Crossing Into New Territory: The Multibay Vertical Lift Module

Jun 20, 2007 9:27 PM  By

The vertical lift module (VLM) was introduced into the material handling industry more than 20 years ago. In that time, we’ve seen a variety of improvements, ranging from larger tray sizes to heavier capacities. All of these enhancements have been small changes to existing features, but this machine has now evolved into its next generation – the multibay VLM. This version builds upon all of the existing benefits of a single-bay machine – increased productivity, improved picking accuracy, better employee ergonomics, valuable floor space recovery, enhanced security, better employee retention, reduced shrinkage and easier housekeeping with a fully enclosed system – and takes it to the next level.

Multibay technology takes the storage provided by multiple VLMs and wraps them into one self-contained storage and retrieval unit, available in two, three, four, and even five bays wide. From the outside, a triple bay unit would look like three single units standing side by side. In reality, it is one unit that has three bays of storage all which are accessed by a common extraction and lift device.

This cross-bay technology consists of a lift bed that spans the entire width of the unit and one extractor that traverses left to right on that lift bed to access product from the required storage bay. Once the tray is retrieved from its storage position the lift bed moves vertically while the extractor traverses left or right to deliver the tray to the correct delivery window.

These machines are configured with the right number of storage bays and delivery window combinations to meet the application requirements. The unit may be supplied with one or two delivery windows per access location. If the application requires, the unit can also be supplied with multiple access locations, allowing the unit to service multiple floors or multiple work cells (front/back configuration).

Simplified, faster picking. Unlike single-bay units, a multibay VLM allows the user to gain access to parts located in multiple storage bays from a single location. This simplifies the picking process and allows the user to fill an entire order without moving to another window. A triple-bay unit with two delivery windows increases productivity with 100% product accessibility, as opposed to three single-bay units, which might require a user to walk to all three delivery windows to complete an order. If there is only one operator logged into the unit, trays are delivered to each delivery window alternately, decreasing waiting time and increasing picking time. Cycle time for single-bays would be much slower unless the order was perfectly balanced across all three units. Typically, you’ll find that one unit has 50% of the order while the other two units have 25% each. This means that two units will sit idle 50% of the time.

Simultaneous picking and replenishment. The multi-bay unit also gives multiple operators access to product almost simultaneously. As the first operator’s tray is delivered to one opening, the second operator’s request is queued for delivery to the second window. This is possible even though both trays required to fill each request may be located in the first bay of storage. The same scenario with three single bay units would create a line of operators waiting to gain access to the first storage unit.

The ability to provide near simultaneous access to the unit also allows the unit to be replenished while another operator is picking. This replenishment can occur from the second delivery window on the same side or a delivery window on another side or even another level. This significantly increases productivity over single-bay technology, which allows only one operation to be performed at a time. What’s more, single-bay units require replenishment to be performed at the correct delivery window. With multi-bay technology, all bays may be replenished from a single window.

Flexible work cell layout. Multi-bay technology also offers users flexibility in work cell layout. Because the unit does not require a delivery window at each bay, it can be installed in areas of the facility that might not have been possible in the past. The bays of storage without the delivery window can be located in any area that was previously unavailable due to accessibility restrictions, for example, behind a building column or another piece of equipment. The unit could even extend from one room and into another. This is not possible with single-bay technology, as each unit requires a delivery window to gain access to product, meaning there must be a clear path to all units.

Maintenance costs are also significantly reduced. For multiple units worth of storage there is now only one unit to maintain, which translates to a lower number of parts to worry about and fewer hours spent on repair and maintenance.

Paul Roy is product manager/manager of distributor services for Lewiston, ME-based Diamond Phoenix, a provider of material handling systems.