Order picking processes are one of the most important parts of a company’s entire supply chain because it is a make it or break it activity — leading directly to customer satisfaction. If an order is mis-picked with the wrong SKU or quantity, or a SKU is out of stock, then customers don’t get their items and are not happy. The order picking process is also one of the most costly and labor-intensive processes, with the average cost of order picking estimated to reach close to 55 percent of the entire warehouse operating expense. Because of this significant cost and the effect on customer satisfaction, leading warehouse managers have been focusing lately on improving the order picking process.
There are a variety of order picking approaches in use in assembly operations and warehouses, which include:
Piece or Parts Picking: This is a simple method of a single order picker picking items for a single order. Pickers select each item according to their pick list and place it in a container for shipping to the customer. This method is appropriate for odd-sized or oversized products; even items that may require special handling. Pickers walk many steps a day to pick this type of orders. Picking rates depend on the size of the orders and the amount of travel time.
Part picking is used in virtually every manufacturing operation and can become a time-consuming process — especially for manufacturers that have yet to embrace and implement lean manufacturing. At a workstation on an assembly line, workers who are assembling products need to pick parts to combine with the item they are working on. When these workstations are depleted, a picker must pick parts from a manufacturing supermarket near the assembly line. When the manufacturing supermarket is then in turn depleted, a worker must pick and transport parts from reserve storage (or from shipping and receiving as new parts are delivered) in order to keep the manufacturing process moving.
Part picking is especially prevalent in subassembly and kitting operations, where multiple parts must be configured or bundled together before the next stage in the manufacturing process can begin. These operations require workers to quickly pick and arrange parts, replenish their supply of parts and remove clutter (like empty totes or containers) without slowing down the assembly line.
In assembly operations, parts are combined in a work cell arrangement where one or more workers pieces together multiple parts to form an assembly, such as a car door or brake assembly. In these work cells, parts are stored by SKU on slanted shelves that allow parts to flow forward towards the pick face once picked. This speeds replenishment and ensures the assembler always has parts on hand. Working in this type of fast-paced operation, minimizes transit time (for finding parts); simplifies workflow as work moves freely from one workstation to the next, within the cell, and from one cell to the next; and gets rid of wasted movement as workers can easily reach each part to create the finished piece.
Zone Picking: Order pickers are assigned to one specific zone to pick within, filling orders with the SKUs located in that area. If the order requires SKUs from another zone, the container is passed to another zone picker(s) for completion. The advantage of this method of picking is that workers are very familiar with items in their zones, which are of a limited size, allowing them to pick faster. Products are typically stored in flow racks or shelving.
Batch Picking: Also known as multi-order picking, this method is characterized by combining product demand from multiple orders into one pick instruction. Orders are arranged in efficient picking sequences. After order picking, goods are sorted/consolidated by order or shipping destination. Batch picking is useful for small items and only a few SKUs per order. It is most commonly used for food, non-food, apparel and ecommerce orders.
Cluster Picking: One SKU is picked to multiple orders or multiple SKUs to one order to a single picker. Pickers select items for multiple orders at one time, placing them into totes or containers, typically located on top of a mobile cart. Often technology like pick-to-light or pick-to-voice solutions guide pickers to the right products, speeding fulfillment and improving accuracy. Pickers pick orders in their entirety before proceeding to pick the next cluster of orders.
Wave Picking: One picker picks one order, one SKU at a time, but orders are scheduled to be picked at certain times of the day, in a specific wave to maximize the picking and packing operations. Wave picking is used when there are a large number of SKUs to pick from. A WMS releases the waves to the warehouse sequentially throughout the day, to allow managers to coordinate parallel and sequential activities such as planned departure times of shipping vehicles or production schedules.
Combinations: Combinations of zone/batch, zone/wave and zone/batch/wave picking exist.
Choosing an order picking system depends on any number of requirements such as cost, complexity, the number of customer orders, size and number of items, etc. Every company has a unique requirement and one order picking solution may suit one business and not another. Determining the requirements will ensure that the most efficient order picking solution is selected. For example, carton flow racks have a high order picking rate of up to 150 picks an hour, but combined with a pick-to-light system that uses lights to show workers what items and how many to pick, you can increase pick rates by three-fold.
Brian C. Neuwirth is VP of Sales & Marketing at UNEX Manufacturing.