RECONFIGURABLE MANUFACTURING SYSTEMS. Autor: Anca Dana SÎRCA, University of Oradea. Coordinator: Radu Cătălin ARCĂ

Transcription

1 RECONFIGURABLE MANUFACTURING SYSTEMS Autor: Anca Dana SÎRCA, University of Oradea Coordinator: Radu Cătălin ARCĂ Key words: Reconfigurable Manufacturing System (RMS), FMS, Reconfigurable robots. Abstract: A Reconfigurable Manufacturing System (RMS) combines Dedicated Manufacturing Lines (DML) with Flexible Manufacturing Systems convertibility. Thus, it has the capacity of producing a wide range of parts, at different production levels and in conditions of high economic efficiency. The combination of high performance communication means - existing or to come - plus high level and standardized modelling of industrial equipment must bring more efficiency in design and operation of computer controlled manufacturing. 1. HISTORY AND DEVELOPMENT In its earliest form, manufacturing was usually carried out by a single skilled artisan with assistants. Training was by apprenticeship. In much of the pre-industrial world the guild system protected the privileges and trade secrets of urban artisans. Before the Industrial Revolution, most manufacturing occurred in rural areas, where household-based manufacturing served as a supplemental subsistence strategy to agriculture (and continues to do so in places). Entrepreneurs organized a number of manufacturing households into a single enterprise through the putting-out system. 2. TYPES OF MANUFACTURING Manufacturing (from Latin manu factura, "making by hand") is the use of tools and labor to make things for use or sale. The term may refer to a vast range of human activity, from handicraft to high tech, but is most commonly applied to industrial production, in which raw materials are transformed into finished goods on a large scale. Traditional Manufacturing Systems as Dedicated cannot face new market requirements because constitutive machine tools were designed to do a single operation. Cellular manufacturing is a fairly new application of group technology. Group Technology is a management strategy with long term goals of staying in business, growing, and making profits. Companies are under relentless pressure to reduce costs while meeting the high quality expectations of the customer to maintain a competitive advantage. Successfully implementing Cellular manufacturing allows companies to achieve cost savings and quality improvements, especially when combined with the other aspects of lean manufacturing. Cell manufacturing systems are currently used to manufacture anything from hydraulic and engine pumps used in aircraft to plastic packaging components made using injection molding. Group Technology or GT is a manufacturing philosophy in which the parts having similarities (Geometry and/or manufacturing process) are grouped together to achieve higher level

2 of integration between the design and manufacturing functions of a firm. The aim is to reduce workin-progress and improve delivery performance by reducing lead times. GT is based on a general principle that many problems are similar and by grouping similar problems, a single solution can be found to a set of problems, thus saving time and effort. The group of similar parts is known as part family and the group of machineries used to process an individual part family is known as machine cell. It is not necessary for each part of a part family to be processed by every machine of corresponding machine cell. This type of manufacturing in which a part family is produced by a machine cell is known as cellular manufacturing. A Flexible Manufacturing System (FMS) is a manufacturing system in which there is some amount of flexibility that allows the system to react in the case of changes, whether predicted or unpredicted. Most FMS systems comprise of three main systems. The work machines which are often automated CNC machines are connected by a material handling system to optimize parts flow and the central control computer which controls material movements and machine flow. The main advantages of a FMS is its high flexibility in managing manufacturing resources like time and effort in order to manufacture a new product. The best application of a FMS is found in the production of small sets of products like those from a mass production. Advantages: The best application of a FMS is found in production of small sets of products. - Productivity increment due to automation; - Preparation time for new products is shorter due to flexibility; - Saved labor cost, due to automation; - Improved production quality, due to automation. Disadvantage: - It is not always necessary that on increasing flexibility productivity also increases. 2. RECONFIGURABLE MANUFACTURING SYSTEMS Definition: A Reconfigurable Manufacturing System (RMS) is one designed at the outset for rapid change in its structure, as well as its hardware and software components, in order to quickly adjust its production capacity and functionality within a part family in response to sudden market changes or intrinsic system change. The Reconfigurable Manufacturing System (RMS) as well as one of its components the Reconfigurable Machine Tool (RMT) were invented in 1999 in the Engineering Research Center for Reconfigurable Manufacturing Systems (ERC/RMS) at the University of Michigan College of Engineering. The RMS goal is summarized by the statement Exactly the capacity and functionality needed, exactly when needed. Ideal Reconfigurable Manufacturing Systems possess six core RMS characteristics: Modularity, Integrability, Customized flexibility, Scalability, Convertibility, and Diagnosability. A typical RMS will have several of these characteristics, though not necessarily all. When possessing these characteristics, RMS increases the speed of responsiveness of manufacturing systems to unpredicted events, such as sudden market demand changes or unexpected machine failures.. The RMS facilitates a quick production launch of new products, and allows for adjustment of production

3 quantities that might unexpectedly vary. The ideal reconfigurable system provides exactly the func tionality and production capacity needed, and can be economically adjusted exactly when needed. These systems are designed and operated according to Koren s RMS Principles. The components of RMS are CNC machines, Reconfigurable Machine Tools. Reconfigurable Inspection Machines and material transport systems (such as gantries and conveyors) that connect the machines to form the system. Different arrangements and configurations of these machines will have an impact on the system productivity. A collection of mathematical tools, which are defined as the RMS Science Base, may be utilized to maximize system productivity with the smallest possible number of machines. To be more specific in the figure under this text is shown the evolution steps: a) b) c) Figure 1. Evolution steps in case of a tool used in assembling operations a Dedicated ; b Flexible; c Reconfigurable. Modular self-reconfiguring robotic systems are autonomous kinematic machines with variable morphology. Beyond conventional actuation, sensing and control typically found in fixedmorphology robots, self-reconfiguring robots are also able to deliberately change their own shape by rearranging the connectivity of their parts, in order to adapt to new circumstances, perform new tasks, or recover from damage. The modular building blocks usually consist of some primary structural actuated unit, and potentially additional specialized units such as grippers, feet, wheels, cameras, payload and energy storage and generation. Stochastic reconfiguration relies on units moving around using statistical processes (like Brownian motion). The exact location of each unit only known when it is connected to the main structure, but it may take unknown paths to move between locations. Reconfiguration times can be guaranteed only statistically. Stochastic architectures are more favorable at micro scales. A current system is M-TRAN which is a hybrid type self-reconfigurable system. Each module is two cube size (65mm side), and has 2 rotational DOF and 6 flat surfaces for connection. It is the 3rd M-TRAN prototypes as it is shown in the following figure.

4 3. RECONFIGURABLE ROBOTS At University of Oradea it is possible to see and handle a reconfigurable robot which can be modified in to 8 configurations. The robot is a Lego type and he can be configured in the following models: Simple robot; Basic robot; Lightseeker; Tracker; Robot with Obstacle Detection; Walking robot (Figure 2.a); Lightseeker with Obstacle Detection (Figure 2.b); Robot with Edge Detection. The main structure a Lego type is that taking or adding few parts in its configuration the robot is able to do a new task. These parts may be sensors, wheels, bumpers, legs, etc. In this way anything that can stop you to build your robot is imagination. The main processor that is able to compile the task into acting is the microcontroller. He is the brain of this robot and can be connected to PC by a serial port cable. a) b) Figure 2. Samples of reconfigurable robot made from Lego a walking robot; b lightseeker with obstacle detection Advantages: - it can be modular; - easy to integrability; - customization; - convertibility obtained within reasonable cost to manufacturers; - rapid scalability to the desired volume; - diagnosability. Disadvantage -because that reconfiguration is quite new, we couldn t find disadvantages to it, but it is also very hard to input some mistakes because of the various combination that can be done with reconfigurable manufacturing systems (RMS)

5 4. CONCLUSION: 1. Up to now, the reconfigurable manufacturing systems is not yet a matured area; this is why the industry feedback is not satisfactory. 2. Further research is necessary at the machine level, where the technical and economic consequences are very important, at entire manufacturing level. 3. The reconfiguration science will form the basis for a vital production technology in this era of global market competitiveness that it will involves into entirely new manufacturing field with enduring benefits for the economy and society. 5. REFERENCES: Goebel, P. (2004) Reconfigurable Manufacturing Systems. Proceeds of the International Conference on Competitive Manufacturing, COMA 04, Stellenbosch, South Africa. Koren, Y., and Kota, S. (1999) Reconfigurable Machine Tools. Radu C. arcă, Sisteme de fabricatie flexibila, U. Oradea Moon, YM and Kota, S.: Design of reconfigurable machine tools. Journal of Manufacturing Science and Engineering, Trans of the ASME, May Shah, SS., Endsley, EW., Lucas, MR, and Tilbury D.: Reconfigurable logic control Proceedings of the American Control Conference, May 2002.