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Integration of Collaborative Design and Process Planning

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Integration of Collaborative Design and Process Planning for Artificial Bone Scaffold 3D Printer Nozzle
Yan-En Wang1, 2, Xiu-Tian Yan1, Raam Kumar Maruthachalam1, and Sheng-Min Wei2
Department of Design, Manufacture and Engineering Management, The University of Strathclyde, Glasgow, UK, G1 1XJ yanen.wang@strath.ac.uk 2 Mechatronic Engineering School, Northwestern Polytechnical University, Xi’an, China, 710072
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Abstract. The requirement for high-quality product with reduced cost and timeto-market in multidisciplinary project is demanding. Integration of design and process planning with computer aided techniques can provide a solution to this challenge. This paper describes a reference model of integrating computer aided techniques to aid the concurrent development of a multi-nozzle 3D printer for fabricating artificial bone scaffold at the University of Strathclyde and the Northwestern Polytechnical University. This integration reference model, including design tools such as Material Computation (MC), Computational Fluid Dynamics (CFD), and CAD, and planning tool such as CAM techniques, is employed to support this special 3D printer development. The high precision multi-nozzle development was used as a case study to validate this integration of concurrent design and process planning. CAD tools were used to provide several nozzle design concepts and a rigorous CFD analysis of several nozzle designs under the same boundary conditions were undertaken to refine and evaluate them by research staff from both institutions. This cooperative conceptual design case study demonstrated that it drastically reduced development time and cost in devising nozzle conceptual sketch design and optimizing the nozzle design for 3D printer. This makes it an important step in designing a high precision artificial bone rapid manufacturing machine.

1 Introduction
Concurrent Engineering (CE) is a systematic approach to integrate product development processes that aims to improve the responses to customer expectation [1]. It can provide a collaborative, collective and simultaneous engineering approach during product development process, especially for tissue engineering which requires multidiscipline collaborative effort and needs to satisfy various customers’ expectations and technological requirements, including important biocompatible issues. The development of an artificial bone scaffold manufacture machine can provide an opportunity to apply collaborative design and process planning. Erens[2] (1996)
Y. Luo (Ed.): CDVE 2006, LNCS 4101, pp. 132 – 140, 2006. ? Springer-Verlag Berlin Heidelberg 2006

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identified four elementary mechanisms that are used in design: decomposition, allocation, composition, and validation. Development team members should figure out various requirements across multi-disciplines. Modern techniques such as simulation, analysis and Rapid Prototyping have been developed and can be used to support product development. But most techniques need to communicate design data and documents among engineers from different disciplines and regions or countries. An effective collaboration among them is vital to the success. The following describes some basic background information about the subject area. Extensive experiments showed that the porous structure of Hydroxyapatite (HAP) provides a template for fibrovascular in growth when followed by osteoblast differentiation, resulting in the deposition of new lamellar bone[3]. But it lacks sufficient bioactive substance to support continuous biodegradation of itself and new bone’s growth. Researchers have found that Bone Morphogenic Protein (BMP) can induce bone cells to adhere to scaffolds and accomplish its biodegradation and new bone growth[4]. In order to satisfy these requirements, at least 70% porosity and the height of deposit of the internal 3D scaffolds are important aspects with respect to the biocompatibility and bioactivity, promoting the formation of new tissues and the blood vessels[5]. However traditional Rapid Prototyping (RP) technology cannot produce the required microstructure and the level of porosity compound BMP and growth factors skeleton. Because these biomaterials can only maintain bioactive at the human body temperature, Stereolithography, Selective Laser sintering and Fused Deposition Modelling are not suitable to make usable bones as the working temperature is far too high. 3D Printing technology can create parts of any complex geometry using several types of material. Furthermore, it can control efficiently the material composition, microstructure, and surface texture at the ambient temperature. Biomedicine, computer aided design and manufacture techniques are “pushed” and “pulled” each other to improve one special RP machine to compensate above defaults and fulfil above requirements. Collaborative effort is therefore required to conduct this research project. Its aims in long-term to design and prototype an accurate rapid artificial bone manufacturing machine which satisfies the above requirements. It has been undertaken by two teams distributed in UK and China. Pursuing an integration of collaborative design and process planning, different concept types have been developed. It requires collaboration between scientists and engineers from different discipline background. The concept of an information-oriented integration requires the integration and collaboration of MC, CFD, CAD and CAM systems. Here the ultimate aim is to enable designers and process planners to switch between different aspects of the present jobs and to develop concurrent working patterns, in order to optimise the product and process modelling in terms of cost, time and quality. In the following, a reference model and the methodology, which support the integration of collaborative design and process planning, are described to provide a better understanding of the approach and illustrate which one is most suitable for the 3D printer developed.

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2 Integration of Collaborative Design and Process Planning
In order to realize a collaborative design and process planning[6], a specification of requirements derived from concurrent engineering principles and best practices is essential. There are three key requirements[7] which should be considered. It covers that: previous sequential working procedures need to be broken down and redefined before design and process planning in a collaborative and parallel manner; the establishment of interdisciplinary development team aims at the coordination of decisions in the early stage of product development; an early consideration of a design decision on manufacture can lead to the avoidance of expensive changes during later life-cycle. It is therefore necessary to optimize the design and process planning procedures to enable an integrated method based on above three requirements. 3D printer development project requires the collaboration among engineers from and integration of material, fluid dynamics, mechatronics domains. Here, a nozzle development was a good example to the application of cooperative and integrated design and process planning approach. 2.1 Model to Support an Integration of Collaborative Design and Process Planning In order to develop the reference model, it is necessary to clarify the types of interdependence existing among the project development process. Erens[2] presented design knowledge decomposition and composition mechanisms which were applied to the product modelling. In fact, design procedure is a mapping process from knowledge to activities. In order to analyze the role of this model in collaborative and integrated design and process planning, the nozzle design, a key component of 3D printer, is explained using the research model in figure 1. Three types of integration have been defined and distinguished, namely a functional domain, a physical domain and a process domain. Each domain has its own product model (see Fig. 1). The

Sub-Project Information and Data (Information Model)

Functional Domain

Process Domain Procedure-oriented Parallelism Object-oriented Parallelism Information-oriented Parallelism

Customer requirments

Physical Domain Technical Systems Model

Activities Model

Methods Model

Fig. 1. Reference model for integration of collaborative design and process planning

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activities in the functional domain are executed by the customer or market engineers in cooperation with product designers and finally result in the functional requirement baseline. Nozzle’s development process includes three models in physical domain and process domain (the core of the reference model is information model and main technical model, and the activity model that contributes to the framework of reference model with regard to the data). It refers multi-disciplines and research tools, so there is a big and important issue on data exchange and communication among different software tools. 2.2 Methodology for Integration of Collaborative Design and Process Planning On the basis of the reference model, a method is proposed which describes the application of inter-related partial models. They exchange and communicate data through the information model. Their relationship is a three-stage procedure for developing potentials of integration in design and process planning. Procedureoriented parallelism, Object-oriented parallelism, and information-oriented parallelism were developed based on Remko’s product development process model [2]. The procedure-oriented parallelism is based on activity and information models. Design and process planning procedures are run concurrently by optimizing the flow of information between activities. Before the procedure-oriented parallelism can be implemented, activities which can be performed simultaneously in the future should be recognized. Primarily in early stages of product development the product itself and possibly individual modules and assemblies can be determined. Thus at these moments only rough planning concerning design objects is possible. When more concrete information is available, the required techniques can be supported during product development, thus facilitating continuous, more precise planning. The information-oriented parallelism, at the start of the development process, is indicated during the product development. They can be selected as required, depending on the application and assuming that the available technical systems and information have been adequately specified. Most of all critical information about the product and the processes can be generated at an early stage by applying these methods. 2.3 Partial Models Integration for Collaborative Reference Model To explain and clarify the principle of these parallelisms and collaboration during product development, a detailed description of partial models will be described as follows. Extensive literature was reviewed [8] on activities and tasks in design and process planning, in order to establish activity model to ensure suitable efficiency and effectiveness are achieved. Similar to most of research models, here activity model comprises tests in practice, extensive literature research and studies on existing models. Figure 2 illustrates the activity model in details. In fact, activities can be interconnected by means of input and outer information. However, available design information must be on early stage down-stream process planning activities. Similarly, process planning model should be passed to up-stream design activities to facilitate life-cycle oriented decision-making. Thus, it is necessary deploy integrating methods for transmission and feedback of information between physical domain.

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Collaborative Design Multi disciplinary Teams

Process Planning Process planning ascertain production requirements defining blanks defining processes ascertain work stations/machines Output defining special equipment Rapid Prototyping Operation Resource defining STL files add biomaterial powder Efficiency defining devices or equipments Input defining the tool for each operation defining manufacture parameters defining the default times

Defining requirements Tasks product requirements Function define function structure Devise principle ascertaining effects principle solution Design roughly design defining assemblies defining the product structure Details specification

Goal

Fig. 2. Efficiency Collaborative Activities model

The technical system model contains the structure of these physical objects within a product (figure 3). All activities in the activity model and all of the information defining products and processes refer at least to one of technical systems. The information model (figure 4) is, to the extent possible, based on generic resources, application resources and application protocols of the standard for the exchange of Product Model Data. These models are not developed for any specific product development.
Data exchange standard for Integration collaborate design and process planning Technical System Multidisciplinary technical system Research disciplinary I Standard for software data exchange Research disciplinary III

Research disciplinary II

Technical system Part D Assembly D Modul D Product

Fig. 3. Technical system model

As for multidisciplinary research, it is complex for different domains using various special tools and software. So at the beginning of project, it is necessary to define above models and clarify the data communication standard or format about different technical tools. A multi nozzle development, the key component of 3D printer fabricating artificial bone research project, is supported by these three models and

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Information for Multidisciplinary collaborative design & Process Planning

Design Information

Process Planning Information

Fig. 4. Multi disciplinary collaborative Information Model

cooperated by specialists in MC, Biomedicine, CAD, CFD, Rapid Prototyping (RP), Product Data Management (PDM), etc.

3 Integration of Collaborative Design and Process for 3D Printer Nozzle Design
Current commercial 3D printer nozzle design did not solve the problem of fabricating HAP scaffold with combining simultaneously BMP and BGF, and no lump will be formed at the tip of a nozzle. Considering biomedical parameters the microstructure of bone porous diameter is from 200 to 500 μm. HAP needs BMP and BGF to handle bone scaffold biodegradation and reconstruction. A new nozzle therefore should be designed to solve these problems. To improve development quality and reduced timeto-market, the integration method of collaborative design and process planning was adopted in multidisciplinary research. Classical design methodologies, Such as Pahl & Beiz[7] or in the VDI-Guideline 2221[7] provide a systematic and well established approach to design process. These methodologies were analyzed to determine their suitability for distributed design scenarios and recommend for improvement. Two development teams distributed between UK and China have to accomplish these activities using different special tools in CAD, CFD and MC development teams. So corresponding to this activity model, the technical model and initial process plan should be built. Some details about the nozzle design by establishing all collaborative design models as above are discussed below. 3.1 Activity Model for Nozzle Design For this 3D printer of artificial bone scaffold, the activity model includes design (sketch to computer graphic files), analysis of requirements, detecting overall function structure, general and special function structure, devising the principles, ascertaining effects, compiling documents and so forth. In order to improve development efficiency and effectiveness, at the beginning of development the multidisciplinary teams discussed the goal and then defined function structure including CAD, CFD, and MC, ascertained effects and principle solution, specified the data transfer methods among Pro/E, Fluid, and methyltrichlorosilane (CH3SiCl3) thermodynamic evaluation (a MC software deployed by Northwestern Polytechnical University, China) and specified objective of nozzle according to figure 2.

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3.2 Nozzle Technical System Model for Nozzle Design Based on activity model, all concrete software tools had been specified. Through concept sketch design, Pro/E (CAD) was deployed and five concept designs were created shown in figure 5. Fluid 5.5 (CFD) was used to evaluate and re-evaluate pressure, fluid flow & velocity, and turbulence for these conceptual designs. The final suitable nozzle design was then obtained based on the visualization analysis. The same boundary conditions of biomaterial and fabricating process parameters were defined in MC software. According to activity model, the concepts were analyzed to define the purpose and behaviour of this novel nozzle.

Design 1

Design 2

Design 3

Design 4

Design 5

Fig. 5. Five design concepts for a nozzle design

3.3 Process Planning Model for Nozzle Design In this process planning, it is necessary to ascertaining production requirements, define process and sequence of processes, and ascertainsoftware tools discussed by the activities model. Operations per process should be defined. And then the tool and technological parameters for each operation should also be specified. To satisfy the tasks and product requirements of nozzle activity model and technical system model, it is useful to get the control parameters from analysis.

Information , Data transferring standard and methods

Pro/E

STL File

Fluid

Material Computational Software

Fig. 6. Methodology for Nozzle collaborative design and process planning

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3.4 The Methodology for a Cooperation in Nozzle Design and Process Planning In this multidisciplinary cooperative project, based on integration design and process planning (as figure 6) the final nozzle design was demonstrated to manufacture the 3D printer for fabricating artificial bone. Its pressure and velocity are stable and high enough to eject fluid uniformly to fabricate 3D scaffolds [9].

4 Conclusion
In this paper, a multi-discipline integration reference model was presented in CE domain. Three partial models namely the activity model, technical system model, and the information model, provided means for helping designers and process planners to improve their multidisciplinary research. It defines the design, along with the required technologies for manufacturing that product. 3D Printer nozzle design, a sub-division project of “3D printer for fabricating artificial bone scaffold”, interpreted that activities are carried out simultaneously and performed by interdisciplinary development designers, technology planners and process planners. Nozzle development demonstrates that integration of multidisciplinary methods, with possibilities for transferring and feeding back information, were deployed to support the main research objectives during process and increase the flexibility. Attempts at integrating design and process planning on the basis of the reference model have been attained. Systematic use of the developed reference model, its partial models, the planning process and execution methods provide a mechanism to exploit existing potential for decreasing development time and costs of new production. The production quality required by the customer is improved by the reshaping of procedures in design and process planning. Acknowledgments. The authors would like to acknowledge of the support from an Asia-Link project, funded by the European Commission with a contract number: ASI/B7-301/98/679-09 and Doctorate Foundation of Northwestern Polytechnical University (CX200509).

References
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6. Marle, F. and J.-C. Bocquet, A Multi-Project Management Approach for Increased Planning Process, in 13th International Conference on Engineering Design, ICED 01 Glasgow. 2001, Professional Engineering Publishing Limited for The Institution of Mechanical Engineers: Glasgow, United Kingdom. 7. Liu.X., Computer Support for Design Coordination in Concurrent Engineering, in Design Manufacturing Engineering Management. 2001, University of Strathclyde: Glasgow, UK. 69. 8. F.J.O'Donnell and A.H.B.Duffy, Performance Management ar Design Activity Level, in 13th International Conference on Engineering Design. 2001, Professional Engineering Publishing Limited: Glasgow. 9. Y.E.Wang, X.T.Yan, et al., Optimizing a Nozzle for an Artificial Bone Mechatronic 3-D Printer, in MX2006 -- MECHATRONICS 2006 The 10th Mechatronics Forum Biennial International Conference. 2006: Penn State Great Valley, Philadelphia,USA.




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