Just-in-time Environment Research Articles

Integrated Vendor–Buyer Lot-Sizing Model with Transportation and Quality Improvement Consideration under Just-in-Time Problem

This paper deals with the problem of transportation and quality within a Just-in-Time (JIT) inventory replenishment system. Formerly, transportation and quality problem are often modelled separately in most integrated inventory lot-sizing models. Hence, this paper develops an integrated vendor-buyer lot-sizing model by considering transportation and quality improvements into a JIT environment. The model is developed for minimising a total vendor–buyer system cost by optimising decisions such as delivery quantity, production batch, number of shipments, and process quality. Numerical examples and sensitivity analysis are provided to illustrate the proposed model. The developed model was also compared with an enumeration method to analyse the effectiveness of the proposed model to find the optimum solution. The results emphasise that the proposed model contributes to a new approach and obtains a near optimum solution for inventory replenishment decisions. The results are also beneficial to JIT practices as the model can improve the transport payload and reduce the chance of defective products and improving quality-related costs.

Negotiation Model for Optimal Replenishment Planning Considering Defects under the VMI and JIT Environment

As the supply chain becomes more complicated and globalized, outsourcing techniques, such as the Vendor Managed Inventory (VMI) under the Just-In-Time (JIT) conditions, are becoming widely adopted, in order to reduce inventory, lead-time and set up costs. For vendors, Third Party Logistics (TPL) is regarded as one of the best alternatives used to improve both their service level and profit. For TPL service providers, their profits must be maximized under economies of scale. However, under the JIT condition, it is very difficult to balance the order quantity whilst satisfying the predefined conditions related to inventory level. In addition, while transporting and keeping items, the exposition to various risk factors is likely. In this paper, we propose the TPL service provider to determine the optimal order quantity, considering defective items under the VMI and JIT conditions. By designing a mathematical decision-making problem based on the EPQ (Economic Production Quantity)/EOQ (Economic Order Quantity) with defective items, we can find the optimal order quantity for TPL service providers under VMI and JIT. With illustrative numerical examples, the procedure and the impacts of the expected defective rates are explained with sensitivity analysis.Copyright © 2019 The Korean Association of Shipping and Logistics, Inc. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

PENGARUH APLIKASI STRATEGI JUST IN TIME TERHADAP EFEKTIVITAS DAN EFISIENSI BIAYA PRODUKSI PADA PT. SANTOSA JAYA ABADI SIDOARJO

Just in time (JIT) is one of concepts that support cost management to anticipate the change that happens in industrial environment because of the advance of technology and automation. In a concept, JIT doing cost elimination through elimination of inventory number (inventory equals 0). This elimination of inventory number automatically lost the cost of storage and transportation, and cause the decrease of tolerate level toward product error. The aim of this research is to know and examine the influence factors of purchase, production, material shipment, product shipment and JIT environment simultaneously that have significant influences toward the cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo, and also to know and examine the dominant influence factors of purchase, material shipment, product shipment, and JIT environment toward cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo. The result of analysis shows that the first hypothesis that proposed in this research that is, “it is factors of purchase, production, and material shipment, product shipment, and JIT environment simultaneously have significant influence toward the cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo” is accepted. This is supported by the result of F-test, in which the result shows that Fcount­ (14.521) > Ftable (3.13). By seeing on the value of R square = 0.729, it means that the up-down variation of Y variable (cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo) as much as 72.9% is influenced by all independence variable in model and the rest as much as 27.1% is stipulated by variable out side of model. It means that the contribution of independence variables in model is good enough because it is more than 50%. Beside this, there are many variables that influences the effectively and efficiently of cost production at PT. Santosa Jaya Abadi Sidoarjo that not examined in this research. The second hypothesis, that is, “JIT environment have dominant influence toward the cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo” is accepted. This is supported by the result of t-test which is the value of tcount is 4.735, and ttable is 1.96, so that tcount > ttable. Beside this, the dominant influence can be stipulated with the highest value of r2 for JIT environment factor, that is, as much as 0.00476.

PENGARUH APLIKASI STRATEGI JUST IN TIME TERHADAP EFEKTIVITAS DAN EFISIENSI BIAYA PRODUKSI PADA PT. SANTOSA JAYA ABADI SIDOARJO

Just in time (JIT) is one of concepts that support cost management to anticipate the change that happens in industrial environment because of the advance of technology and automation. In a concept, JIT doing cost elimination through elimination of inventory number (inventory equals 0). This elimination of inventory number automatically lost the cost of storage and transportation, and cause the decrease of tolerate level toward product error.The aim of this research is to know and examine the influence factors of purchase, production, material shipment, product shipment and JIT environment simultaneously that have significant influences toward the cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo, and also to know and examine the dominant influence factors of purchase, material shipment, product shipment, and JIT environment toward cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo.The result of analysis shows that the first hypothesis that proposed in this research that is, “it is factors of purchase, production, and material shipment, product shipment, and JIT environment simultaneously have significant influence toward the cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo” is accepted. This is supported by the result of F-test, in which the result shows that Fcount¬ (14.521) > Ftable (3.13). By seeing on the value of R square = 0.729, it means that the up-down variation of Y variable (cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo) as much as 72.9% is influenced by all independence variable in model and the rest as much as 27.1% is stipulated by variable out side of model. It means that the contribution of independence variables in model is good enough because it is more than 50%. Beside this, there are many variables that influences the effectively and efficiently of cost production at PT. Santosa Jaya Abadi Sidoarjo that not examined in this research. The second hypothesis, that is, “JIT environment have dominant influence toward the cost production’s effectively and efficiently at PT. Santosa Jaya Abadi Sidoarjo” is accepted. This is supported by the result of t-test which is the value of tcount is 4.735, and ttable is 1.96, so that tcount > ttable. Beside this, the dominant influence can be stipulated with the highest value of r2 for JIT environment factor, that is, as much as 0.00476.

A surcharge pricing scheme for supply chain coordination under JIT environment

Just-In-Time (JIT) system involves frequent shipments of smaller batch sizes from the supplier to the buyer. For the buyer, it results in the reduction of the inventory holding cost. However, it is often accompanied by an increase in the set up cost for the supplier. Thus, the supplier may be reluctant to switch to the JIT mode unless he is assured of some form of compensation. In this paper, we introduce a pricing scheme where the buyer offers the supplier an increase in the wholesale price, to encourage the supplier to switch to the JIT mode. Such a pricing scheme may be termed as a surcharge. We develop the economics of surcharge pricing as a supply chain coordinating mechanism under JIT environment. We also establish the equivalence of surcharge pricing with other common coordination mechanisms like Quantity Discount (QD) and Joint Economic Lot Sizing (JELS) model.

A simulated annealing algorithm based approach for balancing and sequencing of mixed-model U-lines

It is known that two interrelated problems called as line balancing and model sequencing should be solved simultaneously for an efficient implementation of a mixed-model U-shape assembly line in a JIT (Just in Time) environment. On the other hand, three versions of assembly line balancing problem can be identified: Type I, Type II, and Type E. There are only two articles (Kara, Ozcan, & Peker, 2007a and Hamzadayi & Yildiz, 2012) related to simultaneous balancing and sequencing of mixed-model U-lines for minimizing the number of stations (Type 1 problem) by ignoring the fixed model sequence in the current literature. In this paper, a simulated annealing algorithm is proposed for solving a problem of type 1 by ignoring the fixed model sequence. Accordingly, simulated annealing based fitness evaluation approach proposed by Hamzadayi and Yildiz (2012) is enhanced by adding the tabu list, and inserted into the proposed algorithm. Implementation difficulties experienced in meta-heuristics based on solution modification for solving these types of problems are demonstrated. ‘Absolute deviation of workloads’ (ADW) is quite frequently used as performance criteria in the literature. It is found that ADW is an insufficient performance criterion for evaluating the performance of the solutions, and this is showed by means of an illustrative example. The parameters of the proposed algorithm are reviewed for calibrating the algorithm by means of Taguchi design of experiments. Performance of the proposed approach is tested through a set of test problems. The results of computational experiments indicate that the proposed approach is an effective method in solving simultaneous line balancing/model sequencing problems for mixed-model U-lines for minimizing the number of stations.

A supply chain model with defective items and disposal cost in a just-in-time (JIT) environment

Previous studies in the issue of supply chain models with imperfect quality assumed the defectives could be sold at lower unit price by the end of the inspection process and the lot-for-lot delivery policy was employed. However, in practice, defective items may have no salvage value but may need additional disposal cost to process them. The beginning of the printed circuit board (PCB) industry in Taiwan provides a good example of such a situation. Besides, in a just-in-time (JIT) environment, the supplier splits the order quantity into small lot size and delivers them over multiple periods to response the buyer’s need. Therefore, in this paper, a new mathematical model were developed, in which defective items are processed with disposal cost and lot-splitting (single setup, multiple delivers) policy is employed, to determine an optimal single-supplier- single-buyer inventory policy. The objective is to minimize the total joint annual cost incurred by the vendor and buyer in a JIT environment. A procedure free of employing convexity is developed to determine the order quantity, the number of deliveries and the shipping quantity. Numerical example was provided to illustrate the effectiveness of the proposed model. Based on the numerical example, sensitivity analysis was given to investigate the effects of the defective percentage on the optimal solution. Key words: Supply chain, JIT, defective item, inventory.

Using the Complete Squares Method to Analysis the Global Optimal Policy for Vendor-Buyer Integrated Inventory System Within Just in Time Environment

Using the Complete Squares Method to Analysis the Global Optimal Policy for Vendor-Buyer Integrated Inventory System Within Just in Time Environment

Coordinating a two-level supply chain with production interruptions to restore process quality

The classical inventory model, known as the lot size problem (LSP), assumes items produced and stocked to be of perfect quality. In reality, production processes are not defect free. Such imperfect processes generate defects that are reworked, and in some cases scrapped. The move by practitioners towards smaller lot sizes; e.g., just-in-time (JIT), as a mean of improving process and product quality prompted researchers to modify the LSP to represent reality more faithfully. The studies conducted by these researchers confirmed the observed benefits of smaller lot sizes. The inventory models developed in these studies assume that defects increase as the lot size increases, and that adjusting the process within a production cycle is not possible. Contrary to this assumption, in a JIT environment workers are authorized to stop production if a quality or production problem arises. This practice encouraged Khouja [Khouja, M. (2005). The use of minor setups within production cycles to improve product quality and yield. International Transactions in Operations Research, 12(4), 403–416] to reformulate some inventory models which take into account the negative relationship between lot size and quality and the possibility of performing minor setups. This requires stopping the process during a production cycle. This paper investigates the work of Khouja in a centralized decision model where players in a two-level (manufacturer–retailer) supply chain coordinate their orders to minimize their local costs and that of the chain. Mathematical models are developed with numerical results discussed.

Earliness–tardiness production planning for just-in-time manufacturing: A unifying approach by goal programming

With popularity of the just-in-time (JIT) philosophy, researchers have started to seek the integration of Manufacturing Resource Planning (MRP-II) and JIT methodologies. This paper deals with the master production planning problem for a mass manufacturing system in the JIT environment, an earliness–tardiness production planning (ETPP) problem. The objective is to determine the optimum production rate for each product so that the total penalties imposed on the early and tardy production for all production periods be minimized. A goal programming (GP) approach is proposed to formulate the ETPP problem in a more generalized form, which includes several existing models in one unifying model. Moreover, the proposed GP algorithm ensures a global optimum solution, while the existing ones did not. In addition, it also possesses the advantages over others, such as easier to comprehend, easier to solve, and easier to extend it to the problem of multiple goals.

Lot sizing for an imperfect production process with quality corrective interruptions and improvements, and reduction in setups

The just-in-time (JIT) management philosophy advocates the elimination of waste or activities that add cost and not value to the product. Eliminating waste in the production process could be attained through smaller batch (lot) sizes and reduction of in-process inventory, where concepts such as setup reduction and increased quality are fundamental. In a JIT environment workers are authorized to stop production if a quality or a production problem arises, e.g., the production process going out-of-control. In such a case, the production process is interrupted for quality maintenance to bring the process in control again. This paper investigates the lot sizing problem for reduction in setups, with reworks, and interruptions to restore process quality. This paper assumes the rate of generating defects to benefit from any changes for eliminating the defects, and thus reduces with each quality restoration action. A mathematical model is developed and numerical examples are provided with results discussed.

Design and analysis of production control scheme for Kanban-based JIT environment

This paper aims at designing production control scheme for Kanban-based just-in-time (JIT) environment. Synchronization mechanism for a single-stage single-product Kanban-controlled production line is developed, in such a way that yields a feasible operating cost as well as a feasible average of work-in-progress (WIP). The Kanban production line is formulated as ( M / M / s : GD / ∞ / ∞ ) queuing model. A new approach for analyzing the queue model is discussed. An operating cost model is then developed to determine the unknown parameters of the system. Numerical examples are used to demonstrate the computations of different system parameters. Avenue for future research is also indicated.

Balancing and Scheduling Mixed-Model U-Shaped Production Lines

The production line considered in this paper is a U-shaped, mixed-model, asynchronous line where assembly and fabrication tasks are performed to produce a variety of different discrete products or models in a just-in-time (JIT) environment. Two important problems occur routinely with these lines. The first is the assignment of tasks to stations on the line—the line balancing problem—and the second is the selection of the sequence in which models will be produced—the model sequencing problem. The model sequence cannot be set independently of the line balance, because different models require different tasks and the same tasks have different completion times for different models, and, in the JIT environment, the model sequence cannot be set independently of the schedules of other lines and production facilities. JIT uses a pull rather than a push system of production control, which means that the model sequence at the U-shaped mixed-model final assembly line sets the schedules at the other production facilities. JIT requires these latter schedules to be “level” and this requirement imposes an additional constraint on the model sequence. The effect of these two conditions is to require that the line-balancing and model-sequencing problems be solved simultaneously. In this article, we model the joint problem and present a solution algorithm for solving instances of practical size.

Reactive logistics in a JIT environment

In order to realize reactive logistics in a JIT (just-in-time) environment, this paper proposes a reactive logistics system for multi-stage production, inventory and transportation systems with unstable changes in product demand. The lot size and transportation time are considered as the parameters of the transportation process. A mathematical model of the ordering system for production and transportation processes is developed, and the relationship among the lot size, transportation time, buffer size and performance measures of the system is analysed under stable changes in product demand. Based on the relationship, a reactive controller of buffer is proposed and incorporated into the ordering system. The performance of the proposed system is investigated using simulation experiments, and the results show the effectiveness of the proposed system.

Scheduling for non regular performance measure under the due window approach

In the last two decades, Just-In-Time (JIT) production has proved to be an essential requirement of world class manufacturing. This has made schedulers most concerned about the realization of a JIT environment. The JIT concept requires not only a penalty for backorder and lateness but also for earliness. This can be translated into non-regular scheduling objectives. The most obvious objective can be to minimize the deviation of completion times. Concerning earliness/tardiness problems, researchers have usually considered systems where jobs incur no penalty for completion at a certain point of time (i.e. due date). In practice, however, job completions can also be accepted without penalty within an interval in time, which is known as the due window. This paper studies the scheduling problems in terms of the non-regular measure, mean absolute deviation (MAD), under the due window approach. The study is conducted in a dynamic job shop environment. Furthermore, we propose two new rules that perform quite effectively for the MAD measure.

Human resource management in the just-in-time environment

Abstract Successful just-in-time (JIT) implementation requires a multiskilled group-oriented and self-disciplined workforce with good quantitative skills. Little discussion exists in the JIT literature concerning the development of such a workforce. The human resource management (HRM) literature deals with employee issues but does not identify strategies for achieving a JIT workforce. In order to identify appropriate HRM strategies for a JIT environment, a comprehensive model is presented to show the critical linkage between JIT and HRM. Interactions between legal issues, management and union, and human input are examined. The impact of US labour laws on HRM practices is discussed and contrasted with Japanese practices. The literature review of HRM-related JIT articles suggests that HRM practices in the areas of staffing, training and development, compensation, and employee retention can be used to develop an effective JIT workforce. The article will help production managers to understand the impact of specific HRM strategies that are appropriate for developing a JIT workforce.

Optimizing lot size and setup time in a JIT environment: a multiple objective application

Abstract The just-in-time (JIT) system has been studied extensively and implemented by a number of US firms as an ell'ective production system. The core of JIT involves determination of lot size and setup time reduction so as to increase manufacturing flexibility while minimizing the inventory level. This decision problem usually involves multiple conflicting objectives and mixed-model production. In this paper, goal programming (GP) is applied to a real-world JIT problem involving fabrication of different automotive and industrial rubber composite belts. The model results provide new insights concerning the conflicting nature of several goals, especially between meeting demand and reducing setup or idle time. Also, the GP solution is superior to the current JIT practice of the company.

EDI Implementation: A Comparative Study of JIT and Non‐JIT Manufacturing Firms

To compete successfully in the global market, firms are adopting new technologies and manufacturing strategies. The just‐in‐time (JIT) philosophy and electronic data interchange (EDI) are two recent developments that can help these firms. The success of JIT depends on timely and effective exchange of information between the manufacturing firm and its trading partners. The literature suggests that EDI, as a communication tool, can meet this demand. However, no study investigates the impact of EDI in the JIT environment. Also, the literature lacks a thorough investigation of the EDI benefits realized by JIT and non‐JIT manufacturing firms. Examines these issues and finds that the reason for choosing EDI and the benefits realized by JIT firms differ from those of the non‐JIT firms. Suggests that JIT firms benefit more from EDI than non‐JIT firms.

EDI Implementation in JIT and Non‐JIT Manufacturing Firms: A Comparative Study

To compete successfully in the global market, firms are adopting new technologies and manufacturing strategies. The Just‐in‐Time (JIT) philosophy and Electronic Data Interchange (EDI) are two recent developments that can help these firms. The success of JIT depends on timely and effective exchange of information between the manufacturing firm and its trading partners. The literature suggests that EDI, as a communication tool, can meet this demand. However, no study investigates the impact of EDI in the JIT environment. Also, the literature lacks a thorough investigation of the EDI benefits realized by JIT and non‐JIT manufacturing firms. This empirical study examines these issues. It is found that the reason for choosing EDI and the benefits realized by JIT firms differ from those of the non‐JIT firms. Further analysis suggests that JIT firms benefit more from EDI that non‐JIT firms.

Analysis of the AGV loading capacity in a JIT environment

Abstract The problem of transport performance is inherent in just-in-time (JIT) systems where lot sizes are smaller. When the lot size is made smaller to keep inventory low, the number of delivery trips to replenish materials increases, which affects the transport performance. This situation will intensify with increased throughput requirements, as more parts move through the system in the same period of time. Adapting an automated guided vehicle (AGV) to carry multiple loads is an appealing alternative to increasing the number of single-load AGVs in a JIT system. A multiple-load AGV (MLAGV) will not increase traffic congestion, but will require a more sophisticated AGV system (AGVS) model to ensure just-in-time delivery. This paper extends the authors' previous work on modeling an AGVS in a JIT environment. It examines the alternative of using a MLAGV to meet higher throughput requirements in a JIT manufacturing system. Computer simulation was used to evaluate the effects of multiple loads on both transport and logistic performance. The results provide a useful guide in the design of MLAGV systems, particularly in manufacturing environments with low inventory and high throughput requirements.