Gonca Tuncel

Risk assessment and management for supply chain networks: A case study

The aim of this study is to show how a timed Petri nets framework can be used to model and analyze a supply chain (SC) network which is subject to various risks. The method is illustrated by an industrial case study. We first investigate the disruption factors of the SC network by a failure mode, effects and criticality analysis (FMECA) technique. We then integrate the risk management procedures into design, planning, and performance evaluation process of supply chain networks through Petri net (PN) based simulation. The developed PN model provides an efficient environment for defining uncertainties in the system and evaluating the added value of the risk mitigation actions. The findings of the case study shows that the system performance can be improved using risk management actions and the overall system costs can be reduced by mitigation scenarios.

Two-sided assembly line balancing using teaching-learning based optimization algorithm

Assembly line balancing plays a crucial role in modern manufacturing companies in terms of the growth in productivity and reduction in costs. The problem of assigning tasks to consecutive stations in such a way that one or more objectives are optimized subject to the required tasks, processing times and some specific constraints is called the assembly line balancing problem (ALBP). Depending on production tactics and distinguishing working conditions in practice, assembly line systems show a large diversity. Although, a growing number of researchers addressed ALBP over the past fifty years, real-world assembly systems which require practical extensions to be considered simultaneously have not been adequately handled. This study deals with an industrial assembly system belonging to the class of two-sided line with additional assignment restrictions which are often encountered in practice. Teaching-learning based optimization (TLBO), which is a recently developed nature-inspired search method, is employed to solve the line balancing problem. Computational results are compared with the current situation in terms of the line efficiency, and the solution structure with workload assigned to the stations is presented.

Assembly line balancing with positional constraints, task assignment restrictions and station paralleling: A case in an electronics company

In this paper, we present a real-life Assembly Line Balancing Problem for an electronics manufacturing company. The main characteristics of the problem are as follows: (i) a set of operations are related to the front part of the workpiece and others are related to the back part of the workpiece, which in turn makes all tasks dependent on the position of the workpiece, (ii) some of the tasks must be executed on the same station and no other tasks should be assigned to this station due to technological restrictions, (iii) parallel stations are allowed to increase the line efficiency at the required production rate and to overcome the problem of assigning tasks with operation times that exceed the cycle time. Initially, the problem is formulated as a 0-1 integer programming model and solved using CPLEX solver. Then, the effect of alternative work schedules such as multiple shifts and overtime on the expected labor cost of the line is analyzed. Considering alternative work schedules while balancing the line for corresponding cycle times allows us to select an efficient assembly line for the company, resulting in a lower labor cost and a more balanced line with respect to the operation times and the activity of the workers at each station. Lastly, a computational study is conducted to evaluate the performance of the proposed model. It is found that the model is capable of producing high quality solutions in reasonable solution times.

A high-level petri net based decision support system for real-time scheduling and control of flexible manufacturing systems: an object-oriented approach

Petri nets (PNs) are powerful tools for modeling and analysis of discrete event dynamic systems. The graphical nature and mathematical foundation make Petri net based methods appealing for a wide variety of areas including real-time scheduling and control of flexible manufacturing systems (FMSs). This study attempts to propose an object-oriented approach for modeling and analysis of shop floor scheduling and control problem in FMSs using high-level PNs. In this approach, firstly, object modeling diagram of the system is constructed and a heuristic rule-base is developed to solve the resource contention problem, then the dynamic behavior of the system is formulated by high-level PNs. The methodology is illustrated by an FMS.

How Can Risks be Managed in Logistics Networks

Risk Management is a subject of growing interest both in academic research and in business communities. Nowadays the industrial environment is highly dynamic and sometimes unstable. Because of the structural complexity and volatility in logistics networks, there is an increasing need for a decision support system that is integrated with risk assessment and management procedures. In this study, we aim to investigate the fundamental steps of risk analysis and for a well-suited control mechanism and systematic decision-making process of management, then present a conceptual framework of a design methodology logistics networks under the influence of disruptive factors.

Application of activity-based costing in a manufacturing company: a comparison with traditional costing

Activity-Based Costing (ABC) represents an alternative paradigm to traditional cost accounting system and has received extensive attention during the past decade. Rather than distorting the cost information by using traditional overhead allocation methods, it traces the cost via activities performed on the cost objects (production or service activities) giving more accurate and traceable cost information. In this paper, the implementation of ABC in a manufacturing system is presented, and a comparison with the traditional cost based system in terms of the effects on the product costs is carried out to highlight the difference between two costing methodologies. The results of the application reveal the weak points of traditional costing methods and an S-Curve which exposes the undercosted and overcosted products is used to improve the product pricing policy of the firm.