Design of generic modular reconfigurable platforms (GMRP) for future micro manufacturing X. Suna, K. Chenga*, F. P. Wardleb a
School of Engineering and Design, Brunel University, Uxbridge, UB8 3PH, UK b UPM Ltd, Mill Lane, Stanton Fitzwarren, Swindon, SN6 7SA, UK * Corresponding author:
[email protected]
Abstract The need for reduced weight, small size, energy efficiency, higher surface quality and dimensional/form accuracy, whereas at the same time decreasing component costs and batch sizes for components/devices, is forcing the industry to introduce more and more microparts into various industrial products. It is expected that the market for micro products is increasing rapidly and changing frequently in the future. To cope with such a volatile market, manufacturing enterprises will have to be adaptive and response quickly and cost-effectively. However, the existing micro manufacturing systems can not meet the need above because of their limits in setup cost, large footing space, rigid functions and high operation cost. In this paper, a new micro manufacturing platform, i.e. generic modular reconfigurable platform (GMRP) is proposed in order to provide an effective means for fabrication of high quality micro products at low cost in a responsive manner. GMRP is characterized by hybrid micro manufacturing processes, modularity of key components, and reconfigurability. Various micro manufacturing processes can be conducted on a single platform by changing, adding and integrating the component modules or even re-setting up platforms simply, and thus forming an effective micro manufacturing system rapidly and effectively. The paper concludes with a discussion on the potential and applications of the GMRP concepts and methodology for micro manufacturing and micro factory purposes in particular. Keywords: Micro manufacturing, Reconfigurable manufacturing, Micro manufacturing system, Micro factory
1. Introduction Fabrication of miniature compact products is becoming one of key requirements for modern manufacturing industry because of the demand for reduced weight, reduced size, higher surface quality and dimensional/form accuracy, while at the same time decreasing component costs and batch sizes for components/devices ranging from electro-mechanical systems to medical instrumentations and devices [1,2]. Currently, the wide application of micro products has greatly affected every aspect of our life, for instance, from digital cameras, mobile phones, minimal invasive medical equipments to biotechnological or chemical processing facilities [3]. It is micro manufacturing that acts as enable for micro products in electronics, mechanical, electrical and optical applications. Likewise, the application of micro products further promotes the development of micro manufacturing. One of the main micro products, MEMS, which is and will still be one of major driving forces for micro manufacturing. It is also expected that the MEMS/MST market volume will reach $24billion in 2009 from $12billion in 2004. Moreover, completely new products such as micro fuel cells, MEMS memories, chip coolers, liquid lenses for cell phone zoom and autofocus will be included in this category [4]. Fig.1 shows that the market for micro products is increasing rapidly as required continually by customers in the future. To survive in this competitive global market, it is essential for manufacturers to be able to respond quickly and effectively by obtaining high throughput, low cost and industrial scale micro manufacturing.
Fig.1 Market for MST/MEMS product in the future [4] The micro manufacturing processes and facilities/equipment play a key role in the competitive market although the one-off investment is huge. The main existing systems for fabrication of micro products are briefly reviewed below, Conventional ultraprecision machine systems are based on traditional sized machines with good machine characteristics. It is currently the major means to fabricate micro products. Small size, complex geometry and high quality of micro products impose high demands on the machine performance. This will of course increase the investment and operation costs and make the manufacturing SMEs difficult to access the technology and thus the high value-added manufacturing business [3]. Bench-top ultraprecision machine systems focus on machining of micro 3D devices/ components on various engineering materials cost-effectively and industrially feasible. Compared to conventional ultraprecision machines, it renders the benefits of cost,
small space, ease of localized environment control and affordable manufacturing facilities/technologies, etc. [5]. However, each machine system is still individual application-driven rather than modular and reconfigurable. Non-traditional micro manufacturing systems emphasis on production of micro products which are difficult achieved by conventional mechanical methods. Traditional machining processes are based on the principle that the tool is harder than the workpiece, but some materials are too hard or too brittle to be machined with conventional methods. Therefore, various non-conventional processes are developed, such as micro-EDM employed to cut materials regardless of their hardness or toughness. Nonconventional micro manufacturing system is normally expensive due to its dedicated/specified specifications and special facilities. In addition, limited capabilities of each non-traditional manufacturing system cause the impossibility or high cost in the fabrication of micro products having some micro features or high precision requirements. Microfactory is developed aims to miniaturize a production system to match the size of parts it produces. It refers to extreme miniaturization of a manufacturing system [6], so it is suitable to the fabrication of micro products in terms of low cost, less space occupying, low energy consumption and mobility etc. Compared to a conventional factory, a microfactory has the five essential characteristics including decreased heat deformation of machine tools with decrease of their sizes, less material consumption for machine tools building, smaller vibration amplitudes and decrease in space and energy consumption [7]. Although there are lots of distinguished advantages of microfactory, it is still in the laboratory scale application rather than widely accepted by the industry. In this paper, a generic modular reconfigurable platform (GMRP) for micro manufacturing is proposed so as to achieve low cost, rapid reconfigurable integration of various micro manufacturing processes for the fabrication of 3D micro components/products as needed in the dynamic market. The system concept, models and implementation perspectives are explored with respect to rapidly and responsively forming industrial feasible micro manufacturing systems for high throughput, low cost, truly industrial scale micro/nano manufacturing. 2. GMRP virtual models
(a) (b) Fig.2 Virtual models of two GMRP configurations As shown in Fig.2, the authors have proposed two GMRP configurations. Each GMRP is a bench-top hybrid processing machine designed for industrial feasible micro/nano manufacturing especially for manufacturing SMEs. The base of each platform is
generic, and manufacturers can add, change, or remove modular components such as spindles, slideways, tool holders, etc., forming a specified micro/nano hybrid machine as new components/ products manufacturing is required. Furthermore, as a GMRP is modular and reconfigurable in structure, it can thus be used as a generic machine unit for forming a micro manufacturing system at low cost. The unit can have adaptive, associative and intelligent capability, e.g. remembering the past machining experience and configuration setup, etc, which is essential for the rapid and responsive setup of the system in an intelligent way.
2.1 Hybrid manufacturing capability Micro components/products are normally integrated products with different materials and of diverse micro features, which make it necessary for manufacturers to possess hybrid micromachining ability to cope with varied features and materials. For example, micro grinding has been widely applied for machining pins and grooves with small dimensions on hard or brittle materials, but deep micro holes or deep, narrow cavities are not promising for micro grinding. On other hand, micro-EDM is one of the most powerful methods for fabricating micro holes in metals and other electrically conductive materials. The GMRP has hybrid manufacturing capability aiming to broaden the limits of its application and to improve the product manufacturing quality. As illustrated in Fig. 3, the GMRP may integrate many micro processes such as micro-EDM, micro grinding, micro milling, micro drilling, etc. because of their similar kinematic configurations. The seamless integration of micromachining processes on a GMRP will lead to predictability, producibility and productivity of micro/nano manufacturing, with the capability to be adaptive, which is essential in the current competitive global market place.
2.2 Machine platform and modularity Modular structure and reconfiguration are required for micro manufacturing in the current market climate where variations of micro products occur at shorter and shorter intervals. Modularity is one solution for micro manufacturing systems to outlive the products they were originally designed for. The GMRP is designed as a modular system. The manufacturer can easily configure the platform and later reconfigure it to meet customer’s future needs [8]. Modularity is also a cost-efficient solution, and makes later upgrades or modifications to the platform easier. The manufacturer can therefore response to customers or other market changes rapidly and responsively without building or buying new machines. Standardization of key modular components makes it simple and economic to reconfigure a new platform just by adding or changing components or modules. It is possible to produce different micro products on a single platform due to the flexible combination of different modular components or modules.
Fig.3 Hybrid manufacturing capability of a GMRP The key components or modules that can be integrated include: • spindle units • drive and actuation units • tool holders • micro toolings • fixtures • machine structure or frame • measure elements and inspection units • control system Fig.4 illustrates the major modular components of a GMRP.
be easily reconfigured for changes due to its modular components and modules. For example, reconfigurability for changes of products and processes is achieved by changing machine modules, such as spindle units, rotary tables, and linear slideways, with different sizes, accuracy and functionalities. In addition to changing modules, as shown in Fig.5, one or more spindle units can be added to the existing platform to improve the productivity as it is needed. Two spindle units
Fig.5 The reconfigured GMRP
Fig.4 Modular components of a GMRP Taking a spindle unit as an example, it has different speed ranges, powers and rotational accuracy requirements for various micromachining processes. For slideways, different stroke and positioning accuracy may be required with linear motor or rotary motor driven depending on applications. Standardized interfaces enable the use of different drive systems. Moreover, micro tools can be a micro electrode, a micro grinding pencil, a micro milling tool or a micro driller according to the micro processes operated. The selection of these modules is decided by customer requirement, technical requirement or according to the price of the final product. Similar to machine modules, control system on a GMRP can also be modular in terms of software, algorithms and controller, etc.
2.3 Machine platform and reconfigurability Reconfigurability is an important characteristic of modern manufacturing systems [9, 10]. GMRP is designed highly reconfigurable in order to be adaptive to the introduction of new technologies, manufacturing changes and mobility requirements. Mechanical reconfigurability GMRP is able to
Electrical reconfigurability Electrical installation at the GMRP can be reconfigured by choosing modules from the library of electrical components and hardware. This library possibly includes rotary motors, linear motors with diverse specifications, encoders and amplifiers. Rotary motors, for example, can be replaced with linear motors to get better motion performance and neat design of the drive and actuation system. Different types of encoder are also possible to be selected to reconfigure the system for different level of performance requirements. Control system reconfigurability Similar to reconfiguring machine modules and electrical systems, control systems are also capable of being reconfigured by selecting needed software modules (e.g., servo control algorithms, interpolators) and hardware modules (controllers) in the development of openended control architecture. Selection of control modules is directly influenced by the electrical components. 3. Potentials and applications of GMRPs The GMRP concept has the potentials to bring dramatic changes in the modern European manufacturing industry due to its advantages with respect to low cost, reduction of space, diverse functionality, and industrial feasibility. Development of
GMRPs not only delivers modular, reconfigurable, adaptive, reusable manufacturing facilities and methodology for supporting industries (SMEs in particular) to move onto high value-added manufacturing but also renders reconfigurable adaptive manufacturing systems for European manufacturing industry to compete in the dynamic global marketplace. Furthermore, GMRPs likely provide a holistic approach, exemplar pilot systems, implementation protocols and applications for enabling European manufacturing SMEs to engaging in global manufacturing in a highly innovative, responsive and productive manner. The further potential applications of GMRPs possibly stand in the following two areas, (1) Micro manufacturing systems The GMRP platform is an ideal means for micromachining due to its generics, modularity and reconfigurability.
4. Concluding remarks In this paper, the concept and implementation perspectives of GMRP are explored through two exemplar platforms developed by the authors. The aim of the concepts is to develop low cost, industrial feasible reconfigurable bench-top machines for responsively setting up micro manufacturing systems as the dynamic market required. The work presented is the preliminary results, although the authors are currently undertaking substantial simulations of the concepts and models within the virtual manufacturing environment against the requirements of high precision, flexibility and adaptability, high complexity, low cost and rapid reconfiguration, etc. These requirements are essential for moving onto the high value-added manufacturing particularly for European manufacturing SMEs. Acknowledgements The authors would like to thank Brunel University and Nano EDM Ltd for the PhD scholarship award and the helpful discussions within the EU IP MASMICRO Project—its RTD5 Group in particular.
References Fig.6 A micro manufacturing system based on GMRPs Fig.6 demonstrates that a micro manufacturing system formed with GMRPs can be developed for covering the full process chain in fabricating a micro product. In this micro manufacturing system, each GMRP can be configured as specified functional machine by choosing corresponding modular components from the library of modules, which greatly reduces the investment of the whole manufacturing system. The system can be easily reconfigured and reused because of the adoption of GMRPs. (2) Microfactory Micro factory
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Fig.7 A micro factory built with replication of GMRPs A microfactory (as shown in Fig.7) based on micro manufacturing systems equipped with replication of GMRPs can evolve and adapt quickly and effectively at low cost as market and manufacturing change demands. A GMRP–based microfactory is sound in concepts and methodology, but there will be more benefits and challenges resulted from the applications, which need to be investigated in-depth and further explored against a number of applications.
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