APPLICATIONS OF REVERSE ENGINEERING AND RAPID PROTOTYPING TECHNOLOGY IN PRODUCT DESIGN DEVELOPMENT

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1 APPLICATIONS OF REVERSE ENGINEERING AND RAPID PROTOTYPING TECHNOLOGY IN PRODUCT DESIGN DEVELOPMENT Professor Huang Tai-Shen 1 1 Graduate Institute of Design, School of Design, Chaoyang University of Technology, 168 Gifeng E. Rd., Wufeng, Taichung County, Taiwan, 413, tshuang@cyut.edu.tw Abstract The purpose of the design project is to apply and commercialise laboratory research into a marketable product. To apply design method and the correct technological specifications to the final product, utilize comp uter aided integrated design, Reverse Engineering and Rapid Prototyping technique to complete the industry design and develop a product design strategy that can bring the product to manufacture and carry it through to commercialization. This project will present computer aided integrated design, reverse engineering and rapid prototyping techniques which were used to complete a Head Mounted Display (HMD) design-model and test the optics -system for manufacturability. The HMD is a research product developed for visualization of Virtual Reality program material. Experimental laboratory prototypes have now reached a stage of maturity at which it is realistic to define the scope of a marketable product. Key words: Reverse engineering, Rapid prototyping, Industrial design, Commercialized, Head Mounted Display 1. Introduction A product development process can be divided into six generic phases. These are: concept development, design development, engineering development, validation development, manufacturing development, and production development. One of the most tedious processes is dimensional evaluation of parts in the design development phase. Especially when designing a product that has a significant physical human interface, it often necessary to start with a physical three-dimensional form-fit model rather than with a virtual computer-based version. Initial physical modeling helps ensure proper human interface conformance. This physical 3D model can then be converted to a digital computer solid model via reverse engineering and subsequently refined into the final design, ready for production. The latest scanning-based dimensional analysis technologies not only drastically reduce the need for direct physical measurement, - freeing the engineer for more productive activities - but also increase speed, scope, and problem-solving capability. Using a Head Mounted Display as an example, a master form model that both aesthetically and ergonomically fit the human requirements of basic form, fit, and function was firstly made in modelling foam in the shop by the industrial designer. The dimensions of this model were then converted into an I-DEAS CAD solid model where the final design details were refined to completion and ready for rapid prototyping. Head mounted displays (HMD), consisting image source and collimating parts, were originally developed for critical applications in military aerospace, and now is an important equipment for simulating virtual reality (VR) [12]. A HMD consists either of a helmet and small CRTs, or of liquid-crystal displays (LCDs) in a pair of goggles. The field vision on the display screen is expanded by an optical system producing an imaginary screen that appears to be positioned several meters in front of the viewer (Figure 1). Some types are mounted on the face in the form of glasses. In the earlier stage of HMD development the units used for military and industrial purpose, ex. flight simulation, weapons and equipment maintenance were designed by engineers. [4]. This project does not go into any theoretical detail about optical systems because it was not the important factor in the design process. The HMD only serves as an example to illustrate the application of reverse engineering and rapid prototyping technology in product development process.

2 2. Design theory base 2.1 Product development theories. Recently, many theories about product development such as product route, the stage of product development, product evolution have been evolved to describe the relationship between product deployment and the need of human being in the field of product design. The critical point demonstrated by these theories, is that the product evolution as related to the natural needs of the human being is changing from needs to wants (Figure 2). Originally, the development of many products was derived from the insufficient functionality of our body. For example, we made the ladder to reach things in high place because we are not tall enough and because we cannot see far enough, so we made binoculars to enable us to see distant places. All such products were made for our needs in order to compensate the insufficient functions of our body [10]. After the products were made, we still hope that the entire products can be adapted to our body s scale, so the ladder was redesigned to expand and contract and the focus of the binoculars can be regulated, as well as the distance between the two pupils of the eyes. When the product functions are all completed, we still hope products can convey the perception, emotion and ego to increase the joy of living. Therefore, ladders are designed with the dynamic elegance of curves replacing the rigidity of the traditional straight lines, while binoculars have many different forms, textures and colours according to their functions and utilization. These are the wants of human being after we have all the products we need. The relationship between product deployment and the need of human being are based on the Maslow s Hie rarchy of Needs theory. A product to supply the insufficient function of human body. A product fit to the human s body scale and motions. A product to appear the human emotions. Create tools Easy to use Ego realized needs wants Figure 1. CyberEye CE-200W. Figure 2. The process of product deployment. 2.2 Product Commercialized process A process, in the course of which the artefact is changed from manufacture into product and then into a market commodity, is called a commercialized process. Manufacturing belongs to the research phase because it usually contains innovation, new functions, and new techniques to enhance the insufficient functions of the human body. The mass-produced product is the research result of the manufacture. Product has to offer the utilization and manipulation to provide convenient operation, so it must consider the physiological characters of human body. The commodity stage occurs when the manufacturers attempt to awaken the consumer s desire to buy by using different product design methods and marketing strategies. The commo dity must therefore have a good appearance and harmonized colours which meet the consumer s habits and the trends of fashion. All the commodity design strategies must be connected tightly with the consumer psychology for creating greater commercial profit. Manufacture Product Commodity Initial functions setup Functions examine Human system design Human Factor design Manipulation interface User Tool Task Form Objective esthetic Engineering design Engagement interface Figure 3. The relationship of product commercialized and analysis model.

3 In 1982 Kreifeldt [5] announced a user-tool-task analysis model of product design, and R. T. Lin added a form-modelling factor in 1994 (Figure 3). In fact, this model is a product-commercialized process. The manufacture stage emphasized the characters and performance of product function and the product stage focuses on the characters of user, physical function, and operation convenience. Finally, the commodity stage has to stress the cognition of aesthetic sense, psychology function, and user s personality [8]. 3. The HMD commercialized methodology 3.1 Market survey The design process for an HMD can be classified into three categories: research phase, industrial phase and consumer phase according to its functions and purposes. From the commercial point of view, the consumer phase of HMDs have a higher commercial value than the other grades. At this stage, it is important for the manufacturer to research the characteristics of similar product characters and to create a new unique product that matches an identified market niche [2]. 3.2 Understanding the product position in the market [11] The objective of product commercialization for HMDs is for consumer use. Consumer HMDs are just booming on the market, and they will have inexhaustible potential in the fie ld of technique development and functions extension in the future. Compared with product life -cycles for other consumer-electronic products, we already notice that the household HMDs are at the verge of mature stage growth stage which match X and Y generation who have independent consumption capability. These two generations are more used to buy and to operate the electronic technology products than the other generations. It is well worth it for manufacturers to develop and to set up the market position in advance. 3.4 The applications of human engineering The HMD is support by the forehead when in use. Although the electronic and optic components of the HMD weigh under 300g, the comfort and good fit to the users head shape are still very important factors to the success of the product design. Some significant conditions that should be considered when we are going to design a HMD product are that [6]:?It must have the see-through function so that the users can simultaneously observe situations in their surroundings.?the distance between the centres of the two pupils should be adjustable 52mm to 78mm. Otherwise the contact glasses must be enlarged to 20mm [3].?For users with eyeglasses, there must be at least 30mm between the eyes and the HMD to contain the user s glasses.?the weight of HMD must as light as a pair of glasses. The centre of gravity of HMD must pass through the centre of head to avoid influence of head motion.?the HMD must fit a wide range of head shapes and sizes very well, so adjustability is essential function.?no accessories or controllers should prevent operation actions. After we investigated the Sony- Galsstron and Olympus- Eye-Trek products, we found that the support area was concentrated on the nose, ears and forehead. There is a three-dimensional space similar to an inclined trapezoid from forehead incline to the ears. Therefore, if we can find the centre of gravity of this inclined trapezoid space and design a suitable support system, then we can distribute the weight of HMD and its mechanism to the support system. 4.Reverse engineering and rapid prototyping technology According to the above description a designer has to consider three important parts in order to obtain a comfortable, elegant, and usable HMD product: the form design, mechanical design, and construction design. Since time to market, function test, construction evaluation, and digital data have become such essential design factors of the design process, this project tried to develop an integrated design and manufacturing process which could be divided into

4 the following steps: concept design, manual model, shape recognition, reverse engineering, CAD model, rapid prototyping, rapid tooling, and final product (Figure 4) [7]. 4.1 Reverse engineering system Reverse engineering is a very common use in product design process which takes scanned data from an object and manipulates it to create a high-accuracy surface that can be used to manufacture a physical model. The relationship between reverse engineering and rapid prototyping applied in this project is illustrated in Figure 5. Because the design model obtained from concept design normally contains many types of surface such as quadratic surfaces and free-form surfaces, the best way to use reverse engineering technique in this project was to create a CAD solid model from a sample object made of wood. A CAD solid model from which to fabricate a prototype using rapid prototyping technology can then be created in a CAD/CAM system after a refining manipulation process. Finally, the prototype can be used to do optical system assembly testing, function testing, and simulation. Sample Mass production Figure 4. Reverse and forward engineering. 3D Measuring Mould Forming Data Processing Machining Rapid Prototyping CAD Surface construction CAM NC code STL file Form manipulating CAD Solid Model Figure5. Reverse engineering and rapid prototyping process. 4.2 Laser scanning process and creating a surface from a point cloud In general, reverse measuring machines divide into two groups: contact and non-contact machines. In this project, we used an E-Monster laser non-contact scanner (Figure 6(a)) to catch point data (Figure 6(b)). The specifications of the laser measurement machine is: 300mm*300mm scanning range, 450mm to 650mm scanning depth of field, 0.1mm to 0.2mm accuracy, 10 scanning lines/second scanning speed, and 1.2mm to 1.5mm scanning interspaces. For point cloud data processing, we used Digipoly software. In order to create a final and complete surface model, we had to rotate the sample object many times and match all point clouds obtained from the scanning to each other (a). Laser scanning machine. (b). Sample object. (Figure 6(c)). For eventually creating the final surface model we had to build curves from cross sections of the point cloud and then build the surface over the curves. All of these supplementary curves were created in the Digipoly software by cutting cross sections through the complete point cloud. (c). Point cloud. (d). Final solid model. Figure 6. Scanning equipment and data processing.

5 Then all curves were imported into an I-DEAS CAD/CAM system for final smoothing processing and the final solid model was created by using surface/solid modelling commands as shown in Figure 6(d). Next, because it originates from 3D Systems who pioneered the Stereo-Lithographic system, the solid model to be built was converted into a format dubbed the.stl file format. 4.3 Rapid prototyping (RP) system [1] A concept model of the design process (the first phase in Figure 4) was referred to as embodiment design, in which the conceptual solution is developed in some detail, problems are resolved, and weak aspects of the design are eliminated. Frequently during this step of the design it is necessary to ensure that the embodiment is in fact fit for the intended purpose. This is achieved through prototyping. Time to market refers to the time that elapses from the development of the initial products concept until the product is available to the customer [9]. Companies seek to reduce time to market by implementing concurrent engineering and by using rapid prototyping technology. Rapid prototyping is a term used to describe a number of techniques that rapidly produce solid physical models of components and products by a group of relatively new manufacturing technologies using 3D computer data. In general these technologies manufacture products by adding layers of material (or laying down material) rather than by a metal removal process (e.g. machining). In essence, rapid prototyping converts 3D CAD data into physical models without the need for special-purpose tooling. Among the better known rapid prototyping processes are Stereolithography (SL) layered object modelling (LOM) Selective laser sintering (SLS) Fused Deposition Modelling (FDM) Solid Ground Curing (SGC). Once the.stl files are verified to be error-free, the RP system s computer analyses the.stl files that define the model to be fabricated and slices the model into cross-sections. The cress-sections are systematically recreated through the solidification of liquids to form a 3D model. In CPS-250A, used in this project (Figure 7(a,b)), the output file is sliced into cress-sections, 0.2mm in thickness. Meanwhile, we have to decide all building parameters for positioning and stepwise manufacturing in the light such as building orientation, spatial assortments, necessary support structures and slice parameters. This rapid prototyping machine builds parts in a vat of photo-curable liquid resin that solidifies under exposure to ultra-violet (UV) light. The ultraviolet light scans the resin surface in the tank to draw the cross-sectional shape based on the section data. The area of the resin surface which is hit by the light is cured, changing from liquid to solid on the elevator. The elevator descends to allow the next layer to be created by the same process. This is repeated continuously to laminate the necessary number of thin cross-sectional layers to shape the final 3D model (Figure 7(c)). All of the HMD s design parts, including front cover, rear cover, eyeglass frame, nose pad structure, optical adjustment mechanism, and circuit board fixed structure were made by the same rapid prototyping process (Figure 7(d)). Then the final RP model had to pass through an assembly and optical function test. The process of simulation and demonstration is shown in Figure 7(e), and this product was exhibited at the World Fair of Electronic Products in Taipei in (a). CPS-250A. (b). Internal devices. (c). RP model. (d). HMD parts. (e). Product exhibition. Figure 7. The rapid prototyping machine, RP parts, and the final HMD product exhibition. 5. Conclusion Follow the development of micro-electronic technology, 3C products - computers, communications, consumer-electronic - will be the major products of the consumer product market. We can predict furthermore, that because this technology is in continuous development and progress, the product commercialization of the HMD will be part of the new generation of consumer-electronic products.

6 With regard to the industrial design tasks, there are no obvious differences between an HMD and the design of any other new or commercialized product. However, many researchers have raised concern about visual fatigue and the following physiological problems. These problems are well worth paying more attention to in the HMD product design process. Furthermore, how to use contemporary manufacturing methods in new product development process will play a very important role in shortening the time to market and testing assembly and functionality. In this project, reverse engineering and rapid prototyping technologies were used to assist us in designing a new HMD working prototype. Because of the limitation of article length, we cannot present our complete research of HMD product design process and all production process, but have wished to share some important product design principles and new manufacturing technology applications as exemplified by HMD product commercialisation. To examine the principles, methodologies, and theories in this paper, research must follow the practical product design of HMD. Improvement and modification of this research and HMD product design will rely on the response and feedback of consumers and end-users. Acknowledgements The author would like to thank Chou Wen-Chih for his assistance with the experiment reported in this paper and Prof. Gideon Löwy for providing helpful comments on this paper. This project was supported by the Chung-Shan Institute of Science and Technology, Taiwan, ROC. 5. Reference [1] Chua C.K. and Leong K.F., Rapid Prototyping: Princip les and Applications in Manufacturing, Johe Wiley, England. [2] Isono T., 2000, The latest technical trend and the view of HMDs, Institute Electronic, Information communication, Engng, pp [3] Iwasaki T., Akiya S., Inoue T., Noro K., 1992, Viewing distance to accommodation with their after-effects on the pupil, Jpn. J. Ergon. 28-3, pp [4] James E. Melzer and Kirk Moffitt, 1997, Head Mounted Displays: Designing for the User, McGraw-Hill, pp [5] Kreifeldt. J. G., 1982, Consumer Product Design: Pro jects for Human Factors Classes, Proceeding of Human Factors Society 26 th Annual Meeting, pp [6] Lin Z.T., 1992, HMD/HUD Human engineering research, Industrial Design, Vol. 21, No. 2, pp [7] Pahl G. and Beitz W., 1984, Engineering Design, The Design Council/Springer, London. [8] Peli E., 1996, Safety and Comfort Issues with Binocular Head-Mounted Displays, Proceeding of Hoso-Bunka Foundation Symposium. [9] Sak Onkvisit and John. J. Shaw, 1989, Product Life Cycles and Product Management, QUORUMBooks. [10] Shi C.W., 1991, Humanity of Industrial Design, Industrial Design, Vol. 20, No. 1, pp [11] Tang Y.C., 1991, Design and planning of commercialised, Industrial Design, Vol. 20, No. 1, pp [12] Wang Shinpig R., Lin WonYih, Yang Yeayun, Shen Lisheng, 1997, The Hu man Vision of Binocular Stereoscopic Technique for Virtual Reality, CCL Technical Journal, Vol.1, No.5, pp