International Journal of Production Research, May 15, 2018
The problem considered in this paper is motivated from a real life case. Conventional models in d... more The problem considered in this paper is motivated from a real life case. Conventional models in designing block stacked warehouse assume uniform and deterministic inflow and outflow of products in specific quantities and time intervals. These assumptions would lead to underestimation of space requirement for the case. Also, the possibility of leasing additional warehouse space during seasonal spikes was found to be unexplored in block stacking design literature. In this study, we develop a scenario-based model to address the decisions of warehouse size, lane depth and hiring of temporary additional warehouse capacity when flow of products is stochastic and dynamic in nature. A sequential decision model is presented with future operating scenarios assumed to branch out in the form of a tree. On comparison with conventional block stacking design methods, the model is found to provide robust solution in stochastic and dynamic environments in terms of risk reduction and infeasibility avoidance. Further, the model gives additional flexibility to the designer to trade-off model and solution robustness with predicted cost.
The warehouse layout decision is important as it affects several aspects of warehouse performance... more The warehouse layout decision is important as it affects several aspects of warehouse performance such as material handling cost, space cost and storage capacity. We develop an algorithm that determines lane depth, number of storage levels, lateral depth and longitudinal width of a three dimensional order picking warehouse minimizing space and material handling costs. The algorithm is illustrated with an example. Effect of variation of a set of parameters on the optimal layout decision is studied.
The seminal and widely cited paper of Hart (1995) on the natural resource-based view of the firm,... more The seminal and widely cited paper of Hart (1995) on the natural resource-based view of the firm, advocates that the source of competitive advantage in the imminent future will be rooted in emerging sustainable manufacturing capabilities. In order to understand how these capabilities, namely pollution prevention, product stewardship and sustainable development [clean technology] are acquired over period of time, Hart (1995) proposes two competing theories of path dependency and embeddedness. However, there is lack of empirical research on investigation of these two theories. The current study is undertaken to bridge this gap. The paper analyses the available sustainability reports of two multinational firms spanning across a number of years to derive insights on the validity of the two theories. The case observations reveal that the two theories in focus are not necessarily competing in nature but can coexist. The study adds theoretical insights to the literature and provides pointers towards future research directions in the field.
International Journal of Computer Integrated Manufacturing, Jan 18, 2021
ABSTRACT This article considers a multi-aisle AS/RS employing a single aisle-mobile crane and dev... more ABSTRACT This article considers a multi-aisle AS/RS employing a single aisle-mobile crane and develops analytical travel time models for three new storage policies with turnover-based product allocation to aisles. In addition to product turnover, these storage policies also take into account the demand skewness and the characteristics of storage and transport equipment. Based on the proposed travel time models, analytical expressions are derived to determine the physical dimensions of the AS/RS that are optimized with respect to crane travel time. AS/RS designs employing the newly developed storage policies are compared with designs employing three other (non-turnover based) storage policies, using a design methodology proposed in a recent study. The analysis shows that among the three turnover-based storage policies, class-based storage assignment performs better than full turnover-based storage policy when subjected to different evaluation criteria. It is concluded that the inclusion of storage policies in the AS/RS design process, is highly beneficial in the selection of the right storage and transport equipment.
Transportation Research Part E: Logistics and Transportation Review, 2020
The expectation of the largest gap between two consecutive picks in an aisle is a basic building ... more The expectation of the largest gap between two consecutive picks in an aisle is a basic building block in modelling the pick travel distance for the largest gap routing policy in a warehouse. Researchers have predominantly used either simulation or recursive algorithms for its estimation. This paper develops analytical expressions for this statistic in, both, continuous and discrete aisles using the statistical theory of ordered uniform spacings. We further demonstrate how these results can apply to the entire multi-aisle warehouse. Our results show that these expressions are accurate and extremely fast to evaluate as compared to the existing approaches.
International Journal of Production Research, 2018
The problem considered in this paper is motivated from a real life case. Conventional models in d... more The problem considered in this paper is motivated from a real life case. Conventional models in designing block stacked warehouse assume uniform and deterministic inflow and outflow of products in specific quantities and time intervals. These assumptions would lead to underestimation of space requirement for the case. Also, the possibility of leasing additional warehouse space during seasonal spikes was found to be unexplored in block stacking design literature. In this study, we develop a scenario-based model to address the decisions of warehouse size, lane depth and hiring of temporary additional warehouse capacity when flow of products is stochastic and dynamic in nature. A sequential decision model is presented with future operating scenarios assumed to branch out in the form of a tree. On comparison with conventional block stacking design methods, the model is found to provide robust solution in stochastic and dynamic environments in terms of risk reduction and infeasibility avoidance. Further, the model gives additional flexibility to the designer to trade-off model and solution robustness with predicted cost.
Multi-aisle AS/RS using shared S/R machines offer significant cost advantage over AS/RS employing... more Multi-aisle AS/RS using shared S/R machines offer significant cost advantage over AS/RS employing dedicated S/R machines. The expected travel time of the S/R machine is an important warehouse performance measure and it needs to be kept at a minimum. In this paper, we consider a single crane multi-aisle AS/RS using single command cycle and carry out simulation experiments to understand the impact of different design parameters and storage policies on travel time. The interactions of these input factors are studied leading to key insights which can be useful for designers and practitioners.
International Journal of Computer Integrated Manufacturing, 2019
Multi-aisle automated storage/retrieval system (AS/RS) can be applied to situations where the thr... more Multi-aisle automated storage/retrieval system (AS/RS) can be applied to situations where the throughput requirement is low relative to storage requirement for gaining cost advantage. This study considers such a system under class-based and full-turnover-based storage policies, which are generally neglected in the multi-aisle AS/RS context. The study develops expressions to determine the optimal number and dimensions of storage racks for different storage policies, demand skewness, and transport and storage equipment characteristics. Propositions are made related to the optimal dimensions, optimal travel time and equipment characteristics. Further, this study develops a comprehensive and flexible three-stage design methodology that systematically generates design alternatives, and filters and evaluates them using user defined criteria. Finally, this proposed design methodology is illustrated with an example.
Purpose This paper aims to develop an approach to design a warehouse that uses class-based storag... more Purpose This paper aims to develop an approach to design a warehouse that uses class-based storage policy in a way that minimizes both space cost and material handling cost. Design/methodology/approach The authors argue for and develop an optimization model for joint determination of lane depth, lateral width and product partitions for minimizing the sum of handling and space costs. In doing so, the assumption of perfect sharing is also relaxed. Using computational experiments, the authors characterize the operating conditions based on pick density and cost ratio. The authors further outline an approach to decide the conditions under which it is advantageous to implement multiple classes. Findings More classes are preferred when both the pick density and cost ratio are higher and vice versa. Factors such as demand skewness, lane depth and stacking height affect the space-sharing dynamics. Practical implications The paper gives the practical insights on when the conditions under whic...
Journal of Manufacturing Technology Management, 2016
Purpose The purpose of this paper is to explore the relationship of strategic manufacturing effec... more Purpose The purpose of this paper is to explore the relationship of strategic manufacturing effectiveness utilizing the four-stage model of Hayes and Wheelwright (H-W) with overall performance of manufacturing, market alignment and production competence (PC). In addition, it attempts to understand the relationship of strategic manufacturing effectiveness with manufacturing capability development modes, strategic groups of companies and the nature of improvement programs being employed. Design/methodology/approach Structured questionnaire was used to capture data from manufacturing organizations. Responses from managers of 47 Indian manufacturing companies were used to test the seven propositions that were developed to examine the paradigms of manufacturing competence. Findings The analysis revealed that the strategic manufacturing effectiveness of manufacturing companies based on H-W’s four-stage model has significant positive correlation with the overall performance of manufacturin...
The International Journal of Advanced Manufacturing Technology, 2016
This paper considers the layout design problem of a single block order-picking rack-based warehou... more This paper considers the layout design problem of a single block order-picking rack-based warehouse that employs turnover-based storage assignment in both vertical and horizontal dimensions. An analytical expression for vertical travel distance is derived which is incorporated in the pick distance model. The effect of inventory staggering on storage space requirement is considered in arriving at warehouse dimensions. A model that incorporates area cost along with handling cost in optimizing warehouse design is developed and a solution algorithm is presented. The analytical model for vertical travel and the optimization model are applied to data from a real life case. It was found that the model would offer considerable operational cost savings, especially when space costs are high. Computational experiments show that the effect of inventory staggering is quite significant in the estimated storage space. Experiments also demonstrated the importance of segregating products based on turnover in the vertical dimension.
International Journal of Production Research, 2016
The pick distance models for a unit load warehouse employing fishbone layout conventionally use s... more The pick distance models for a unit load warehouse employing fishbone layout conventionally use semicircular approximation for distance contour which can result in significant error. This paper develops discrete and continuous pick distance models for fishbone layout under random, full turnover, and class-based storage policies based on exact polygonal distance contour. Class-based storage policy with three classes was found to give pick distance comparable to full turnover policy over a range of demand skews and warehouse shapes studied. The discrete and continuous models are compared considering finite storage space, aisle width and discontinues in the ABC curve for a real life data. The sensitivity of warehouse performance over a range of warehouse parameters is studied. We also outline a methodology for class-based storage design where class partitions can be derived for a warehouse of any dimension from the results of a unit area warehouse.
A 3D finite element heat flow model has been developed which treats weld pool convection in a sim... more A 3D finite element heat flow model has been developed which treats weld pool convection in a simple way by enhancing thermal conductivities artificially and changing heat source distribution. This model is not very computer intensive because it does not solve the fluid flow equation; however, it gives reasonably accurate results. The model can output data for the determination of cooling rates needed in further investigations such as microstructural and strength predictions. The results have been validated with previous experiments and it is suggested that this method has potential to be used in controlling or planning welding operations.
2010 IEEE International Conference on Management of Innovation & Technology, 2010
Competence in manufacturing can be assessed in dimensions such as cost, quality, delivery speed, ... more Competence in manufacturing can be assessed in dimensions such as cost, quality, delivery speed, delivery reliability, flexibility and innovation. Manufacturing strategy literature refers to three paradigms of competence building in manufacturing namely, trade-off, cumulative and integrative. It is likely that companies depending upon their strategic orientation use different approaches of competency building. A widely accepted four-stage model due to Wheelwright
K eyw ords concurrent engineering, integration of manufacturing functions, production planning, p... more K eyw ords concurrent engineering, integration of manufacturing functions, production planning, product design, process planning A bstract. In manufacturing engineering, product design, process planning and production planning activities are often considered independently. However, in order to e ectively respond to changes in business situations, such as changes in demand forecast, product mix and technology, it is desirable to consider them concurrently. For this purpose, a large-scale linear programming model has been developed. The model considers minimization of the sum of processing cost, late shipment cost and inventory holding cost as the objective, and concurrently selects product designs, and generates process plans and production plans. The number of columns in the formulation can be large and, hence, an e cient column generation scheme is developed to solve the model. The model and solution procedure are illustrat ed with examples.
International Journal of Production Research, May 15, 2018
The problem considered in this paper is motivated from a real life case. Conventional models in d... more The problem considered in this paper is motivated from a real life case. Conventional models in designing block stacked warehouse assume uniform and deterministic inflow and outflow of products in specific quantities and time intervals. These assumptions would lead to underestimation of space requirement for the case. Also, the possibility of leasing additional warehouse space during seasonal spikes was found to be unexplored in block stacking design literature. In this study, we develop a scenario-based model to address the decisions of warehouse size, lane depth and hiring of temporary additional warehouse capacity when flow of products is stochastic and dynamic in nature. A sequential decision model is presented with future operating scenarios assumed to branch out in the form of a tree. On comparison with conventional block stacking design methods, the model is found to provide robust solution in stochastic and dynamic environments in terms of risk reduction and infeasibility avoidance. Further, the model gives additional flexibility to the designer to trade-off model and solution robustness with predicted cost.
The warehouse layout decision is important as it affects several aspects of warehouse performance... more The warehouse layout decision is important as it affects several aspects of warehouse performance such as material handling cost, space cost and storage capacity. We develop an algorithm that determines lane depth, number of storage levels, lateral depth and longitudinal width of a three dimensional order picking warehouse minimizing space and material handling costs. The algorithm is illustrated with an example. Effect of variation of a set of parameters on the optimal layout decision is studied.
The seminal and widely cited paper of Hart (1995) on the natural resource-based view of the firm,... more The seminal and widely cited paper of Hart (1995) on the natural resource-based view of the firm, advocates that the source of competitive advantage in the imminent future will be rooted in emerging sustainable manufacturing capabilities. In order to understand how these capabilities, namely pollution prevention, product stewardship and sustainable development [clean technology] are acquired over period of time, Hart (1995) proposes two competing theories of path dependency and embeddedness. However, there is lack of empirical research on investigation of these two theories. The current study is undertaken to bridge this gap. The paper analyses the available sustainability reports of two multinational firms spanning across a number of years to derive insights on the validity of the two theories. The case observations reveal that the two theories in focus are not necessarily competing in nature but can coexist. The study adds theoretical insights to the literature and provides pointers towards future research directions in the field.
International Journal of Computer Integrated Manufacturing, Jan 18, 2021
ABSTRACT This article considers a multi-aisle AS/RS employing a single aisle-mobile crane and dev... more ABSTRACT This article considers a multi-aisle AS/RS employing a single aisle-mobile crane and develops analytical travel time models for three new storage policies with turnover-based product allocation to aisles. In addition to product turnover, these storage policies also take into account the demand skewness and the characteristics of storage and transport equipment. Based on the proposed travel time models, analytical expressions are derived to determine the physical dimensions of the AS/RS that are optimized with respect to crane travel time. AS/RS designs employing the newly developed storage policies are compared with designs employing three other (non-turnover based) storage policies, using a design methodology proposed in a recent study. The analysis shows that among the three turnover-based storage policies, class-based storage assignment performs better than full turnover-based storage policy when subjected to different evaluation criteria. It is concluded that the inclusion of storage policies in the AS/RS design process, is highly beneficial in the selection of the right storage and transport equipment.
Transportation Research Part E: Logistics and Transportation Review, 2020
The expectation of the largest gap between two consecutive picks in an aisle is a basic building ... more The expectation of the largest gap between two consecutive picks in an aisle is a basic building block in modelling the pick travel distance for the largest gap routing policy in a warehouse. Researchers have predominantly used either simulation or recursive algorithms for its estimation. This paper develops analytical expressions for this statistic in, both, continuous and discrete aisles using the statistical theory of ordered uniform spacings. We further demonstrate how these results can apply to the entire multi-aisle warehouse. Our results show that these expressions are accurate and extremely fast to evaluate as compared to the existing approaches.
International Journal of Production Research, 2018
The problem considered in this paper is motivated from a real life case. Conventional models in d... more The problem considered in this paper is motivated from a real life case. Conventional models in designing block stacked warehouse assume uniform and deterministic inflow and outflow of products in specific quantities and time intervals. These assumptions would lead to underestimation of space requirement for the case. Also, the possibility of leasing additional warehouse space during seasonal spikes was found to be unexplored in block stacking design literature. In this study, we develop a scenario-based model to address the decisions of warehouse size, lane depth and hiring of temporary additional warehouse capacity when flow of products is stochastic and dynamic in nature. A sequential decision model is presented with future operating scenarios assumed to branch out in the form of a tree. On comparison with conventional block stacking design methods, the model is found to provide robust solution in stochastic and dynamic environments in terms of risk reduction and infeasibility avoidance. Further, the model gives additional flexibility to the designer to trade-off model and solution robustness with predicted cost.
Multi-aisle AS/RS using shared S/R machines offer significant cost advantage over AS/RS employing... more Multi-aisle AS/RS using shared S/R machines offer significant cost advantage over AS/RS employing dedicated S/R machines. The expected travel time of the S/R machine is an important warehouse performance measure and it needs to be kept at a minimum. In this paper, we consider a single crane multi-aisle AS/RS using single command cycle and carry out simulation experiments to understand the impact of different design parameters and storage policies on travel time. The interactions of these input factors are studied leading to key insights which can be useful for designers and practitioners.
International Journal of Computer Integrated Manufacturing, 2019
Multi-aisle automated storage/retrieval system (AS/RS) can be applied to situations where the thr... more Multi-aisle automated storage/retrieval system (AS/RS) can be applied to situations where the throughput requirement is low relative to storage requirement for gaining cost advantage. This study considers such a system under class-based and full-turnover-based storage policies, which are generally neglected in the multi-aisle AS/RS context. The study develops expressions to determine the optimal number and dimensions of storage racks for different storage policies, demand skewness, and transport and storage equipment characteristics. Propositions are made related to the optimal dimensions, optimal travel time and equipment characteristics. Further, this study develops a comprehensive and flexible three-stage design methodology that systematically generates design alternatives, and filters and evaluates them using user defined criteria. Finally, this proposed design methodology is illustrated with an example.
Purpose This paper aims to develop an approach to design a warehouse that uses class-based storag... more Purpose This paper aims to develop an approach to design a warehouse that uses class-based storage policy in a way that minimizes both space cost and material handling cost. Design/methodology/approach The authors argue for and develop an optimization model for joint determination of lane depth, lateral width and product partitions for minimizing the sum of handling and space costs. In doing so, the assumption of perfect sharing is also relaxed. Using computational experiments, the authors characterize the operating conditions based on pick density and cost ratio. The authors further outline an approach to decide the conditions under which it is advantageous to implement multiple classes. Findings More classes are preferred when both the pick density and cost ratio are higher and vice versa. Factors such as demand skewness, lane depth and stacking height affect the space-sharing dynamics. Practical implications The paper gives the practical insights on when the conditions under whic...
Journal of Manufacturing Technology Management, 2016
Purpose The purpose of this paper is to explore the relationship of strategic manufacturing effec... more Purpose The purpose of this paper is to explore the relationship of strategic manufacturing effectiveness utilizing the four-stage model of Hayes and Wheelwright (H-W) with overall performance of manufacturing, market alignment and production competence (PC). In addition, it attempts to understand the relationship of strategic manufacturing effectiveness with manufacturing capability development modes, strategic groups of companies and the nature of improvement programs being employed. Design/methodology/approach Structured questionnaire was used to capture data from manufacturing organizations. Responses from managers of 47 Indian manufacturing companies were used to test the seven propositions that were developed to examine the paradigms of manufacturing competence. Findings The analysis revealed that the strategic manufacturing effectiveness of manufacturing companies based on H-W’s four-stage model has significant positive correlation with the overall performance of manufacturin...
The International Journal of Advanced Manufacturing Technology, 2016
This paper considers the layout design problem of a single block order-picking rack-based warehou... more This paper considers the layout design problem of a single block order-picking rack-based warehouse that employs turnover-based storage assignment in both vertical and horizontal dimensions. An analytical expression for vertical travel distance is derived which is incorporated in the pick distance model. The effect of inventory staggering on storage space requirement is considered in arriving at warehouse dimensions. A model that incorporates area cost along with handling cost in optimizing warehouse design is developed and a solution algorithm is presented. The analytical model for vertical travel and the optimization model are applied to data from a real life case. It was found that the model would offer considerable operational cost savings, especially when space costs are high. Computational experiments show that the effect of inventory staggering is quite significant in the estimated storage space. Experiments also demonstrated the importance of segregating products based on turnover in the vertical dimension.
International Journal of Production Research, 2016
The pick distance models for a unit load warehouse employing fishbone layout conventionally use s... more The pick distance models for a unit load warehouse employing fishbone layout conventionally use semicircular approximation for distance contour which can result in significant error. This paper develops discrete and continuous pick distance models for fishbone layout under random, full turnover, and class-based storage policies based on exact polygonal distance contour. Class-based storage policy with three classes was found to give pick distance comparable to full turnover policy over a range of demand skews and warehouse shapes studied. The discrete and continuous models are compared considering finite storage space, aisle width and discontinues in the ABC curve for a real life data. The sensitivity of warehouse performance over a range of warehouse parameters is studied. We also outline a methodology for class-based storage design where class partitions can be derived for a warehouse of any dimension from the results of a unit area warehouse.
A 3D finite element heat flow model has been developed which treats weld pool convection in a sim... more A 3D finite element heat flow model has been developed which treats weld pool convection in a simple way by enhancing thermal conductivities artificially and changing heat source distribution. This model is not very computer intensive because it does not solve the fluid flow equation; however, it gives reasonably accurate results. The model can output data for the determination of cooling rates needed in further investigations such as microstructural and strength predictions. The results have been validated with previous experiments and it is suggested that this method has potential to be used in controlling or planning welding operations.
2010 IEEE International Conference on Management of Innovation & Technology, 2010
Competence in manufacturing can be assessed in dimensions such as cost, quality, delivery speed, ... more Competence in manufacturing can be assessed in dimensions such as cost, quality, delivery speed, delivery reliability, flexibility and innovation. Manufacturing strategy literature refers to three paradigms of competence building in manufacturing namely, trade-off, cumulative and integrative. It is likely that companies depending upon their strategic orientation use different approaches of competency building. A widely accepted four-stage model due to Wheelwright
K eyw ords concurrent engineering, integration of manufacturing functions, production planning, p... more K eyw ords concurrent engineering, integration of manufacturing functions, production planning, product design, process planning A bstract. In manufacturing engineering, product design, process planning and production planning activities are often considered independently. However, in order to e ectively respond to changes in business situations, such as changes in demand forecast, product mix and technology, it is desirable to consider them concurrently. For this purpose, a large-scale linear programming model has been developed. The model considers minimization of the sum of processing cost, late shipment cost and inventory holding cost as the objective, and concurrently selects product designs, and generates process plans and production plans. The number of columns in the formulation can be large and, hence, an e cient column generation scheme is developed to solve the model. The model and solution procedure are illustrat ed with examples.
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Papers by Gajendra Adil