Small packages: Big savings on small parts storage

The parts may be small, but the headaches associated with storing them can be big.

By Bob Trebilcock, Editor at Large -- Modern Materials Handling, 4/2/2008

The parts may be small, but the headaches associated with storing them can be big. That’s because everything from the manpower associated with picking them, maintaining an accurate inventory, and replenishing active pick locations requires more thought and work than handling pallets or cases. 

Sure you can store small parts on shelves or in drawers, but the most efficient method for small parts storage and picking comes down to four automated technologies: Horizontal carousels, vertical carousels, vertical lift modules, and mini-load automated storage and retrieval systems (AS/RS). Each has its pluses and minuses. 

Horizontal carousels

Horizontal carousels consist of a series of bins or carriers that rotate horizontally around a track much like a merry-go-round. 

Software manages the putaway and picking activities. An operator enters order information into a station at the front of the system. The carousel then rotates until the right bin is brought to the operator station. That eliminates the time an operator usually spends traveling from one pick face to the next. Horizontal carousels can be grouped tightly together in pods of two to four carousels for batch picking. While the operator is retrieving a part from one carousel, another system in the pod is retrieving the next pick. Depending on how the unit is slotted, you can get 200 to 400 line picks per hour from a pod configuration. 

Vertical carousels

While a horizontal carousel resembles a merry-go-round, a vertical carousel is like a ferris wheel. The whole unit rotates elliptically to deliver the right shelf or pan to the operator positioned at the pick window.

These systems combine high-density, vertical storage and retrieval technology in a small footprint. That makes them ideal for point-of-use storage of components and parts in manufacturing operations with high ceilings and limited floor space. It is not uncommon for vertical storage systems to reach 40 feet tall, and some systems are 60 feet with pick windows on multiple floors. And since many designs are enclosed, vertical carousels are also ideal for safely storing high-value inventory. As appropriate, the system can be secured to prevent theft.

Despite these advantages, vertical carousels have design limitations. Because the entire unit rotates, parts must be stored evenly to prevent an imbalance. For that reason, vertical carousels are most often used for lightweight products, like components in the electronics industry.

Vertical lift modules

From the outside, a vertical lift module, or VLM, resembles an enclosed vertical carousel.

Both systems take advantage of high ceilings: VLMs have been built up to 90 feet tall, although most are 15–20 feet tall. And like a vertical carousel, stored inventory can be accessed at pick windows from multiple floors.

On the inside, however, VLMs more closely resemble an AS/RS than a vertical carousel. While the entire vertical carousel rotates to bring the right bin to the picking window, storage locations in a VLM are stationary and an automatic inserter/extractor performs putaway and retrieval one storage tray at a time. That allows the VLM to make more efficient use of the storage space inside the unit.

Since only the tray required for putaway or picking is moving, there is less vibration with a VLM than a vertical carousel, which makes it suitable for highly sensitive or fragile parts.

Mini-loads

A mini-load system is an automated storage and retrieval system designed to handle cartons and totes instead of pallet loads of material in high-density manufacturing and distribution settings. Mini-load systems typically handle totes or containers measuring 2 feet by 4 feet in a variety of heights with loads of 250 to 750 pounds.

Mini-load systems are most often used to replenish picking stations. Another typical application for mini-load AS/RS is handling slow-moving stock keeping units (SKU) in a distribution or production environment. That eliminates a pick face in the warehouse for each slow mover, freeing up valuable space.

Learn more about each of these small parts handling solutions along with hybrid solutions. Let us know how you’re handling the headaches associated with small parts in your facility.