(Courtesy: Prime Distribution Services)
In my last two blogs I discussed the general topic of picking and went into some detail about piece picking. In Part III of the series on Picking I will go into detail about the method of Case Picking.
Case Picking is collecting full cartons or boxes of product on to a pallet. So if a picker is working on an order that needs 25 units of an item and the case contains 23, then the order picker is required to pick one full case plus two individual units. This method is broken down into four categories –- basic case picking, batch picking, zone picking, and wave picking.
· Basic case picking. The most frequent method of the case picking category, basic case picking calls for the products to be stored in pallet racks or in bulk in floor locations. Pickers use a hand pallet jack or motorized pallet truck and pick cases out of bulk floor locations. The method works best when dealing with high storage density and high pick rates.
· Batch picking. This style of picking is ideal when dealing with a large number of SKUs that share an attribute or feature like size. It requires a picker to amass multiple orders at one time and pick all the cases for that group of orders. The cases for each SKU are then sorted into the respective orders for shipping. Batch picking enhances productivity because the picker makes one journey through the pick location and picks for a number of orders.
· Zone picking. This category of case picking is most advantageous when you have enough cases per order in each zone to fill a pallet. The picking area is divided into individual zones and pickers are assigned to a specific zone.
· Wave picking. This category is ideal for a case picking method when there are very large orders with a lot of picks for each order and you want to decrease cycle time. It involves assigning orders into groups or waves. Once the group or wave of orders is picked, the orders are then sorted down to individual orders.
Equipment used in case picking include:
· Pallet rack
· Flow rack
· Carousels
· Automated storage and retrieval systems (ASRS)
· Pick-to-light
· Bar-code scanners
· Voice-directed picking
· Automated conveyor and sortation systems
· Lift trucks
Case picking offers high productivity and short cycle times and is very accurate. It is highly labor intensive. There are a number of automated systems that are designed to lower labor cost. These include automated mixed case palletizing, conveyor-based automated case picking systems, layer order fulfillment systems, Automated Guided Vehicles (AGV), vertical cascading order release system, Gantry robot-based automated case picking system, and Automatic Storage & Retrieval (AS/RS) system.
Whatever picking method you select, its goal should be threefold –- higher productivity, lower cycle time, and efficient picking.
Finally, satisfy the most basic principle of warehouse operation –- store items in the appropriate storage media. Putting slow moving SKUs in pallet racks may prove to be as wasteful as having fast moving SKUs in shelving bins. This is achieved if you follow the variable of cube movement velocity. This measures the volume of movement for each SKU. The cube movement velocity = movement in units x cubic dimensions of the unit.