Full Case Order Picking System

Innovative Full Automated Crate Picking System (Automated Storage and Retrieval Cell System (ASRCS))

Transportsysteme & -Logistik, Univercity Duisburg-Essen

Mohammed Ruzayqat, M.Sc.

Email: mohammed.ruzayqat@uni-due.de

Email: zhou.zhou@stud.uni-due.de

Transportsysteme & -Logistik, Univercity Duisburg-Essen

Prof. Dr.-Ing. Bernd Noche

Email: bernd.noche@uni-due.de

Abstract

Order picking is the most costly and labor intensive activity in warehouses, some authors argues that order picking might account for up to 55% of the operational costs in the warehouse. This fact might be more important for companies that handle large volumes of fast moving commodities. The ASRCS introduces a new technique for storage and retrieval that contributes significantly to total operational cost reduction through minimizing labor requirements, space requirements, and errors potentials, and consequently increase productivity and enhance efficiency.

The ASRCS deals mainly with large volumes of product handled in plastic crates or trays. It has the ability to handle a variety of standard crates. As a full case crate picking system, ASRCS is typically applicable for commodities such as food, beverage, dairy, flowers, sausage, and bread picking process.

In this system crates are stored in ‘Cells' with the design of a vertical elevator system, in other words vertical elevator will be used as a flow rack, many elevators will be installed one after another to make a row of elevators, many rows will be installed to form the storage system. Storage and retrieval processes are executed from the bottom side of the elevators, and the horizontal movements are undertaken by conveyors installed in the bottom side of the elevators and this conveyor extends through all elevators in the row and the storage strategy will be as LIFO strategy. Crates will be picked, transported, and palletized automatically without manual labor.

The ability to access all articles, which are need to fulfillment an order at one time, and the high ability to increase the throughput of the system without increasing in the investment cost are of the biggest advantages of this system.

Keywords – automated crate picking solution, model layout, productivity, order picking strategy.

1 Introduction

Nowadays with the rapid development of warehouse technology, a lot of traditional problems of storage and retrieval process are already solved such as classify of different commodities, zone management, sorting and so on, but numerous problems are still waiting for people to figure them out.

With the limited fixed cost the key of benefiting utilization of warehouse is to find out a better strategy of storage process and order picking operation. Order picking can be defined as the activity by which a small number of goods are extracted from a warehousing system, to satisfy a number of independent customer orders [1]. Until today nobody can easily say that he has the best strategy because it de-pends on different characteristics of goods --- one strategy can't fit for all situa-tions, but people have to find a better solution, because in logistic process, order picking operation is one of the most controlled part, and it also can be seen as the most costly activity for the warehouse, it is estimated to be as much as 55% of the total warehouse operating expense [2]. Moreover, a good order picking operation can increase the satisfaction level of customers. Each coin has its' two sides, with the huge importance of order picking operation in warehouse, it is also a risk, because many errors are made in this part. With the increasing quantity of articles and requirement of customer, the traditional warehouse has to hire more people to control it, so the cost of manpower increases.

In an ASRCS, except order picking operation, storage strategy takes also a very important position in the whole system. Storage process happens before order picking operation, so the strategy of storage process will influence the result of or-der picking operation. So let's say if order picking operation can be seen as 55% of total warehouse operating expense, then storage takes 20% of it, the rest are re-ceive, shipping, and packaging [3].

The purpose of this research is to define a new full automated storage and retrieval system with specific new order picking operation and storage strategy, which can enhance accuracy of order picking, reduce total time of goods in system, and increase the throughput. The application of this system fits for the articles which contain big quantity and not too much classification. Our system effectively utilizes the space in warehouse, also, compare to the traditional AS/RS, the throughput is much more increased, and operating time for retrieval of each article can be reduced, and which is capable of handling peak volumes.

2 System Description

In our research an automated storage & retrieval system will be presented. The whole system can be seen as three parts of the increasing gradually, which are cell, a group of cells along one conveyer, and the whole system which contains lots of cells along numerous conveyers.

The operation process is input process and output process, like figure 1 shows, the goods in a crate will be transported from the input direction and the distance be-tween point A and B is the height of the crate, when the first crate arrive cell1, it will be raised up to the first location (location 1), when the second crate arrives, the first crate will be stored in location 2, and second crate will be raised up to lo-cation 1. The output process is totally opposite and in chapter strategy 1 and strategy 2, the operating process will be described specifically.

Figure 1 Operating process of Cells

2.1 Cell Structure

The cell structure is the basic component in our ASRCS, and it also can be sepa-rated into 2 parts, cell motor and cell frame.

2.1.1 Cell Motor

After incoming of crates which used to contain the goods, the cell motor start to work, by rotation of electrical motor, the transporting belt moves up and down, therefore the crates can be stored or retrieved.

2.1.2 Cell Frame

The cell frame is constructed of transporting belt and cell stair, and the cell stair is fixed on the belt. With the movement of transporting belt, the cell stair goes up or down. So that the crate can be held by the cell sorter, the figure 2 shows detail of cell structure.

Figure 2 cell frame [4]

2.2 One Cell along One Conveyer

In our system, a cell means the space of one column locations, which is construct-ed by several individual spaces. These individual spaces are the smallest storage units in the system, and one cell is assembled of the basic storage units.

Figure 3 One cell along conveyer

2.3 Cells along One Conveyer

With increasing of cells in the horizontal direction, a group of cells along the con-veyer is formed. The conveyer in the system belongs to the guided transporter [5], which means, the goods on the conveyer move in strict accordance with the path we designed, and when the front goods stop, the target good stops also, therefore, the movement of goods can be seen as a continuous process. The transport time between two points depends on the velocity of the conveyer, path, and situation of jams.

Nowadays the roller conveyors have become essential for materials handling, many businesses utilizing them on a daily basis. Whether operated by power or natural gravitational forces, the roller conveyor assists with simple material movement and is suitable for a variety of industries [6]. Obviously, with natural gravity a fall of both ends of conveyer must be needed, so if we build the conveyer very long, then the area can't be saved, and as we know, more area we use on conveyers, less area left for other equipments like cell storage system. According the blueprint we designed the conveyer should be in a plane, and with the limited safety moving velocity of conveyer, slip-off of goods can be avoided. On this occasion, a powered roller conveyer is required. On one powered roller conveyer there is not only one cell, but more cells which are installed one after another. When the first cell is full, the crate starts to be stored in the second cell. Figure 4 shows the 3D layout of cells along one conveyer.

Figure 4 3D layout of cell structure

2.4 Cells along Parallel Conveyers

Obviously the entire storage area needs numerous locations to store the goods, therefore the cells along only one conveyer is far from enough, but let's see the cells along one conveyer as the basic component, with increasing of the compo-nent, whole storage area is present in the eyes. Figure