The added dimension

Manufacturing & Logistics IT spoke with Jan Van der Velden, Market Director at Vanderlande Industries, about the benefits of three-dimensional storage and order-picking systems for optimal scalability and flexibility in the parts & components distribution centre.

Companies in the parts & components industry offer a broad range of products, varying from fasteners and electronic components to installation equipment and spare parts. The one thing they all have always had in common is that they distribute a high volume of smaller articles, often delivered individually or in small packaged units.

The Internet effect

However, something that has noticeably changed in recent times is the way customers search for products and place their orders, as Vanderlande Industries' Jan Van der Velden explained: "Within the consumer goods marketplace, people have become comfortable with e-commerce; the process of ordering goods from the Internet. Indeed, the choice of consumer goods available on line is become increasingly broad and delivery times are becoming very quick – even same-day delivery is becoming an increasingly affordable option.

Therefore, people come to take this level of convenience as a given, and now increasingly expect a similar level of service and range of goods when ordering goods within the business environment."

Van der Velden reflected that a few years ago many suppliers offered thick product catalogues to their customers. "This, of course, wasn't a very integrated way of doing business," he said. "Customers were expected to order by phone or fax and delivery could take several days. Now, Internet ordering has become so popular that parts & components suppliers need to widen their product ranges. Indeed, the supplier who has the widest range is likely to secure the most business online because many customers like the speed and convenience of a 'one-stop shop'-type environment. So, this scenario has raised greater customer expectations in terms of availability, delivery times and price."

However, as Van der Velden pointed out, this naturally can lead to increasing stock level requirements and/or increased numbers of SKUs in the warehouse or distribution centre. This in turn has led to some considerable challenges that are amplified by other trends, such as ongoing pressure to keep costs low and the increasing complexity of logistical operations.

Because of this, Van der Velden believes companies need a standard order fulfilment system that is able to process every order as efficiently and effectively as possible, regardless of size, delivery time and quality. In his view, this system must also be exceptional in its scalability and flexibility, allowing for quick and easy adjustments to meet changing needs. What is required, according to Van der Velden, is an intelligent system with an operating facility capable of translating every customer-specific request into standard processes carried out by a single machine.

Shuttle systems

A new generation of storage and order-picking systems has been created over the past few years to meet today's demands. Some of the most crucial parts of these systems are the shuttles – small, quick vehicles for the storage and retrieval of totes on shelves. Orders that are received by the ERP or warehouse management system (WMS) are forwarded to the fleet control system (FCS), which controls the shuttles.

The FCS then instructs the shuttles to retrieve the totes with the requested items from the racks and transport them to the appropriate order-picking station. An operator then takes the correct number of articles out of the tote and places them in the correct shipping carton. The accurate timing and sequencing of tote delivery to the order-picking station is crucial for a quick and efficient process.

Van der Velden makes the point that the performance of each shuttle system varies significantly, depending on the number of dimensions in which the shuttle can move. He explained that one-dimensional shuttles are limited to a single aisle and level and are only able to retrieve the correct tote from the rack, transport it forward and place it onto a lift, which then provides vertical transport. This captive system requires each level of every aisle to be equipped with a shuttle in order to serve all storage locations.

In the case of a two-dimensional shuttle system, Van der Velden explained that this is limited to a single aisle and can move horizontally as well as vertically. These aisle-captive shuttles do not transport a tote to a lift, but enter into the lift together with the tote. This means that not only the tote, but also the shuttle can be transported and change levels. One shuttle can therefore serve all of the storage locations in one aisle.

Three-dimensional advantage

A three-dimensional system, on the other hand, is designed so that shuttles can travel across all aisles and levels. "These full-roaming shuttles can move vertically with the help of lifts, similar to the aisle-captive shuttles, but can also move between the aisles on every level due to specially designed cross rails," said Van der Velden. "That means that one shuttle is sufficient to serve all storage locations in the system.

Van der Velden added that another key advantage of a 3-dimensional system is that storage and order-processing capacities can be scaled up or down independently of each other. "Distributors that need to extend their range of parts and components, or levels of SKUs, can simply add more racks without the need to put extra shuttles in place, while companies who are seeing an increase in their order numbers can simply add more shuttles," he said, adding: "With its ability to a free-roam in three dimensions the shuttle has no relationship to any specific part of your storage. If the flow in the beginning is low you can start with a few shuttles and a few pick stations, and gradually as the flow increases you can increase the number of shuttles deployed. It's this level of flexibility and independence that's so valuable to today's distribution centres."

In terms of other benefits, Van der Velden explained that there are no conveyors involved. "One- or two-dimensional systems have to be supplemented with a complicated set of conveyors in order to feed the totes and articles to the correct order-picking station," he said. "These conveyors are unnecessary in a three-dimensional system as the order-picking stations can be situated directly alongside each lift. Shuttles can reach every order-picking station via the integrated cross rails in the racks."

Van der Velden added that, with three-dimensional shuttle systems, buffers become unnecessary. "One of the main challenges regarding one- and two-dimensional systems is sequencing," he said. "The totes must arrive at the order-picking stations at the correct moment and in the right order. The buffers not only cost more and take up additional space, but also lead to longer processing times. Extra buffers are not necessary in a three-dimensional system due to the countless possibilities the cross rails offer for reaching the order-picking stations."

Also, as Van der Velden explained, fewer shuttles are needed with the three-dimensional model. "In a one-dimensional system where each level of every aisle requires its own shuttle, it is inevitable that these vehicles will sometimes be stationary due to a lack of orders," he said. "In a three-dimensional system, however, the ability to tailor shuttle capacity to the required order-processing capacity is greatly enhanced. This equates to a 30 to 40 per cent reduction in the number of shuttles required."

Easier control

Three-dimensional shuttles also afford easier control, according to Van der Velden. He elaborated: "In systems with captive or aisle-captive shuttles, complex algorithms are needed to divide the workload optimally across the aisles and achieve maximum processing capacity.

Furthermore, the algorithms need to be tailored exactly to the unique configuration of the relevant shuttle system. In a full-roaming shuttle system, these algorithms are almost entirely unnecessary. Even if that leads to several shuttles operating in the same aisle, the wide selection of alternate routes means that there is very little congestion or delay in transporting totes to order-picking stations." Van der Velden also explained that the algorithms help to utilise the full capacity of the three-dimensional system, ensuring that the most efficient route is calculated for each shuttle.

And due to the scalability, flexibility and modular design, Van der Velden pointed out that the initial investment in a three-dimensional system is lower than with other systems. He concluded: "All these benefits result in a storage and order-picking system that can be implemented more quickly, and easily expanded, adjusted and improved in accordance with the distribution centre's changing requirements. Flexibility to changing requirements is the key in today's distribution centre environment."