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Plastic tote and container basics

Choosing the right plastic tote or container for your application can be tricky. Here's some help.

By Sara Pearson Specter, Editor at Large -- Modern Materials Handling, 9/1/2007

Available in hundreds of sizes and configurations, reusable plastic bins, totes and containers reduce packaging waste, protect products, and improve inventory management through standardization. Additionally, returnable boxes can generate dramatic cost and efficiency benefits.

But facing the volume of options can be daunting, even for an experienced packaging engineer.

“There are so many different products out there that it's important to start with a job-specific need when you're shopping around,” says Doug Popek, industrial market manager for Akro-Mils (330-253-5592). “Look at what you're handling first, then select your handling method, then select a container.”

It seems there are just as many names for these plastic totes and containers as choices. “The word 'tote' is like 'Kleenex' for containers,” agrees Ray Niemeyer, director of knowledge management at Material Handling Industry of America (MHIA), and managing director of the Reusable Plastic Container & Pallet Association (RPCPA) (704-676-1190). “It depends on what part of the country or industry you work in if you call it a dunnage bin or a tote or a container.”

Bin
Bin
Bins are used for storage of small parts prior to use in manufacturing and assembly.

A box used for storage and organization of small parts prior to use in manufacturing and assembly, frequently with a hopper (or open) front. Bins are generally stackableand may feature an integrated tab in the back so they can be hung from a louvered storage unit. They may be constructed of solid or corrugated plastic.

Bins are often found in workcells and rarely leave one area. Lids are incorporated in clean environments, and dimensions range from 3 x 3 inches to 24 x 12 inches.

Tote (also called a crate, handheld, hand-held container, reusable security container or work-in-process tote)

A box transported by hand, with molded-in ergonomic handles. Totes are typically offered in two designs: nestable and stackable.

Nestable totes feature drafted, or sloped, sidewalls that allow them to nest inside each other when empty. Stackable totes have an identical footprint top and bottom, and feature an integrated lip that prevents shifting when stacked.

Bin
Totes, like this stackable model, are boxes transported by hand, often with molded-in ergonomic handles.

Flap lids may be attached to the top of totes, hinged on either long side and meet in the middle when closed (commonly found on nestable totes), or they may be detached. Maximum capacities range from 40 pounds for totes handled by people to 80 pounds for totes handled by automated equipment.

Container (also called a bulk container, bulk box, bulk bin, or shipping container)

The largest of the reusables, containers include four straight walls built on pallet-sized footprints with fork openings on two or four sides.

Generally used for discrete component parts delivered to assembly lines, these heavy-duty units can only be moved by pallet jack or lift truck. Sidewalls can collapse down into the container when empty. The walls may be designed with openings or drop doors for easier access, and unattached lids or covers are sometimes used. Containers stack when full or empty, with capacities ranging from 1,000 to 2,000 pounds.

Bin
Containers are generally used for discrete component parts delivered to assembly lines.

Less common are nestable bulk containers that are typically used for bulk ingredients and bulk packs that are comprised of a collapsible corrugated plastic sidewall unit sandwiched between a pallet base and top cap. The two most common sizes are 40 x 48 inches and 45 x 48 inches.

The smaller is for general product handling: a standard established by the Grocery Manufacturer's Association (202-337-9400), it's similar to the European 1000 x 1200 millimeter standard. The larger is for the automotive industry: a standard set by the Automotive Industry Action Group (248-358-3570).

Now that we've established what each type is called, here's how they work.

Manufacturing and assembly

All three types of reusable plastic boxes are incorporated in manufacturing and assembly operations. Small parts for assembly are organized in bins captive to the facility. Also captive are totes storing work-in-process as they travel through different workstations in a facility.

“Internal totes tend to be the stack and nest style,” says Bill McMahon, director of new business development for Orbis Corporation (262-560-5449). “The efficiency comes from being able to turn them to stack when full or to condense when empty.” These totes, often with footprints of 24 x 16 inches or 20 x 12 inches in a variety of heights, are sized to both the product shape and weight considerations.

Non-captive totes and containers make the rounds in a closed-loop system—trucked from a supplier's facility full of components and arriving just-in-time to the assembly line at the manufacturer's plant.

The majority of totes are straight wall style and modularly designed so that when fitted together, the smaller footprints combine to form a unit load equivalent to the standard pallet footprint used by that industry. The load is topped with a cap and secured to prevent shifting.

Similarly, larger containers carry larger parts, and stack together for transport. Because the standard footprints are so established, users generally have a choice of off-the-shelf totes and containers from a variety of suppliers.

“In manufacturing, the part source is usually close to the point where it's being used, so users are less concerned about getting a good return ratio and they use a straight wall tote or container rather than something that nests,” explains Joe Borer, automotive market manager for Buckhorn (800-543-4454). “Also, customized dunnage is often used to protect the contents—and it's easier to pull parts and dunnage from a straight wall unit.” When emptied of product, the dunnage stays inside, eliminating the need for it to collapse.

For closed-loop systems between manufacturing operations, however, maximizing trucking efficiencies is important, says Niemeyer. “Manufacturers shipping product to distribution centers want to cube out trailerloads, then bring the maximum number of empty, collapsed containers back to be refilled,” he notes.

Automated systems/storage

Facilities with automation moving and storing product from the receiving dock to the primary pick location—particularly those with mini-load automated storage and retrieval systems (AS/RS)—incorporate reusable plastic totes as the standard unit load to maximize their investment.

There are two different philosophies about which tote style works best for automation, says Orbis's McMahon. “Stack-only totes optimize cube in the system, yielding 10 to 20% more volumetric efficiency than a nestable tote, depending on the height. Alternately, when the tote completes its circuit and comes to the end of the line empty, nestables are more compact and can be handled more easily. Companies are going both ways and it is working equally well,” he observes.

The most commonly used footprint is a 24 x 16 inch tote. Although plenty of standard, off-the-shelf totes are available in this size from numerous suppliers, custom totes are frequently created for these applications because a tote is often the last thing considered in a new system design, says Clinton McDade, senior designer at Schaefer Systems International (704-944-4500).

“It may not be a problem finding an off-the-shelf box to fit a mini-load AS/RS or a carousel, but when moving that piece around conveyor turns in a facility, the length of a box is very sensitive to how big of a curve it goes through,” McDade notes. “The other challenge can be finding a tote that will fit in the bay width allowed for it.”

In addition to considering the conveyor layout, it's important to consider the conveyor itself, says Akro-Mils' Popek. “Belt conveyor needs textured bottom totes that grip as they ride along,” he notes. “A tote with a smooth bottom would get about half-way up and then slide back down.”

Distribution

In the past, maximizing truckload efficiencies was a key consideration in distribution from warehouse to retailer, but today many companies are focusing on total supply chain optimization, picking to store aisles to reduce overall costs.

Typically defined by less-than-caseload picking, nestable totes with securable attached flap lids to prevent pilferage are the reusable box of choice for this application. Being nestable allows the totes to stack when empty and waiting for their return trip from the retailer to the DC.

The returnable totes have replaced corrugated paper boxes for a variety of reasons, says Tim Daughton, distribution market manager for Buckhorn. “Security is the No. 1 benefit, but returnables also reduce product damage because heavy loads in corrugated paper boxes can be crushed when stacked,” he notes. “The plastic totes' molded-in handle on both ends makes them easier to handle, and their life cycle is about 300 round trips, versus a few trips for corrugated paper.”

Footprints and heights vary. For handling general merchandise, totes typically have a 21 x 15 inch footprint and are 9 or 12 inches high. Hardware and automotive aftermarket products tend to ship in a slightly larger footprint of 27 x 17 inches in heights of 9 or 12 inches to accommodate the larger contents. A 28 x 21 x 15 inch container typically ships to department store retailers, as that size was built to accommodate a man's suit on a hanger, folded in half, Daughton says.

One of the biggest challenges to incorporating reusables into supply chain distribution can be managing those assets.

Subsequently, third-party providers have entered the field, offering the totes on a pay-per-use basis and managing their retrieval, tracking, cleaning and redistribution, says Eric Fredrickson, president of Thor Consulting and a member of the communications team for The Reusable Pallet & Container Coalition (RPCC, 202-625-4899).

“Reusables can be used for cost savings and to reduce environmental impact, but it takes a third party focused on the management of the reverse logistics to make it work,” Fredrickson says.

Supplier Web site Phone Bins Nestable totes Stackable totes Containers Bulk bins Bulk packs
Akro-Mils www.akro-mils.com 330-253-5592 x x x
Buckhorn Inc. www.buckhorninc.com 800-543-4454 x x x
C.R. Daniels, Inc. www.dandux.com 800-933-2638 x x x
Durham Manufacturing Co. www.durhammfg.com 800-243-3774 x
Flexcon Container www.flexcontainer.com 973-467-3323 x x x x
Georg Utz, Inc. www.georgutz.com 812-372-2790 x x x x
InterMetro Industries, Inc. www.metro.com 570-825-2741 x x
IPL Products, Ltd. www.ipl-mh.com 800-818-1318 x x
LewisBins+ www.lewisbins.com 877-975-3947 x x x
Molded Fiber Glass Tray Co. www.mfgtray.com 800-458-6050 x x x x
Monoflo International, Inc. www.miworldwide.com 540-665-1691 x x x
Nexel Industries, Inc. www.nexelwire.com 800-245-6682 x x
Norseman Plastics Ltd. www.norsemanplastics.com 416-745-6980 x x
ORBIS Corporation www.orbiscorporation.com 262-560-5449 x x x x x x
Quantum Storage Systems www.quantumstorage.com 305-687-0405 x x x
Rehrig Pacific Company www.rehrigpacific.com 323-262-5145 x
Remcon Plastics www.remcon.com 323-262-5145 x x x x x
Rotonics Manufacturing, Inc. www.rotonics.com 310-538-4932 x
SCA Packaging North America www.scapackagingna.com 724-843-8200 x
Schaefer Systems International www.ssi.schaefer-us.com 704-944-4500 x x x x
Thermodynamics www.okpallets.com 800-627-9037 x
Wilbert Plastic Services www.wilbertplasticservices.com 866-273-1810 x
Unifuse, Division of B&R Specialties www.unifuse.com 585-223-6880 x x x


Plastic resins and manufacturing processes

Two of the primary factors affecting bin, tote and container costs are the plastic resin and the manufacturing process used. Polyethylene (PE) is the most commonly used resin because of its toughness, durability strength and resistance to chemicals. It remains stable in temperatures ranging from -0 to 120°F. Polypropylene (PP) is a stiffer resin with many of the same characteristics of PE. It tends to crack in colder temperatures, but remains structurally sound up to 150°F.

The chart below explains the different processes used in forming returnables, as well as those used in the creation of some of their accessories and related storage cousins.

Process Description Considerations Common products
Thermoforming Heated sheets are formed over molds. Twin sheet process welds two sheets together. Low cost tooling and prototype parts High production rates Can totally encapsulate substrates Pallets Containers Sleeves Dunnage Totes
Injection molding A hollow mold is filled under high pressure. High tool costs Totes Containers
Structural foam molding A hollow mold is partially filled with plastic and a foaming agent; the mix expands to fill the mold. High tool costs Stiffer, more brittle parts Pallets Containers
Rotational (roto) molding Melting pellets line the inside of a mold, which tumbles on three axes. Low cost prototypes Slow process Pallets Containers
Compression molding A molten billet of plastic is squashed between the closing mold halves. Can use very stiff materials Totes
Reprinted with permission from Wilbert Plastic Services, 866-273-1810, www.wilbertplasticservices.com

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