7 Critical Factors When Choosing an Order Picking System

"What do I need to know about my operation before choosing the order picking solution that is right for my company?"

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It's a fair question. And since the order picking process is typically the most labor-intensive and costly activity for distribution centers, the follow-up question could easily be: "And how will that solution help me cut costs and stay competitive?"

Controlling costs, maximizing productivity, increasing throughput and improving accuracy are always critical factors for companies operating a warehouse or distribution center.

Fortunately, selecting the proper order picking technologies can move a company forward faster in reaching those objectives. To arrive at the correct order picking solution, here are guidelines that will help companies make the appropriate determination:

1. Minimize picker travel time and distances. Perhaps the most significant obstacle that undermines efficiency is the time order pickers spend in non-picking travel.

There are four concepts or methodologies and technologies that can be employed within the design of the order picking system to help minimize the impact of travel time and distance on productivity.

A. Implement an order picking methodology that makes sense for your business and your customers:

  • Batch picking, where an order picker is assigned and picks multiple orders simultaneously. This will minimize the number of "trips" to each location.
  • Zone picking, where the picking area is divided into zones and order-pickers are assigned to specific zones along with the responsibility of picking all products within their zones.
  • Wave picking, where an order-picker picks one product at a time for a group of orders.

B. Set up a forward pick area that allows all the fastest moving SKUs to be picked from a much smaller, more compact area than that occupied by the overall picking system, again helping to reduce picking travel time.

C. Implement proper slotting techniques and procedures that can minimize the amount of travel time and distance by locating the fastest moving SKUs in the forward pick area, such as near the end of the aisles closest to the shipping doors, or near major cross aisles.

D. Utilize "part to picker" technologies such as horizontal carousels, vertical carousels, vertical storage units and automated storage and retrieval systems (AS/RS), which can virtually eliminate all picker travel time.

2. Minimize product touches. Whether a distribution center uses basic order picking, batch picking, zone picking or wave picking, it's important to identify and record the number of times an item is "touched" or handled from the time it is ordered to the time it leaves the facility.

Using automated conveyors to move picked SKUs within the distribution center is a major solution for eliminating unnecessary touches. It's also possible to reduce product touches in some operations by picking directly from the storage locations, rather than replenishing to forward (or fast) pick areas.

3. Use of "golden zoning" principles. This is the process of placing the fastest moving SKUs within easy reach of the order-pickers. This minimizes pick retrieval times and, as a result, improves productivity.

This principle can be utilized across a number of different storage and picking mediums. For instance, in manual pick operations, it can be applied to shelving and carton flow rack, as well as automated pick operations such as carousels and automated storage and retrieval systems.

When applying this approach to automated material handling solutions, you are not just placing the fastest moving SKUs within easy reach of the order pickers; rather, you are placing the fastest moving SKUs in the same general area within the carousel. This minimizes the distance traveled between picks, since the fastest moving SKUs are near the input and output points of the crane aisles, which reduces the crane's travel distance.

An added benefit in a manual order picking operation is improved safety and ergonomics as the majority of the picks will be from proper heights, which minimizes reaching and bending by the order-pickers.

4. Incorporate dynamic work zones or flexible picking zones. When utilizing zone picking methodologies, the use of dynamic or flexible zoning techniques allows the boundaries of the pick zones to be shifted to match changing workload requirements.

For example, at times when business is slower, the work zones can be increased to allow for fewer order-pickers. On the flip side, in peak business periods, the work zones can be reduced so additional order-pickers can be introduced into the system.

This makes it possible for improving the management of operating throughout the year, based on day-to-day or seasonal picking needs.

To receive the maximum benefits from dynamic work zones, the picking operation requires a warehouse management system (WMS) or warehouse control system (WCS), and utilizing one, or some combination, of the three picking technology aids: radio frequency (RF), pick-to-voice (PTV) or pick-to-light (PTL).

5. Utilize slotting principles and techniques. Before setting up a picking system, it is essential to gather as much data as possible on the movement of SKUs. This can be accomplished by measuring the dimensions and weights of all existing and in-bound new SKUs with a suitable measuring device.

Order history reports can be helpful in determining how much product of each SKU has moved over time and how it has moved. With this information, you can determine which equipment is appropriate for each SKU and where each SKU should be slotted.

Many operators make the mistake of limiting the necessary and appropriate time to slotting a warehouse and picking system to when the facility first went into operation. But in fact, slotting is the recurring task of effectively determining the best locations for SKUs based on sales velocity, physical dimensions and storage constraints.

Distribution centers that do not dedicate the necessary time and resources for properly re-slotting a warehouse, making sure products are stored in ideal locations, are candidates for serious problems.

While SKU turnover and activity will generally determine the appropriate frequency for re-slotting, there are indicators for when it is time to re-slot. One is when order-pickers in the forward/fast pick zones are spending more time searching, stretching, reaching or bending for products instead of picking from the waist-high golden zone. Another is when order-pickers leave the forward/fast pick zones frequently to retrieve product from other locations in the system.

6. Use of task interleaving. This principle applies to full pallet picking operations only, and targets some of the loss of productivity associated with travel time and distance.

Task interleaving refers to the process of combining active picking with the put-away or other value-added processes. In short, the return leg of travel from the dock is used to kill as many birds with as few stones as possible.

For instance, the lift truck driver may be directed by the WMS from the shipping area to the adjacent receiving area to pick up and move a pallet into storage when returning for the next pick. The principle basically provides for maximum return on investment and best utilization of the operation's manpower and equipment investments by preventing the operator from returning "empty handed" from the picking leg of the operation.

7. Use of picking technology aids. Having dealt with the first six factors, it is time to consider and evaluate the appropriate order picking technology — RF, pick-to-voice or pick-to-light — recognizing that the best picking solution may be some combination of the three.

When finally choosing an order picking technology, factor in the density of SKU locations, required throughput, characteristics of the items being picked and any specialized procedures, such as serial number and barcode tracking.

In general, an RF system will provide for some small productivity gains over a paper-based system, but the greatest gains — and generally the reason most companies move from paper-based to RF-based systems — will be achieved with improved accuracy.

When considering both pick-to-voice (PTV) and pick-to-light (PTL), be aware that the voice systems generally provide for higher picking accuracy, while the light systems provide for higher pick rates and throughput.

It might seem that selecting the most appropriate picking technology requires more "due diligence" than might be expected. It does. And your patience will be rewarded with the proper picking and equipment technology that will maximize a distribution center's picking capabilities and, at the same time, minimize operating expenses.