Miniloads Maximize Small Parts Handling

Aug. 1, 2002
Automatic storage and retrieval machines integrated with pick-to-light systems combine the best of orderpicking technologies for efficient small parts picking.
Miniloads Maximize Small Parts Handling

Automatic storage and retrieval machines integrated with pick-to-light systems combine the best of two orderpicking technologies for efficient small parts picking.

by Christopher Trunk, managing editor

“Combining miniloads and pick-to-light is a success,” says Paul Roche, director of sales for Swisslog N.A. “Both are proven technologies that add speed, efficiency and accuracy to manual picking operations.” He says that many benefits are to be found even with small miniload systems, in the 500 to 1,000 SKU range. “If you needed 1,000 dedicated pick-to-light pickfaces, it would require much longer picking aisles that would take up considerably more space and require more walking, which would slow pick rates,” adds Roche.

Jeff Hedges, director of market development for HK Systems, describes how these systems look. A miniload is a robotic crane with a dedicated vehicle that moves up and down a tall aisle of shelving racks. To the left and right of the vehicle are pans, totes or boxes containing small parts. Some miniloads are 30 to 40 feet tall or higher, and range from 30 feet to 300 feet long. The robotic crane (automatic storage and retrieval system) rides on wheels on a rail in the aisle. It zooms in on the correct shelf location, and using an extractor robot, grasps the pan, tote or box to deliver it to a workstation or gravity flow lane. The miniload can be a single-aisle or multi-aisle configuration.

As inventory is loaded into the miniload, it can be bar coded and scanned to create unique storage locations for each SKU. Random storage can make the best use of cube space, and when items are retrieved, another bar code scan ensures the right product was picked.

“Before a miniload is installed, the system might typically be run manually with conventional storage. The huge number of SKUs makes it difficult for manual handling of picks and putaways, and the recordkeeping job is tremendous,” says Ken Matson, president of Cleco Systems, a division of FKI Logistex. “With miniloads, the key to finding a part quickly is knowing where to go. Without the high inventory accuracy that a miniload offers, speedy picking is that much harder.”

In addition to delivering product to gravity flow lanes, the miniload can also service a workstation where workers pick from totes or boxes loaded with product into totes that represent store orders. The machine can be replenished via workstations as well. It is important that the workstation be ergonomically designed so the worker is presented totes and product comfortably.

“Miniloads can have shelf storage in the upper section and gravity flow rack with light-directed panels on the lower portion. The miniload feeds the gravity flow rack to keep enough inventory on hand, and the machine can replenish pick-to-light stations overnight to meet the morning’s pick orders,” says Hedges.

A smart, dense-storage system

Miniloads fitted with gravity flow rack can be sized to your requirements. You may have 1,000 active SKUs that represent all possible lines, though only about 400 SKUs are needed to fill the day’s orders. “The machine dynamically changes those pick-to-light slots based on the day’s orders. The financial advantage of using the miniload in this kind of small parts handling is that it makes for better cube use in space-constricted areas and keeps aisles of lighted pickfaces shorter with dynamic pickfaces,” says Roche.

Swisslog sees more miniloads being installed in the United States in the next two years, so it is bringing its new ProPicker miniload to the U.S. market from Europe. The ProPicker is used in Europe for pharmaceutical and grocery distribution. Miniloads like it can also be used in manufacturing to assemble kits of small parts for production lines.

“In the last few years, Cleco has focused on scalability, with smaller-size miniloads, reusable control software and easy-to-apply worker interfaces,” says Matson. Cleco offers small, one-aisle systems that are just seven feet wide and from 100 to 300 feet long and 15 to 25 feet tall, holding a minimum of 1,000 SKUs. “Larger systems can be built with modular miniload aisles as your business needs grow — ranging in size up to 50 feet tall and eight aisles holding 50,000 SKUs,” adds Matson. Such systems pay for themselves in one to three years. Matson finds that light-directed picking also takes place at workstations by extinguishing all lights except a single beam of light that shines on the tote from which a pick should be made.”

An advancement in miniloads is the ability to store and extract boxes that come right from the manufacturing or distribution center, rather than using conventional uniform totes. “One of the risks is that carton sizes change all the time, and it’s important that the miniload crane, the racks and the gravity flow line be adjustable to meet load sizes that vary over time,” says Matson. Cleco offers miniload crane extractors that handle changing box sizes. “The worst thing that can happen to a customer is to buy a miniload that fits what’s needed today and can’t adapt to tomorrow,” advises Matson.

Application highlights

Making the most of miniloads means finding applications where both a small footprint and many SKUs come together. One application is for maintenance facilities at airports. “As an airplane is scheduled for maintenance, a miniload pulls all the parts needed for the plane’s typical maintenance procedures. Then when the plane arrives, all the parts are ready in the hangar,” says Hedges.

Another approach is when a part fails when a plane is on the tarmac. The miniload can be alerted to the parts problem, and the part can be delivered to the plane in minutes. An automated system that immediately knows part storage location is critical to such operations.

HK Systems has installed miniload/pick-to-light machines for major catalog retailers that supply mail-order and retail stores, as well as e-catalog fulfillment.

Planning five years ahead so the miniload will still meet your needs is important. HK Systems tells of the Sonoma State University library that studied how fast its collections would grow over the next five-year period. “You need to study your future needs when applying these machines, and design for growth; otherwise you’ll be left with a system that you quickly exceed and be forced to store items elsewhere,” warns Hedges.

In pharmaceutical applications, miniloads lend themselves to product security as metal panels or wire mesh can be fitted to the outer sides of the machines. Only pickfaces are accessible.

Software and data controls

With today’s advanced software controls, miniloads can deliver more productivity than before. “We’ve developed techniques for rates of 250 to 350 picks per hour with just one operator. This is especially useful for e-commerce and other small order applications,” says Jim Neuner, vice president of sales for Eskay Corporation. He says the miniloads are best applied not to the fastest-moving SKUs, but to the greater volumes of slower-moving part numbers. Miniloads deliver more small parts because faster, more lightweight cranes combine with ergonomic presentation of parts to the worker, more effective crane controls and better planning of orders by order management software.

Roche says that Swisslog offers smaller-scale WMS (warehouse management system) software developed especially to control miniloads. “The Automation Appliance software lets a company integrate a miniload with any existing WMS. It receives order information from the host and handles all the processes to build the various dynamic pick-to-light pickfaces for the day’s orders. The software helps eliminate stockouts at pick locations,” says Roche.

A critical element in making the best use of a miniload is slotting it correctly, and that takes time and study. “Customers send us a year’s worth of order data,” says Matson. “We analyze the data and help them understand the seasonality and movement of inventory from a cubic-volume standpoint.” This data affects how the miniload is replenished and how inventory in it is configured and delivered to any particular gravity flow location.

Adding pick-to-light racks to the miniload minimizes demand on the crane when faster-moving, greater-cubic-volume SKUs are slotted into the flow rack. Typically, slower-moving, lesser-cubic-volume inventory is delivered to a workstation. The art and science come in determining the thresholds for SKU velocity and cubic volume moved, and that’s where your vendor’s expertise in handling your kind of product is essential.

This is the last piece of advice that most vendors have for you: “Make sure you look for a vendor with experience handling the type of product you are picking and storing.” With this experience, the vendor will be able to give accurate advice on slotting, size and controls for your miniload/pick-to-light system. MHM

Miniload Sources

Contact these industry resources for more on miniloads:

Cleco, [email protected]

Eskay, [email protected]

HK Systems, [email protected]

Siemens-Dematic, [email protected]

Swisslog, [email protected]

Witron, [email protected]

Case Histories

Book Distributor Fills Orders with Miniload/Pick-to-Light

In 2000, Witron, a material handling systems integration company, installed a Dynamic Picking System (DPS) at the Libri book distribution center in Frankfurt, Germany. Libri distributes up to 400,000 books a day to more than 5,000 retail bookstores in Germany, Belgium and Holland. The system includes a miniload with more than 300,000 SKUs and 16,000 pick stations.

Each station is controlled by a pick-to-light system for directing workers to fill store orders. Each pickface can be configured as one SKU or two SKUs. Fewer than 100 workers are needed to pick up to 40,000 books per hour.

The miniload stores up to 7.5 million books in a footprint of only 150,000 square feet. Witron.

Littlewoods Consolidates Warehouses for Small Parts Distribution

Littlewoods is a home shopping and retail giant with 10 warehouses. The company decided to consolidate most of the warehouses at one site at Shaw in Oldham, U.K. The site stores and fills orders for clothing, small textiles, toys, small electrical devices and household goods. More than 60,000 product lines are stored totaling about 8 million items.

To store and retrieve so many SKUs, the company chose a miniload system. Prior to the investment in the consolidated warehouse, Littlewoods averaged 42 million picks a year. Now picks have risen to 48 million at just one site with a capacity of 60 million.

The miniload features 19 aisles, each about 65 feet tall. The cranes are specially designed with twin-tray carriages so that more trays can be stored and retrieved at a time. The plastic trays that hold full cases protect the product from damage as it winds its way from storage locations to pickfaces. Cleco.

Miniload Keeps Small Parts Flying at Northwest Airlines

The Minneapolis maintenance hub for Northwest’s fleet of 400 aircraft is kept busy with a three-aisle miniload, 25 feet high, that stores 60,000 SKUs. In replacing an older orderpicking system with automation, the company has reduced the storage footprint by 12,000 square feet while reducing the time it takes to pick its 32,000 monthly orders by 60 percent. Each of the miniload’s 7,000 storage locations holds multiple bins of small parts. Each divided bin area has its own bar code to identify part numbers for many tiny components.

The company uses the miniload spare parts system to get necessary parts to its mechanics as quickly as possible. This reduces the number of airplanes held on the ground due to maintenance problems.

Ergonomics is addressed at the miniload front-end workstations where workers perform orderpicking tasks at tables set at a comfortable height. As totes are delivered to the workstation, PC displays tell workers which items to pick, what the pick quantity is and which aircraft hangar should receive the order. For high-priority picks for planes needing emergency parts, the system triggers a yellow light at the workstation until the rush part is picked. Eskay Corporation.

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