Most businesses use one employee (picker) to pick one customer’s order, one at a time. This is called discrete picking.
As order volume and complexity increases, so too do picking methods. A well-optimized picking strategy depends on order volume, SKU variety, product size, warehouse layouts, shipping schedules, and more.
So which picking method is best? The short answer is it depends.
A WMS system often can help you design the best picking strategy based on your order patterns. However we’ll go over the most common picking concepts below.
Note: The picking techniques detailed in this post are simplified and distilled down to the basics. In practice, most high volume environments won’t employ a single picking method, but instead combine a hybrid of methods.
This is the simplest and most common form of order picking.
Discrete picking is also referred to as single order, individual, or piece picking. In this method, a picker goes through one order at a time, grabbing an item line by line before moving onto the next order.
Most businesses that discrete pick are low order volume, or have large/heavy products.
When order volume becomes high, the most common bottleneck in order throughput is picker walking time.
According to a now-famous study, a Dutch distribution center obtained a “reduction between 17 and 34% in walking time, by simply routing the pickers more efficiently.” Further reduction can be made by clustering orders, and optimizing warehouse layouts.
Batch picking can also be referred to as consolidated or multi-order picking. With this method, a single picker grabs items with the same SKU for multiple orders at the same time.
Batch picking is best for high order volumes with a high rate of shared SKU overlap.
Zone picking is typically more expensive than batch.
With zone picking, SKUs are divided into separate areas, or zones. Each picker is assigned to pick from a single zone per shift.
If an order requires items from multiple zones, an order box moves down (often using a conveyor) to next zone. This is also called “pick and pass” or “sequential zone picking.”
Zone picking often reduces picker congestion in high volume environments.
Instead of a “pick and pass” zoned system, each zone can be picked at the same time. This is called “pick and merge” or “simultaneous zone picking.”
In simultaneous zone picking, parts from each zone are consolidated at a packing station (rather than one at a time via a conveyor belt).
The parallel nature of pick and merge can often lead to faster order fulfillment than other methods.
“Wave picking” is another commonly used term. In my research, I found numerous incompatible definitions of wave picking. There’s a lot of confusion over this term, so I’ll do my best to simplify.
Wave picking is conceptually similar to batch picking. Like batch, ordered items are queued and grouped (batched) into combined pick lists.
Traditionally, batch picking is done once per day and solely focused on maximizing the amount of product overlap between orders. Wave picking, on the other hand, is executed multiple times per day (or shift) and balances more factors than product overlap.
In addition to maximizing product overlap, wave picking balances pick list capacities, product weight, shipping schedules, worker shifts and more.
In reality, the comparison below is simplified. Typically in high order volumes businesses will employ hybrid models i.e. a combination of batch and zone, allowing pickers to pick multiple orders at a time for each zone.
|Picker Walk Time||Highest||Low||Mid|
|Order Throughput||Low||High||Very high|
|Fulfill speed||Slow||Slowest||Mid (sequential), fast (simultaneous)|
|Best For||Low order volumes, large/heavy products||High order volumes with common SKUs||High order volumes, alleviate picker congestion, multiple daily ship deadlines (simultaneous)|
Other assistive picking tech can be used in conjunction to improve picker efficiency and reduce errors. Some examples include (from most common to least):
Barcode/RFID scanners - Pickers use a mobile scanner to scan a barcode or RFID to ensure the right products are selected. Packers can also use the mobile scanner to double check the accuracy during the packing process.
Pick-to-light - Light guided systems use lighting to signal what aisle, shelf, bin pickers need to access. Useful for organizations with multi-lingual pickers. Can be confusing in congested picker environments.
Voice picking headsets - Pickers use headsets that instruct where to go and what to grab. Often pickers can verbally confirm collection of items, making for a paperless and handsfree environment.
Vision picking - Pickers wear augmented reality glasses that instruct where to go, what to grab, and automatically scans product tags. Also makes for a handsfree environment.
Does your business need help designing a picking strategy? Or do you need to optimize your order efficiency? See our buyer’s guide on warehouse management software for more info.