The use of bucket brigades in zone order picking systems

As the transactions through electronic commerce and TV home shopping increase, the warehouses often receive a large amount of small orders to be picked within tight time windows. One of the important warehousing activities is order picking, the process of retrieving a number of items from warehouse storage to meet a number of independent customer orders. This paper examines a new order picking method, bucket brigade order picking (BB picking). Bucket brigade is a way of coordinating workers who progressively perform a set of operations on a flow line. In the BB picking system, a worker performs operations on an order until the next worker downstream takes it over; then goes back to the previous worker upstream to take over a new order. We discuss distinct characteristics in order picking systems when bucket brigades are applied. We identify some efficiency losses under the BB picking and present a new BB picking protocol to improve the performance of order picking systems. The new BB picking is compared with the existing BB picking and zone picking through simulation experiments.     

Robotics in order picking: evaluating warehouse layouts for pick,place, and transport vehicle routing systems

Motivated by recent technological advances in mobile robotics, this paper explores a novel approach for warehouse order picking. In particular, this work considers two types of commercially available mobile robots – one that can grasp items from a shelf (a picker) and another (a transporter) that can quickly deliver all items from the pick list to the packing station. A new vehicle routing problem is defined which seeks to minimise the time to deliver all items from a pick list to the packing station, a problem termed the pick, place, and transport vehicle routing problem. A mixed integer linear programming formulation is developed to answer three related research questions. First, what combination of picker and transport robots is required to obtain performance exceeding traditional human-based picking operations? Second, how should the composition of the robot fleet be altered to affect the greatest performance improvements? Finally, what are the impacts of warehouse layout designs when coordinated mobile robots are deployed? An extensive numerical analysis reveals that, (1) increasing the number of cross aisles decreases system performance; (2) centrally located packing stations improve system performance; and (3) the average distance from each pick location to the packing station and the average distance between pick locations are effective metrics for identifying specific fleet modifications that are likely to yield system improvements.     

Additional effort estimation due to ergonomic conditions in order picking systems

Within a warehouse, the picking activity often relies on human operators. Therefore, when designing and evaluating a manual picking system, it is important to consider that, besides the high flexibility the pickers are able to warrant, they inevitably require an additional effort due to their ergonomic working conditions. In this paper, the authors propose a new model to consider such additional effort, starting from the concepts of human availability and rest allowance. The new method allows the evaluation of the current configuration of a certain warehouse, considering two different operative situations (directly employed operators and indirectly employed ones). Moreover, it makes it possible to estimate and to understand the benefits that can be achieved by introducing some ergonomic improvements. The proposed procedure has also been applied to a real industrial case study.     

Interdependent order allocation in the two-echelon competitive and cooperative supply chain

In this paper, we consider an order allocation problem in a two-echelon supply chain with multiple suppliers and multiple demanders. The orders from the demanders are interdependent in terms of execution sequence. We consider both the competition and cooperation relationships between the suppliers and demanders. We provide formal definition for the order allocation problem and propose a negotiation mechanism which includes a two-stage negotiation protocol and two heuristic negotiation algorithms. Different negotiation strategies are proposed for the demanders and suppliers to resolve the order interdependency and competition conflict. An automated negotiation approach is introduced to implement the negotiation mechanism. The computational experiments show that orders under different supply chain contexts can be allocated with high success rate. We also numerically compare the influence of different negotiation strategies and investigate the interaction of conflict resolutions.     

Dynamic order batching in bucket brigade order picking systems with consecutive batch windows and non-identical pickers

The blocking mitigation mechanism contained in a batching and sequencing model improves order picking performance in bucket brigade order picking systems by adjusting the batch formation in a given batch window. The batch formation of a given batch window affects the transition to the next batch window and limits the batch formation’s structure in the next window. In addition, imbalance in picker capability increases the variation of batch formation while mitigating blocking delay. Our paper proposes a dynamic indexed batching model to smooth the transition between consecutive batch windows and give a better approximation of non-identical pickers’ capability. We develop a mixed integer programming solution for a dynamic indexed batching model in a bucket brigade order picking system (DIBMB). Simulation experiments show that the DIBMB smooths the transition between batch windows as measured in the delay experienced by the first batch in each batch window. Comparisons to the available batching models show that under DIBMB, the blocking delay gradually increases throughout the sequence of batches.     

Automated order picking systems and the links between design and performance: a systematic literature review

With new market developments and e-commerce, there is an increased use of and interest in automation for order picking. This paper presents a systematic review and content analysis of the literature. It has the purpose of understanding the relevant performance aspects for automated, or partly automated, OPSs and identifying the studied links between design and performance, i.e. identifying which combinations of design aspects and performance aspects have been studied in previous research. For this purpose, 74 papers were selected and reviewed. From the review, it is clear that there has been an increased number of papers dealing with the performance of automated, or partly automated, OPSs in recent years. Moreover, there are differences between the different OPS types, but, overall, the performance categories of throughput, lead time, and operational efficiency have received the most attention in the literature. The paper identifies links between design and performance that have been studied, as well as links that appear to be under-researched. For academics, this paper synthesises the current knowledge on the performance of automation in OPSs and identifies opportunities for future research. For practitioners, the paper provides knowledge that can support the decision-making process of automation in OPSs.     

Restructuring the Indian agro-fresh food supply chain network: a mathematical model formulation

Clean Technologies and Environmental Policy - In traditional Indian agro-fresh food supply chain (AFSC), authors identify the following four shortcomings through the literature survey: (1)...     

Analysis of order timing tradeoffs in multi-retailer supply systems

We analyse the implications of order timing decisions in multi-retailer supply systems in a single period, newsvendor setting. Specifically, we investigate a supply chain with multiple retailers and a single supplier where one of the retailers is considered a preferred or primary customer of the supplier. In the base model (delayed commitment), customers order after observing demand and the supplier rations its production quantity to retailers according to a generalised uniform allocation rule. In the early-commitment model, the primary retailer commits to an order quantity prior to the selling season and receives her order in full. We compare the expected supplier and retailer profits under each of these strategies and specify conditions under which a particular commitment scheme benefits the supplier, the primary retailer, and the entire system. Our findings indicate that the supplier prefers early commitment under mild conditions, whereas the primary retailer's preference depends on the tradeoff between the supply risk and demand risk. We also compare our findings with a single-retailer system, and observe that both the supplier and the primary retailer benefit from the existence of additional customers under delayed-commitment in many contexts.     

Improving the supply chain performance: Use of forecasting models versus early order commitments

This paper evaluates the impact of forecasting models and early order commitment in a supply chain with one capacitated manufacturer and four retailers under demand uncertainty. Computer simulation models were used to simulate different demand forecasting and inventory replenishment decisions by the retailers as well as production decisions by the manufacturer under a variety of demand patterns and capacity tightness scenarios. This study found that early order commitments significantly affected the total costs and service levels, to various degrees, for the manufacturer and the retailers, suggesting that the benefits of early order commitment could be influenced by a combination of forecasting models, demand patterns and capacity tightness.     

Scheduling in production,supply chain and Industry 4.0 systems by optimal control: fundamentals,state-of-the-art and applications

This paper presents a survey on the applications of optimal control to scheduling in production, supply chain and Industry 4.0 systems with a focus on the deterministic maximum principle. The first objective is to derive major contributions, application areas, limitations, as well as research and application recommendations for the future research. The second objective is to explain control engineering models in terms of industrial engineering and production management. To achieve these objectives, optimal control models, qualitative methods of performance analysis and computational methods for optimal control are considered. We provide a brief historic overview and clarify major mathematical fundamentals whereby the control engineering terms are brought into correspondence with industrial engineering and management. The survey allows the grouping of models with only terminal constraints with application to master production scheduling, models with hybrid terminal–logical constraints with applications to short term job and flow shop scheduling, and hybrid structural–terminal–logical constraints with applications to customised assembly systems such as Industry 4.0. Computational algorithms in state, control and adjoint variable spaces are discussed.     

Investigation of relationships in a supply chain in order to improve environmental performance

This paper presents a methodology to combine environmental assessment information and knowledge on supplier relationships. The work is based on a case study of production of a chair. The methods used are shown to be effective to reduce the number of suppliers that should be managed from an environmental point of view and also obtain an overview over which suppliers that can be influenced. It is also shown how suppliers with the presumably highest potential for improvements are identified. The end-producer can thus obtain control over most of the environmental impact originating from upstream activities through a limited number of suppliers. In the case study the number of suppliers that should be managed is reduced to 3. Small and medium sized enterprises have often limited possibilities to influence the suppliers, but in this paper it is demonstrated how this problem can be overcome by cooperative purchasing within a branch of industry with a common demand for information from the suppliers.

Reconfigurable supply chain: the X-network

Research on supply chain (SC) digitalization, resilience, sustainability and leagility has remarkably progressed, most of it focused on the individual contributions of these four major frameworks. However, a lack of integration spanning these individual frameworks can be observed. In this conceptual paper, we hypothesize that reconfigurability can be considered such an integral perspective that consolidates the research in SC adaptation to ever changing environments. We theorize a new notion – a Reconfigurable SC or the X-network – that exhibits some crucial design and control characteristics for complex value-adding systems in highly vulnerable environments. We support our argumentation and conceptual viewpoints by a literature analysis along with tertiary studies to review and structure contextual factors of designing the X-networks. We propose respective frameworks and discuss the implementation principles and technologies at the macro and micro levels. Two novel concepts – dynamic SC meta-structures and dynamic autonomous services – are introduced. Distinctively, we go beyond the existing knowledge to predict proactively the future directions in the reconfigurable SCs. Our results can be of value for decision-makers to decipher chances and barriers in contemporary SC transformations.     

Synchronization,cross-docking,and decoupling in supply chain networks

At any distribution centre (DC), the decision of whether to synchronise inbound and outbound flows for cross-docking, or to decouple these flows by maintaining inventory, has a significant impact on supply chain performance. Key drivers of this decision, in turn, are the sizes of the discrete lots that comprise the flows. Thus, we formulate an original optimisation model that determines order lot-sizing decisions to minimise, for given constant arc flows, the sum of ordering cost and pipeline inventory cost on arcs and buffer inventory at DCs. The model employs an average throughput as a surrogate to estimate buffer inventory at facilities at which synchronisation is not economical and therefore serves to decouple inbound and outbound flows. Perfect lot-for-lot matching of shipments would impose very restrictive constraints on supply chain operations, but equality of average throughput indicates an innovative, relaxed mode of synchronisation. This mode is practicable for cross-docking by means of bulk-breaking or consolidation of shipments. A heuristic approach based on the Lagrangian relaxation and subgradient optimisation is developed for the non-linear mixed-general integer optimisation model, which is illustrated by numerical examples and tested using a benchmark data set.     

Realization of a short cycle time in warehouse replenishment and order picking

Today's competitive and dynamic environment forces companies to be highly responsive and customer oriented to survive and be successful. This paper considers an automated gantry picking complex with 16 pick zones and 16 replenishment zones. Currently, it operates on a 24-h cycle time. A short cycle time operation allows a warehouse manager to be more responsive, flexible and competitive. For example, it allows insertion of late arriving, but high priority, orders into the current cycle. However, to operate in a short cycle environment, the warehouse operations' planning and execution must be more dynamic, real-time and intelligent. To realize a short cycle time without loss of productivity, a new replenishment process logic for the gantry-picking complex is developed. The main idea of the new replenishment logic is to minimize the set-up time. Experimental results demonstrating the efficiency of the new approach are also presented.     

The performance impact of supply chain agility and supply chain adaptability: the moderating effect of product complexity

Even though research has suggested that supply chain agility and supply chain adaptability are distinct capabilities, little is known about their performance effects and about the contextual conditions under which they are effective. Based on a sample of 143 German firms, we empirically investigate the effects of supply chain agility and supply chain adaptability on cost performance and operational performance using hierarchical regression analysis. We ground our investigation in the dynamic capabilities view and contingency theory. We find that supply chain agility and supply chain adaptability positively affect both cost performance and operational performance. We further find evidence for a mediating role of supply chain agility in the links between supply chain adaptability and performance. Product complexity positively moderates the links between supply chain adaptability and cost performance, and supply chain adaptability and operational performance. The results contribute to the literature by offering a more nuanced understanding of the performance implications of supply chain agility and supply chain adaptability, thereby addressing the crucial question of why their benefits may or may not materialise under varying levels of product complexity.     

Counterfeit capacitors in the supply chain

Counterfeit electronic components have become a significant concern in the electronic parts supply chain. Original equipment manufacturers in particular are concerned about counterfeit components as there have been several recent reports of counterfeit parts entering the supply chain of the US military. This paper presents a case study of multilayer ceramic capacitors for use in a printed circuit assembly in an electronic system on a military aircraft. The capacitors failed during a high temperature screening test. Upon failure analysis it was revealed that the capacitors were not made to the correct specifications and were suspected to be counterfeit and not the authentic military grade capacitors manufactured by Kemet. Further investigation revealed that the suspect multilayered ceramic capacitors had entered into the electronics parts supply chain and were sold as authentic Kemet capacitors that met the higher military-specified requirements. The manufacturing and distribution of the counterfeit capacitors were traced to locations where, according to Kemet, its authentic capacitors are neither manufactured nor distributed.     

Penetration of boron carbide, aluminum, and beryllium alloys by depleted uranium rods: Modeling and experimentation

As part of the US stockpile stewardship program, it is necessary to perform experiments with various metallic components and explosives. These experiments will be conducted within specially designed blast vessels to ensure that the debris from the experiment is contained. The debris includes fragments that are launched at hypervelocities. The blast vessels are built primarily of steel, but have windows of either aluminum or beryllium alloys for diagnostic equipment requirements. To contain the hypervelocity depleted uranium fragments, ceramic armoring of the windows and steel vessel is used. To develop the necessary design tools, a program of experiments and modeling was begun. Preliminary pre-test predictions were made to design experiments. The experiments were conducted with targets representative of the armored windows in the vessel. To assist in the vessel design, two- and three-layered target analytical models were developed to predict the penetration of depleted uranium rods striking at velocities up to 2 km/s into layered targets of ceramic (boron carbide and silicon carbide) and aluminum, beryllium and steel alloys. The agreement between the pre-test predictions, the developed layered-target analytical model, and the experiments is good.     

Bending of silicon plate crystals through superficial grooving: Modeling and experimentation

Permanent and reproducible deformation of silicon mono-crystals has been experimentally attained by mechanical grooving of one of its surfaces. The method produces uniform deformation that can be controlled by proper choice of the parameters of grooving. The strain in silicon plates was modeled analytically in terms of a superficial compression occurring in the material between the grooves. The superficial grooved region acts as if it were like a tensile film with the strain propagating deep into the bulk, which results in spherical and homogeneous curvature of the whole crystal plate. Thereby, the classic Stoney's formula was reconsidered and adapted for explanation of the experimental behavior. Minimum radius of curvature experimentally achieved was about 3 m. Curved crystals are the basis for many applications, e.g. for x-ray optics to manipulate high energy photons for the construction of very sensitive instruments for x-ray astronomy.     

An integrated operations-marketing perspective for making decisions about order penetration point in multi-product supply chain: a queuing approach

This study is dedicated to strategic decision-making regarding order penetration point (OPP), which is the boundary between make-to-order (MTO) and make-to-stock (MTS) policies. This paper considers a supply chain in which a manufacturer produces semi-finished items on an MTS basis for a retailer that will customise the items based on MTO policy. This two-echelon supply chain offers different products to a market comprised of homogenous customers who have different preferences and willingness to pay. The retailer wishes to determine the optimal OPP, the optimal semi-finished goods buffer size, and the price of the products with assumption of price sensitive demand function. Moreover, we consider both shared and unshared capacity models in this paper. A matrix geometric method is utilised to evaluate various performance measures for this system, and then, optimal solutions are obtained by enumeration techniques. The suggested queuing approach is based on a new perspective between the operations and marketing functions which captures the interactions between several factors including inventory level, product pricing, OPP, and delivery lead time. Finally, parameter sensitivity analyses are carried out and the effect of demand on the profit function, the effect of prices ratio on completion rates ratio and buffer sizes ratio and the variations of profit function for different prices, completion percents, and buffer sizes are examined.     

Consumer search,transshipment, and bargaining power in a supply chain

We study a decentralised supply chain with one manufacturer and two symmetric retailers who could transship their excess inventory between each other. Without transshipment, the retailer’s unsatisfied customers search and buy the product at the other retailer with some probability. With transshipment, the retailer can transship the other retailer’s excess inventory to fulfil its own unmet demand. However, a transshipment price is often charged by one retailer for transshipping goods to another. We show the retailer’s profit is unimodal in the transshipment price, and the manufacturer’s profit increases in the customer search probability. Although the retailer’s preference over transshipment depends on the magnitude of search probability and transshipment price, the retailer may always prefer the transshipment no matter their magnitude. We then study the effect of bargaining power over the transshipment decision (whether to transship between retailers and at what transshipment price). Our analysis suggests that the manufacturer always prefers to control the transshipment price rather than to control whether to transship, while the retailer can prefer both. We also find that increasing bargaining power always benefits the manufacturer but could hurt the retailer. We finally check the robustness of our results by investigating the case with asymmetric retailers