Browsing by Subject "Manufacturing"

Now showing 1 - 20 of 21

Open Access
Analyses of serial production line systems for interdeparture time variability and WIP inventory systems
(International Journal of Operations and Quantitative Management, 2004) Erel, E.; Sabuncuoglu, I.; Kok, G. A.
This paper investigates the well-known and extensively studied unpaced production line problem for the interdeparture time variability and work-in-process (WIP) inventory. The primary objective is to examine the relationships between the interdeparture time variability and some system design factors such as the number of stations, buffer capacity, and location of a bottleneck station. The performance of the system is also evaluated for average and variance of WIP inventory. Simulation is used as a modeling and analysis tool with the results being tested by appropriate statistical procedures. The analysis of the results reveals several important findings on the interdeparture time variability and WIP inventory. We confirm and strengthen some of the previous findings on throughput. In this paper, we also discuss managerial implications and suggest further research areas.
Open Access
Analysis of the (Q, r) inventory model for perishables with positive lead times and lost sales
(Institute for Operations Research and the Management Sciences (INFORMS), 2008) Berk, E.; Gürler, Ü.
We consider a perishable inventory system with Poisson demands, fixed shelf lives, constant lead times, and lost sales in the presence of nonnegligible fixed ordering costs. The inventory control policy employed is the continuous-review (Q, r) policy, where r < Q. The system is modeled using an embedded Markov process approach by introducing the concept of the effective shelf life of a batch in use. Using the stationary distribution of the effective shelf life, we obtain the expressions for the operating characteristics and construct the expected cost rate function for the inventory system. Our numerical study indicates that the determination of the policy parameters exactly as modeled herein results in significant improvements in cost rates with respect to a previously proposed heuristic. We also compare the (Q, r) policy with respect to a time-based benchmark policy and find that the (Q, r) policy might be impractical for rare events, but overall appears to be a good heuristic policy.
Open Access
A case study in marketing-manufacturing interface
(1995) Eren, Demet
The coordination between the marketing and manufacturing departments plays an important role in the implementation of the corporate strategy. The conflicts and gaps between these two departments impede the successful implementation of corporate strategy. Therefore understanding and managing the marketingmanufacturing interface is critical for the success of the company. This study investigates the gaps and factors affecting these gaps in the marketingmanufacturing interface and developes and uses a survey instrument in a case study.
Open Access
A case study in marketing-manufacturing interface : Ateş Mobilya
(1994) Gezer, Melih
The coordination between Marketing and Manufacturing departments is a key determinant of an organization’s level of competitiveness. The lack of coordination between these two functions can be attributed to various factors. The aim of this study is to develop a qualitative research tool for understanding the effects of such factors on the Marketing - Manufacturing interface and to provide an empirical case study by applying this tool to a manufacturing organization. The study is concluded with an analysis of the findings and recommendations for future use.
Open Access
A comparative study of cell formation in cellular manufacturing systems
(Taylor & Francis, 1994) Kandiller, L.
This paper analyses and evaluates six of the promising cell formation techniques by comparing and contrasting them in relation to the scores of efficiency indices of the exceptional elements and inner-cell densities, work-load balance, and under-utilizations in different scenarios. Accordingly, all six are more or less altered with proper extensions to realize a broader capability. Effectiveness of the suggested efficiency measures in the evaluation is also illustrated. Each technique seems to have a favourite operating area of its own considering a variety of factors. © 1994 Taylor & Francis Group, LLC.
Open Access
The demand for energy in the large-scale manufacturing sector of Pakistan
(Elsevier BV, 1990) Mahmud, Fakhre; Chishti, S.
The extent of interfuel substitution, as well as substitution between energy and non-energy inputs, in the large-scale manufacturing sector of Pakistan has been examined. The model has been estimated in two stages. In the first stage input demand for various energy components is estimated and hence an aggregate Divisia index is constructed. In the second stage this index is used as an instrument to estimate aggregate input demand for capital, labour and energy along with their price and substitution elasticities. It seems that there is little interfuel substitution. The results also show that energy and labour are substitutes while energy and capital are complement.
Open Access
Determinants of the marketing-manufacturing interface
(1993) Akıncı, Hikmet Burcu
Marketing and manufacturing departments play important roles in day-today implementation of the corporate strategy. The conflicts and interfacial gaps between these two functional departments will impede the successful implementation of corporate strategy. Therefore, understanding and managing the marketing-manufacturing interface are crucial for the company's success. This study investigates the gaps in the interface of marketing and manufacturing, and identifies the factors that affect these gaps within a theoratical framework. Furthermore, a survey instrument is developed to emprically identify the gaps and significant factors that affect these gaps.
Open Access
Development of multi-axis laser micromachining system suitable for machining non-linear contoured surfaces
(2016-08) Kerimoğlu, Serhat
In recent years, studies on manufacturing systems have proved the importance of cooperation of positioning systems with laser cutting technology. The performance of the manufacturing system can be improved by utilizing both laser and positioning systems together. In this study, design and development of a micromachining system which can perform on non-linear contoured surfaces is presented. Laser micromachining system is designed and assembled including a nanosecond Q-switched pulsed ber laser, a 6-DOF hexapod manipulator, a granite table in order to absorb vibrations and an external cabin system to isolate the whole system for safety and health issues. Performance characteristics of micromachining devices mainly determined by precision and characteristics of each individual components of the system. Therefore, the studies to improve the performance of the laser micromachining system are related with laser, isolation and positioning systems. A dynamic model of the positioning system is derived to obtain the control parameters for the actual positioning system. By using these parameters, the performance of the laser micromachining system on nonlinear contoured surface is improved and discussed in detail. The simulation environment MATLAB/Sim- Mechanics is used to model the dynamics of the positioning system. With the kinematic and dynamic model of the manipulation system simulations, signi cant performance enhancements are obtained on non-linear contoured surfaces.
Open Access
Dynamic lot sizing and tool management in automated manufacturing systems
(Elsevier, 2002) Aktürk, M. S.; Önen, S.
The overall aim of this study is to show that there is a critical interface between the lot sizing and tool management decisions, and these two problems cannot be viewed in isolation. We propose "ve alternative algorithms to solve lot sizing, tool allocation and machining conditions optimization problems simultaneously. The "rst algorithm is an exact algorithm which "nds the global optimum solution, and the others are heuristics equipped with a look-ahead mechanism to guarantee at least local optimality. The computational results indicate that the amount of improvement is statistically signi"cant for a set of randomly generated problems. The magnitude of cost savings is dependent on the system parameters.
Open Access
The energy demand in the manufacturing sector of Pakistan: some further results
(Elsevier BV, 2000) Mahmud, S. F.
The purpose of this study was to re-examine the role of energy in the manufacturing sector of Pakistan using a Partial Equilibrium Approach. GL restricted cost function along with the factor demand equations were estimated using Zellner's iterative procedure. Higher energy prices do not seem to adversely affect investment in capital. Substitution possibilities between energy and non-energy inputs are very limited and therefore energy price hikes may directly affect the cost of production. Inter-fuel cross price elasticities indicate that there are substitution possibilities between electricity and gas. (C) 2000 Elsevier Science B.V. All rights reserved. JEL classification: Q41.
Open Access
Marketing manufacturing interface in Biltepe AS
(1996) Ayırga, A. Oğuz
Marketing manufacturing interface in Biltepe Inc. is analyzed by a qualitative research tool in this thesis. The competitive advantages of an organization relies on the coordination between marketing and manufacturing departments. Inadequate coordination between these two departments can be originated from various factors. The study determines the factors that have effect on the marketing manufacturing interface and provides an empirical case study by applying research tool in a manufacturing organization in the advanced construction materials industry. The study also includes analysis of the company related issues which have been scrutinized from a strategic perspective. In the final part recommendations made for future use of both this company and this study.
Open Access
Marketing-manufacturing interface in Turkish tractor industry
(1995) Karaçoban, Özlem
Marketing-manufacturing interface in Turkish tractor industry is analyzed by a quantitative research tool in this thesis. The study determines two factors that have effect on the marketing-manufacturing interface and develops two hypotheses related with those factors. These hypotheses are also tested and proved to be valid in Turkish tractor industry. Furthermore, a detailed analysis is carried out by both quantitative and qualitative techniques in order to understand the effect of factors on the marketing-manufacturiiig interface in a manufacturing organization in the tractor sector. The study also includes recommendations made for fiiture use of this particular company.
Open Access
Money and productive efficiency: evidence from a high-inflation country
(Routledge, 2007) Başçı, E.; Mahmud, S. F.; Yucel, E. M.
This paper examines how money balances held by manufacturing firms affect their efficiency in generating sales revenue in a high-inflation economy. The analysis employs data from Turkish firms to estimate a stochastic frontier model, finding a strong positive association between the firms' money holdings and their efficiency. However, the role of money balances seems to diminish as firms hold higher raw material inventories. © 2007 M.E. Sharpe, Inc. All rights reserved.
Open Access
On the distribution of throughput of transfer lines
(Palgrave Macmillan, 2000) Dinçer, C.; Deler, B.
Transfer lines simply characterise the interrelationship of manufacturing stages with their buffers and they are used to model the key features of such manufacturing environments with simplifying assumptions. There is a vast literature on these systems, however, little has been done on the transient analysis of the transfer lines by making use of the higher order moments of their performance measures due to the difficulty in determining the evolution of the stochastic processes under consideration. This paper examines the transient behaviour of relatively short transfer lines and derives the distribution of the performance measures of interest. An experiment is designed in order to compare the results of this study with the state-space representations and the simulation. Furthermore, extensions are briefly discussed and directions for future research are suggested.
Open Access
Optimization of a flow shop system of initially controllable machines
(IEEE, 2008-12-22) Gokbayrak, K.; Selvi, O.
We consider an optimization problem for deterministic flow shop systems of traditional machines with service costs penalizing small service times. A regular completion-time cost is also included so as to complete jobs as early as possible. The service times are assumed to be initially controllable, i.e., they are set at the startup time. Assuming convexity of the cost functions, we formulate a convex optimization problem after linearization of the max constraints. The numeric solution of this problem demands a large memory limiting the solvable system sizes. In order to relieve the memory bottleneck, some waiting characteristics of jobs served in fixed-service- time flow shop systems are exploited to result in a simpler equivalent convex optimization problem. These characteristics and the benefit of CNC machines are demonstrated in a numerical example.We also show that the simplifications result in significant improvements in solvable system sizes and solution times.
Open Access
Patterns of productivity growth and the wage cycle in Turkish manufacturing
(Routledge, 2001) Voyvoda, E.; Yeldan, A. E.
In this paper we investigate the distributional consequences of the post-1980 accumulation patterns and technological change in the Turkish manufacturing industries. We utilise two quantitative techniques. First, we make use of the Hodrick-Prescott filter to disintegrate the cyclical variations in productivity growth and wage rates from their respective historical trends, and study the evolution of the wage cycle against the long term productivity patterns in the sector. Next, we decompose the fundamental characteristics of the contributions of productivity growth of the manufacturing sub-sectors to the overall total. Our results suggest very little structural change in the sectoral composition and nature of productivity advances under the post-1980 structural adjustment reforms and outward-orientation, and underscore that the gains in productivity in this period did not materialise as gains in remunerations of wage labour. Contrary to the prognostications of the orthodox theory, the post-1980 export orientation of Turkish manufacturing was not found to lend itself to productivity contributions, and could not be sustained as a viable strategy of 'export-led industrialisation'.
Open Access
Real wages, profit margins and inflation in Turkish manufacturing under post-liberalization
(Routledge, 2005) Gunay, A.; Ozcan, K. M.; Yeldan, E.
This article reports investigations into the behaviour of gross profit margins (mark-ups) in Turkish manufacturing industries for the post-1980 liberalization period in relation to price inflation, trade liberalization (openness) and real wage costs. Panel data econometrics over 29 subsectors of Turkish manufacturing are used over the period 1980-1996. Results suggest that profit margins are positively and significantly related both to price inflation and real wage costs. However, openness is found to have very little impact on profit margins. © 2005 Taylor & Francis.
Open Access
Receding horizon control of mixed line flow shop systems
(2011) Gokbayrak, K.
We consider reliable mixed line flow shop systems that are composed of controllable and uncontrollable machines. These systems are assumed to receive arrivals at random instants and process jobs deterministically in the order of arrival so as to depart them before their deadlines that are revealed at the time of arrival. We model these flow shops as serial networks of queues operating under a non-preemptive first-come-first-served policy. Defining completion-time costs for jobs and process costs at controllable machines, a stochastic convex optimization problem is formulated where the control variables are the constrained service times of jobs at the controllable machines. As an on-line solution method to determine these service times, we propose a receding horizon controller, which solves a deterministic problem at each decision instant. We quantify the available future information by the look-ahead window size. Numerical examples demonstrate the value of information and that the no-waiting property of the full-information case is not observed in the partial-information case.
Open Access
Service time optimization of mixed-line flow shop systems
(IEEE, 2010-02) Gokbayrak, K.; Selvi, O.
We consider deterministic mixed-line flow shop systems that are composed of controllable and uncontrollable machines. Arrival times and completion deadlines of jobs are assumed to be known, and they are processed in the order they arrive at the machines. We model these flow shops as serial networks of queues operating under a non-preemptive first-come-first-served policy, and employ max-plus algebra to characterize the system dynamics. Defining completion-time costs for jobs and service costs at controllable machines, a non-convex optimization problem is formulated where the control variables are the constrained service times at the controllable machines. In order to simplify this optimization problem, under some cost assumptions, we show that no waiting is observed on the optimal sample path at the downstream of the first controllable machine.We also present a method to decompose the optimization problem into convex subproblems. A solution algorithm utilizing these findings is proposed, and a numerical study is presented to evaluate the performance improvement due to this algorithm.
Open Access
Tool allocation and machining conditions optimization for CNC machines
(Elsevier, 1996) Aktürk, M. S.; Avcı, S.
In the literature, there exist many variations of machining economics problem in terms of modelling approaches and solution methodologies. However most of the existing studies focus on the single machining operation which is seldom in practice. On the other hand, tool management approaches at the system level fail to relate the tooling issues to the machining conditions, and ignore the tool availability and tool wear restrictions. A new solution methodology is developed to determine the optimum machining conditions and tool allocation simultaneously to minimize the production cost of a multiple operation case where there can be alternative tools for each operation. As a result, we can both improve the solution by exploiting the interaction between these two decisions, and also prevent any infeasibility that might occur for the tool allocation problem due to tool contention among the operations for a limited number of tool types by considering the tool availability and tool life limitations.