Order Release Control Research Articles

Job sequencing and selection within workload control order release: an assessment by simulation

Recent research has highlighted the potential impact of pool sequencing on order release performance but it suffered from two shortcomings. First, arguably the best release solution for workload control in practice combines periodic with continuous release. Although the two types of releases serve different functions, recent work assumed the same sequencing rule should be used for both. Here, the use of different sequencing rules for periodic and continuous releases is evaluated. Using a job-shop simulation, we demonstrate that the rule applied during continuous releases has only a negligible impact on performance. Therefore, jobs can be pulled intermediately from the pool by workers using a more straightforward sequencing rule than the one applied for periodic release. Second, it was assumed that all jobs in the pool are sequenced and then a subset is selected for release. But for some load-oriented sequencing rules, the priority value used for sequencing jobs should be updated after each job selection from the pool. Our simulation results show that although this may improve load balancing at release, it does not in fact improve overall shop performance. Therefore, the greedy heuristic of first sequencing and then selecting jobs can be maintained, which allows the release decision-making process to retain its simplicity. The work has important implications for the use of sequencing rules in practice.

Order release in the hybrid MTO–FTO production

In this paper, we analyse and compare the impact of the choice of the release method in a hybrid make-to-order (MTO)–finish-to-order (FTO) production system composed of two stages. The study is motivated by a practical problem from the aluminium profiles manufacturing industry, where for shortening throughput times it is allowed to start production of standard and regular items without confirmed orders, holding a stock of semi-finished products. The first stage manufactures both, items to order and items to a stock of semi-finished products, while the second stage is a customization stage based on customer demand requests and specifications. The paper addresses the questions of where order release control should be exercised, i.e., at only one stage or at both stages, and when should it be exercised. Simulation results suggest that load-based order release can be successfully applied to this hybrid production system when combined with a replenishment control policy for semi-finished products. Load-based order release contributes to reduce the total throughput time and the percentage of tardy orders of both, MTO and FTO, while contributing to a reduction of the semi-finished products inventory levels required to achieve a given fill rate. The study is a contribution toward the alignment of workload control theory to industrial practice.

Continuous workload control order release revisited: an assessment by simulation

Order release is a key component of the Workload Control concept. Jobs do not enter the shop floor directly – they are retained in a pre-shop pool and released in time to meet due dates while keeping work-in-process within limits or norms. There are two important groups of release methods: continuous methods, for which the workload falling to a specified level can trigger a release at any moment in time; and, periodic release methods, for which releases take place at fixed intervals. Continuous release methods in general have been shown to outperform periodic release methods. Yet, there is incongruence in the results presented in the literature on the relative performance of the various continuous release methods. We use a job shop simulation model to examine the performance of continuous release methods from the literature and find that the contradictory results are explained by the different rules applied to sequence jobs in the pool – a factor neglected in previous work. Finally, a new breed of continuous release methods has recently emerged, but these have not been compared with prior approaches. Therefore, we also examine these methods and show that they significantly improve overall performance, although this is to the detriment of jobs with large processing times.

Lean Control for Make‐to‐Order Companies: Integrating Customer Enquiry Management and Order Release

A lead time that is short, predictable, and reliable is an increasingly important criterion in supplier selection. Although many companies may achieve this through lean implementation, high‐variety manufacturers, for example, small and medium‐sized make‐to‐order companies, have found that lean's planning and control techniques do not apply. This article outlines a planning and control concept known as workload control (WLC) that integrates customer enquiry management, including a due‐date setting rule, with order release control. Simulation is then used to assess its impact on shop performance. Results demonstrate that an integrated WLC concept can reduce the percentage of tardy jobs—so short lead times can be realistically quoted—while also reducing and stabilizing workloads. WLC can level demand and production over time when work is not standardized and it is not possible to synchronize flows on the shop floor. Results are shown to be robust to changes in routing characteristics, the mix of orders with due dates specified by the customer and proposed internally, and the strike rate (or order‐winning probability). Hence, an integrated approach to WLC represents an important step toward achieving lean in make‐to‐order companies.

An Order Release Control Mechanism Based on self-Adaptive Neural Fuzzy Inference System and Theory of Constraints

Order release is the key premise for the semiconductor wafer fabrication system to perform well, which is also one of the paramount significant components in the scheduling strategies. Most order release strategies merely have focused on the workloadbut failed in considering the remarkable influence oncycletime of common orders that is brought by unexpectedrushones.In this paper an on-linemechanismbased on Theory of Constraintsfor lot releaseusingself-Adaptive Neural Fuzzy Inference System modelswas presentedwhich is able to adjust the release rhythmdynamicallyaccording to dynamics of fabs.In our approach, an ANFIS model was established to predict the ratiobetweenhotand common lotsin wafer fabto perform adjustments on the order release schedule in advance.Simulated experimentsbased on the HP24 model were carefully performed and experimental results proved a better performance of common lotsthan original TOC on a large scale, especially when it comes to the situation of disturbance. DOI: http://dx.doi.org/10.11591/telkomnika.v11i11.3488 Full Text: PDF

Coping with finite storage space in job shops through order release control: an assessment by simulation

Most literature on job shops assumes that an infinite storage space is available on the shop floor. But in practice, storage space is limited or finite. The job shop control problem with finite storage space has received little attention; it is a complex problem for which optimised scheduling may lead to unfeasible and poor quality solutions. The alternative to a scheduling solution is the use of controlled order release. This study uses simulation to assess the performance of four order release control rules. Results indicate that the best results are achieved by the workload control order release (WLCOR) rule. This rule produces results comparable to the optimum solution identified by analytical modelling in terms of the storage space required to achieve a certain production rate. The advantage of WLCOR is that it does this while simultaneously controlling lead times and the percentage of tardy jobs. Results have significant implications for practice, particularly where space is at a premium.

Towards an Integrated Workload Control (WLC) Concept: The Performance of Due Date Setting Rules in Job Shops with Contingent Orders

Workload control (WLC) is a production planning and control concept developed for make-to-order companies. Its customer enquiry management methodology supports due date setting, while its order release mechanism determines when to start production. For make-to-order companies, due date setting is a strategically important, complex task where unconfirmed jobs place demands on capacity which are contingent on a quotation being accepted by the customer. Yet most prior WLC research has begun at the order release stage with a set of confirmed orders with predetermined due dates. In contrast, this paper focuses specifically on customer enquiry management and uses simulation to compare and contrast the performance of 11 due date setting rules in a job shop where part of the workload consists of unconfirmed or contingent orders. The best results are achieved by a finite loading rule which explicitly considers the workload of contingent orders when estimating lead times. This enables demand to be levelled over time, allowing due dates to be short and reliable – thereby improving both the competitiveness of a make-to-order company and the customer service level it is able to offer. Future research should focus on integrating customer enquiry management, and its due date setting rule, with order release control.

Improving the applicability of workload control (WLC): the influence of sequence-dependent set-up times on workload controlled job shops

Simulation has demonstrated that the workload control (WLC) concept can improve performance in job shops, but positive empirical results are scarce. A key reason for this is that the concept has not been developed to handle a number of practical considerations, including sequence-dependent set-up times. This paper investigates the influence of sequence-dependent set-up times on the performance of a workload-controlled job shop. It introduces new set-up-oriented dispatching rules and assesses the performance impact of controlled order release. Simulation results demonstrate that combining an effective WLC order release rule with an appropriate dispatching rule improves performance over use of a dispatching rule in isolation when set-up times are sequence dependent. The findings improve our understanding of how this key implementation challenge can be overcome. Future research should investigate whether the results hold if set-up time parameters are dynamic and set-up times are not evenly distributed across resources.

Controlled order release: a performance assessment in job shops with sequence-dependent set-up times

Findings from recent implementations of Workload Control (WLC) have called for research to investigate how sequence-dependent set-up times can best be handled within the design of the concept. In response, this study assesses the performance of four of the best-performing release methods from the literature in a job shop with sequence-dependent set-up times by simulation. First, the four methods are compared without considering set-up requirements at release. Second, the methods are refined to consider set-up requirements before being compared against the original methods. A release method that combines continuous and periodic release emerges as the best-performing method. Findings further suggest that considering set-up requirements at release do not have a significant positive effect on performance and may even be counterproductive: conflicting goals between the selection rules employed at release and dispatching may lead to an increase in the percentage of tardy jobs. Future research should consider whether the results hold if set-up times are not distributed equally across job types and work centres.

Input-output control order release mechanism in a job-shop: how workload control improves manufacturing operations

This paper presents and evaluates an order release decision rule in a job-shop, based on the input-output control concept. The order release mechanism is part of a global decision-making scheme that includes four main decisions: accept/reject orders, define the order's due date, release the accepted jobs and dispatch it on the shop floor. This paper also presents an evaluation of two acceptance rules, four release mechanisms, and two dispatching rules, using four levels of due date tightness. Extensive simulation experiments were performed to compare the different decision rules, using several criteria: mean tardiness, percent tardy, mean absolute deviation, mean queue time in the shop floor and in the system, and machine usage. We conclude that considering the four decisions simultaneously improve the job-shop performance, and planning both the input and the output when deciding to release a job, leads to an improvement of the operational performance measures.

P‐77: CONWIP for Order Release and WIP Control in Color Filter Fabs

AbstractA Constant Work‐in‐Process (CONWIP) approach for color filter fabs was proposed to control order release and WIP level. An AutoMod simulation model was developed based on real fabs and used to evaluate CONWIP's performance. Results indicated that CONWIP can increase throughput and decrease cycle time and WIP.

Shop Floor Control Mechanism of Aerospace Machine Shop

The production environment of aerospace industry is make-to-order. The life cycle of aircraft is more than 20 years. Aircraft parts should have higher precision and lightweight to achieve the requirements of safety, payload, and controllability. Machine parts are the important portion of aero-structures. Base on the strength, function, contour of machine parts, then assign to suitable machine center for machining. This study construct the shop floor control mechanism of aerospace machine shop which combine the concept of order release control, gateway control, queue level control, color code control, cycle time control, and apply the on-time dispatch and on-time completion as an indicator to monitor the performance of shop floor control. Thus, we can improve the weakness and increase the competitive advantages of machine shop in the global competitive aerospace market.

Generic POLCA—A production and materials flow control mechanism for quick response manufacturing

A production and materials flow control mechanism for quick response manufacturing (QRM) is proposed. This is called generic paired-cell overlapping loops of cards with authorization (GPOLCA). It is an adaptation of the POLCA mechanism developed as part of the QRM strategy. GPOLCA implements an input–output control order release strategy based on an inventory of production authorization cards instead of materials. It is best suited for companies that manufacture large variety of products with variable demand. A description of GPOLCA is made together with a comparative study of its performance in relation with other mechanisms namely MRP and POLCA. The results show that GPOLCA attains better performance.

An integrated model for order release and due‐date demand management

In this paper, an integrated model for order release and due‐date management is developed to enhance manufacturers’ confidence in the due‐dates offered to customers. The proposed model utilised the backward finite scheduling order release control method and five different due‐date assignment rules. The proposed model is implemented using C++ computer programming language. Due‐date of each order is calculated by a due‐date assignment rule selected. Then the program tries to schedule the whole order with as lowest value as possible of tightness parameter (k). The output of the C++ program is production schedule of the whole order using backward finite scheduling order release method. Experiment results indicate that the modified number of operations due‐date rule_MNOP is superior with respect to the other due‐dates rules of the whole order.

Integrating order release control with due-date assignment rules

This study integrates order release control methods with due-date assignment rules and assesses its impact on the accuracy of inter-operation time estimation and performance of due-date assignment. The assessment is made by using an experimental design with three due-date assignment rules, three scheduling rules and three order release models. The three order release models are: (1) Basic model, in which three due-date assignment rules consider the order arrival time as the order release time; (2) Control model, in which three due-date assignment rules integrate with the order release control method developed here; and (3) Adjustment model, in which the control model integrates with the order release control adjustment developed here. Simulation results in this study indicate that integrating the order release control method with due-date assignment rules will significantly enhance not only the accuracy of interoperation time estimation, but also the performance of due-date assignment rules.

Fuzzy control in a single-machine system

Abstract As a new application area we have been tried to apply the fuzzy control concept in discrete event dynamic systems (DEDS) control problems. The fuzzy control of a single-machine system is presented. Simulation studies have been performed on the basis of a descriptive model for investigating the control performance. Two other control approaches, namely proportional control (P-control) and load-oriented order release control (LOOR-control), are employed to compare with the fuzzy control approach. It is concluded that fuzzy control is a practical and effective way to control DEDS. The fuzzy control module developed during this study can be easily adapted for fuzzy control of other DEDS, for example job-shop systems. This paper should be considered as the first step in using fuzzy control concept for the control of DEDS.

An order release mechanism for a flexible flow system

Order release is where orders are released to the shop floor for processing. An Order Release Mechanism (ORM) can control order release, such that orders are selectively released so as to improve shop management and performance. This paper reports on the development of an ORM for a specific Flexible Flow System (FFS), where the primary criterion in running the system is flow time. The ORM determines what order to release when, and makes the routeing decisions for each order. Using a simulation model, the performance of the FFS with the ORM was compared to present practice without an ORM and an ‘off-the-shelf’ ORM from the literature, namely CONWIP. It is found that the ORM not only improves the mean time that orders spend in the shop under all load conditions, but also reduces the variance of this measure. It would be expected that the total time that orders spend in the system increases with the ORM, at least compared to immediate release, but at high load levels it is found that this measure also decrea...