Digitalization Integrated Design and Rapid Manufacturing-The Head-Mounted Display Modelling Design as an Example

Professor Huang Tai-Shen1 1

Graduate Institute of Design, School of Design, Chaoyang University of Technology, 168 Gifeng E. Rd., Wufeng, Taichung County, Taiwan, 413, [email protected]

Abstract: This paper describes a digitalization integrated design and manufacturing process which combines both of industrial product design development project and rapid manufacturing technologies. The purpose of the design project is to apply and commercialise laboratory research into a marketable product. Using a Head Mounted Display (HMD) product as an example in order to arrive at a functionally and commercially viable product for mass production, this project will present computer aided integrated design, reverse engineering and rapid prototyping techniques which were used to complete a HMD design-model and test the optics-system for manufacturability. Head mounted displays are image display units t hat are mounted on the head. Experimental laboratory prot otypes have now reached a stage of maturity at which it is realistic to define the scope of a marketable product. The design processes focus on human factors in industrial design, image scale, the method and theories of product design etc., leading toward a commercialisable design product. To apply design method and the correct technological specifications to the final product, utilize helpful digital design tools such as computer aided design, reverse engineering and rapid prototyping technique to complete the industry design product and develop a product design strategy that can bring the product to manufacture and carry it through to commercialization. Key words: Reverse Engineering, Rapid Prototyping, Industrial Design, Commercialized, Head Mounted Display

1. Introduction Developing new products is both important and risky for company advancement. Key factors for new product development can be divided into five stages that are feasibility and specification development, design and development, production engineering, validation, and manufacture and sales. As a new product development project starting, firstly marketing established the product requirements and handed these over to design and development; design and development then developed the product to the point of a working prototype and handed it over to production engineering; production engineers then sorted out how the product could be manufactured [2]. It is very clear that marketing, design and development and production engineering must work together. There are tow reasons for this. Firstly we have to shorten the development lead times for new products, and ensure that the products does everything it must to be a commercial success. 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 modelling helps ensure proper human interface

conformance. For the final production engineering, we can utilize reverse engineering to convert the physical 3D model to a digital computer solid model and then use rapid prototyping technology to create the final product. For example, HMD is a commercial product that should both aesthetically and ergonomically fit the human requirements of basic form, fit, and functions. The industrial designer firstly made it in modelling foam in the shop according to concept design. The dimensions of this model were then converted into a CAD solid model by using laser-scanning system, and then the final design details were refined in I-DEAS CAD/CAM system and ready for rapid prototyping manufacturing. Head mounted displays consist either of a helmet and small CRTs or of liquid - crystal displays (LCDs) in a pair of goggles. It was originally developed for critical applications in military aerospace, and now is important equipment for simulating virtual reality (VR), games for the amusement industry, and a personal theatre system [14]. 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. Some types are mounted on the face in the form of glasses. Development and improvement of the technical aspects of these systems have been recently carried out [11]. Until 1990s, HMD is applied in multi-media and related areas, and became a consumer product. For example, Walt Disney, Virtuality Group Plc, and Sega have set up HMD’s for the video games at their amusement parks. For commercial HMD, the “i-glasses” of Virtual CO. was the leader product, then Philips, Sony, Olympus followed with their own research and development [5]. It is likely that HMD products will enter the consumer-electronic product market as part of the personal computer, and become the major component of video games and home theatre [3].

Because the optical system was not the important factor in the design process, this project does not go into any theoretical details about it. The HMD product only serves as an example to illustrate the application of reverse engineering and rapid prototyping technology in product development process. 2. Design Methods 2.1 Design Requirements In the field of product design, many theories about product development have been evolved to describe the relationship between product deployment and the need of human being such as “product route”, “the stage of product development”, “product evolution”. The relationship between product deployment and the need of human being are based on the Maslow’s “Hierarchy of Needs” theory. 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”. 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 [12]. 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, and colours according to their functions and utilization. These are the “w ants” of human being after we have all the products we need.

2.2 Design development A product-commercialized process of technology products is a good example to illustrate the product development requirements as described above. For instance, the computer was originally created in order to assist us to make up for the insufficient calculating power of the normal human brain in its earliest development stage. Now, the functional performance of computer has developed far too far for ordinary human beings and we usually need only few of these functions on a daily basis. We always wish that a computer should have perfect functional performance, good appearance and smaller volume. As the “I-Mac” by Apple Computers illustrates, in addition to these features it must own that special quality that makes it desirable, making it a “want” as well as a “need”. 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 “commodity” must therefore have a Manufacture

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

Initial functions setup

with the consumer psychology for creating greater Functions examine

commercial profit. For the analysis model of product design, Kreifeldt announced a “user-tool-task” method in 1982, and R. T. Lin added a “form-modelling” factor

Human system design Engineering design

Tool

Engagement interface

User

Manipulation interface

Product

Human Factor

in 1994 [6]. The final combination result is shown in Figure

Task

1,

and

this

model

actually

is

a

product-commercialized process. The characters and performance of product function are emphasized in the

Commodity

“manufacture” stage and the “product” stage focuses Form

on the characters of user, physical function, and operation convenience. Finally, the “commodity” stage

Objective esthetic

has to stress the cognition of aesthetic sense, Figure 3. The relationship of product commercialized psychology function, and user’s personality [8]. and analysis model. 2.3 Product life cycle (PLC) In order to increase a company’s competition around the world, they have to development a new product and put it into the market at the right time. Once the product begins to be accepted by customers, sales growth starts to accelerate. The period when sales growth slows down is called the shakeout phase. By this stage, competitors have had a chance to catch up with a new product, or have cut their price in order to prevent losing too much market share. When all market outlets have been fully stocked and replacements stock is ordered only as cus tomers purchase the product, sales growth starts to slow down. The implications of the product life cycle for the strategic planning of product development are simply that a development plan should be prepared for every product in, or

decrying stage

competitive stage

mature stage

Shakeout

life cycle can be separated into “initial stage”, “growth stage”, “mature initial stage growth stage

sell profit

approaching, its maturity phase. The main stages of a product’s business

Time

stage”, “competitive stage” and “decrying stage” five stages. The relationship between the product life cycle and sell profit are shown in Figure 2. The producer can measure the circular to understand his product at which stage and where is the product market position and assist him to make a decision to find the market niche [10].

Fig.2 Product Life Cycle

3. The HMD commercialized methodology 3.1 Past research into usability HMDs attempt to immerse the user within the VR environment and allow more human/computer interaction within the graphic surroundings [15,16]. From the viewpoint of mounting the unit on the human head the development of an image presentation method that matches the head’s motion. The points of the development are the ways to miniaturize and reduce the weight of the equipment, improve resolution, create wide field of view, etc. The Eye-Trek (Olympus optical CO., LTD) product is a very good example for the miniaturization and weight reduction, and its display unit is about 85 g [3]. For the high resolution and a wide viewing field, Datavisor (n-vision, inc.) is capable of 1280*1024 (SXGA) resolution and 120-degree field of view. Though 640*480(VGA) and 800*600(SVGA) resolutions have recently become mainstream. Since it is very difficult for designer to achieve miniaturization, high resolution, and a wide field of view simultaneously, the HMD must be developed according the intended application [11]. According to HMD’s functions and purposes , the design process can be classified into three categories: research phase, industrial phase and consumer phase. 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. 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 field of technique development and functions extension in the future [13]. 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. 3.2 Making a prediction about market fashions and consumer requirements In the field of industrial design, an image scale is a tool originally used for predicting product sales and market position, and it is also used to predict or decide the factors of consumers’ demands. An X and a Y-axis define an image scale containing four quadrants. At the two ends of the X and Y-axis we set two sets from the survey of semantic differentials for consumers such as colour, form, or texture etc. We can for example put “Soft-Hard” and “Cool-Warm” at the end of each respective axis. A product’s image will be marked in one of the quadrants according to the matching degree of two phrases. After repeat this task until all images are put into the image

scale, we can find and discern different groups of products within the image scale, and give them suitable names according to each group’s characteristics. The researcher or the designer can integrate this image scale with their product strategies to find out the niche in which they want to include or create a new product market. The image scale is a very useful tool in idea creation and project development at the initial stages of product design. 3.3 Ergonomics Although the electronic and optic components of the HMD weigh under 300g, the comfort and good fit to the users’ head shape and distribution of weight are still very important factors to the success of the product design. 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. Some significant ergonomics conditions concerning the design of HMDs should be considered when we are going to design a HMD product [7]: ? Due to the fact that the optic display equipment is at the front, we should consider distribution of weight, and he

weight of HMD must as light as a pair of glasses. Meanwhile, the centre of gravity of HMD must pass through the centre of head to avoid influence of head motion [9]. ? In order to satisfy all users, the distance between the centres of the two pupils should be adjustable and the range is from 52mm to 78mm. Otherwise the contact glasses must be enlarged to 20mm [4]. ? It must has at least 30mm between the eyes and the HMD for users with eyeglasses. ? It can accommodate a wide variety of head sizes, and easy any adjustments are to implement correctly. 4. Computer aided integrated design and manufacturing 4.1 Reverse engineering This project tried to develop an integrated design and manufacturing process which could be divided into the following steps: concept design, manual model, shape recognition, reverse engineering, CAD model, rapid prototyping, rapid tooling, and final product[8]. Since digital data, function test, construction evaluation, and “time to market” have become such fundamental design factors of the design process, product 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. In product design process, reverse engineering is a very familiar method and it takes scanned data from an object and manipulates these point data to create a high-accuracy surface/solid CAD model that can be used to manufacture a physical model by using traditional CNC machining or rapid prototyping. The application of both reverse engineering and rapid prototyping applied in this project is to demonstrate the convenience of digitalisation design. 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. According to measuring ways, reverse measuring machines divide into contact and non-contact machines. In

this project, an E-Monster laser non-contact scanner was used to catch point data from the hand-made wooden model. 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. 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. Then all curves were imported into the I-DEAS CAD/CAM system for final smoothing processing and the final solid model was created by using surface/solid modelling commands. 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. 4.2 Rapid prototyping (RP) Rapid prototyping technologies have emerged for quickly creating 3D products directly from computer -aided design system. These technologies significantly improve the present prototyping practices in industry. However, there are a number of obstacles in true integration of computer-aided design with computer-aided manufacturing for rapid development of new products. Although substantial

research has been done in the past for

computer-aided design and manufacturing integration, such as feature recognition, CNC programming and process planning, the gap between CAD and CAM remains unfilled in the two aspects which are rapid creation of 3D models and prototypes and cost-effective production of patterns and moulds with complex surfaces. A concept model of the design process 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 [10]. To substantially shorten the time for developing new products, moulds, and prototypes, some manufacturing enterprises have started to use rapid prototyping methods for complex patterns making and components prototyping. Companies seek to reduce time to market by implementing concurrent engineering and by using rapid prototyping technology. Over the past few years, a variety of new rapid manufacturing technologies, generally called rapid prototyping and manufacturing. 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) [1]. This project utilizes a CPS-250A rapid prototyping machine, and 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. 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. 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. Then the final RP model had to pass through an assembly and optical function test. This working model, which contains structure parts and optical components, was exhibited at the World Fair of Electronic Products in Taipei in 2000, and the reverse engineering process and rapid prototyping manufacturing are shown in figure 3.

Scanning

Point cloud

3D CAD Solid models

RP model

HMD parts Product exhibition

Fig.3 RE, 3D solid models, RP model, HMD Parts, and the Final Product Exhibition

5. Conclusion The paper has shown that the roles of digital design and rapid manufacturing in improving the design process speed are a very important issue. A case execution of the HMD market was carried out which showed that integrated design and manufacturing can be used to improve or differentiate a production process in many ways. Thus, the design of the whole product or key components may be used to improve its basic technical performance; to provide the styling that immediately attracts customers; to reduce manufacturing, distribution or life cycle costs; to improve quality, reliability or durability; to improve ease of use; to provide new functions; and/or to unify or extend a product range. 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. We have utilized design methods, reverse engineering, and rapid prototyping technologies to assist us in designing an integrated and complete HMD working prototype in this project. Due to 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. According to the development of micro-electronic technology and new rapid manufacturing methods, 3C products will be the major products of the consumer product market, and we can predict furthermore that the product commercialization of the HMD will be part of the new generation of consumer-electronic products. To examine the principles, methodologies, and theories described in this paper, researcher must follow the practical product design of HMD, and any improvement and modification of this research and HMD product design will rely on the response and feedback of consumers and end-users.

Acknowledgements This research project reported on here has been funded by the Chung-Shan Institute of Science and Technology, Taiwan, ROC. Thanks are due to our colleagues in the Department of Industrial Design, Chaoyang University of Technology, Taiwan, especially Prof. Wenchih Chou and Gideon Löwy, for their assistance with the experiment and helpful comments on drafts of this paper. Reference 1.

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