Showing papers in "Robotics and Computer-integrated Manufacturing in 2007"

Multiple-attribute decision making methods for plant layout design problem

Abstract: The layout design problem is a strategic issue and has a significant impact on the efficiency of a manufacturing system. Much of the existing layout design literature that uses a surrogate function for flow distance or for simplified objectives may be entrapped into local optimum; and subsequently lead to a poor layout design due to the multiple-attribute decision making (MADM) nature of a layout design decision. The present study explores the use of MADM approaches in solving a layout design problem. The proposed methodology is illustrated through a practical application from an IC packaging company. Two methods are proposed in solving the case study problem: Technique for order preference by similarity to ideal solution (TOPSIS) and fuzzy TOPSIS. Empirical results showed that the proposed methods are viable approaches in solving a layout design problem. TOPSIS is a viable approach for the case study problem and is suitable for precise value performance ratings. When the performance ratings are vague and imprecise, the fuzzy TOPSIS is a preferred solution method.

Development of design for remanufacturing guidelines to support sustainable manufacturing

Abstract: Developing sustainable approaches to manufacture is a critical global concern. Key measures towards this include practicing design for environment (ecodesign), for example by improving remanufacturing efficiency and effectiveness. Remanufacturing is a process of bringing used products to a ''like-new'' functional state with warranty to match. Its significance is that it can be both profitable and less harmful to the environment in comparison to conventional manufacturing. Remanufacturing has a low profile in world economies and is poorly understood because of its relative novelty in research terms. However, environmental and competitive pressures are changing the global and business environment and this is fuelling interest in the practice. This paper provides the background to remanufacturing together with the findings from workshops recently undertaken in the UK as part of research into design and manufacturing approaches to facilitate remanufacturing.

Design and application of industrial machine vision systems

Abstract: In this paper, the role and importance of the machine vision systems in the industrial applications are described. First understanding of the vision in terms of a universal concept is explained. System design methodology is discussed and a generic machine vision model is reported. Such a machine includes systems and sub-systems, which of course depend on the type of applications and required tasks. In general, expected functions from a vision machine are the exploitation and imposition of the environmental constraint of a scene, the capturing of the images, analysis of those captured images, recognition of certain objects and features within each image, and the initiation of subsequent actions in order to accept or reject the corresponding objects. After a vision system performs all these stages, the task in hand is almost completed. Here, the sequence and proper functioning of each system and sub-systems in terms of high-quality images is explained. In operation, there is a scene with some constraint, first step for the machine is the image acquisition, pre-processing of image, segmentation, feature extraction, classification, inspection, and finally actuation, which is an interaction with the scene under study. At the end of this report, industrial image vision applications are explained in detail. Such applications include the area of automated visual inspection (AVI), process control, parts identification, and important role in the robotic guidance and control. Vision developments in manufacturing that can result in improvements in the reliability, in the product quality, and enabling technology for a new production process are presented. The key points in design and applications of a machine vision system are also presented. Such considerations can be generally classified into the six different categories such as the scene constraints, image acquisition, image pre-processing, image processing, machine vision justification, and finally the systematic considerations. Each aspect of such processes is described here and the proper condition for an optimal design is reported.

RFID-based wireless manufacturing for walking-worker assembly islands with fixed-position layouts

Abstract: A walking-worker fixed-position flexible assembly line is a shop-floor where products are placed at work centres, the workers move from one work centre to another, and tools and components are brought to the work centre for assembly according to the process and production plan. Such assembly shop-floor configuration is not only suitable for producing large, bulky, heavy or fragile products, but also offers necessary flexibility and competitive operational efficiency for products of modest variety and production volumes. However, the shop-floor with a fixed-position assembly islands typically suffers from limited spaces at work centres and high dynamics of material and manpower flows in addition to common shop-floor problems. This paper presents an affordable solution to these problems by using wireless manufacturing (WM)-an emerging advanced manufacturing technology (AMT). WM relies substantially on wireless devices such as radio frequency identification(RFID) auto ID sensors and wireless information networks for the collection and synchronization of the real-time field data from manufacturing workshops. A simplified example is used to illustrate how to deploy WM technology for implementing the concept of Just-In-Time (JIT) manufacturing to reduce the shop-floor work-in-progress (WIP) inventories and smoothening their flows through real-time information visibility and traceability.

Kinematic analysis of a 3-PRS parallel manipulator

Abstract: Although the current 3-PRS parallel manipulators have different methods on the arrangement of actuators, they may be considered as the same kind of mechanism since they can be treated with the same kinematic algorithm. A 3-PRS parallel manipulator with adjustable layout angle of actuators has been proposed in this paper. The key issues of how the kinematic characteristics in terms of workspace and dexterity vary with differences in the arrangement of actuators are investigated in detail. The mobility of the manipulator is analyzed by resorting to reciprocal screw theory. Then the inverse, forward, and velocity kinematics problems are solved, which can be applied to a 3-PRS parallel manipulator regardless of the arrangement of actuators. The reachable workspace features and dexterity characteristics including kinematic manipulability and global dexterity index are derived by the changing of layout angle of actuators. Simulation results illustrate that different tasks should be taken into consideration when the layout angles of actuators of a 3-PRS parallel manipulator are designed.

Flexible job-shop scheduling with routing flexibility and separable setup times using ant colony optimisation method

Abstract: This paper proposes an ant colony optimisation-based software system for solving FMS scheduling in a job-shop environment with routing flexibility, sequence-dependent setup and transportation time. In particular, the optimisation problem for a real environment, including parallel machines and operation lag times, has been approached by means of an effective pheromone trail coding and tailored ant colony operators for improving solution quality. The method used to tune the system parameters is also described. The algorithm has been tested by using standard benchmarks and problems, properly designed for a typical FMS layout. The effectiveness of the proposed system has been verified in comparison with alternative approaches.

An agent-based service-oriented integration architecture for collaborative intelligent manufacturing

Abstract: The rapidly changing needs and opportunities of today's global market require unprecedented levels of interoperability to integrate diverse information systems to share knowledge and collaborate among organizations. The combination of Web services and software agents provides a promising computing paradigm for efficient service selection and integration of inter-organizational business processes. This paper proposes an agent-based service-oriented integration architecture to leverage manufacturing scheduling services on a network of virtual enterprises. A unique property of this approach is that the scheduling process of an order is orchestrated on the Internet through the negotiation among agent-based Web services. A software prototype system has been implemented for inter-enterprise manufacturing resource sharing. It demonstrates how the proposed service-oriented integration architecture can be used to establish a collaborative environment that provides dynamic resource scheduling services.

Measuring the impact of Lean tools on the cost-time investment of a product using cost-time profiles

Abstract: Traditional costing systems consider the accumulation of costs, but not their timing. Value stream mapping presents a good picture of the time consumed and operations performed for the production of a product within a manufacturing facility, but it does not track the accumulation of costs. The cost-time profile (CTP) is a tool that follows the accumulation of cost in the manufacturing of a product through time; and it finds the cost-time investment (CTI), which is an indicator of the use of resources in the manufacturing of a product through quantities and timing. In this paper, the expected impact of Lean implementations on the CTP and CTI is discussed. The CTP is proposed as a useful tool for the evaluation of the improvements achieved by the implementation of Lean tools and techniques.

A systematic approach for product families formation in Reconfigurable Manufacturing Systems

Abstract: The aim of this work is to establish a methodology for an effective working of Reconfigurable Manufacturing Systems (RMSs). These systems are the next step in manufacturing, allowing the production of any quantity of highly customised and complex products together with the benefits of mass production. In RMSs, products are grouped into families, each of which requires a system configuration. The system is configured to produce the first family of products. Once it is finished, the system is reconfigured in order to produce the second family, and so forth. Therefore, the effectiveness of a RMS depends on the formation of the best set of product families. Therefore, a methodology for grouping products into families, which takes into account the requirements of products in RMSs, is an issue of core importance. These requirements are modularity, commonality, compatibility, reusability, and product demand. The methodology starts by calculating, for each product requirement, a matrix that summarises the similarity between pairs of products. Then, through the use of the AHP methodology, a unique matrix that comprises the similarity values between products is obtained. The Average Linkage Clustering algorithm is applied to this matrix in order to obtain a dendogram that shows the diverse sets of product families that may be formed.

Autonomous robot calibration using vision technology

Abstract: Unlike the traditional robot calibration methods, which need external expensive calibration apparatus and elaborate setups to measure the 3D feature points in the reference frame, a vision-based self-calibration method for a serial robot manipulator, which only requires a ground-truth scale in the reference frame, is proposed in this paper. The proposed algorithm assumes that the camera is rigidly attached to the robot end-effector, which makes it possible to obtain the pose of the manipulator with the pose of the camera. By designing a manipulator movement trajectory, the camera poses can be estimated up to a scale factor at each configuration with the factorization method, where a nonlinear least-square algorithm is applied to improve its robustness. An efficient approach is proposed to estimate this scale factor. The great advantage of this self-calibration method is that only image sequences of a calibration object and a ground-truth length are needed, which makes the robot calibration procedure more autonomous in a dynamic manufacturing environment. Simulations and experimental studies on a PUMA 560 robot reveal the convenience and effectiveness of the proposed robot self-calibration approach.

Developing a framework for sustainability management in engineering SMEs

Abstract: Sustainability issues in manufacturing and production are growing exponentially. Initially referring to environmental considerations, sustainability now also encompasses social, ethical and economical responsibilities. This paper focuses on engineering and manufacturing SMEs and outlines a regional study undertaken on a small number of these companies which have succeeded in developing appropriate tools and strategies to satisfy the current ISO 14001 standard. Their experiences, strategies and solutions are used to devise and develop a framework for sustainability management, taking an incremental approach in moving from environmental management, using ISO 14001 as a foundation, to sustainability management which will contribute to an annual sustainability report which is currently only undertaken by large corporations. The framework consists of two levels, with the first focusing on ISO 14001 and the second aimed towards managing all social, environmental and economical aspects within an engineering SME. Key results from the regional study of ISO 14001 certified engineering SMEs highlight the importance of environmental and sustainability awareness programs for top management, eliciting and obtaining their full support and commitment.

Trajectory generation for open-contoured structures in robotic fibre placement

Abstract: Composites have become common engineering materials in industries where the strength to weight performance of structures is a key design consideration. The major limiting factors are the high-manufacturing costs and low-production rates. Robotic fibre placement (RFP) is one alternative process to overcome the limiting factors and it is generally suitable for open-continuous components. A novel path planning algorithm for open-contoured structures, entitled the surface curve algorithm for robotic fibre placement (SCAR) is proposed. The algorithm aims to produce a uniform lay-up of composite lamina, without gap and overlap between subsequent tows. A numerical investigation into the characteristics of the algorithm is performed and presented. The algorithm is implemented on complex contoured surface and some of the results are presented in this paper.

RFID-enabled automation in support of factory integration

Abstract: In recognition of the need for more effective and efficient factory system integration solutions, this paper improves the method proposed in our previous work, focusing on new mechanisms to bridge the gap between shop floor automation and factory information systems. As one of the mainstream identification technologies, radio frequency identification (RFID) technology makes possible all products uniquely identifiable across factories. By taking advantage of data capacity stored in an RFID tag, critical manufacturing information on a product can be locally stored with the product. RFID technology provides a means for a product to rapidly retrieve its needed information as it advances through shop floors. A corresponding framework to enable the instant delivery of pertinent data and information on a uniquely identifiable job/product at point-of-need across factories is proposed. A small-scale manufacturing application is presented to show how the proposed approach can be implemented on the shop floor.

Robotic sanding system for new designed furniture with free-formed surface

Abstract: In this paper, a sanding system based on an industrial robot with a surface following controller is proposed for the sanding process of wooden materials constructing furniture. Handy air-driven tools can be easily attached to the tip of the robot arm via a compact force sensor. The robotic sanding system is called the 3D robot sander. The robot sander has two novel features. One is that the polishing force acting between the tool and wooden workpiece is delicately controlled to track a desired value, e.g., 2kgf. The polishing force is defined as the resultant force of the contact force and kinetic friction force. The other is that no complicated teaching operation is required to obtain a desired trajectory of the tool. Cutter location (CL) data, which are tool paths generated by a CAD/CAM system, are directly used for the basic trajectory of the handy tool attached to the robot arm. The robot sander can be applied to the sanding task of free-formed curved surface with which conventional sanding machines have not been able to cope. The effectiveness and promise are shown and discussed through a few experiments.

Assembly and manipulation of micro devices-A state of the art survey

Abstract: This paper provides a comprehensive review of research efforts in the emerging field of micro devices assembly (MDA) as well as identifies future directions for research. The general domain dealing with both manual and automated assembly of micro devices can be referred to as MDA. The study of computer-based methods to accomplish the assembly of micron-sized parts can be described as Automated MDA (AMDA). The primary focus of this paper is to provide an overview of concepts related to MDA as well as a review of various segments of MDA research including study of the role of interactive forces at the micro level, the design of innovative gripping and assembly techniques as well as the use of information technology (IT) based approaches.

PCBN tool wear modes and mechanisms in finish hard turning

Abstract: The use of polycrystalline cubic boron nitride (PCBN) cutting tools in hard turning applications is continuously growing with the number of commercially available grades increasing, allowing new application areas to be explored. In order to take full advantage of the benefits offered by PCBN it is necessary to understand the behaviour of the material in application. Tool behaviour is influenced by many factors which include the composition of the PCBN material, the steel workpiece, the nature of the cutting operation, the cutting conditions and the tool geometry. The focus of this paper is the continuous turning of hardened steels. A significant amount of research has been carried out in this area and a literature review of the relevant work is presented. This identifies the primary wear modes and discusses the many theories proposed to explain the mechanisms contributing to PCBN tool wear and failure. The final section of the paper considers the critical factors that influence the behaviour of PCBN tools in continuous hard turning and how this knowledge can be applied to optimise tool performance.

Process control in CNC manufacturing for discrete components: A STEP-NC compliant framework

Abstract: With today's highly competitive global manufacturing marketplace, the pressure for right-first-time manufacture has never been so high. New emerging data standards combined with machine data collection methods, such as in-process verification lead the way to a complete paradigm shift from the traditional manufacturing and inspection to intelligent networked process control. Low-level G and M codes offer very limited information on machine capabilities or work piece characteristics which consequently, results in no information being available on manufacturing processes, inspection plans and work piece attributes in terms of tolerances, etc. and design features to computer numerically controlled (CNC) machines. One solution to the aforementioned problems is using STEP-NC (ISO 14649) suite of standards, which aim to provide higher-level information for process control. In this paper, the authors provide a definition for process control in CNC manufacturing and identify the challenges in achieving process control in current CNC manufacturing scenario. The paper then introduces a STEP-compliant framework that makes use of self-learning algorithms that enable the manufacturing system to learn from previous data and results in eliminating the errors and consistently producing quality products. The framework relies on knowledge discovery methods such as data mining encapsulated in a process analyser to derive rules for corrective measures to control the manufacturing process. The design for the knowledge-based process analyser and the various process control mechanisms conclude the paper.

Design for adaptability (DFAD)-a new concept for achieving sustainable design

Abstract: This paper discusses the concepts associated with a new methodology, design for adaptation (DFAD), under development for achieving advanced sustainable designs. The DFAD methodology concept is based on the hypothesis that product life ends because a product is unable to adapt to change. A product may be retired for myriad reasons including that it is broken, out of style, or has become inefficient due to technology obsolescence. In these cases, the product was not able to adapt to change-it was unable to self-heal, it could not modify or reconfigure to meet changing fashion needs, or it could not be upgraded, for physical or economic reasons, to utilize new technology. To address these and similar issues, we are developing the DFAD methodology. DFAD is based on classical control theory and products are conceptualized and modeled as dynamic systems with feedback control strategies to respond, or adapt, effectively to changes in product performance criteria. The DFAD concept takes into account that changing performance requirements may be based on physical, cultural, environmental, and/or economic considerations, among others.

Dynamic data sharing and security in a collaborative product definition management system

Abstract: Product definition management (PDM) is a system that supports management of both engineering data and the product development process during the total product life cycle. The formation of a virtual enterprise is becoming a growing trend, and vendors of PDM systems have recently developed a new generation of PDM systems called collaborative product definition management (cPDM). This paper presents the concept of a virtual engineering community (VEC) to support concurrent product development within geographically distributed partners. A previous case study has shown that collaborative engineering design may be modelled from a parameter perspective [1]. Effective implementation of the parameter approach raises the following problems: how to support data sharing and secure that span the partner borders. This paper describes the system architecture, deployed security mechanisms, the prototype developed within cPDM, and the system demonstration using a real test. The implementation of this architecture extends a common commercial PDM system (Axalan(TM)) and utilizes standard software to create a security framework for the involved resources. Collaboration infrastructure, shared team spaces and shared resources are essential to enable virtual teams to work together. Various organizational and technical challenges are implied. The outlined architecture features a federated data approach. These issues are discussed and potential perspectives in the area of collaboration engineering are identified.

Adaptive robotic assembly of compliant aero-structure components

Abstract: The application of robotics to the assembly of large aero-structures has been limited by the large size and inherent compliance of the components involved. The compliance of the components is significant and simple 'pick and place' approaches cannot be used due to the inherent dimensional variability between mating parts. The research described in this paper aims to solve this problem by using a non-contact sensing system to measure part deformation and misalignment in real time. The acquired data can then be processed through a mathematical algorithm to calculate the relative component positions required for optimal assembly. The data can also be used to check gross distortion of components and to reject those outside the specification limits. Existing part-to-part holes were used to provide alignment for individual components within the structure. A series of experiments were performed to investigate the feasibility of the method. Results are presented along with a discussion of the problems that may be encountered during robotic assembly. The experimental results show that robots when combined with non-contact metrology can be used for the assembly of compliant aero-structure components within required tolerance limits.

Development of an agent-based Virtual CIM architecture for small to medium manufacturers

Abstract: Today's global competitions are forcing enterprises to rely on integrated manufacturing systems to satisfy constantly changing market requirements. Whereas Small to Medium Enterprises (SMEs) often feel difficult to compete with large organisations due to having insufficient resources. By integrating resources of many partners, the SMEs can form global integrated manufacturing systems in the form of Virtual CIM (VCIM) and thus achieve a competitive edge. VCIM is a concept towards integrating globally distributed manufacturing resources across enterprise boundaries. In order to implement VCIM, this research project develops an agent-based architecture to support the integration and scheduling of distributed manufacturing resources. This architecture accommodates all agents for VCIM with a three-layered structure and permits new agents to be connected with the existing structure through the Internet when and where necessary. In this architecture, many Facilitator agents coordinate activities of manufacturing resources in a parallel manner. Meanwhile, the Facilitator agents achieve proposal messages through agent negotiation based on distributed resources' real time information and use a backward network algorithm for shortest-path to perform optimisation for resource allocation. With these approaches, an optimised production schedule has the lowest cost as the primary criteria and the shortest production time as the secondary criteria while satisfying customer required due date/time and delivering destination.

Multi-plant production scheduling in SMEs

Abstract: Traditionally, companies used to view themselves as separate entities and did not devote efforts to collaborate with other echelons of the extended enterprise. This even happened at multi-site companies owning different plants that belonged to the same supply chain. However, manufacturing facilities of the same supply chain should intensively share information and coordinate planning and scheduling tasks in order to get a globally optimized solution. This paper discusses some specific characteristics of the planning and scheduling problem in the extended enterprise including an analysis of a case study, and reviews the available state-of-the-art research studies in this field. Most studies suggest that integrated approaches can have a significant impact on the system performance, in terms of lower production costs, and less inventory levels. The paper provides some conclusions and suggestions of future works.

Virtual assembly technologies based on constraint and DOF analysis

Abstract: Assembly constraint is an important factor for product assembly. Constraint is not only necessary for accurate locating of parts but also an important way to realize assembly operation process in virtual assembly (VA) system. In this study, to realize VA reasonably, uniform representations of assembly constraint, equivalent relation between constraint and degree of freedom (DOF), and movable DOF reduction are defined. Several algorithms including based-constraint assembly relation recognition, assembly parts location solving under free and constrained spaces, and movement navigation are developed. These algorithms have been applied to integration virtual assembly environment (IVAE) software system. An example is illustrated, and the results prove that the algorithms provide a good support for the constraint treatments in IVAE and the high consistence between virtual and real assembly process is realized.

Flexible manufacturing of sheet metal parts based on digitized-die

Abstract: Digitized-die forming (DDF) is a flexible manufacturing technology through which a variety of three-dimensional sheet metal parts can be produced in a DDF system. It eliminates the need to design and produce the conventional die. The central component of DDF system is a pair of matrices of punches, the punches are controlled by computer and the desired shape of die is constructed by changing the heights of punches. Based on the flexibility of DDF, new forming processes are designed that cannot be realized in conventional stamping. In varying deformation path DDF, a sheet part is manufactured along an optimal forming path, and large deformation can be achieved for the material with poor formability. In sectional DDF, a sheet part is formed section by section, and this technique makes it possible to manufacture large-size parts in a small DDF press. A closed-loop forming system was built by combining DDF with rapid 3D-shape measurement system. It is used to compensate for material springback and improve dimensional accuracy of the formed part. And a DDF system with multi-point blankholder control system was developed to control the material flow, thereby to prevent sheet parts from wrinkling and tearing. The DDF integrated system is described, and the detailed forming procedures are explained in the paper. Typical examples are presented showing the applicability of the DDF technology.

Automated geneartion of the D-H parameters for configuration design of modular manipulators

Abstract: Analysis models are to describe the relationships between design variables and robotic Kinematic and Dynamic (K&D) behaviors. In designing modular robotic system configuration, design variables are identified through the description of the modular system architecture. Once the design variables have been determined, two alternative ways can be employed to build K&D models from design variables: direct modeling and indirect modeling. The first method builds up the K&D model directly based on design variables of the modular architecture, while the second method builds up the K&D model based on a set of the D-H parameters, which is derived from design variables. The advantage of the second method is that most of analysis theories and tools, which were developed in designing non-modular robotic configurations, can be utilized directly for designing modular robotic configurations. In this paper, we propose a more general architecture of modular manipulator systems. Based on this new architecture, we propose a systematic procedure to generate a mapping from modular design variables and the configuration description in terms of the D-H notation.

Applying New JIT-Toyota's global production strategy: Epoch-making innovation of the work environment

Abstract: In order to strengthen management technology strategy, the author has recently developed a new management technology principle, New JIT, based on TMS, TDS, TPS and TQM-S. In developing ''Global Marketing'' that can win the global competition for quality and cost, the key for domestic and foreign companies is to successfully achieve ''Global Production'' that enables simultaneous production start-up (the same quality and production at optimal locations) throughout the world. This paper analyzes and proves the significance of strategically applying New JIT-a global production strategy activity called AWD6P/J-for epoch-making innovation of the work environment, as verified at Toyota. While many vehicle assembly shops depend on a young, male workforce, innovation in optimizing an aging workforce is a necessary prerequisite of TPS-a production strategy of New JIT. Elements necessary for enhancing work value and motivation, and work energy, including working conditions and work environment (amenities and ergonomics), were investigated through objective survey and analyzed from labor science perspectives.

Disassembly sequence planning in a disassembly cell context

Abstract: In this paper a two-phase approach is proposed for determining the optimal disassembly sequence when the disassembly system has a cellular configuration. Operations are first grouped into cells based on the resources they require with the goal of minimizing machine acquisition costs. The aim is to group together those operations that use similar equipment in order to achieve good utilization levels of such equipment. A maximum cell size may be imposed. Once the cells have been formed and the operations have been assigned to them, a metaheuristic algorithm (namely GRASP) is used to search for the disassembly sequence for each product that leads to the minimum number of intercellular movements. To account for uncertainty regarding the condition in which the product may arrive, each disassembly task is assumed to be required with a certain probability, regardless of the other tasks. AND/OR precedence relations among the disassembly tasks are also considered. The proposed approach is illustrated on a randomly generated disassembly problem.

A framework for extending computer aided process planning to include business activities and computer aided design and manufacturing (CAD/CAM) data retrieval

Abstract: Computer aided process planning (CAPP) systems have had limited success in integrating business functions and product manufacturing due to the inaccessibility and incompatibility of information residing in proprietary software. While large companies have developed or purchased complex order management and engineering applications, smaller manufacturers continue to use semi-automated and manual methods for managing information throughout the lifecycle of each new product and component. There is a need for reconfigurable and reprogrammable systems that combine advances in computer aided design (CAD/Computer Aided Manufacturing (CAM) technology and intelligent machining with product data management for documentation and cost control. The goal of this research is to demonstrate an architecture in which customer service, CAPP and a costing methodology known as activity based costing (ABC) are incorporated into a single system, thereby allowing companies to monitor and study how expenditures are incurred and which resources are being used by each job. The material presented in this paper is the result of a two year university and industry sponsored research project in which professors and students at the Costa Rica Institute of Technology developed a software application for FEMA Industrial S.A., a local machining and fabrication shop with sixty five employees and both conventional and CNC capabilities. The final results represent not only a significant contribution to local industry and to the students' education but, also to the continuing growth of CAPP. Implementing better decision making tools and standardizing transactions in digital format would reduce the workload on critical personnel and archive valuable knowledge for analyzing company methods and expertise.

An intelligent NC program processor for CNC system of machine tool

Abstract: NC program interpreting is one of the most important tasks of CNC in machine tool system. The existing CNC systems only support vendor-specific NC program input, which restrict the applying of other similar functional NC programs with different program format. Especially for those users owning several machine tools with different CNC from the same provider, the diversity of NC programs dramatically increases their cost and time on operator training and machine tool maintenance. In order to deal with the variety of NC program, an intelligent NC program processor (NCPP) is proposed in this paper. The proposed NCPP has a novel structure with separated NC specification dictionary and processing engine, which ease the CNC system to adapt to a new NC program specification by only updating the NC specification dictionary (NCSD). This paper explains the NC specification dictionary structure by using EBNF representation, which is further implemented in tool command language, an embedded script language tool. Meanwhile, the unchanged processing engine has been designed from a compiler's point of view to process the data dictionary. A NCPP prototype is built to evaluate the proposed design. Case study shows that the proposed NCPP handles different NC program inputs successfully.

Time-optimal traversal of curved paths by Cartesian CNC machines under both constant and speed-dependent axis acceleration bounds

Abstract: Algorithms are developed to compute the feedrate variation along a curved path, that ensures minimum traversal time for a 3-axis CNC machine subject to both fixed and speed-dependent axis acceleration bounds arising from the output-torque characteristics of the axis drive motors. For a path specified by a polynomial parametric curve, the time-optimal feedrate is determined as a piecewise-analytic function of the curve parameter, with segments that correspond to saturation of the acceleration along one axis under constant or speed-dependent limits. Break points between the feedrate segments may be computed by numerical root-solving methods. For segments that correspond to fixed acceleration bounds, the (squared) optimal feedrate is rational in the curve parameter. For speed-dependent acceleration bounds, the optimal feedrate admits a closed-form expression in terms of a novel transcendental function whose values may be efficiently computed, for use in real-time control, by a special algorithm. The optimal feedrate admits a real-time interpolator algorithm, that can drive the machine directly from the analytic path description. Experimental results from an implementation of the time-optimal feedrate on a 3-axis CNC mill driven by an open-architecture software controller are presented. The algorithm is a significant improvement over that proposed in [Farouki RT, Rajan VT. Algorithms for polynomials in Bernstein form. Comput Aided Geometric Des 1988;5:1-26], since the addition of motor voltage constraints precludes the possibility of arbitrarily high speeds along linear or near-linear path segments.