Vision-based automated inspection system in computer integrated manufacturing

The industrial application of an automated inspection system that aims to enhance the efficiency and flexibility of a computer integrated manufacturing system (CIMS) is proposed in this paper. A machine-vision-based approach is adopted to utilise its advantages of measurement flexibility, high resolution, and non-destruction. With a closed-loop feedback control architecture, the inspection procedures are fully integrated with the production process to detect and to recover abnormal operations in a real-time mode. Implementation of such a system at a physical shop floor for socket inspection is presented as an example.     

On-machine measurement using a noncontact sensor based on a CAD model

Once a machining process is finished, an inspection process is carried out to check whether the part is within dimensional tolerances. A coordinate measuring machine (CMM) is a general metrological device for assessment of dimensions on the shop floor. It cannot be ignored, however, that CMM measurements require significant resources in operating time and cost, which has led to many studies into on-machine measurement (OMM) systems. This study aims to develop an OMM system with a noncontacting laser displacement sensing apparatus and a computer-aided design (CAD) model for ease of operation, improved operating speed, and free form profiling. The system is composed of two software modules, one for sensor alignment with the machine tool and the other for measurement based on CAD/CAM (computer-aided machining). Consequently, the system was verified on the shop floor at a numerical control (NC) machining center.     

A Multi-Agent-Based Agile Shop Floor Control System

The ability of an enterprise to deliver new products quickly and efficiently to market is often the chief determinant of competitive success. The shop floor control system must be an open dynamic system with the capability of adapting and accepting radical unpredictable changes in its structures and industrial practices. This paper presents a new architecture for an agile shop floor control system. The architecture is based on the methodology of multi-agent systems in distributed artificial intelligence (DAI). The multi-agent system has some common characteristics such as: distribution, autonomy, interaction, and openness, which are helpful for transferring traditional architecture to a distributed, cooperative architecture for a shop floor control system. A bidding method based on the required production cost and processing time is also proposed. Using a distributed object-oriented technique, a CORBA-based multi-agent framework for an agile shop floor control system is constructed to integrate all the activity of the shop floor into a distributed intelligent open environment. To implement the framework, a coordination model between agents and behavioural models of some representative agents are established.     

Thermo-mechanical analysis in pulsed laser cladding of WC powder on Inconel 718

The increasing interest towards intelligent systems has led to a demand for the development of zero-defect strategies, with a paradigm shift from off-line and dedicated to in-line metrology with integrated robotic systems. However, a major barrier preventing the systematic uptake of in-line metrology is the lack of evaluation of system capability in terms of accuracy, repeatability and measurement time, when compared to the well-established coordinate measuring machine (CMM). In this study, a robotic Laser Radar (LR) solution is assessed in the context of automotive dimensional inspection of Body-In-White (BIW) applications. The objective is both to understand the effect of robot re-positioning error on measurement accuracy and repeatability and to compare measurement results against a CMM. Eighty-one surface points, six edge points, twenty-five holes and sixteen slots were selected from an industry standard measurement plan. Whilst LR exhibits a lower measurement accuracy than twin-column CMM, its repeatability is well within the specification limits for body shell quality inspection. Therefore, as a real-time in-line metrology tool, it is a genuine prospect to exploit. This research makes a significant contribution toward in-line metrology for dimensional inspection, for automotive application, for rapid detection and for correction of assembly defects in real time, with subsequent reduction of scrap and number of repairs/re-works.     

Hybrid shop floor control system for Computer Integrated Manufacturing (CIM)

A shop floor can be considered as an important level to develop Computer Integrated Manufacturing system (CIMs). However, a shop floor is a dynamic environment where unexpected events continuously occur, and impose changes to the planned activities. To deal with this problem, a shop floor should adopt an appropriate control system that is responsible for the coordination and control of the manufacturing physical flow and information flow. In this paper, a hybrid control system is described with a shop floor activity methodology called Multi-Layered Task Initiation Diagram (MTD). The architecture of the control model contains three levels: i.e., the shop floor controller (SFC), the intelligent agent controller (IAC) and the equipment controller (EC). The methodology behind the development of the control system is an intelligent multi-agent paradigm that enables the shop floor control system to be an independent, an autonomous, and distributed system, and to achieve an adaptability to change of the manufacturing environment.     

Stigmergic cooperation mechanism for shop floor control system

Inspired by the collective behaviour of ant colonies, a stigmergic cooperation mechanism for shop floor control is proposed. In stigmergic shop floor control systems, one piece agent takes charges of one work piece and chooses a manufacturing resource for it in the light of pheromones stored in information environment. Piece agents also update these pheromones to guide subsequent agents routing. Experiments confirm that a stigmergic cooperation mechanism has an excellent scheduling performance in a static environment, good suitability for the stochastic machining-time problem and good adaptability to shop floor changes.     

User interface for optical multi-sensorial measurements at extruded profiles

Nowadays the process control of concave extruding is a measuring task with rising requirements. A novel optical bi-sensorial measurement system - consisting of a shadow- and a light-section-system - as well as suitable methods of analysis for the in-line inspection are presented. The proposals help to ensure the product quality on a higher level than before. The combination of dimensional accuracy and data-density leads to excellent results. The optical multi-sensor measurement system has to be calibrated and aligned to detect the same surface zone despite of high refresh rates and optical resolutions. The metered characteristics will be coordinate transformed to extrinsic world-coordinates for evaluating form deviations of complex parts. An appropriate user interface enables to re-calculate measurement objects in-line and evaluate the conformity of the part consequently. Finally the real length information assists to influence the process control. After successful test in laboratory the results will be proved in production to the target: measurement uncertainty of better 0.1 mm at every profile.     

In-line metrology of nanoscale features in semiconductor manufacturing systems

Quality control and defect monitoring are of great importance to the semiconductor industry. This article presents a system to enable inspection of nanoscale features in-line with nanomanufacturing processes. The ultimate goal of this research is to integrate this metrology system into current semiconductor manufacturing processes to enable true in-line wafer inspection and quality control. In the system presented in this paper, AFMs that have been shrunk down on to a single MEMS chip are used to scan the surface of a sample. A flexure-based mechanism allows the MEMS-based AFM to be positioned over a millimeter range of motion, with nanometer level precision when properly actuated. The performance of the system in areas such as positioning repeatability, AFM stability and measurement resolution are evaluated in this study. Owing to the small size of single-chip AFM (1 million times smaller than a conventional AFM instrument), it is a good candidate for multipoint detection. Overall, the system presented in this paper significantly shortens inspection time and dramatically decreases the setup time required for an AFM to load, approach, and measure a sample making in-line inspection of nanoscale features in semiconductor manufacturing systems feasible.     

TOWARDS AUTONOMOUS COMPILATION OF TURNING FORCE DATABASES: UTILIZATION OF ON-MACHINE MEASUREMENT OF MACHINED PARTS

Several hitherto unrealized advantages would follow if each shop floor machine could compile its own machining database autonomously. This paper focuses on CNC turning to develop a shop floor friendly method for determining the cutting force component normal to the machined surface as well as the lumped static stiffness parameters of the machining set up solely from on-machine part inspection data gathered immediately after machining. It is shown that one can also estimate the shear and chip flow angles as well as the tangential and feed forces by combining this method with a suitable predictive model of the turning operation.     

TOWARDS AUTONOMOUS COMPILATION OF TURNING FORCE DATABASES: UTILIZATION OF ON-MACHINE MEASUREMENT OF MACHINED PARTS

Several hitherto unrealized advantages would follow if each shop floor machine could compile its own machining database autonomously. This paper focuses on CNC turning to develop a shop floor friendly method for determining the cutting force component normal to the machined surface as well as the lumped static stiffness parameters of the machining set up solely from on-machine part inspection data gathered immediately after machining. It is shown that one can also estimate the shear and chip flow angles as well as the tangential and feed forces by combining this method with a suitable predictive model of the turning operation.     

生产车间混合式控制结构模型和协商机制研究

为了提高车间控制系统的柔性、开放性和全局优化性能,在分析现有车间控制体系结构的基础上,融合Agent技术,提出了一种适应性混合式车间控制系统体系结构模型。该模型利用递阶结构将控制功能设计成系统优化Agent、单元协调Agent和单实体Agent三层结构,并允许同层Agent及上下层Agent之间的协商。为了进一步提高协商效率,集成分布式协商和全局控制,设计了基于招投标机制和示例学习方法的协商机制,详细分析了包括时间约束算法和基于示例的学习方法的协商机制核心算法。在JADE(Java Agent development framework)平台上构建了原型系统。     

Automatic control of a One-of-a-Kind Production cell

This paper reports the outcome of a research project which aims to solve the problems in automatic control of the shop floor in One-of-a-Kind Production (OKP) through developing a prototype control system for an experimental OKP cell at the laboratory. The main problems in automatic control of the shop floor in OKP are the frequent changes of product structure or type and consequent changes of production system configuration. These changes in OKP make it necessary to have a highly flexible and robust automatic control system. To resolve the problems, a distributed control system has been developed at the CIM laboratory of the Department of Production, Aalborg University, Denmark. This control system has enough flexibility and robustness to cope with the aforementioned changes in OKP. To support the design and implementation of the control system, several concepts, algorithms and control principles, such as task logic routes, address code of production resources, automatic task decomposition algorithm, generic control modules and distributed control principles are also proposed in this paper.     

Additive manufacturing tooling for the automotive industry

Micro injection moulding is a mass production of micro optics that offers the possibility of a high functional integration within a single micro part by insert moulding. Since the functionality of the micro parts depends on the homogeneity of the overmoulded polymer layer, a robust, accurate and fast metrology system is needed for a quantitative quality assessment. Here, we demonstrate an in-line metrology approach for the optical inspection of insert molded micro parts. In contrast to standard interferometers, the proposed system has low demands regarding the coherence of illumination. Thus, an LED light source can be used instead of a laser, reducing the cost and increasing the safety of the production platform. In addition, the system is robust against mechanical distortions, since it is based on a common path approach. These advantages make the system a good candidate that fulfills the needs in regard to the in-line inspection of insert molded micro parts. As an example of application, the proposed system is used to inspect a cannula with overmolded thermoplastic as a light sleeve providing illumination over a specific area of surgery.     

Development of a rapid profilometer with an application to roundness gauging

This paper presents the development of a real-time, contact-based, high frequency, response profilometer employed as a roundness gauge for measuring circular form error for 100% part inspection on the shop floor with an accuracy of better than 0.5 μm with measurement times of less than 1 s. The gauge head is a closed-loop controlled mechanism comprising a contact force probe that is rigidly attached to a high bandwidth linear translator. The gauge head assembly is, in turn, attached to a precision spindle. The objective of the complete tool is to contact the sidewall of the circular feature, translate the probe tip to produce a defined contact force with the workpiece and rotate the gauge head assembly. During rotation of the spindle, this contact force is maintained at a nominally constant value by dynamically translating the force probe along a radial direction to follow surface deviations. The gauge head assembly (including force probe and servo drive) has a fundamental mode natural frequency of 330 Hz while scanning the workpiece with a constant contact force typically less than 100 mN. Form error (deviation from a nominal circle) is measured using a capacitance-based displacement sensor measuring the relative radial displacement of the probe with the spindle rotating at a constant rotation speed. This paper discusses the design and characterization of this metrology tool.     

A Cascading Auction Protocol as a Framework for Integrating Process Planning and Heterarchical Shop Floor Control

A new contract net-style auction protocol is proposed as a framework for integrating process planning and shop floor control in heterarchical manufacturing systems. Process planning is partitioned into on-line and off-line activities; off-line process planning decisions are represented in a graph format and used as input for on-line process planning activities performed by machine controllers. Triggered by the opening round of an auction, the final on-line stages of process planning are dovetailed with the resource allocation process in the shop floor control system. The auction process allows final process planning decisions to be based on timely information, relying on the distribution of static process planning information rather than the distribution of a model of dynamic shop floor status and allowing a controller to identify all the primary and secondary resources and operations that must be provided for the incremental processing of a part.     

深度互检在车间的应用

通过笔者在公司东部车身车间进行品质管理改进的实践,阐述一种有效地提高车间制造一致性及杜绝缺陷逃逸的具体实施方法,即深度互检制度。深度互检制度是笔者和车间生产团队在生产实践中,通过对GMS现有互制实施的现状下,对互检方法存在的问题研讨,从而形成的一种创新方法,是对传统GMS互检制度的一种深度执行中的补充。通过实施深度互检,东车的缺陷逃逸得到大副抑制。是一种有效的生产实践。     

A Dynamic Programming Based Process Planning Selection Strategy Considering Utilisation of Machines

Computer-aided process planning (CAPP) has been recognised as a key element in computer-integrated manufacturing (CIM). Despite the fact that tremendous efforts have been made to develop CAPP systems, the benefits of CAPP in real-life manufacturing environments are not obvious. One of the main difficulties in applying CAPP in real manufacturing settings is the missing link between generated process plans and shop-floor activities. The assumptions that the shop floor remains static and there are unlimited resources available have caused a typical CAPP system to make a repetitive selection of the same most desirable machines for manufacturing different parts. When process plans for various parts are finally sent to the shop floor, process bottlenecks normally arise, making the generated plans ineffective. Some efforts have been made in the integration of process planning and shop floor activities; however, the problems associated with the lengthy time and impractical attempts at the generation of process plans, remain unsolved. Since in most cases, it is possible that several alternatives exist for machining a part by using different equipment, a stage-type network structure can be constructed. This paper introduces a dynamic programming based process plan selection strategy, enabling the efficient solution of this stage-type network prob-lem. In this proposed strategy, the use of workstations is also taken into consideration so that the resulting plan is valid for the conditions that exist on the shop floor at the time an order is released. A case study has been provided to substantiate the effectiveness of this proposed strategy.     

Performance Modelling and Evaluation of Dynamic Tool Allocation in Flexible Manufacturing Systems using Coloured Petri Nets: An Object-Oriented Approach

Manufacturing systems are faced with ever-increasing customisation and unstable demand. The traditional hierarchical control structures for shop floor (pre-release planning, scheduling, dispatching and activity control) are often inflexible in responding to unexpected scenario changes and are thus not robust to system disturbances. In this paper, an object-oriented approach to modelling of FMS dynamic tool allocation and control under a non-hierarchical shop floor control scheme using coloured Petri nets is presented. A client–server paradigm is used in the proposed modelling method. The complete FMS model is partitioned into individual classes (machines, magazines, tool transport system, SGVs, tool storage, etc.) thereby significantly reducing the complexity of the model to a tractable size. The system performance under different tool request selection rules is also evaluated using coloured Petri net simulation. The proposed method can provide the designer of a tool management system with a high-level and structured representation of the tool-sharing control. It also provides an effective method for prototyping and evaluating performance of object-oriented shop floor control software.     

Knowledge-based workcell controller for production planning in the electronics industry

The paper describes the analysis, design and implementation of a workcell controller using knowledge-based system technology in the electronics industry. The central task of the workcell controller is to bridge the gap between the high level production planning system of the logistics department and short-term planning at the shop floor level. Today the latter is mainly based on heuristic knowledge of a foreman. Due to the number of shop floor components involved and their rapid change the foreman is overloaded which leads to large stocks in the production and reduced flexibility. The production planning will be described as an optimisation problem optimising the degree of refinement of the production plan issued by the high level production planning system. As an analytical solution only based on operation research techniques is not feasible the proposed approach is to partly use the empirical knowledge of the foreman to reduce the solution space. To facilitate the formal specification of such combined approaches the optimisation process is presented using the terminology of production management systems (GRAI). The underlying CIM reference model is an extension of the NBS reference model towards the use of knowledge-based system technology.