Warehouse Picking Processes

Warehouse Picking Processes

There are several different processes operators can use to pick goods. Some of the most common are batch/cluster picking and wave and zone picking. There are also different picking models that can be used in support of these processes. For example, a pick and pass model is used with zone picking when the order is being passed between zones so that it reaches completion at the end and is staged for verification, packing, and shipping. A parallel picking model is used when picking is from all zones simultaneously, and then at the end, there is some form of an order consolidation, staging, or buffering to bring all the component parts of the order together for verification, packing, and shipping.


Pick Face Cube Size


Overstock Cube Size


Location Bin Map Layout for Database Move "from/to" Labels


Stock Item Profile (velocity, cube, etc.)


Common Overstock Cube Sizes


Distribution of Slot Sizes Item Pick Face Size

Understanding Picking Options

Batch Picking

Batch picking is optimal when there are extremely large quantities of the same SKU, and significant quantities of the same SKU/part number are needed to fulfill several orders. For example, if a quantity of 1,000 of the same SKU is picked and it is going to go to 500 or 700 orders, it would be completely impractical to segregate orders like these at the time of pick. Instead, the volume is so high that batch picking is most efficient, and segregation is either done after the pick or by a separate sortation system.

Batch and cluster picking are both used to pick multiple orders simultaneously. The difference between batch and cluster is that with cluster picking, the operator puts picked items into a tote or license plate identifier for a specific order while picking. With batch picking, large pick quantities of the same item for multiple orders are taken to some form of a breakout table or sortation system. Then, the disbursement of the product into separate orders is a separate step that occurs after picking. Typically, batch picking involves picking multiple quantities of the same SKU/product, at the same time, for a very large number of orders. The business driver behind whether to use batch or cluster picking depends on the operational requirements, sortation system automation available, and the order and SKU/product profiles for the business.

Cluster Picking – Hands Free

Cluster picking is very effective when used in combination with hands-free picking. Whether it’s from a horizontal carousel, vertical carousel, vertical lift module (VLM), voice directed in flow rack, or some other type of automated system, the operator needs to be hands-free so they have the time available to actually segregate the order to each component order being picked.

Wave Picking

Wave picking is often used in wholesale and retail distribution, trucking routes, and route delivery warehouses. In instances like these, the warehouse labor force is trying to match-up with the schedule to build a certain number of orders for a truck and a route as close to in-sequence and on time as possible. This allows the warehouse to load the truck, get the truck off the dock, and then move through the next wave. Wave picking is common with route based operations, truck loading, and full truck based business operations. It is not used as often with pick-pack-and-ship e-commerce operations because in e-commerce, orders flow in constantly, and picking is not done to a certain capacity of labor within a defined time frame to meet trucking requirements. Instead, every order that’s picked can be shipped and the orders are balanced differently, often with real-time capabilities to move Next Day and 2nd Day orders to the top of the picking queue rather than being manually built into waves.

Zone Picking

Zone picking is a common form of picking used in warehouses. Typically, zone picking requires a WMS/WES/WCS solution that can segregate and allocate what needs to be picked by zone or area of the warehouse. For example, carousels may be in one area of a warehouse, bag and full case picking in another, and freezers or refrigerators in a third. It’s not always practical because of the attributes of the SKUs/products and how they are stored to have one operator pick in all of these different areas. Zone picking allows optimization of pick by area of the warehouse and in conjunction with other automation systems in use at the warehouse. It also enables operators to use a pick and pass model or a parallel pick model or a hybrid of the two.

Manufacturing Work Order Picking

Manufacturers do not operate their warehouses the same way distributors do. For instance,  rather than wave picking to a route delivery schedule, manufacturers tend to use wave to discrete zone picking to a production schedule in order to gather all the component parts for a production run, accurately, and on time. All manufacturing processes require set up time and switch over time, and if parts aren’t available in a timely fashion and in the appropriate sequence, then the operation cannot be efficient and the manufacturing process is impeded. That’s why it is critical to choose the right type of picking for your environment. The end goal is to increase operational accuracy as well as at the same time lowering labor costs through productivity improvements.

Picking Optimization

A picking optimization review can be completed during a warehouse operational audit and is used to identify areas that are candidates for improvement. The first component to be analyzed is the picking labor. This evaluation process is similar to a Kaizen event in manufacturing that looks at where the labor hours are going. Questions to ask include: How much labor goes towards travel time? How much labor is devoted to manual processes, such as using paper, marking up paper, manually producing labels, updating paper manually, redundant or non-value-added steps with mobile devices or with the ERP or WMS? Is the only method of picking single-order picking? Is labor only being used to improve accuracies? Is labor cost increasing disproportionately to order volume? Remember, labor costs should be reducing proportionally to increased business volume—not the other way around. Accuracy is another indicator for picking optimization. If inventory accuracy by absolute variance is less than 99% to 99.5%, or order accuracies are less than 99.5%, those are indicators for picking optimization benefit.  Accuracies may be good but if the labor costs to maintain those accuracies are too high, more automation or a change in picking processes may be needed.

ERP and ERP WMS Module Picking Limitations

ERP and ERP WMS module picking limitations can have significant impacts on labor costs and accuracy. ERP systems are not always designed for optimal warehouse distribution center and manufacturing operations. In addition, WMS solutions that bolt onto ERPs often inherit the same architecture as the ERP and are challenged to improve efficiencies because they are not architected to support picking and other operations optimization. Some WMS solutions do support advanced picking and some do not; however, ERP WMS module bolt-on solutions do not. Intek and Minerva are unique because they combine all these capabilities in a WMS/WES/WCS package that also has direct control of hands-free picking, pick by light, and all forms of automation.

Proven Picking Solutions

Look for a vendor that has contributed to picking success in a similar industry or in an operational configuration similar to yours. In fact, ask the vendor to provide the exact results that the customer achieved. Oftentimes in the WMS world, the acronyms are given too much significance. WMS, WCS, WES are not all built the same. While marketing literature may mention vast and deep capabilities, where the rubber meets the road is with actual results from existing customers where they’ve accomplished these things as opposed to just promises.

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