I have often reminded colleagues that, as we diagram the flow of products and orders through manufacturing and warehousing, it is important to capture the reverse flow of empty containers. In some cases, the reverse flow volume is as great as the forward flow.

Another frequently overlooked, but significant flow is that of shipping cartons making their way to the first picking location.

There seems to be a prevailing attitude that anytime a picker or stocker has time available, it should be used to make shipping cartons for use during busy periods. Unfortunately, empty boxes are bulky and don't stack very well. This combination usually leads to messy stacks tucked into every available corner.

I have always thought of this as primarily a poor use of space. But there's more to it.

Recently, I began counting the number of times that these boxes are handled before any product is placed in them. It is often in the range of four to six times. And for single line orders, the empty box handling time is often equal to the picking time.

Try the count for yourself, and you may be surprised. I sure was.

Fortunately, there's an easy solution— make the box only when it's needed.

I have seen several approaches that minimize the space and time consumption of empty box handling.

For starters, evaluate the trade-off of having the picker make his, or her, own cartons as needed from a supply of knocked down cartons along the pick face. Cartons with self-forming bottoms, although more expensive, make this a fast task for the picker.

In consumer direct operations, it is common to pick products into carts or totes and then deliver them to packing stations. A big advantage is that the operator can select the most appropriate size box based on a visual check of the order's cube and shape.

An extension of this concept batches orders based on their packaging size. Orders are handled at the station that specializes in that package size. Where small, single-line orders are the norm, this concept has been further developed into an automated packing line with carton erectors feeding filling stations, followed by automated taping and labeling machines.

Order size is also an issue in one other regard. Based on current carrier and service level selection, many of us have been led to believe that a somewhat oversized box is the simplest solution, and has no shipping cost penalty. This is often true. But, there is a cost to add dunnage, and hassle for the customer to remove it.

That means we are best to continuously re-evaluate order sizes and real customer service requirements to ensure that we are using the most cost effective shipping mode. Make sure that the carton itself is not driving the choice.

It's best to look for alternative packaging that conforms to the product size, and still provides adequate protection. Standards, such as CD mailers and Jiffy packs, may provide both a shipping cost and packaging savings. Wrap-around packages, like Amazon uses, handle a range of order cube while eliminating voids and protecting the products.

Empty boxes may be the least glamorous aspect of warehousing, but may be among our best opportunities for improvement.