scholarly journals Workload Control and Order Dispatching Rules

Author(s):  
Bruna Strapazzon do Couto ◽  
Miguel Afonso Sellitto

The purpose of this study is to choose an order dispatching rule and measure the work-in-process and lead-time in the production process of a conveyor chain manufacturer. The main strategic issue for the manufacturer is dependability, which requires meeting deadlines and managing internal lead-times. The study integrates two techniques, workload control (WLC) and an analytical hierarchy process (AHP), respectively systems for production planning and control, and multi-criteria decision support, both widely used in handling manufacturing strategic issues. The research method is a field experiment. Supported by the AHP and according to strategic criteria, practitioners selected the early due date rule (the order with the closest due date comes first) to release 231 orders. Then, employing a methodology designed to support WLC applications, the study measured key parameters that provide information regarding the overall performance of the manufacturer, the input rate, work-in-process, lead-time, throughput performance, and the level of safety stock. Using the model and a graphical tool derived from queuing theory, the throughput diagram, the study provides evidence that, although the manufacturing process is satisfactorily balanced and achieves acceptable performance, the level of safety stock is small and should be increased to prevent starvation on the shop floor.

2018 ◽  
Vol 58 (6) ◽  
pp. 395-401 ◽  
Author(s):  
Miguel Afonso Sellitto

The purpose of this article is to present a method for calculating the lead-time, the inventory, and the safety stock or buffer in job shop manufacturing, which are essentially stochastic variables. The research method is quantitative modelling. The theoretical foundation of the method relies on the techniques belonging to the WLC (workload control) body of knowledge on the manufacturing management. The study includes an application of the method in a manufacturing plant of the furniture industry, whose operation strategy requires high dependability. The company operates in a supply chain and must have high a reliability in deliveries. Adequate safety stocks, lead times, and inventory levels provide the protection against the lack of reliability in the deliveries. The inventory should remain within a certain range, being as small as possible to maintain low lead times, but not too small that it could provoke a starvation, configuring an optimization problem. The study offers guidelines for a complete application in industries. Further research shall include the influence of the variability of the lot size in the stochastic variables.


2012 ◽  
Vol 433-440 ◽  
pp. 2230-2236
Author(s):  
Ya Rong Chen ◽  
Hong Ming Zhou ◽  
Zai Lin Guan ◽  
Xin Yu Shao

In the mixed-production context of make-to-stock (MTS) and make-to-order (MTO), the manufacturing system becomes more complex for comprehensive balance of multiple objectives, including resource utilization, work in process (WIP), on-time delivery and throughput. To deal with this complexity, a dynamic production plannning and control (PPC) model with the hybrid of workload control (WLC) and theory of constraint (TOC) is presented. While the proposed three-tiered hierarchy construction model is relatively similar to WLC model, but the way in which the workloads are controled has changed dramatically. The order acceptance deals with issues of order review and delivery setting in order to balance the overall resource capacity and requirements that is necessary for on-time delivery. The order release deals with issues of release mechanisms and rules in order to control the flow of work to the production floor that is necessary for WIP and resource utilization.And the scheduling deals with issues of bottleneck identicification and task sequencing in order to protect the bottleneck capacity that is necessary for throughput.


Author(s):  
Federica Costa ◽  
Alberto Portioli-Staudacher

AbstractThe paradigm shift toward Industry 4.0 is facilitating human capability, and at the center of the research are the workers—Operator 4.0—and their knowledge. For example, new advances in augmented reality and human–machine interfaces have facilitated the transfer of knowledge, creating an increasing need for labor flexibility. Such flexibility represents a managerial tool for achieving volume and mix flexibility and a strategic means of facing the uncertainty of markets and growing global competition. To cope with these phenomena, which are even more challenging in high-variety, low-volume contexts, production planning and control help companies set reliable due dates and shorten lead times. However, integrating labor flexibility into the most consolidated production planning and control mechanism for a high-variety, low-volume context—workload control—has been quite overlooked, even though the benefits have been largely demonstrated. This paper presents a mathematical model of workload control that integrates labor flexibility into the order review and release phase and simulates the impact on performance. The main results show that worker transfers occur when they are most needed and are minimized compared to when labor flexibility is at a lower level of control—shop-floor level—thus reducing lead time.


Mathematics ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1029
Author(s):  
Ying-Mei Tu

Since last decade, the cluster tool has been mainstream in modern semiconductor manufacturing factories. In general, the cluster tool occupies 60% to 70% of production machines for advanced technology factories. The most characteristic feature of this kind of equipment is to integrate the relevant processes into one single machine to reduce wafer transportation time and prevent wafer contaminations as well. Nevertheless, cluster tools also increase the difficulty of production planning significantly, particularly for shop floor control due to complicated machine configurations. The main objective of this study is to propose a short-term scheduling model. The noteworthy goal of scheduling is to maximize the throughput within time constraints. There are two modules included in this scheduling model—arrival time estimation and short-term scheduling. The concept of the dynamic cycle time of the product’s step is applied to estimate the arrival time of the work in process (WIP) in front of machine. Furthermore, in order to avoid violating the time constraint of the WIP, an algorithm to calculate the latest time of the WIP to process on the machine is developed. Based on the latest process time of the WIP and the combination efficiency table, the production schedule of the cluster tools can be re-arranged to fulfill the production goal. The scheduling process will be renewed every three hours to make sure of the effectiveness and good performance of the schedule.


2014 ◽  
Vol 1018 ◽  
pp. 563-570
Author(s):  
Marcel Wagner ◽  
Tim Schleimer ◽  
Tobias Seeberger ◽  
Gunther Reinhart

Production Planning and Control (PPC) does not only play an important role in the classical field of production. Concerning a trend to more customer related products and a so called buyers market, also the not yet strongly automated businesses have to think about topics like PPC. By forming a new automated shop floor in a commercial kitchen for example, new optimization criteria in the PPC play a crucial role. Especially in the manner of scheduling jobs different constraints concerning the handled products come up. This paper demonstrates a possibility to extend the criteria of PPC with the subjective parameter of product quality. This approach allows influencing an oven-control to reach the best product quality in its processing.


2017 ◽  
Vol 8 (2) ◽  
pp. 30-40 ◽  
Author(s):  
Peter Nielsen ◽  
Zbigniew Michna ◽  
Brian Bruhn Sørensen ◽  
Ngoc Do Anh Dung

AbstractLead times and their nature have received limited interest in literature despite their large impact on the performance and the management of supply chains. This paper presents a method and a case implementation of the same, to establish the behavior of real lead times in supply chains. The paper explores the behavior of lead times and illustrates how in one particular case they can and should be considered to be independent and identically distributed (i.i.d.). The conclusion is also that the stochastic nature of the lead times contributes more to lead time demand variance than demand variance.


2020 ◽  
Vol Vol. 36 (No. 2) ◽  
pp. 49-57
Author(s):  
István Vajna ◽  
Anita Tangl

The case study shows the re-optimization of an initial new factory layout design with Value Stream Design (VSD). The VSD is a quantitative method and its’ final goal is to make a waste free optimized material flow. The primary goal of arrangement is to reduce transportation distances and frequencies, optimize human load. Initially the whole factory shop floor layout design was already made in push concept. The plans were made by production management, logistics, engineering department at the headquarter of the multinational automotive company with based on VDI2870 holistic concept linking strategy on tactics and operation. On the layout (v1.) the hundreds of machines were placed and arranged by CAD (Computer Design) engineers to fit the space. The factory building has 15,000 m2 with empty shop floor waiting for the final decisions for equipment. The factory production area was shared into six main production areas (P1-P6), which correlates with their product complexity of the product families. Each production area output can be finished product (FP) or semi-finished product (SFP) for the next production areas. To validate the whole factory layout it was necessary to involve lean experts that identified disadvantages and constraints. Without lean implementation the company’s transportation waste would be 49% more per year. The Value Stream Design importance nowadays is upgrading to a higher level, when the whole global business is changed, the labor force fluctuates, and the cost and delivery time reduction plays a vital role in the company’s profit and future. The research shows that if the decision taking is based on real data and facts the controlling and management can do its best in time. Using VSD and re-evaluating the transportation routes, frequency and costs is the first step to define a smooth, low cost, material flow (v2.). This development ensured the company to drive from push to pull production through mixed production system. Originally, the production flow was clockwise orientation. It was changed step by step to mixed production by eliminating work in process storages, implementing FIFO lanes, Milk Run, and Kanban. The total annual transportation distances were reduced from 4,905,000 m between the rump-up and serial production period. The warehouse storage size was reduced to 50% and implementation cost from €75,000 to €32,500. By eliminating work in process storages along production lines it was possible to open a new two way transportation road that also will serve the AGV’s operations in industry 4.0 projects. Due to decreased lead time the logistic labor productivity increased by 45%. Besides taking measurements for the VSD it was used Value Stream Mapping as a lean tool and an own designed VSD evaluation and a simulation software. The VSD team’s cooperative actions reduced the evaluation and validation time with 65% then it was initially planned. The implementations were evaluated from the rump-up phase to the first serial productions and the results were confirmed by controlling and management


2021 ◽  
Vol 11 (3) ◽  
pp. 7069-7074
Author(s):  
M. Masmali

The lean manufacturing concept is a systematic minimization of waste and non-value activities in production processes introduced by the Toyota production system. In this research, lean manufacturing is implemented in a cement production line. Value Stream Mapping (VSM) is applied to give a clear picture of the value chain in cement production processes and to highlight the non-value-added in the shop floor. To begin, the existing VSM is constructed based on the information and data gathered during visiting and observing the manufacturing process in the firm. As a result, the excess inventory between workstations was identified as a major waste generation, hence, the proposed VSM conducts further improvement and makes action plans to alleviate the unwanted activities. Then, the takt time to ensure smooth material flow and to avoid any occurring delay or bottleneck in the production line was figured out. The supermarket pull-based production control is suggested to be adopted in the future map. Two pull production strategies are selected in this case. The first is applying the Kanban system to control the level of inventory between workstations. The other is the CONWIP approach to control the amount of work in process to the entire production line. The outcome of the proposed models indicates a decrease of the none-value time from 23 days in the current state to about 4 and 2 days in Kanban and CONWIP systems respectively, so the CONWIP was suggested as most efficient. Some suggestions for further research are also mentioned.


2014 ◽  
Vol 15 (1) ◽  
Author(s):  
Peter Bent Hansen ◽  
Rodrigo Gomes Da Rocha ◽  
Fernando De Oliviera Lemos
Keyword(s):  
De Se ◽  

As mudanças que afetaram o segmento industrial nas últimas décadas conduziram ao desenvolvimento de técnicas destinadas ao aumento de produtividade e eliminação de perdas, entre as quais o Sistema Toyota de Produção (STP). Porém, o STP pode apresentar resultados diferenciados dependendo do ambiente onde é aplicado. O objetivo desta pesquisa é analisar os potenciais resultados e melhorias de produtividade passíveis de se alcançar pela aplicação de conceitos e técnicas do Sistema Toyota de Produção em uma célula de manufatura de uma empresa metal-mecânica, através da simulação computacional. O estudo constitui uma pesquisa aplicada, qualitativa e se caracteriza como um estudo de caso. Foram realizados 3 tipos de experimentos de aplicações de técnicas do STP via simulação computacional, tendo-se constatado que os mesmos produzem efeitos diferenciados em termos de produtividade, lead time, work-in-process e ociosidade dos operadores, apesar de todos convergirem para o aumento de produtividade da célula conforme esperado, porém em diferentes graus.


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