Picking

Picking Procedure

Of all stockroom processes, order picking tends to get the most attention. It is just the nature of distribution and fulfilment that you generally have more outbound transactions than inbound transactions, and the labour associated with the outbound transactions is likely a big part of the total stockroom labour budget. Another reason for the high level of importance placed on order picking operations is its direct connection to customer satisfaction. The ability to, quickly and accurately, process customer orders, has become an essential part of doing business.

The methods for order picking vary and the level of difficulty in choosing the best method for your operation will depend on the type of operation you have. The characteristics of the product being handled, the total number of transactions, the total number of orders, picks per order, quantity per pick, picks per picker, a total number of pickers, value-added processing (such as private labelling), and whether you are handling piece pick, case pick, or full-pallet loads are all factors that will affect your decision on a method for order picking. A combination of picking methods is often needed to handle diverse product and order characteristics.

Designing an Order Picking Operation

The key objectives in designing an order picking operation include an increase in productivity, reduction of cycle time, and increase in inaccuracy. These goals may often conflict with one another in that a method that focuses on productivity may not provide a short enough cycle time, or a method that focuses on accuracy may sacrifice productivity.

Productivity: Productivity in order picking is measured by the pick rate. Piece pick operations usually measure the pick rate in line items picked per hour, while case pick operations may measure cases per hour and line items per hour. In pallet pick operations, the best measure is actual pallets picked per hour. Since the actual amount of time it takes to physically remove the product from the location tends to be fixed, regardless of the picking method used, productivity gains are usually in the form of reducing the travel time.

Cycle Time: Cycle time is the amount of time it takes to get an order from order entry to the shipping dock. In recent years, customers’ expectations of companies, to provide same-day shipment, has put greater emphasis on reducing cycle times from days to hours or minutes. Immediate release of orders to the stockroom for picking, and methods that provide concurrent picking of items within large orders, are ways to reduce cycle times.

Accuracy: Regardless of the type of operation you are running, accuracy will be a key goal. Virtually every decision you make in setting up a stockroom will have some impact on accuracy, from the product numbering scheme to the design of product labels, product packaging, the design of picking documents, location numbering scheme, storage equipment, lighting conditions, and picking method used. Technologies that aid in picking accuracy include pick-to-light systems, counting scales, and barcode scanners. In addition to the design aspects of an order picking operation, employee training, accuracy tracking, and accountability are also essential to achieving high levels of accuracy.

Piece Picking Methods

Piece picking, also known as broken case picking or pick-pack operations, describes systems where individual items are picked. Piece pick operations have a large picker base (in the thousands or tens of thousands of items), small quantities per pick, and short cycle times. Mail-order catalogue companies and repair parts distributors are good examples of piece pick operations.

Basic Order Picking: In the most basic order-picking method, products are stored in fixed locations on static shelving or pallet rack. An order-picker picks one order at a time, following a route up and down each aisle until the entire order is collected. The order-picker will usually use some type of picking cart. The design of the picking flow should be such that the order-picker ends up fairly close to the original starting point. The picking document should have the picks sorted in the same sequence as the picking flow. Fast-moving products should be stored close to the main cross aisle and other cross aisles to allow shortcuts. Larger/bulkier items would be stored towards the end of the pick flow. This basic order-picking method can work well in operations with a small total number of orders and a high number of picks per order. Operations with low picks per order will find the travel time excessive in this type of picking and operations with large numbers of orders will find that the congestion from many pickers working in the same areas slows down the processing.

Batch Picking – Multi-order Picking in Batch Picking: Multiple orders are grouped into small batches. An order-picker will pick all orders within the batch in one pass, using a merged picklist. Usually, the picker will use a multi-tiered picking cart and keep a separate tote/carton on the cart for each order. Batch sizes usually run from 4 to 12 orders per batch depending on the average picks per order in that specific operation. Batch picking systems are programmed to consolidate orders of the same items. In operations with low picks per order, batch picking can reduce travel time by allowing the picker to make additional picks while in the same area. Since you are picking multiple orders at the same time, systems and procedures will be required to prevent the mixing of orders. In busy operations, batch picking is often used in conjunction with zone picking and automated material-handling equipment. To get maximum productivity in batch pick operations, orders must be accumulated in the system until there are enough similar picks to create batches. This delay in processing may not be acceptable in same-day shipping operations.

Zone picking: Zone picking is the order picking version of the assembly line. In zone picking, the picking area is divided into individual pick zones. Order pickers are assigned a specific zone, and only pick items within that zone. Orders are moved from one zone to the next as the picking from the previous zone is completed (also known as "pick-and-pass"). Usually, conveyor systems are used to move orders from zone to zone. In zone picking, it is important to balance the number of picks from zone to zone to maintain a consistent flow. Zones are sized to accommodate enough picks for one or two order pickers. Creating fast pick areas close to the conveyor is essential in achieving high productivity in zone picking. Zone picking is most effective in large operations with high total numbers of orders and low to moderate picks per order. Separate zones also provide for the specialization of picking techniques such as having automated material handling systems in one zone and manual handling in the next.

Wave picking: A variation on zone picking and batch picking, where, rather than orders moving from one zone to the next for picking, all zones are picked at the same time and the items are later sorted and consolidated into individual orders/shipments. Wave picking is the quickest method (shortest cycle time) for picking multi-item orders. However, the sorting and consolidation process can be tricky. Operations with a high total number of pickers and moderate to high picks per order may benefit from wave picking. Wave picking may be used to isolate orders by specific carriers, routes, or zones.