Design for assembly and design for manufacturability are two key ways in which RP can help control expenses. By addressing these issues in the earliest stages of product development, production supervisors, and others are given a basis for reaching agreement on initial design criteria. The final can then reflect the highest level of thinking with respect to ease of assembly, reducing part count, and minimizing seller quotes for components and subassemblies. The process I went through to get a rapid prototype After decided what I would like to make for my rapid prototype, I started to draw a CAD model of a reading table which was my design for the other project. I think I am quite easy to get on with drawing models on the Solidworks because I need to used this program nearly every day, so it didn t take me for a long time to drew this product. The only problem I found when I was drawing the model is what my rapid prototype is going to look like if I finished my CAD drawing in an assembly mode but not part mode, especially my product was going to be like a adjustable table but not a static one. The answer was I am not sure. So I went to talked to my lecturer if it is possible that I can make my prototype in parts separately and assembly them afterwards. And he said ofcourse, you can. Before I put my CAD drawing into printing machine, another problem I found is the thickness and size of my model. I didn t think of any failure from the size of the model might occurred when I was doing the CAD drawing. The lecturer said the thickness of my product was too thin and the whole thing might break while he take 11

12 out the model from the machine for us, so he suggested me to make the all the components thickness thicker. I found out this really helped, because few of my course mates broke their models when the models being taking out and most of the reason is because the thickness was so thin. The coming stage is transferring the CAD drawing to the Z-print program and there are two ways to do this. I could either save my models into a STL file or WRL file in Solidworks. If I wanted a plane model then I save it as STL file, but if I wanted a coloured model then I need to save it as a WRL file. I chose to make a plane one because I haven t decided what colours I am going to use for my product at that moment and I didn t want to waste the ink. When the model was opened in the Z-print program, I needed to adjust all my parts in the good position which means make them closer to each other but without touching each other in order to save more space for the other people to print at the same go. After all the things was setting up alright in the Z-print program, then pressed Print, the machine stared printing. After the model was finished printed, then it needed to be clean out the remaining materials by a brush before taking the models out, and then I need to wore gloves and a mask to get ready to put the resin on the model in order to varnish the product. Leaved the model to dry for overnight, the next day I assembled all the parts together and then the whole model was done. Discussion The model looks good but not exactly the same as I expected, some parts size are slightly different to what I thought it would be. The holes for the turning parts are too small for me to assemble the rail into it. In addition, because the holes are not the right size, so I broke the few rails when I was trying to put the rail part into the hole to make it adjustable. At the post processing stage, I didn t put enough resin on my model and this lead to a problem is my product end it up with the surface finishing material very easily coming off, and also the whole model wasn t rigid enough. Figure 9 the components of my model. 12

13 Critical Discussion From thousands of years of humankind history, we can see that most of our civilization was founded on the base of forming/shaping technology, and actually the history of humankind civilization has been pushed on by the evolvement of forming/shaping technology. And we can conclude that our beautiful future will benefit a lot from the modern forming technology which we are now absorbing in, such as rapid prototyping and manufacturing (RPM) and its other techniques. Modern forming/shaping science is the science that researches on orderly organizing the materials into a three-dimensional (3-D) part with determined shape and functions. According to the method for organizing the materials, it can be divided into four basic categories: (1) Removal forming an ancient method to form a part by orderly removing unnecessary materials from original rough model, such as traditional lathing, milling, planing, drilling, grinding, laser cutting, and electrical discharge machining (EDM). It is now the most important processing method. (2) Forced forming an ancient method to form a part by imposing external constraints like a cavity or exerting pressures onto the material stuff, such as traditional forging, casting, and powder metallurgy. It is mostly used for roughcast while some like precision casting and precision forging are aslo for direct end-forming of net or near net shape. (3) Dispersed-accumulated forming a novel method to form a part by first dispersing the materials (gas, liquid or solid state) into points or lines, and then piling up them into layers and bodies. (4) Growth forming the forming process of all natural organism bodies (plants, animals, etc), mostly relied on the proliferation and self-assembly process of materials like cells; for example, the spiral fractal geometry of a trumpet shell is developed from its natural growth process. It is now the most complicated and highest forming level. Since the late of 20th century, the original removal and forced forming methods have been hard to meet all demands in increasingly competitive manufacturing market of globalized economy, and a personalized and flexible forming method has been required. On the other side, computer-aided design (CAD) technology, laser technology, numerical control technology, and material technology have been rapidly developed. Thus in this background, a new subject of rapid RPM technology came out, which is the general term for all technologies based on the dispersed- accumulated forming principle. It disperses the process of forming a complicated 3-D physical part into forming a series of two-dimensional layers, and then piles up the layers together. This 13

14 is a typical order reduced and material-increased forming technology. It can complete forming a 3-D entity with a complicated structure directly controlled by its digital CAD model. This dispersed-accumulated forming principle has been mentioned long ago. In 1892 s US patent (No ), Blanther proposed a method to compose a topographic map by layered manufacturing, and after 1950s hundreds of RPM-related patents were proposed. However, the fundamental developments came out in 1980s. The most known is that Charles W Hull was inspired by ultraviolet (UV) light-curing resin and proposed the stereolithography (SL) technology (US patent, No ) in 1986, based on which 3D System Corporation produced the first modern rapid prototyping machine (SLA-250) in Since then, tens of RPM technics have emerged out, and there were 274 patents registered in US during period. As issued in Terry Wohlers s annual RPM report, it has already achieved a lot in many fields. And the GARPA (global alliance of rapid prototyping associations) was set up and have been promoting this technology into much wider and deeper applications. After two decades of development, RPM have stepped into the maturity. Many new technics came out, and a lot of measures were developed to promote the RPM. Though it was originally used as an assist method for developing the new product in the process of design, test, and assembly, now it can directly create functional object like metal parts. It is also applied in nano-/mirco- fabrication and biomanufacturing as a powerful forming method. The use of rapid prototyping: 1. Concept models a. It can be used in industrial design and marketing demonstration b. Improve the speed of product confirmation by high quality of rapid prototype c. 3D models are more reliable, and easier to understand customer needs 2. Rapid tooling ( Soft tooling, Bridge tooling, and Hard tooling) a. Suitable for small amount of industrial manufacturing b. It is faster to make the model( time saving) c. The polymer can be used in this process, such as Polyurethanes, ABS,PP, and Nylon 3. On the medical propose a. To stimulate before operation b. The model for healing the damage region c. Educational models d. The mould of teeth 14

15 4. Jewellery design a. Reduce production process b. Decrease the mistakes of manufacturing process and the waste of materials c. Understanding the ability of machine in the production process I believe there is a good reason that rapid prototype is becoming more and more important in the world. Prototyping helps us to design better experiences. Dan Harrelson who wrote an article about rapid prototyping tool, he said, We are working in a world of rich, dynamic interfaces, both on the web and on our devices. The experiences we design are interactive, responsive, and have emotion. Prototypes allow us to articulate the feeling and function of a design in a way that a wireframe does not. Conclusion In this report, I have shown the rapid prototyping process, from the beginning of how did I make a decision for something ought to be done and the final realization of this concept in a piece of a prototype software. I have shown this prototype software is not only a machine that you can only print a 3D model, but the main outcomes are this 3D model can help us to community with the others, easily finds out the weakness of the product, and the size of the model is more accurate created by the 3DP machine. One of the central issues in rapid prototyping is flexibility, in both the designer s approach and the capabilities of the development system. You cannot assume that anything is written in unchangeable. Therefore, you always need to be roughly estimating the stability of each of the tasks you are performing. Another thing is the rapid manufacturing coupled with the cost analysis. Reductions in machine and material cost coupled with increases in machine throughput and material proper will help rapid manufacturing to grow. The cost analysis combined with opinions generated that small parts with high geometric complexity to be made in relatively small volumes are the most suitable candidates for rapid manufacturing. Finally, my effort in learning rapid prototyping will never be made obsolete by developments in computer science, at least not until these developments do away with the need for programmers entirely. The whole rapid prototyping process has giving me information I need to successfully deal with the realities of modern software design, and allow me to use the tools and techniques available to me to the limit of their capabilities. 15

16 Reference Alan, A., Phillip, D., and Richard, C (1996). Using rapid prototyping to produce electrical discharge machining electrodes. Rapid Prototyping Journal, pg Anna, K (1995). Rapid developments in rapid prototyping. Assembly Automation, pg Anna, K (1997). Features Rapid growth for rapid prototyping. Assembly Automation, pg Anna, K (2000). Rapid prototyping gains speed, volume and precision. Assembly Automation, pg Arnaud, B., Paul, B., Christian, V., and Philippe, R (2000). Rapid prototyping of small size objects. Rapid Prototyping Journal, pg Ashok, K and Anirban, D (2003). Investigation of an electrophotography based rapid prototyping technology. Rapid Prototyping Journal, pg Carol, A (1997). Rapid prototyping and manufacturing in the USA. Rapid Prototyping Journal, pg Charles, H., Michael, F., Yehudah, B., Roy, S., Emanuel, S., Allan., L and Terry, W (1995). Rapid prototyping: current technology and future potential. Rapid Prototyping Journal, pg Dan, H (2009). Rapid Prototyping Tools. Adaptive Path Blog, filed under Experience Implementation, Prototyping. Dilip, I., Abhay, K., Shashank, T., and Amol, T (2009). Rapid prototyping a technology transfer approach for development of rapid tooling. Rapid Prototyping Journal, pg Hongjun, L., Zitian, F., Naiyu, H., and Xuanpu, D (2003). A note on rapid manufacturing process of metallic parts based on SLS plastic prototype. Journal of Materials Processing Technology, pg

17 Jeng-Ywan, J., Jia-Chang, W., and Tsung-Te, L (2000 ). A new flexible layer fabrication method for the jet deposition system to accelerate fabrication speed. Rapid Prototyping Journal, pg Neal, J (1994). Rapid prototyping using the selective sintering process. Assembly Automation, pg Samuel, L and Paul, W (2002) The role of rapid prototyping in the product development process: A case study on the ergonomic factors of handheld video games. Rapid Prototyping Journal, pg Simon, G (2000). Rapid prototyping: a key to fast tracking design to manufacture. Assembly Automation, pg Y. G. Im, S. I. Chung, J. H. Son, Y. D. Jung, J. G. Jo and H. D. Jeong (2002) Functional prototype development: inner visible multi-color prototype fabrication process using stereo lithography. Journal of Materials Processing Technology, pg Kevin, J (1999). Standards for the rapid prototyping industry. Rapid Prototyping Journal, pg Kruth, J., Leu, M., and Nakagawa, T (2007). Progress in Additive Manufacturing and Rapid Prototyping. CIRP Annals - Manufacturing Technology, pg Mark, M (1990). Rapid prototyping for object-oriented systems. America, England, Bonn, Sydney, Singapore, Tokyo, Madrid, and San Juan: Addison Wesley Publishing Company, Inc. Neil, H and Phill, D (2001). Rapid prototyping for direct manufacture. Rapid Prototyping Journal, pg Paul, J (1996). Stereolithography and other RP&M Technologies: from rapid prototyping to rapid tooling. America: Society of Manufacturing Engineers. Simchi, A., Petzoldt, F., and Pohl, H (2003). On the development of direct metal laser sintering for rapid tooling. Journal of Materials Processing Technology, pg

18 Yongnian, Y., Shengjie, L., Renji, Z., Feng, L., Rendong, W., Qingping, L., Zhuo, X., and Xiaohong, W (2009). Rapid Prototyping and Manufacturing Technology:next term Principle, Representative Technics, Applications, and Development Trends. Tsinghua Science & Technology, pg