Research for Major-Parts Digital Assembly System of Large-Scale Airplane ZOU JIHUA RIAZ AHMAD FAN YUQING School of Mechanical Engineering and Automation Beijing University of Aeronautics and Astronautics Xue Yuan Lu No.37, Beijing P.R.CHINA Abstract: - In view of greater complexity and high precision needed for assembling large-size airplane parts, we propose the digital flexible assembly technology system (DFATS) concept, for assembly of major-parts and alignments. The concept has been described and demonstrated by presenting the flexible assembly workstation prototype system for major-parts assembly and positioning. All the primary key techniques related to large-scale airplane parts assembly, and related content of items have been described. The paper analyzed data set organization and coordination relationship based on Digital Mock-Up, provided assembly simulation content, and defined Digital Master Tooling (DMT) concept with a specific approach. It explained function and content of mechanical follow-up positioning device, control software, its effect, operating principle and method of the laser tracking measurement assembly technique. Key-words: - Digital Assembly; Flexible Assembly Workstation; Digital Master Tooling; Mechanical Follow-Up Positioning; Laser Tracking Measurement 1 Introduction Modern large-scale airplanes are characterized by complex structure and configuration. Enormous volume of parts (up to more than three million pieces), is often difficult to organize in compact inner space, anfractuous coordination relationships, and for bad work access for assembly and installation. More often the workload of airplane assembly accounts for more than 50 percent of the whole airplane manufacturing. Therefore the assembly technology of airplane, especially large-body airplane, is hard, complex involving multidiscipline integrated work. It decides the airplane final quality, manufacturing cost and cycle to a large extent, thus a core and the key technology in airplane manufacturing. Large body civil airliner manufacturing is marked by three distinct features. the first, its large volume of parts with variety of disciplines, is hard to assemble. The second, its long service life entails long system legacies, such as the B777 has 40 years designed life span, extendable up to 70 years. Third comes the demand of high reliability in flight, as aero planes are becoming most popular means for international transportation. Companies with experience of handling only small aero plane face challenges in assembly when switching to wide body aero plane manufacturing. The booming digital technology has brought a promising, new approach to airplane assembly. World wide the digital flexible assembly technology system (DFATS) is an innovative and revolutionary research area, and its primary focus is aircraft assembly realm. We have practically collected and deeply analyzed the characteristic of large-scale airplane digital major-parts connections. We here in study and present an advanced assembly workstation prototype system, and expound each key technique referred to the system. 2 Characteristics of Airplane Major- Parts Assembly Conventionally airplane assembly still uses the “model line-template-master tooling” (molding board, sample parts, gauge, etc) work method mainly based on the analog transfer mode. This method slow, tedious, needing intense coordination steps. The complex techniques entail use of excessive use of baroque, hard and special entity master tooling and assembly jigs. Its expensive with poor changeability and re-forming abilities. Even today assembly method for connecting major parts remain hand pushing and shoulder lifting First, workers put each to be connected part onto tow truck. Usually there are a trail of connection holes and pins between two linked components. Secondly, several workers push one part close up to another part. Thirdly they observe and adjust if the connection Proceedings of the 5th WSEAS Int. Conf. on CIRCUITS, SYSTEMS, ELECTRONICS, CONTROL & SIGNAL PROCESSING, Dallas, USA, November 1-3, 2006 337
Transcript
Research for Major-Parts Digital Assembly System of Large-Scale Airplane
ZOU JIHUA RIAZ AHMAD FAN YUQING
School of Mechanical Engineering and Automation Beijing University of Aeronautics and Astronautics
Xue Yuan Lu No.37, Beijing P.R.CHINA
Abstract: - In view of greater complexity and high precision needed for assembling large-size airplane parts, we propose the digital flexible assembly technology system (DFATS) concept, for assembly of major-parts and alignments. The concept has been described and demonstrated by presenting the flexible assembly workstation prototype system for major-parts assembly and positioning. All the primary key techniques related to large-scale airplane parts assembly, and related content of items have been described. The paper analyzed data set organization and coordination relationship based on Digital Mock-Up, provided assembly simulation content, and defined Digital Master Tooling (DMT) concept with a specific approach. It explained function and content of mechanical follow-up positioning device, control software, its effect, operating principle and method of the laser tracking measurement assembly technique. Key-words: - Digital Assembly; Flexible Assembly Workstation; Digital Master Tooling; Mechanical Follow-Up Positioning; Laser Tracking Measurement 1 Introduction Modern large-scale airplanes are characterized by complex structure and configuration. Enormous volume of parts (up to more than three million pieces), is often difficult to organize in compact inner space, anfractuous coordination relationships, and for bad work access for assembly and installation. More often the workload of airplane assembly accounts for more than 50 percent of the whole airplane manufacturing. Therefore the assembly technology of airplane, especially large-body airplane, is hard, complex involving multidiscipline integrated work. It decides the airplane final quality, manufacturing cost and cycle to a large extent, thus a core and the key technology in airplane manufacturing. Large body civil airliner manufacturing is marked by three distinct features. the first, its large volume of parts with variety of disciplines, is hard to assemble. The second, its long service life entails long system legacies, such as the B777 has 40 years designed life span, extendable up to 70 years. Third comes the demand of high reliability in flight, as aero planes are becoming most popular means for international transportation. Companies with experience of handling only small aero plane face challenges in assembly when switching to wide body aero plane manufacturing. The booming digital technology has brought a promising, new approach to airplane assembly.
World wide the digital flexible assembly technology system (DFATS) is an innovative and revolutionary research area, and its primary focus is aircraft assembly realm. We have practically collected and deeply analyzed the characteristic of large-scale airplane digital major-parts connections. We here in study and present an advanced assembly workstation prototype system, and expound each key technique referred to the system. 2 Characteristics of Airplane Major- Parts Assembly Conventionally airplane assembly still uses the “model line-template-master tooling” (molding board, sample parts, gauge, etc) work method mainly based on the analog transfer mode. This method slow, tedious, needing intense coordination steps. The complex techniques entail use of excessive use of baroque, hard and special entity master tooling and assembly jigs. Its expensive with poor changeability and re-forming abilities. Even today assembly method for connecting major parts remain hand pushing and shoulder lifting First, workers put each to be connected part onto tow truck. Usually there are a trail of connection holes and pins between two linked components. Secondly, several workers push one part close up to another part. Thirdly they observe and adjust if the connection
Proceedings of the 5th WSEAS Int. Conf. on CIRCUITS, SYSTEMS, ELECTRONICS, CONTROL & SIGNAL PROCESSING, Dallas, USA, November 1-3, 2006 337
holes match together with pins and inserts. This traditional method has the following limitations: Aircraft parts, especially the major-parts of airplane are very ponderous, manhandling them is difficult and inefficient. The assembly quality lacks the coordinated precision of the joint holes and pins low, and always create the force-press assembly, resulting into stresses and fatigue. On the even-joint assembly coordination, the traditional method is still the original analog transfer mode. For example, to ensure that even-joint assembly goes on wheels and is reliable, the relevant master tooling is designed and manufactured on the even-joint position for coordination. That not only prolongs the assembly cycle without interchangeability, but also exhibit disadvantages of the analog transfer mode. This conventional method is not practical for section-joint assembly of large-airplane, but also not recommended technically. So we have no alternative to digital technology assembly for major-parts. 3 DFATS for Major-Parts Assembly 3.1 Concept and Structure Digital flexible assembly technology system (DFATS) is a new, advanced airplane assembly technology, which aims at particular manufacturing aspect, making use of the digital techniques, concluded from study of the parts/components assembly and the section joints. Substantially it is deep application of digital techniques that extend into airplane design and manufacturing process. DFATS synthetically utilizes digital product definition (DPD), digital master tooling (DMT) based coordination, digital mock-up (DMU), laser tracking measurement (LTM), automation mechanical follow-up positioning (MFUP) and control technology, and many other advanced techniques. DFATS overcome shortcomings of traditional airplane assembly process, with objective to reduce all kinds of special tooling and jigs, by increasing assembly tooling commonality. It reduces the tooling factory cost, achieves digital automation assembly, cuts tooling preparation time, and upgrades the airplane assembly efficiency maximizing quality. Structure applications of airplane assembly can be classified into three kinds: structure-parts assembly, components assembly and sections (major-parts) connection assembly. We focus the last type for flexible assembly technology wide body airplane
sections. Figure 1 show the structural composition and cooperative relationship of DFATS for large-scale airplane section links.
Fig.1 Digital Flexible Assembly Technology System Based on the 3-D data set and digital mock-up in the single source of product data (SSPD), DFATS can pick up data, analyze key characteristic (KC), build the DMT model, and then deal with the data obtained from 3-D data set by using the DMT-based digital coordinate technology. The obtained data is used to simulate/analyze assembly process, and to check the 3-D DMU accuracy with results. If necessary, the analysis result can be fed back to the original data set to correct the iffy 3-D DMU and process. When analysis and simulation results are satisfactory (including DMU and process, etc.), these will be transferred to the control and measurement system of flexible assembly workstation (FAW) through computers. Then major-parts assembly is completed by using mechanical follow-up positioning (MFUP) device and control software and laser tracking measurement (LTM). Simultaneously the measurement device can gather data from SSPD directly for assembly. When using FAW to assemble the major-parts connection, the assembly results need to be compared with the simulation and analyze results to verify and modify the theory data set, as well as when assembly procedure encounters error. 3.2 FAW Prototype System Multiplicative flexible assembly technology integrates with each other and work together to realize some parts assembly, and so these grouped flexible assembly work devices compose the flexible
Proceedings of the 5th WSEAS Int. Conf. on CIRCUITS, SYSTEMS, ELECTRONICS, CONTROL & SIGNAL PROCESSING, Dallas, USA, November 1-3, 2006 338
assembly workstation (FAW). Digital FAW supported by DFATS, shows the integrated application of many flexible assembly key techniques. According to the design construction, the flexible assembly workstation of major-parts connection, assembles components to an airplane with full functions. It has the ability of real-time detecting the position data of each anchor point, and auto-regulating each part orientation in space to realize final assembly work between major-parts. The major-parts connection digital flexible assembly workstation prototype system is composed of actuating mechanism, control system, measurement system, computer software, shown in figure 2. The actuating mechanism is usually made up of mechanical follow-up positioning (MFUP) device. Besides supporting the even-joint major-parts, it is controlled through a system that control driving mechanism, and completes position adjusting, fastening, clamping and other actions. Its machine part is mainly consist of locators and fixtures. These locators and fixtures can move along several degrees of freedom (DOFs). When their heads contact airplane components, load-measuring cells survey the load size continuously and feed to control system for restricting the load that locators exert on airplane parts, thus avoiding overload.
Measure system
Analysis software
Control system Control software
Driving mechanism
Measure software
Actuating mechanism Measure reference point
3-D digital model
Connection measure surface
Measure reference point
Actuating mechanism
Actuating mechanism Computer software
Actuating mechanism
Control system Measure system
Computer software
Driving Mechanism
Fig.2 FAW Prototype System
The control system is mainly used for receiving those control commands sent out by software. It drives corresponding dynamo servo driver or hydrometric drivers to realize the adjusting and positioning of actuating mechanism, and uses GUI mode to realize the control of position measuring and target motion. The measurement system is mainly used for data collecting and monitoring in the course of assembly, and its aim is to improve precision and assembly accuracy. The data-collecting and position-monitoring is achieved by laser tracking
measurement system, and the measured result fed back to computers, where subsequent operations are executed by software. The computer software functions include gathering, ordering, analyzing, handling, and transferring the measured data, and forwarding controllable instructions. Its role is the bridge and ground between measurement system and control system. 4 Support Technology in DFATS 4.1 DMU-Based Assembly Process Simulation Digital mock-up (DMU) main content is three-dimension product digital model. A fully defined airplane 3-D digital model, depicting all information and released by design department as engineering data (ED) set. According to different function and purpose, ED set can be divided into three subclasses: parts manufacturing data (MD) set, assembly data (AD) set, inspecting data (ID) set. They separately include the parts manufacturing tooling manufacturing information, assembly tooling, assembly process information, parts/assembly/tooling inspection information, and enabled to eliminate irrelative information to their function from engineering data set. Figure 3 shows the organization and coordination relationship of all data sets.
Engineering data set
Assembly data set Manufacture data set Inspecting data set
Assembly tooling data
set
Part inspecting
data set
Tooling inspecting
data set
Assembly process data
set
Assembly inspecting data
set
Part tooling manufacture data
set
Parts manufacture
data set
Assembly tooling manufacturing
Parts manufacturing
Part tooling manufacturing
ASSEMBLY
Digital Mock-up
Fig.3 Data Set Organization and Correspondence
Assembly process simulation (APS) utilizes the digital pre-assembly (DPA) for DMU, and is mainly used for interference inspection and assembly ability analysis. It is based on 3-D entity model of parts and tooling, the product data management (PDM) and the design share; it can coordinate the product structure design, the system design, the parts assembly and
Proceedings of the 5th WSEAS Int. Conf. on CIRCUITS, SYSTEMS, ELECTRONICS, CONTROL & SIGNAL PROCESSING, Dallas, USA, November 1-3, 2006 339
disassembly inspection effectively reducing the design-redoing and changes emerging from design mistakes. Only based on applying uniform 3-D configuration software for airplane database modeling, we can realize the simulation and analysis of assembly process better. The objects of DMU-based assembly process simulation and analysis are the assembly between toolings, tooling and parts, or the direct assembly relationship between the parts. Its four main aspects are: (1) Assembly feasibility; (2) Coordination route analysis; (3) Operating ability analysis; (4) Assembly interference analysis. 4.2 DMT Technology for Digital Coordination The digital master tooling (DMT) definition (or DMT model) is not an entity, but a mathematical model including geometry shapes and dimensions of some product sectors. It may be an engineering digital model, or a tooling digital model adding the essential process information. It is the digital criterion of manufacturing, inspection, coordinating parts and tooling, laying important foundation to ensure dimension and shape coordinating and interchange, between product tooling, assembly tooling and parts. Commonly it can be realized by CAD/CAM and advanced optical measurement system. Thus, the technology of using DMT is a digital coordination approach that uses 3-D (CATIA) model data and datum reference system to produce tools for detailed manufacturing, sub-assembly, major-parts assembly and inspection. Software is installed into the laser tracking measuring system to enable measurements to be taken or features to be set in a defined coordinate system. Software also allows real-time measurement and allows the measurement data to be compared directly with the 3-D model definition (parts or tooling) [1]. The DMT model is mainly used in the place with high coordination accuracy request, such as key nodical positions, connection surfaces. Its purpose is replacing the hard master tooling, and acting as coordination standard and inspection principle, in each product process between different product departments or within department. The DMT model also guarantees the correctness of different members in different tooling. In figure 4, there is a Key Hole on the part, and the part is assembled on three suits of tooling in turn, and then every suit of tooling needs one assembly pin and one inspection pin. Usually the assembly pin has a little larger dimension and tolerance than the inspection pin in the same outfit of tooling, such as 0.001 inch. In addition, the inspection pin in the last
outfit of tooling can be copied as the assembly pin in the next outfit of tooling. So we can reduce a number of pins in this method, and we need 4 pins in this example at least. The round 3-D model on the right of the figure 4 include the dimension and tolerance requirement to the hole in each tooling and its pins, such as Hole (/Pin) diameter, tolerance, concentricity, position tolerance, etc. Subsequently during design of three suits of tooling, tooling assembly and parts assembly, the technologists will need not build special hard master tooling; and those are according to the 3-D data of the “Step4 – final” model in the figure. In addition other methods are adopted like NC machining, laser tracker direct assembly such that requirement of high coordination accuracy could be easily satisfied. In the figure, the “Step4-final” model on the right is just the DMT definition (or DMT model).
Assembly Tooling 2
Part
Hole
Assembly Pin 1 Assembly Tooling 1
Firs
t Ass
embl
y Φ、±Δ、 、
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Inspecting Pin 1
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Assembly Tooling 3 Inspecting Pin 2
Assembly Pin 3
Φ,±Δ, ,
Φ,±Δ, ,
Φ,±Δ, ,
Seco
nd
Ass
embl
y Th
ird
Ass
embl
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Fig.4 Digital Master Tooling Definition Model
Table 1 is the comparison between two major-parts in a certain type airplane before and after using DMT method [1]. Evidently we find that the total lifecycle from design to final assembly is shortened by about 10 months. This is because the DMT model is defined at the beginning of design, such that sequel parts and tools which need master tooling can be designed, manufactured and assembled ahead of schedule. When using DMT-based digital coordination technology, the key characteristic (KC) of airplane digital model should be considered. Key characteristic (KC) is, the character whose change makes maximal influence to the interchange ability and coordination of products in material, parts or process. It must be measurable through computation
Proceedings of the 5th WSEAS Int. Conf. on CIRCUITS, SYSTEMS, ELECTRONICS, CONTROL & SIGNAL PROCESSING, Dallas, USA, November 1-3, 2006 340
or count datum. KC problem mainly includes the KC choice and determine, KC disassembly (transfer),
building the KC tree and KC analysis control. [2]
Table 1 the Compare of Total Design and Manufacture Cycle Before and After Using DMT
ID Task Name Start Finish1 WITH HARD MASTER Mon 12/22/03 Fri 12/2/05
2 FLOW LINES FROZEN Mon 12/22/03 Mon 12/22/03
3 DATUM SCHEME SET UP Tue 12/23/03 Mon 1/5/04
4 BONDMENTS DESIGNED Tue 12/23/03 Mon 3/1/04
5 BONDMENT TOOLS DESIGN AND MANU Tue 12/23/03 Mon 3/29/04
10/12 1/4 3/28 6/20 9/12 12/5 2/27 5/22 8/14 11/6 1/29January July January July January
4.3 MFUP and Control Software In airplane digital assembly, the mechanical follow-up positioning (MFUP) is a digital auto-control high precision device, its structure and work mode are decided by employing targets. The actuating mechanism is the positioning mechanism of MFUP, and it is adjusted and supported by auto control mode. It completes positioning of the assembled major-parts under the lead of driving mechanism, it even completes the clamping and other assembly work. The assembled major-parts positioning on the flexible assembly workstation (FAW) can adopt two forms: the bracing or the sucking disc, and these two are all controlled by computer. Sense technique can also be used for assisting accurate positioning in flexible orientation. Figure 5 is a high precis MFUP device and mock-up of a certain airplane [3].
Fig.5 High Precise Mechanical Follow-up
Positioning Device and Mock-up The function of the control software is to organize
and keep contact with standard data set, i.e. practice data gathered from laser tracker, servo-control hardware system, laser tracking measurement device and relative equipments. Besides the 3-D modeling design software (CATIA, etc.) and assembly simulation software, following two kinds of control software are needed: 4.3.1 Tooling and device control software Control software offer a very convenient interactive interface, enabling operators observe the airplane major-parts motion and the movement of MFUP locators expediently and intuitively. On the GUI operators can control airplane major-parts rectilinear or rotational movement judged by them. Shown in figure 6 [4], the software has two main interfaces: while working the first system interface is used to confirm the positions of the flexible assembly system and the assembly targets, and to set each parameter; the second one is used to operate the fine adjustment of control system, in order that MFUP device gets positioned accurately.
Fig.6 the Interactive Interface in Control System
Proceedings of the 5th WSEAS Int. Conf. on CIRCUITS, SYSTEMS, ELECTRONICS, CONTROL & SIGNAL PROCESSING, Dallas, USA, November 1-3, 2006 341
Hardware controlling software is mainly employed on the mechanical section of driving mechanism and actuating mechanism. It works with NC drilling and riveting device, allowing laser tracker to finish auto drilling and riveting, auto sealing operation, and so on. So this kind of software should have nice integration with the hardware of control system, and hardware system itself. 4.3.2 Measure and analysis software On one hand, this kind of software must be used collectively with measurement system device. The software has self-contained dataset input/output channels, it precisely obtain theoretical data from digital model and actual measurement data, compare the original 3-D data to the actual data. It too can perform simulation and analysis. On the other hand, it ought to cooperate with hardware-controlled software, such as transferring the analysis result to device control software, in order to drive fixture and actuating mechanism movement. Furthermore, it can implement functions such as detecting abnormal states, hyper dimension state identification, and visualization of the invisible information etc. 4.4 Laser Tracking Measurement Technology With the application of controllable MFUP device and DMU-based digital coordination method, effective space positioning can be achieved using optics measurement, accurate position survey and other assembly works. Compared to the traditional measurement method which uses three-coordinate measuring machine, digital optics measuring technology has characteristics of no touch, no guild rail, rapid inspecting speed, good portability, and so on [5]. To conclude here we can say laser tracker is one of the most advanced measurement device worth application and study. Coordinate transformation and calculations, while using laser tracker assembly, be performed as following. Set points, A1 B1 and C1 as a Cartesian coordinates(local coordinates system) to act as reference at random, any where on airplane body or tooling. Then we take three reference points [A B C](airframe coordinates system) in the software, which are then related to earlier set of points i.e. A1, B1, and C1 thru laser tracker reference. How we relate and transform these coordinates is explained in following subparagraphs. Measure the spatial position of one key point E in even-joint assembly, and judge if it is accurate enough to the theoretical position, as following: (1) From the digital airplane design model, get the
relative position relationship of point E to the airframe Cartesian coordinates. Marking it as vector E:
E→[A B C] (1) (2) Using the laser tracker, accurately measure the relative position of the assembly local Cartesian coordinates to the “Home Point” D. Marked vector:
[A1 B1 C1]→D (2) (3) Now consider the two coordinates coincidence, namely fit the two coordinates in the work software of the laser tracker. Adopt the best fit algorithm for following relationship:
[A B C]= [T] [A1 B1 C1] (3) Where [T] is the best fit matrix of coordinate transformation, then:
(D→[A B C]) = [T] (D→[A1 B1 C1]) (4) (4) To sum up, we can push out: (E→[A B C]) = (E→D) + (D→[A B C]) =(E→D) + [T] (D→[A1 B1 C1]) －= (E→D) [T] ([A1 B1 C1]→D) (5) Where (E→D) represents the vector coordinate from measured target E to the Home Point. So, in the assembled local Cartesian coordinates, we need at least three points to be measured randomly, beside surveying the point E toward “Home Point” D. Then the measured position of E under the airframe Cartesian coordinates can be obtained, and compared with theatrical value. This method is basically an algorithm principle of laser tracker. If the point E is key point in the fixture, then we can do the fixture positioning; if E is the key characteristic of parts or sections, then we can do the parts inspection. Laser tracking measurement technology is mainly used for: (1) Confirming the spatial positions of locating points on the tooling platform. (2) Monitoring and adjusting in the assembly process. (3) Inspection after assembly. (4) Maintenance of flexible assembly tooling platform. Beside laser tracker, two alternate methods gaining acceptance are indoor GPS spatial orientation measure method [6,7] and digital photographing measurement. The first one specializes in the positioning and adjustment assembly work to large-size measured objects. The later adapts to measure shape-complex product with little temperature influence. 5 Conclusion Digital flexible assembly technology (DFAT) points to the modern and futuristic assembly techniques
Proceedings of the 5th WSEAS Int. Conf. on CIRCUITS, SYSTEMS, ELECTRONICS, CONTROL & SIGNAL PROCESSING, Dallas, USA, November 1-3, 2006 342
which hold promise to overcome the traditional assembly weaknesses. Such technology is inevitable for developing any large-scale airplane, and boosting the assembly efficiency and quality. There are convincing reasons for adoption of digital assembly method to induce agility, product quality and efficiency in the process. Reference [1] GE, Nacelle Tool Mastering Discussion,
2004.1.15 [2] Liu Zhicun, Zou Jihua, Fan Yuqing, Research
and Analysis on Key Characteristics in subassembly of frame kind Manufacturing, Aerospace Materials & Technology (Be Accepted)
[3] http://www.novatechengineering.com [4] Gary Williams, Edward Chalupa, and Steven
Rahhal, Automated Positioning and Alignment Systems, Advanced Integration Technology, Inc. 2000
[5] Zhang Fuchun, Zhang Jun, Tang Wenyan, Lu Honggen, Application of Laser Tracker on Geometric Parameters Measurement of Large Dimensional Workpieces, Tool Engineering, No.5(2002), p. 26-28
[6] Russ Olexa, Measuring the Big Stuff, Manufacturing Engineering, April 2003 Vol. 130 No. 4
[7] Mike Richman, Advances in Large-Scale Assembly, http://www.qualitydigest.com/feb05/articles/01_article.shtml, February 2005 issue
[8] Michael C. Richey, Robert S. McIvor, Scott C. Sandwith, Computer Aided-Design-Manufacturing & Measurement Integration, Coordinate Measurement System Committee, August 13-17 2001
[9] Fan Yuqing, Modern Airplane Manufacture Technology, Bei Hang Press, 2001, Beijing
Proceedings of the 5th WSEAS Int. Conf. on CIRCUITS, SYSTEMS, ELECTRONICS, CONTROL & SIGNAL PROCESSING, Dallas, USA, November 1-3, 2006 343
