Miniload System Research Articles

ТРАНСПОРТНА ЛОГІСТИКА ТА СУЧАСНІ СКЛАДСКІ ТЕХНОЛОГІЇ

Warehouses are an important division responsible for the efficient storage and movement of company stocks. In conditions of increasing competition, the level of warehouse equipment predetermines such critical parameters as time and workability of cargo handling. Effectively organized warehousing activity has a positive effect on reducing the logistics costs of an enterprise. Innovations and innovative equipment in the supply chain reduce the likelihood of errors in the logistics system. The article identifies the main problems of transport logistics in the context of globalization and the possibility of overcoming them through efficiently organized warehousing activities, and also defines the main goal of transport logistics. The necessity and efficiency of introducing modern warehouse technologies is also considered. The requirements for warehouses in the context of market globalization are considered. The article provides examples of modern warehouse systems: self-supporting warehouses, Radio-Shuttle system for warehouses with a limited area, and an automated Mini-Load system. Examples of modern storage technologies and equipment (gravity racks; conveyors: roller, spiral, turning, carousel; stacker cranes) are given to reduce costs and improve the quality of warehouse operations. The article discusses the features of the organization and management of transport logistics in the United States, the countries of Western Europe, Central and Eastern Europe, and the countries of the Central Asian region in order to apply their experience in domestic practice. Defined two main models of logistics management abroad.

Automated or manual storage systems: do throughput and storage capacity matter?

Selecting the appropriate type of capital-intensive storage systems is an important decision for warehouse managers. However, such a decision is complex due to various available storage systems. In addition, warehouse requirements such as storage capacity and throughput influence this decision. This research provides insights that enable managers to select the suitable type of storage system which minimizes the investment and operational costs while the warehouse design requirements, in particular the storage capacity and throughput, are met. To obtain these insights, an Excel®-based decision support system is developed for a set of most common types of manual and crane-based automated storage systems in pallet and case warehouses. The decision support system uses the closed-form formulas from the warehousing literature and also Monte Carlo simulation to approximate the travel time in each storage system. The results show that the choice of automated or manual storage system and the associated costs depend on the required capacity and throughput. When the storage capacity and throughput are low, the manual pallet racks are the preferred storage system and incur the lowest costs. As the storage capacity and throughput increase, there is a need for more compact storage systems that can store more loads in a smaller footprint. Thus, for medium to high capacity levels, double-deep automated storage systems and deep-lane compact storage systems are the ones with the lowest investment and operational costs. The results for the case warehouses show that the investment and operational costs increase rapidly with an increase of the throughput. In particular, the increase is noticeable for operational costs of the shelf rack system and the investment cost of the miniload system where the storage capacity and throughput level are high.

A simulation-based comparison of two goods-to-person order picking systems in an online retail setting

Design and analysis of order picking systems continues to be an active topic of interest both in academia and practice, especially in light of the significant increase in online retail sales. In this paper, we examine two types of well-known, goods-to-person order picking systems, namely, a miniload system and a Kiva system. Using a simulation model, we compare the performance of the two systems on the basis of expected throughput and expected container retrieval times to process the same set of customer orders. We also discuss some of the advantages and limitations of the two systems.

Modelling internal logistics systems through ontologies

Industry is facing an era characterised by unpredictable market changes and by a turbulent competitive environment. The key to compete in such a context is to achieve high degrees of responsiveness by means of high flexibility and rapid reconfiguration capabilities. The deployment of modular solutions seems to be part of the answer to face these challenges. Semantic modelling and ontologies may represent the needed knowledge representation to support flexibility and modularity of production systems, when designing a new system or when reconfiguring an existing one. Although numerous ontologies for production systems have been developed in the past years, they mainly focus on discrete manufacturing, while logistics aspects, such as those related to internal logistics and warehousing, have not received the same attention. The paper aims at offering a representation of logistics aspects, reflecting what has become a de-facto standard terminology in industry and among researchers in the field. Such representation is to be used as an extension to the already-existing production systems ontologies that are more focused on manufacturing processes. The paper presents the structure of the hierarchical relations within the examined internal logistics elements, namely Storage and Transporters, structuring them in a series of classes and sub-classes, suggesting also the relationships and the attributes to be considered to complete the modelling. Finally, the paper proposes an industrial example with a miniload system to show how such a modelling of internal logistics elements could be instanced in the real world.

Simulation analysis of mini-load multi-shuttle automated storage and retrieval systems

Technological developments in warehouses have changed processes of storage operations, which reflect in short response times of the storage or retrieval of goods, the reduction of stocks and the volume of storage work as well as the automation of the entire warehouse management. Many companies are replacing traditional warehouses with automated storage and retrieval systems, which can be classified into unit-load and mini-load systems. In this paper, the simulation analysis of mini-load multi-shuttle systems is discussed and evaluated. Multi-shuttle systems are based on the quadruple and sextuple command cycle and could therefore achieve higher throughput capacities due to single-shuttle systems. Different analytical models are used by practitioners for designing multi-shuttle systems. The problem arises with the selection of the appropriate analytical model for which the condition of minimal differences with actual circumstances in practice is fulfilled. For the evaluation of the two well-known analytical models, the discrete event simulations have been used. Beside the evaluation of analytical models, the results of simulation analyses showed throughput improvements for triple-shuttle systems according to dual-shuttle systems. The main objective of this paper is to determine the performance of presented models (analytical and simulation models) of multi-shuttle systems, which represents the main share and support in design process of mini-load multi-shuttle automated storage and retrieval systems.

Performance of miniload systems with two-class storage

To increase throughput, the higher turnover items are often stored near the input/output point of a miniload system. We analyze the performance of such a miniload with a square-in-time rack containing two storage zones: high turnover and low turnover. First, we derive the distribution of the dual command travel time. System performance measures such as the throughput depend upon the distribution of the dual command travel time and the distribution of pick times. We work out the details and obtain closed-form expressions for throughput for two important families of pick time distributions: deterministic and exponential. Finally, we investigate how the size of the high turnover region affects throughput.

Performance of automated storage/retrieval systems with non-square-in-time racks and two-class storage

We determine the mean and variance of the single and dual command travel time for automated storage/retrieval systems with non-square-in-time racks and two-class storage. We present detailed numerical results of the travel time analysis for selected rack shape factors and skewness parameters, followed by some interesting observations for two-class storage. We then show, as an application example, how the mean and variance can be used to approximate or bound the miniload system throughput for non-square-in-time racks with two-class storage.

Back-of-the-envelope miniload throughput bounds and approximations

We derive simple formulas bounding and approximating the throughput of an end-of-aisle miniload system with exponentially distributed pick times and either uniform or turnover-based storage. For typical configurations, the worst-case relative error for the bounds is less than 4%. We use our bounds to show that, for all practical purposes, regardless of the configuration, the picker utilization determines the storage/retrieval machine utilization, and vice versa. Thus, a system designer cannot hope to independently achieve separate goals for the utilization rates.

Dual command travel times and miniload system throughput with turnover-based storage

We analyze travel times for automated storage/retrieval systems. In particular, we apply our travel time model to turnover-based storage systems and determine the mean and variance of dual command travel times. We present detailed numerical results for selected rack shape factors and ABC inventory profiles. We then investigate the effect of alternative rack configurations on travel time performance measures. We also show how to determine the throughput of miniload systems with turnover-based storage and exponentially distributed pick times.

Throughput bounds for miniload automated storage/retrieval systems

To compute miniload system throughput, the distribution of the pick times is needed. Unfortunately, during the design phase, only partial information may be available such as the mean pick time. In this paper, we determine tight upper and lower bounds on throughput for several different types of partial information. We also give numerical examples to show how to apply the bounds.

Throughput bounds for miniload automated storage/retrieval systems

To compute miniload system throughput, the distribution of the pick times is needed. Unfortunately, during the design phase, only partial information may be available such as the mean pick time. In this paper, we determine tight upper and lower bounds on throughput for several different types of partial information. We also give numerical examples to show how to apply the bounds.

Buffer sizing models for end-of-aisle order picking systems

We study an end-of-aisle order picking system with inbound and outbound buffer positions. The system is referred to as a miniload system with a horse-shoe front-end configuration, and is modeled as a two-stage cyclic queueing system with limited capacity. We analyze the system by utilizing known queueing results. Closed form expressions are developed for system performance measures, including the steady-state probability and system throughput. To provide some decision criteria in the design of buffer capacity, we examine the effect of the buffer size on system throughput. We give examples to illustrate how the results developed can be applied to solving real world problems. It is also shown that under heavy retrieval system demand, the system naturally achieves its optimal operating condition in the long run and it always performs dual command cycles.

Buffer sizing models for end-of-aisle order picking systems

We study an end-of-aisle order picking system with inbound and outbound buffer positions. The system is referred to as a miniload system with a horse-shoe front-end configuration, and is modeled as a two-stage cyclic queueing system with limited capacity. We analyze the system by utilizing known queueing results. Closed form expressions are developed for system performance measures, including the steady-state probability and system throughput. To provide some decision criteria in the design of buffer capacity, we examine the effect of the buffer size on system throughput. We give examples to illustrate how the results developed can be applied to solving real world problems. It is also shown that under heavy retrieval system demand, the system naturally achieves its optimal operating condition in the long run and it always performs dual command cycles.

Throughput analysis in an automated material handling system

Throughput analysis in an automated material handling system, such as an Automated Storage and Retrieval System(AS/RS), may be a complex problem. In the past, several approaches have been used for such an analysis. This paperpresents a combinatorial ap proach to evaluating the throughput performance of a mini-load system, with simulation as the primary method of investigation.