Levels Of Routing Flexibility Research Articles

Effect of Routing Flexibility on the Performance of Order Release Policies in a Flexible Job Shop with Sequence-Dependent Setup Time: A Simulation Study

ABSTRACT Order review and release (ORR) in a flexible job shop considering sequence-dependent setup time (SDST) is a complicated job shop problem. Routing flexibility helps in increasing the flexibility of the system by providing alternative routes to jobs. This research work assesses the effect of routing flexibility on order release policies in a flexible job shop considering SDST within a stochastic and dynamic (SCDM) manufacturing environment. In this study, five order release policies, viz., Corrected Aggregate Load Approach (CALA), Aggregate Workload Trigger (AGGWLT), Corrected Workload Trigger (CorrWLT), Work Center Workload Trigger (WCWLT), and Lancaster University Management School Corrected Order Release (LUMSCOR), are considered with planned release date sequencing rule. Four performance measures are considered in the present research work, i.e., mean throughput time, mean lead time, mean tardiness, and total setups. For experimental purposes, a simulation model is developed with six routing flexibility levels with the help of Promodel® software. Results indicate that the performance of all ORR policies can be improved by considering routing flexibility along with it. For a given ORR policy, as routing flexibility increases, there is a decrease in system performance measures up to a certain level, and after that, it starts increasing. Thus, routing flexibility has an optimum level. The least value of workload trigger level for all ORR policies provides the best results for mean throughput time performance measure. Further, as the workload trigger level increases, the best results are obtained for the other three performance measures except the mean throughput time.

An energy-efficient scheduling and rescheduling method for production and logistics systems†

Scheduling can be defined as the allocation of available resources over time while optimising a set of criteria like early completion time of task, holding inventory, etc. The complexity of the scheduling problem, already known to be high, increases if dynamic events and disruptions are considered. In addition, in production and logistics, designers of scheduling systems must consider sustainability-related expectations. This paper presents an energy-efficient scheduling and rescheduling method (named Green Rescheduling Method, GRM). GRM aims at the solving of the dynamic scheduling problem under the condition of a certain level of routing flexibility enabling the reassignment of tasks to new resources. The key performance indicators integrated into the proposed GRM are effectiveness and efficiency-oriented. Applications concern the domains of production and logistics. In order to assess the proposed approach, experimentations have been made and results illustrate the applicability of GRM to build efficient and effective scheduling and rescheduling both for flexible manufacturing systems and inventory distribution systems in a physical internet network. A mathematical formulation for flexible job shop problem with energy consumption is also proposed using mixed Integer programming to evaluate the performance of the predictive part of GRM.

Toward high degree flexible routing in collision-free FMSs through automated guided vehicles’ dynamic strategy: A simulation metamodel

The present study proposes a simulation-based model of high degree flexible routing to prevent collisions and deadlocks in flexible manufacturing systems (FMSs). High degree flexible routing concurrently involves classical routing strategies (specifies the destination and static/dynamic routing between origin and destination) with routing flexibility (considers alternatives to select as destination). A new approach named Tandem-Queue-Link with a look-ahead (TQL-A) is proposed in which the look-ahead mechanism supports deadlock prevention. The TQL-A performs a collision-free status for automated guided vehicles (AGVs) routing with flexible dynamic strategy. The main contribution of the present study is to implement the routing flexible levels (RFLs) by dynamic flexible routing (DFR) as a high degree flexible routing strategy. The most efficient parameters of this highly complex FMS are designed using a multi-objective nonlinear programming model extracted from simulation metamodels based on different hypotheses. Results support some of the considered hypotheses and show the complicated relationship between different values of FMS design parameters and different levels of routing flexibility. Metamodel validity through a typical case study defines that the higher values of velocity and acceleration/deceleration can compensate the level of routing flexibility but other parameters that are influenced by the active parameter (i.e. those related to loading/unloading time) have not any sensible influence on the output.

Simulation analysis of multi-node manufacturing system under design and scheduling strategies

To cater for dynamic and variable performance matrices, manufacturing industries use automation tools and technologies to impart manufacturing flexibility in their processes. To successfully cater for its performance, manufacturing requirements should be designed into the system and then appropriate planning and operational policies need to be followed to support it. This research work validates this using an industrial size flexible manufacturing system (FMS) as a multi-node manufacturing framework having eight machines. While FMS design spectrum is modelled by different levels of its routing flexibility (RF) and number of pallets (NP), planning and operational strategies are implemented through various combinations of dispatching and sequencing rules (DR/SR). This work is a simulation study to evaluate FMS performance for which makes time (MST) and machine utilisation have been used as a performance metric. This research provides a framework for the decision makers in identifying the appropriate levels of routing flexibility, number of pallets and appropriate combination of dispatching and sequencing rules for optimising system performance under a given manufacturing environment.

A Highly Efficient and Optimised Simulation Based Multi objective Decision-Making for FMS Control

Optimized and efficient decision-making systems is the burning topic of research in modern manufacturing industry. The aforesaid statement is validated by the fact that the limitations of traditional decision-making system compresses the length and breadth of multi-objective decision-system application in FMS. The bright area of FMS with more complexity in control and reduced simpler configuration plays a vital role in decision-making domain. The decision-making process consists of various activities such as collection of data from shop floor; appealing the decision-making activity; evaluation of alternatives and finally execution of best decisions. While studying and identifying a suitable decision-making approach the key critical factors such as decision automation levels, routing flexibility levels and control strategies are also considered. This paper investigates the cordial relation between the system ideality and process response time with various prospective of decision-making approaches responsible for shop-floor control of FMS. These cases are implemented to a real-time FMS problem and it is solved using ARENA simulation tool. ARENA is a simulation software that is used to calculate the industrial problems by creating a virtual shop floor environment. This proposed topology is being validated in real time solution of FMS problems with and without implementation of decision system in ARENA simulation tool. The real-time FMS problem is considered under the case of full routing flexibility. Finally, the comparative analysis of the results is done graphically and conclusion is drawn.

Effect of routing flexibility on system performance in stochastic environment

This paper focuses on a simulation-based experimental study of the performance of flexible manufacturing system with routing flexibility, system load conditions and sequencing rules. Four routing flexibility levels, four system load conditions (i.e. LUB, LFB, LBMUPT, and LUMBPT) and four rules for part sequencing decision (i.e. FCFS, SPT, HPT, and LCFS) are considered for the investigation. The performance of the FMS is evaluated using make-span time, work-in-process and resource utilization. After full factorial experimentation we applied the Taguchi's method to study the various factors contributing to the system performance and identify the key factors for enhancing performance of the system. Furthermore, the most significant factor is determined by using the analysis of variance (ANOVA). Based on the analysis of the relevant data collected through simulation the results were analyzed. The analysis of results reveals that system performance can be improved substantially by incorporating routing flexibility. However, the benefit of this flexibility diminishes at higher levels of routing flexibility in all the combinations. Sequencing rules and system load conditions also affect the performance of the system.

Simulation of Manufacturing System at Different Part Mix Ratio and Routing Flexibility

In present market scenario, manufacturing industries need to focus towards capability to provide high product variety and availability of products at the point of demand. This situation creates pressure on manufacturing firms to be flexible and to reduce lead time to fulfill customer's demand on time. Flexible Manufacturing Systems (FMS) with appropriate Routing Flexibility (RF) in addition to different scheduling strategies is the appropriate manufacturing alternative in such a case. Such systems are capable to adjust changing product mix yet providing higher performance in dynamic business environment. This research work presents simulation analysis of a FMS with varying Routing Flexibility (RF) level at different part mix ratio to validate this. The results show that varying part mix ratio has appreciable effect on the system performance, when no routing flexibility is present in the system. Also for all product mix ratios, increase in routing flexibility levels continues to improve MST performance with diminishing return.

A Simulation Study of FMS Under Routing and Part Mix Flexibility

This paper studies the performance of a flexible manufacturing system under different manufacturing strategies. Manufacturing strategies under consideration are manufacturing flexibility, lot size and scheduling of jobs in the system. The impact of all these strategies is evaluated on the make-span performance of the flexible manufacturing system. The methodologies involved include simulation, Taguchi experimental design and analyzing the results with help of ANOVA. Number of different simulation models is developed with the help of JAVA language. The first model relates to the manufacturing system, which is conventional in nature without any flexibility embedded in the system. The second model takes into partial manufacturing flexibility in the form of routing flexibility. Finally, the third models incorporate much higher level of routing flexibility. All these models are further evaluated at different level of part mix flexibility. Also the scheduling of parts is considered with the objective of minimizing the total make-span time of parts. The results show that considering different manufacturing strategies decisions in a simultaneous manner can significantly improve the performance of the flexible manufacturing systems.

The effect of responsiveness of the control-decision system to the performance of FMS

In Flexible Manufacturing System (FMS), decision-making process is one of the key aspects for its performance enhancement, particularly for shop-floor control, where operation managers need to make a large number of control decisions. A term called ‘response-time’ in decision-making process has been defined in this study, which refers to a lead time in decision-making and its implementation. This paper contributes a methodology for decision-maker to study the decision-making process and identify a suitable decision-making approach, while considering critical factors such as decision automation levels, routing flexibility levels, and control strategies. Considering the complexity in modelling an FMS with routing flexibility levels, control strategies (sequencing and dispatching rules), and decision-making process with information system, computer simulation modelling has been employed to study the makespan performance. The results show that decision-making process with response-time for FMS control performs as good as with the real-time control when routing flexibility level is low. Furthermore, under some specific situations, it even outperforms the real-time control. This research gives insight to decision-maker to identify whether a decision system with response-time will be more suitable and economically justified, or real-time decision-making system is more appropriate.

Effects of flexibility and scheduling decisions on the performance of an FMS: simulation modelling and analysis

This paper focuses on a simulation-based experimental study of the effects of routing flexibility, sequencing flexibility, and part sequencing rules on the performance of a typical FMS. Three routing flexibility levels, five sequencing flexibility levels, and four scheduling rules for part sequencing decision are considered for detailed investigation. The system work load characterised by the mean interarrival time of parts has been set at different levels. The performance of the FMS is evaluated using various measures related to flow time and tardiness of parts. The simulation results are subjected to statistical analysis. Multiple regression-based metamodels have been developed using the simulation results. The analyses of results reveal that deterioration in system performance can be minimised substantially by incorporating either routing flexibility or sequencing flexibility or both. However, the benefits of either of these flexibilities diminish at higher flexibility levels. When flexibility exists, part sequencing rules such as the earliest due date and earliest operation due date provide a better performance for all the measures.

A Decision-Information-Synchronisation perspective on the performance of FMS

The performance of a Flexible Manufacturing System (FMS) largely depends on how the control system can control the flow of entities in the system. The control system takes control decisions based on the information provided as an input to the decision-making process. Therefore, it is important that the decision-making process and information systems operate in a synchronised manner with respect to the FMS characteristics. This can also be referred to as a Decision-Information-Synchronisation (DIS) operating zone implemented in the control system. To study the DIS in the present research, three types of visibility for decision-makers in FMS shop-floor control have been identified: (1) no local visibility, (2) physical local visibility and (3) physical and information local visibility of decision-maker/operator. These alternative visibilities and automation levels of decision and information system provide the hybrid environments of FMSs control. The current paper presents an approach to identify the DIS operating zone of FMS with suitable visibility of decision-maker and automation level. Simulation results show that under non-real-time control (low automation level in decision and information system) with physical local visibility, the FMS system performs comparable with the real-time control (high automation level in decision and information system) when routing flexibility levels are presented. Under the current global competitive environment, this study helps industrial managers determine a suitable level of visibility and automation in planning an FMS control system in order to obtain the desired performance at the lower cost.

Evaluation of routing flexibility of a flexible manufacturing system using simulation modelling and analysis

Routing flexibility is a major contributor of the flexibility of a flexible manufacturing system (FMS). The present paper focuses on the evaluation of the routing flexibility of an FMS with the dynamic arrival of part types for processing in the system. A typical FMS configuration is chosen for detailed study and analysis. The system is set at five different levels of routing flexibility. Operations of part types can be processed on alternative machines depending upon the level of routing flexibility present in the system. Two cases have been considered with respect to the processing times of operations on alternative machines. A discrete-event simulation model has been developed to describe the operation of the chosen FMS. The performance of the system under various levels of routing flexibility is analyzed using measures such as mean flow time, mean tardiness, percentage of tardy parts, mean utilisation of machines, mean utilisation of automatic-guided vehicles, and mean queue length at machines. The routing flexibility for producing individual part types has been evaluated in terms of measures such as routing efficiency, routing versatility, routing variety and routing flexibility. The routing flexibility of the system has been evaluated using these measures. The flexibility levels are ranked based on the routing flexibility measure for the system. The ranking thus obtained has been validated with that derived using fuzzy logic approach.

Effects of routing flexibility, sequencing flexibility and scheduling decision rules on the performance of a flexible manufacturing system

This paper focuses on a simulation-based experimental study of the interaction among routing flexibility, sequencing flexibility and part sequencing rules in a typical flexible manufacturing system (FMS). Two scenarios are considered for experimentation. Three routing flexibility levels, five sequencing flexibility levels and four scheduling rules for part sequencing decision are considered for detailed investigation. The performance of the FMS is evaluated using various measures related to flow time and tardiness of parts. The simulation results are subjected to statistical analysis. The analysis of results reveals that deterioration in system performance can be minimized substantially by incorporating either routing flexibility or sequencing flexibility or both. However, the benefits of either of these flexibilities diminish at higher flexibility levels. Part sequencing rules such as earliest due date and earliest operation due date provide better performance for all the measures at higher flexibility levels.

Analysis of dynamic due-date assignment models in a flexible manufacturing system

This paper investigates the effects of dynamic due-date assignment models (DDDAMs), routing flexibility levels (RFLs), sequencing flexibility levels (SFLs) and part sequencing rules (PSRs) on the performance of a flexible manufacturing system (FMS) for the situation wherein part types to be produced in the system arrive continuously in a random manner. The existing DDDAMs considered are dynamic processing plus waiting time and dynamic total work content. A new model known as dynamically estimated flow allowance (DEFA) has also been developed and investigated. The routing flexibility of the system and the sequencing flexibility of parts are both set at three levels. A discrete-event simulation model of the FMS is used as a test-bed for experimentation. The performance measures evaluated are mean flow time, mean tardiness, percentage of tardy parts and mean flow allowance. The statistical analysis of the simulation results reveals that there are significant interactions among DDDAMs, RFLs, SFLs and PSRs for all the performance measures. The proposed DEFA model provides the minimum percentage of tardy parts in all the experiments. Regression-based metamodels have been developed using the simulation results. The metamodels are found to provide a good prediction of the performance of the FMS within the domain of their definition.

Simulation-based metamodels for the analysis of dynamic due-date assignment in a flexible manufacturing system

This paper investigates the effects of dynamic due-date assignment models (DDDAMs), routing flexibility levels (RFLs), sequencing flexibility levels (SFLs) and part sequencing rules (PSRs) on the performance of a flexible manufacturing system (FMS). The existing DDDAMs considered are dynamic processing plus waiting (DPPW) time and dynamic total work (DTWK) content. A new model known as dynamically estimated flow allowance (DEFA) has also been developed and investigated. The routing flexibility of the system and the sequencing flexibility of parts are both set at three levels. A discrete-event simulation model of the FMS is used as a test-bed for experimentation. The performance measures evaluated are mean tardiness, percentage of tardy parts and mean flow allowance. The statistical analysis of the simulation results reveals that there are significant interactions among DDDAMs, RFLs, SFLs and PSRs. Multiple regression-based metamodels have been developed using the simulation results. The proposed DEFA model provides the minimum percentage of tardy parts.

Simulation modelling and analysis of routing flexibility of a flexible manufacturing system

Routing flexibility is a major contributor of the flexibility of a flexible manufacturing system (FMS). This paper focuses on the evaluation of the routing flexibility of an FMS with the dynamic arrival of part types for processing in the system. A typical FMS configuration is chosen for detailed study and analysis. The system is set at five different levels of routing flexibility. Operations of part types can be processed on alternative machines depending upon the level of routing flexibility present in the system. Two cases have been considered with respect to the processing times of operations on alternative machines. A discrete-event simulation model has been developed to describe the operation of the FMS. The routing flexibility of the system has been evaluated using the measures such as routing efficiency, routing versatility and routing variety. The flexibility levels are ranked based on the routing flexibility measure for the system.

Modelling and analysis of routing flexibility, sequencing flexibility and scheduling decisions in a flexible manufacturing system

This paper focuses on a simulation-based experimental study of the interaction among routing flexibility, sequencing flexibility and part sequencing rules in a typical FMS. Two scenarios are considered for experimentation. Three routing flexibility levels, five sequencing flexibility levels and four scheduling rules for part sequencing decision are considered for detailed investigation. The performance of the FMS is evaluated using various measures related to flow time and tardiness of parts. The simulation results are subjected to statistical analysis. The analyses of results reveal that deterioration in system performance can be minimised substantially by incorporating either routing flexibility or sequencing flexibility or both. However, the benefits of either of these flexibilities diminish at higher flexibility levels. Part sequencing rules such as earliest due date and earliest operation due date provide better performance for all the measures at higher flexibility levels.

Development of simulation-based metamodels for the analysis of routing flexibility, sequencing flexibility and scheduling decision rules on the performance of an FMS

This paper focuses on the development of simulation-based metamodels for analysing the effects of routing flexibility, sequencing flexibility and part sequencing rules (PSRs) on the performance of a typical flexible manufacturing system (FMS). Three routing flexibility levels, five sequencing flexibility levels and four scheduling rules for part sequencing decision are considered for detailed investigation. The performance of the FMS is evaluated using measures related to flow time and tardiness of parts. Multiple regression-based metamodels have been developed using the simulation results. The analysis of results reveals that deterioration in system performance can be minimised substantially by incorporating either routing flexibility or sequencing flexibility or both. However, the benefits of either of these flexibilities diminish at higher flexibility levels. When flexibility exists, PSRs, such as earliest due date and earliest operation due date, provide better performance for all the measures.

Effect of Scheduling and Manufacturing Flexibility on the Performance of FMS

A framework for studying the effect of scheduling and manufacturing flexibility on the performance of flexible manufacturing system has been presented in this paper. Scheduling and manufacturing flexibility are among the many manufacturing strategies considered by the researchers to improve the system performance. In this paper in addition to scheduling and manufacturing flexibility other manufacturing strategies being considered are system configuration, buffer capacity, routing flexibility (manufacturing flexibility), number of pallets, volume of parts, dispatching and sequencing rules (scheduling). Performance of systems is evaluated on make-span time, cost, machine utilization and queue waiting time. The key issues which are addressed in this paper are the impact of different levels of routing flexibility, dispatching and sequencing rules and the increase in number of pallets on the system performance. Simulation results indicate that, with increase in routing flexibility, make-span time decreases. However the maximum benefit is obtained when routing flexibility increased from level 1 to 2. Combinations of sequencing and dispatching rules are identified, which can yield best results for make-span, cost of production, queue waiting time and machine utilization. It is suggested that the proposed methodology can be used in practice for not only setting priorities on specific manufacturing factors but also for highlighting likely factor level combinations that could yield improved shop performance.

An operational measure of routing flexibility in a multi-stage multi-product production system

The high degree of variety in customer demands causes mass production to become outdated and flexible production to be favored. Routing flexibility can be found in systems that implement general-purpose machines, alternative or identical machines, redundant machine tools, or the versatility of material handling systems. It is recognized that routing flexibility can be treated as a tool for enhancing system performance, such as lead time and inventory reduction. However, its implementation entails a huge cost of installation of flexible machines, automated tool changers and fixtures, and machine operators possessing multiple skills. Therefore, system managers must determine the appropriate level of routing flexibility for a specific system configuration in order to balance benefits and costs incurred. This paper presents a background to and a rational for a routing flexibility measure for a multi-stage flow shop. Instead of merely counting the number of available routes, this measure takes into account the loading balance between machines. Therefore, a manufacturing system with overloaded machines will have less routing flexibility as compared with one that is not overloaded, when both systems have the same number of available routes. An example for demonstrating the applicability of the proposed measure is also illustrated.