Reconfigurable Machine Research Articles

Solution method of the kinematic function scheme for reconfigurable machine tools based on kinematic transformation

The kinematic function scheme is the basis of the reconfigurable machine tool (RMT) design. However, the diversity and complexity of the scheme are not conducive to the realisation of reconfiguration. To solve this problem, this paper proposes a solution method of the kinematic function scheme based on kinematic transformation. A tool-feature pose matrix is established based on an analysis of the relationship between machining surface features and machining tools to obtain a kinematic function expression that shows the kinematic requirements of the machine tool. The kinematic feature domain and the kinematic transformation domain are used to describe the motion type, motion direction and other information to describe the kinematic parameters of the module. The solution method of the kinematic function chain based on the kinematic decomposition and module combination is proposed to establish the kinematic function scheme of a RMT.

Evaluation of Control Approaches for Capacity Adjustment in Job Shop Systems

Nowadays, manufacturers increasingly face demand fluctuations while working on a variety of products. To flexibly react to these disturbances, capacity adjustments via flexible working time and staffs are common measures. Within this paper, we focus on a machinery-oriented approach by introducing reconfigurable machine tools into an existing job shop system. As these tools need to be included into the production plan, we tackle the strategic question on how to contemplate hardware with software for a given manufacturing system. To this end, we consider PID as the current standard in capacity control and compare it to two classes of advanced techniques from operator theory and predictive control. While analyzing advantages and disadvantages of these methods, we illustrate differences using operator-based right coprime factorization and model predictive control as representatives of these advanced classes and applying them to a simulated four-workstation job shop system.

Solution method of the kinematic function scheme for reconfigurable machine tools based on kinematic transformation

The kinematic function scheme is the basis of the reconfigurable machine tool (RMT) design. However, the diversity and complexity of the scheme are not conducive to the realisation of reconfiguration. To solve this problem, this paper proposes a solution method of the kinematic function scheme based on kinematic transformation. A tool-feature pose matrix is established based on an analysis of the relationship between machining surface features and machining tools to obtain a kinematic function expression that shows the kinematic requirements of the machine tool. The kinematic feature domain and the kinematic transformation domain are used to describe the motion type, motion direction and other information to describe the kinematic parameters of the module. The solution method of the kinematic function chain based on the kinematic decomposition and module combination is proposed to establish the kinematic function scheme of a RMT.

Dynamic design and management of reconfigurable manufacturing systems

This research proposes an approach to design and to manage Cellular Reconfigurable Manufacturing Systems (CRMSs) from a multi-product and multi-period perspective. The production environment consists of multiple cells of machines equipped with Reconfigurable Machine Tools (RMTs) made of basic and auxiliary custom modules to perform specific tasks. The approach acts into two steps; the former is the machine cell design phase, assigning machines to cells, the latter is the cell loading phase, assigning modules to each machine and cell. The goal is to guarantee the economic sustainability of the manufacturing system by exploring how to best balance the part flow among machines already equipped with the required modules and the effort to install the necessary modules on the machine on which the part is located.

VERIFIKACIJA REKONFIGURABILNE ARHITEKTURE ZA HARDVERSKU AKCELERACIJU PREDIKTIVNIH MODELA MAŠINSKOG UČENJA

U ovom radu je predstavljena funkcionalna verifikacija rekonfigurabilne arhitekture za hardversku akceleraciju prediktivnih modela mašinskog učenja - Reconfigurable Machine Learning Classifier (RMLC).

Evaluation and optimization of the design schemes of reconfigurable machine tools based on multiple-attribute decision-making

A reconfigurable manufacturing system is one designed for rapid change in its structure, to quickly adjust its production capacity and functionality within a part family. Aiming at the diversity, cost and complexity of reconfiguration design, a method for evaluating the design scheme of a reconfigurable machine tool based on VIKOR is proposed. The module similarity between a reconfigurable machine tool and a prototype machine tool is defined, and on this basis, three quantitative evaluation indicators are established as follows: the module chain similarity determines the difficulty, effort, time and efficiency of machine tool reconstruction; the module interface complexity determines the feasibility and complexity of the disassembly and assembly of the reconfiguration module; and the reconfiguration cost determines the economic advantages of reconfigurable machines relative to fixed-structure equipment. According to three indicators, a multi-attribute decision-making method based on VIKOR is used to evaluate, calculate and sort the design scheme set of the reconfigurable machine tool, and the optimal feasible solution is obtained. An example of the reconfiguration design of a machine tool is analysed to verify the validity and feasibility of the proposed method compared with the methods of simple average weighting and technique for order preference by similarity to an ideal solution.

Ontology-based module selection in the design of reconfigurable machine tools

Reconfigurable machine tools (RMTs) are important equipment for enterprises to cope with ever-changing markets because of their flexibility. In design of such equipment, selection of appropriate modules is a very critical decision factor to effectively and efficiently satisfy manufacturing requirements. However, the selection of appropriate modules is a challenging task because it is a multi-domain mapping process relying heavily on experts’ domain knowledge, which is usually unstructured and implicit. To effectively support RMT designers, an ontology-based RMT module selection method is proposed. First, a knowledge base is built by development of an ontology to formally represent the taxonomy, properties, and causal relationships of/among three domain core concepts, namely, machining feature, machining operation, and RMT module involved in RMT design. Second, a four-step sequential procedure is established to facilitate the utilization of encoded knowledge from a knowledge base to aid in the selection of appropriate RMT modules. The procedure takes a given part family as the input, automatically infers the required machining operations as well as the RMT modules through rule-based reasoning, and eventually forms a set of RMT configurations that are capable of machining the part family as the output. Finally, the efficacy of the ontology-based RMT module selection method is demonstrated using a plate family manufacturing example. Results show that the approach is effective to support designers by appropriately and rapidly selecting modules and generating configurations in RMT design.

A tree-based decision method for the configuration design of reconfigurable machine tools

A reconfigurable machine tool (RMT) can repeatedly be configured to respond to a wide range of requirements (such as a change in function or capacity) in a cost-effective manner. One of the challenges in RMT reconfiguration is the high complexity of the modular configuration due to customization. Furthermore, the possible design space may be enormous as the number of modules increases. Hence, an effective way to describe the diverse configurations of an RMT and evaluate its performance is needed.In this paper, we propose a tree-based method to determine the configuration design for reconfiguration of an RMT. The method includes: 1) defining a computational common model for a reconfigurable machine tool configuration using a tree structure, 2) identifying concepts that combine the desired function and capability, and 3) determining those concepts which satisfy two goals: minimizing cost and maximizing reconfigurability.The proposed method is illustrated by designing an RMT for a transmission box for three different production scenarios: the RMT initial operation, a change in operational features and a change in operational quantity. The benefit of using the proposed method is its improved functionality.

Combining MPC and integer operators for capacity adjustment in job-shop systems with RMTs

With today's worldwide competition, manufacturing companies are faced with challenges to respond to volatile market demands quickly and flexibly while maintaining a cost-effective level of production. Capacity adjustment is one of the major approaches to cope with such uncertain fluctuations, balance capacity and load and improve the effectiveness of manufacturing control. Instead of flexible staffs, working time and outsourcing, in this paper, we consider a machinery-based capacity adjustment via Reconfigurable Machine Tools (RMTs) to compensate for unpredictable events. To include these tools effectively on the operational and tactical layer, we propose a complementing feedback approach using model predictive control (MPC) to identify the potential of RMTs for a better compliance with logistics objectives and a sustainable demand oriented capacity allocation. To this end, we formulate a reconfiguration rule for the determination of the triggered RMTs and propose three strategies for resolving the integer assignment of RMTs: floor operator, genetic algorithm as well as branch and bound. Utilising simulation, we demonstrate the effectiveness of the proposed method for a four-workstation job-shop system.

Best-by-simulations: A framework for comparing efficiency of reconfigurable architectures on workloads with deadlines

Energy consumption is a major concern in multicore systems. Perhaps the simplest strategy for reducing energy costs is to use only as many cores as necessary while still being able to deliver a desired quality of service. Motivated by earlier work on a dynamic (heterogeneous) core allocation scheme for H.264 video decoding that reduces energy costs while delivering desired frame rates, we formulate operationally the general problem of executing a sequence of actions on a reconfigurable machine while meeting a corresponding sequence of absolute deadlines, with the objective of reducing cost.Using a transition system framework that associates costs (e.g., time, energy) with executing an action on a particular resource configuration, we formulate a very simple version of simulation relations for cumulative cost transition systems. This notion of simulation forms the basis for specifying deadline/budget-conformant executions, and appropriate notions for comparing such executions. We believe these simulation-based notions can provide the basis for an operational theory of optimal cost executions and performance guarantees for approximate solutions, in particular relating the notion of simulation from transition systems to that of competitive analysis used for, e.g., online algorithms.

Machine configuration and workload balancing of modular placement machines in multi-product PCB assembly

ABSTRACTA popular gantry-type placement machine includes several interconnected, autonomously operating component placement modules and the machine was designed so as to able to use different kinds of placement heads and vacuum nozzles in the modules, which can be easily changed. Although this increases the flexibility of the production line, the reconfiguration phases of the modules may be unproductive and one should keep them to a minimum. In addition, the production times can be shortened by balancing the workloads of the machine modules. Here, a two-step optimisation method for the machine reconfiguration and workload balancing in the case of multiple Printed Circuit Borad (PCB) batches of different sizes and PCB types is presented. The objective is to minimise the total production time, and keep the machine configuration the same for all batches. The proposed algorithm is iterative and it applies integer programming for the workload balancing along with an evolutionary algorithm that searches for the best machine configuration. In experiments, for single PCB types the proposed algorithm obtained optimal or near optimal solutions. For multiple PCB types the solutions favour the PCB types that have a bigger production time due to greater batch sizes, but the total production time is still close to optimal.

Optimum machine capabilities for reconfigurable manufacturing systems

Reconfigurable manufacturing systems constitute a new manufacturing paradigm and are considered as the future of manufacturing because of their changeable and flexible nature. In a reconfigurable manufacturing environment, basic modules can be rearranged, interchanged, or modified, to adjust the production capacity according to production requirements. Reconfigurable machine tools have modular structure comprising of basic and auxiliary modules that aid in modifying the functionality of a manufacturing system. As the product’s design and its manufacturing capabilities are closely related, the manufacturing system is desired to be customizable to cater for all the design changes. Moreover, the performance of a manufacturing system lies in a set of planning and scheduling data incorporated with the machining capabilities keeping in view the market demands. This research work is based on the co-evolution of process planning and machine configurations in which optimal machine capabilities are generated through the application of multi-objective genetic algorithms. Furthermore, based on these capabilities, the system is tested for reconfiguration in case of production changeovers. Since, in a reconfigurable environment, the same machine can be used to perform different tasks depending on the required configuration, the subject research work assigns optimum number of machines by minimizing the machining capabilities to carry out different operations in order to streamline production responses. An algorithm has also been developed and verified on a part family. As a result of the proposed methodology, an optimized reconfigurable framework can be achieved to realize optimal production of a part family. Finally, the proposed methodology was applied on a case study and respective conclusions were drawn.

Application of reconfigurable machine tools in the capacity control of job shop systems

In today's market, demand fluctuation is a big challenge for manufacturers. They have to respond quickly and flexibly to satisfy customers' demands to improve competitiveness. Moreover, it renders the production systems complex and dynamical. In this paper, we use capacity adjustment to deal with the fluctuation in demand. We derive an extended mathematical model of a typical job shop manufacturing system by introducing reconfigurable machine tools (RMTs) to analyse the impact of this new class of machine tools on the dynamic behaviour of the system. To improve the ability of capacity adjustment, we include the operations of RMTs into the classical proportional integral derivative (PID) controller. Simulation results of a four-workstation job shop system demonstrate the proposed method can adjust the capacity effectively and show the potential of RMTs in the context of Industry 4.0.

Reconfigurable machine tool: CNC machine for milling, grinding and polishing

Reconfigurable machine tool means that by the use of mechanical, control, hydraulic/pneumatic, and electrical modules, a rapid adaptability can be achieved. The main goal of a reconfigurable machine tool is to handle various changes in the product or parts to be machined. By the development of machine modules which can be quickly assembled and disassembled, one can enhance the efficiency of the machine tool. Designing different machining processes, using the same machine tool, can reduce the total energy consumption during the manufacturing process, the need for larger floor space in the plant and the cost per part. In this paper, the design and implementation of modular machine subsystems that enables various machining processes on the same CNC vertical milling machine, is reviewed. Milling, ceramic grinding and stainless steel polishing are carried out on the same machine, using modular designed subsystems.

Capacity Control in Disturbed and Time-Delayed Job Shop Manufacturing Systems with RMTs

Within dynamic job shop manufacturing systems, delays and disturbances represent big challenges. In this context, the work-in-process (WIP) level has great influence on the system properties, such as production rate and lead time. The aim of this work is to derive a controller, which allows to track a predefined WIP level despite delays and disturbances. To this end, we combine a classical proportional-integral-derivative (PID) controller with reconfigurable machine tools (RMTs). Based on the Nyquist criterion, we show the stability of the control system. To illustrate the effectiveness, we present a four-workstation job shop manufacturing system with three products.

New Perspectives in Manufacturing: An Assessment for an Advanced Reconfigurable Machining System

Traditionally manufacturing cycle involves several production processes that are carried out according to the required technologies tacking into account the constraint due to the production capacity provided by machine tools and the customers’ orders time scheduleIn this paper, a new modular, reconfigurable and scalable machining centre is presented. The resulting system is characterized by the possibility of modifying the machining capacity as well as exchanging the role between workpieces and machining/operating resources. This augmented flexibility creates new opportunities for efficient manufacturing; however, the increased system complexity demands a new approach for the jobs scheduling and machining control. An architecture based on agents modelling is proposed and discussed.

Application of reconfigurable machine tools in the capacity control of job shop systems

In today's market, demand fluctuation is a big challenge for manufacturers. They have to respond quickly and flexibly to satisfy customers' demands to improve competitiveness. Moreover, it renders the production systems complex and dynamical. In this paper, we use capacity adjustment to deal with the fluctuation in demand. We derive an extended mathematical model of a typical job shop manufacturing system by introducing reconfigurable machine tools (RMTs) to analyse the impact of this new class of machine tools on the dynamic behaviour of the system. To improve the ability of capacity adjustment, we include the operations of RMTs into the classical proportional integral derivative (PID) controller. Simulation results of a four-workstation job shop system demonstrate the proposed method can adjust the capacity effectively and show the potential of RMTs in the context of Industry 4.0.

Configuration design in scalable reconfigurable manufacturing systems (RMS); a case of single-product flow line (SPFL)

The dynamic nature of today’s manufacturing industry, which is caused by the intense global competition and constant technological advancements, requires systems that are highly adaptive and responsive to demand fluctuations. Reconfigurable manufacturing systems (RMS) enable such responsiveness through their main characteristics. This paper addresses the problem of RMS configuration design, where the demand of a single product varies throughout its production life cycle, and the system configuration must change accordingly to satisfy the required demand with minimum cost. A two-phased method is developed to handle the primary system configuration design and the necessary system reconfigurations according to demand rate changes. This method takes advantage of Reconfigurable Machine Tools in RMS. In fact, by adding/removing modules to/from a specific modular reconfigurable machine, its production capability could be increased, with lower cost. A novel mixed integer linear programming formulation is presented in the second phase of the method to optimise the process of selecting the best possible transformation for the existing machine configurations. Two different cases are designed and solved by implementing the established method. The results of these cases in terms of capital cost, capacity expansion cost, unused capacity and number of transformations, are compared with two hypothetical scenarios. Analyses of the obtained results indicate the efficiency of the proposed approach and offer a promising outlook for further research.

An approach to identify the optimal configurations and reconfiguration processes for design of reconfigurable machine tools

A reconfigurable machine tool (RMT) is a special machine that can deliver different machining functions through reconfiguration processes among its configurations during the machine utilisation stage. In this research, a new approach is developed to identify the optimal configurations and the reconfiguration processes for design of the RMTs. In this work, a generic design AND-OR tree is used to model different design solution candidates, their machine configurations and parameters of these configurations. A specific design solution is created from the generic design AND-OR tree through tree-based search and modelled by different machine configurations. For a reconfiguration process between two machine configurations, a generic process AND-OR graph is used to model reconfiguration operation candidates, sequential constraints among operations and operation parameters. A graph-based search is used to generate all feasible reconfiguration process candidates from the generic process AND-OR graph. The optimal design is identified by multi-level and multi-objective hybrid optimisation. A case study is developed to show how this new approach is used for the optimal design of a RMT.

Experimental Verification of Dynamic Behavior of a Capsule-Type Modular Machine Tool for Multifunctional Processes

A capsule-type modular machine tool was developed, which was capable of multifunctional processes with a single setup. This mechanism was designed according to the concept of a reconfigurable machine tool (RMT), which can transform from a machining center to a lathe, and is capable of multiple functional processes, such as laser, milling, and grinding processes. After addressing the kinematics of the machine, a static structural analysis was performed and some ribs were added to enhance the stiffness. A frequency response function (FRF) simulation was conducted on the modified machine and natural frequencies were determined to avoid resonance in processing. Then, an FRF test was performed to find the actual natural frequencies, to confirm the simulation results. After investigating the natural frequencies, high-speed machining was performed to make 300 μm sized patterns.