By Ian Hobkirk
Managing Director of Commonwealth Supply Chain Advisors
Under increasing pressure to work faster, better, and smarter in today’s omni-channel and e-commerce business environment, companies need help getting their distribution operations up to speed with customer demands and expectations. To help, I’ve identified 10 key tactics that successful companies are employing in order to make a graceful transition to higher levels of e-commerce in the distribution center.
In this ten-part blog series I’m covering four basic, three intermediate and three advanced tactics that will help your firm achieve e-commerce distribution success. This blog, Part 4 will focus on the last Basic Tactic, Determine an Optimal Pick Methodology.
Tactic #4: Determine Optimal Pick Methodology
Once the pick strategy has been determined, attention can be turned to pick methodology. There are many confusing terms for different types of picking, and there is not a universally accepted definition for some of them. Here’s a breakdown of each:
Discrete Order Picking
With this method, one order at a time is picked, start-to-finish, by one picker. Without a Warehouse Management System (WMS), this may be the only method of picking that can be practically executed in some distribution centers. Discrete order picking is simple to learn and not very prone to error. For companies used to picking large-cube orders, this method may be very effective; there simply may not be a good way for a picker to transport more than one order around the warehouse at any given time. However, discrete order picking is colossally inefficient for small- cube item picking. To pick five orders, each of which might fit in the size of a shoe box, a worker must make five separate trips around the entire warehouse. Walking is excessive, and labor costs are as well.
Advantages:
- Simple for operators
- Less error prone
- Little/no technology required
- May be the only practical method to pick very high-cube items
Disadvantages
- Very high levels of walking
- Operators return to home-base after each order is picked
- Each order requires a trip through the entire warehouse
Cluster Picking
Moving from discrete order picking to cluster picking is one of the single greatest leaps forward in efficiency that a company can take in the distribution center. With cluster picking, multiple orders at a time are picked, start-to-finish, by one picker. As the orders are picked, they are placed in discrete, separate containers. In the analogy mentioned previously, the same five orders now involve only a single trip through the distribution center. Cluster picking is much easier with a real-time warehousing system where pickers are directed in an efficient pick path, and are told exactly what to pick and where to put it. However, good results are still attainable with paper-based systems, using batch pick-tickets. Paper-based cluster picking is certainly more error prone than discrete order picking, so if automatic data capture like bar-code scanning is not used to ensure accuracy, then secondary checking will need to be employed.
Advantages:
- Dramatically reduces walking
- Possible to do on a limited scale without a high degree of technology
- Each order is only touched once
- Orders are ready-to-ship as soon as picking is done
Disadvantages
- Hard to pick a large group of orders without real-time instructions
- Orders may travel significant distances without any picks being performed
- Travel distances are excessive in large warehouses with many SKUs
- Increased likelihood of errors
Zone Picking
Zone picking involves multiple pickers each picking separate portions of the same order. It is often deployed in conjunction with cluster picking, where multiple pickers each pick separate parts of multiple orders at the same time. Zone picking works best when there are a variety of types of SKUs or very large SKU sets that orders can be drawn from. There are two flavors of zone picking:
Pick-and-Pass, or sequential zone picking, involves one picker “passing” a group of orders to another picker who then performs additional picks for the same orders. The product is still placed in a discrete tote or carton that is handed off to multiple picks in sequence until the order is picked to completion. Pick and pass can be used with cart-based picking (the entire cart is passed to the next picker) or with conveyor-based picking. With the latter strategy, more complex zone routing can be employed, where totes can skip over zones where there are no picks for maximum efficiency. Zone picking must almost always be deployed with a real-time warehousing system.
Advantages:
- Reduces walking in larger distribution centers
- Each order can only be routed to zones where there are picks
- Orders are ready-to-ship as soon as picking is done
Disadvantages:
- Almost impossible to manage without real-time warehousing
- Zone routing can only be done with complex conveyor systems
- All of the SKU’s in the order travel through the entire DC
Pick-and-Consolidate, or simultaneous zone picking, involves multiple pickers picking parts of the same orders at the same time. The items ore picked into discrete totes which must then be married up or consolidated in a secondary process downstream. This method is well suited for situations where the total cube of an order is fairly large, or where there is a wide disparity in characteristics amongst the various SKUs in an order. For example, there may be some large, non-conveyable items on an order along with smaller conveyable items. Each type of SKU would be picked in its own zone and the entire order would be married up at the end of the process.
Advantages:
- Reduces walking in larger distribution centers
- Each order can only be routed to zones where there are picks
- Orders are ready-to-ship as soon as picking is done
Disadvantages
- Almost impossible to manage without real-time warehousing
- Zone routing can only be done with complex conveyor systems
- All of the SKU’s in the order travel through the entire DC
Batch Picking
Batch picking involves picking the entire quantity of a SKU, which is required for multiple orders, and then sorting it to those individual orders in a secondary process. Batch picking works best in a “few-to-many” environment, when there are a small number of very fast moving SKUs which are required for a large number of orders. For instance, a picker may pick an entire pallet of product, bring it to a sorting area, and then perform a “put” process and distribute the items to each of the outbound orders. Batch picking can be used in conjunction with other forms of picking as well. For example, a picker can perform a cluster pick – picking ten orders simultaneously into discrete containers – and then drop those orders at a “put” station where a few fast moving SKUs are put to the orders.
Advantages:
- Reduces walking in larger distribution centers
- Each order can only be routed to zones where there are picks
- Orders are ready-to-ship as soon as picking is done
Disadvantages
- Almost impossible to manage without real-time warehousing
- Zone routing can only be done with complex conveyor systems
- All of the SKU’s in the order travel through the entire DC
Related Content: “Distribution Center Design Series, Part II – Developing a Throughput Design Tool and Determining a Pick Strategy.”
In the next installment of this ten-part blog series we’ll move on to cover the first of three Intermediate Tactics: Practice Real-Time Warehousing.