Warehouse Picking Methods
Warehouse Picking Methods
There’s another number of methods of picking. The two most common that can also include batch cluster wave and zone picking is with pick and pass process and a parallel pick process. A pick and pass process is used with zone picking and but the order is being passed from zones so that it reaches completion at the end and is staged for packing verification and shipping.
Parallel picking is when picking from all zones simultaneously, and then at the end, you have some form of an order consolidation staging, or buffering solution to bring all the component parts of the order together for packing verification and shipping. Batch and cluster and wave and zone picking are methods of picking within the operation that are either in addition to, or part of a parallel pick or pick and pass environment.
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 and cluster picking get confused often, but both pick multiple orders simultaneously. The difference between batch and the cluster is that with cluster picking the operator is putting picked items that you pick into a tote or license plate identifier for a specific order. Batch picking typically has large pick quantities for multiple orders, the items are taken back to some form of a breakout table. The disbursement of the product into separate orders is a separate step. Batch picking is when you are picking multiple quantities of the same skew, at the same time, for multiple orders. The difference between batch and cluster picking is whether or not you associate and pick to a specific order. Cluster picking associates picked items to the order at the time of the pick while with batch picking it is done as a secondary step. The business driver behind which type to use depends on the operational guidelines and the SKU profiles.
Cluster picking is very effective with hands-free picking, because whether it’s from a carousel or voice, or what have you, the operator has hands-free so they have the time available to actually segregate the order to a component or segregate the parts to component orders.
Batch picking is used more when there are extremely large quantities of the same SKU, the same part number is going to a number of orders. It could be completely impractical to segregate those by order at time of pick. Segregation is done after the pick or a separate sortation system is used. For example, if a quantity of 1000 of one SKU part number is picked and it is going to go to 500 or 700 orders, the volume is so high that batch picking is most efficient.
Wave picking is often seen in conjunction with warehouses that are route delivery type operations. Wave picking is popular with wholesale distribution, retail distribution, with trucking routes, and route to delivery. 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 you can. This allows the warehouse to load the truck, get the truck off the dock, and then move through the next wave. Wave picking a is common with routes, truck loading, and trucking based warehouses.
It is not as popular with the pick pack and ship e-commerce because in e-commerce orders flow in constantly, and picking is not done to a certain capacity of labor. Every order that’s picked can go out the door and you balance it differently.
Zone picking is the simplest form of picking in a warehouse. An order is received, and one operator picks that entire order, route, wherever the parts and SKUs are in the warehouse. Zone picking done with a WMS, WES or WCS, is basically segregating and allocating what’s picked by zone or area of the warehouse. You might have one area of the warehouse where you have carousels. You might have one area of the warehouse where you have bag and full case picking. You might have a freezer or refrigerator in your operation. It’s not always practical because of the attributes of the SKUs and the products and how they’re stocked and stored to have one operator go pick all of those. Zone picking allows you to pick by area of the warehouse and in conjunction with what other automation you’re using in those parts of the warehouse. Then you can then utilize that with a pick and pass methodology or a parallel pick methodology and/or a hybrid of the two.
In a manufacturing environment instead of wave picking to a route delivery schedule, manufacturers typically use wave to sometimes discrete zone picking to a production schedule to get all the component parts there for a production run, accurately, and on time. There is set up time, switch over time, for any kind of manufacturing process. If you can’t get your parts there in a timely fashion sequence that they need them there, then you will be inefficient. The timely fashion sequence that they need them there, then you’re basically going to slow down and impede your manufacturing process.
The types of picking are important in any kind of a warehousing operation, whether it’s manufacturing and distribution. The end goal is to increase operational accuracy as well at the same time lowering labor costs through productivity improvements. And what areas would you review for optimization? How would you determine you have an optimized process or you could benefit from one?
A picking review can be accomplished during a warehouse operational audit to identify where those areas exist that are candidates for improvement. The first thing to analyze is to determine how the picking labor is be used. An evaluation process in the form of a kaizen event to look at where’s the labor going? How much labor do I have going towards travel time? How much labor do I have that’s going towards manual processes, such as using paper, marking up paper, manually producing labels, updating paper manually, or redundant, non-value-added steps with mobile devices.
The other review is whether or not the only method throughout the facility is single-order picking. So are they operating in a simple fashion and just using pure labor to improve? Is labor cost increasing disproportionately to order volume, labor costs should be reducing proportionally to business volume increases not the other way around.
Accuracy is another indicator for picking optimization. If inventory accuracy by absolute variance is less than 99% or 99.5%, or order accuracies are less than 99.5%, those are indicators for picking optimization. Accuracies may be good but the labor costs to maintain those accuracies are too high is also another indicator.
ERP and WMS Picking Optimization
These types of advanced picking strategies are more conducive to using a WMS rather than an ERP system. In fact, it is rare to see them used within an enterprise resource planning system. The ERP systems are not always designed for optimal warehouse distribution center and manufacturing operations. Bolt-on WMS solutions to ERPs often inherit that same architecture as the ERP and are challenged to improve efficiencies as they are not architected to support items like this. Some WMS do support advanced picking and some do not. The uniqueness of Intek and Minerva is that they combine all these capabilities in a WMS, WES, WCS package that also has direct control of all the automation equipment with pick by light and other automation capabilities.
Proven Picking Solutions
Look for a solution that has accomplished this in a similar industry or in an operational configuration and the vendor can 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. Marketing literature may mention vast and deep capabilities, but where the rubber meets the road and reality kicks in is with actual results from existing customers where they’ve accomplished these things as opposed to just promises.