A surprising number of warehouse operators do no storage planning at all.
In the absence of any instruction, the lift truck operator at the receiving dock will make the decision about where to store the material he or she unloads. Not surprisingly, that decision is to store the material in the first available empty spot.
Storage decisions are easier if you develop a strategy that governs the location decision.
Items that are shipped together should also be stored together. Will storage locations be fixed or random, or a combination of both? In some operations, fixed locations are used in a forward pick area that contains the most popular items. In a reserve storage area, locations are random. Most of the order-picking activity is in the forward area.
Should product be stored by family or by manufacturer? In a grocery warehouse, the decision might be made to store all tomato products together, or instead to store all Campbell products together.
Often the size or shape of the unit to be stored will govern its location. For example, long items such as pipe, ladders or lumber are difficult to handle and store, so they should be kept together in a cantilever rack area. Small replacement parts are stored in a bin area. Full pallets or large units such as home appliances are kept in a bulk-storage area.
When the advance shipping notice arrives, the warehouse manager should have ample detail describing the inbound shipment. That is the time to determine the best storage location for each item coming to the warehouse.
Some warehouse management systems can be programmed to determine storage locations, but the process can also be done manually by a person who understands the warehouse layout as well as the current storage strategy. There should be a planned level for each item in the inventory. When actual levels move higher than planned, management has an early warning.
What do we need to know about the product to be stored? The critical factor is the amount of cube displaced by each new SKU. This is determined by multiplying length by width by height, and the process can be expedited by using a Cubiscan, a device that scans the carton and calculates its cubic displacement.
Products that require refrigeration or humidity control are stored in temperature-controlled spaces. Separation is also required for hazardous materials, items with strong odor or products that are vulnerable to pilferage.
How do you know when the warehouse is full, and what would you do about it? The visual cues are obvious, but they may come too late. A few warehouse management systems provide a daily report about how full the warehouse is, and how many additional truckloads can be effectively handled.
When the warehouse is too full, one temporary remedy is to rent highway trailers and use them for storage. What items will go in the trailers, and where will those trailers be located? If a public warehouse or a leased building is used to handle the overflow, which items will be placed in off-site?
Obviously, there is no quick answer to these questions, but testing the options should be part of the storage-planning process.
A critical factor in deciding where and how to store an item is to determine how orders are picked. Discrete picking involves one order selector and one order. Batch picking is the process of picking more than one order. Zone picking may require more than one order selector, with one working in each zone.
Are you picking full pallets, full cases, eaches (broken cases) or all three? The storage layout may be designed to accommodate each of these three order-picking options.
Materials-handling equipment will also provide limits on the storage layout. Small parts stored in bins might be handled with rolling carts similar to those used in a grocery store.
The conventional forklift requires a minimum aisle width that is the basis of layout design. If narrow aisle equipment is used to save space, a staging area is needed to transfer material unloaded with a conventional forklift to the equipment that is used for put away. When order selection is done with a pallet mover or a picking cart, all items are stored low enough to be reached from the floor.
Ergonomic considerations are always a factor in developing storage plans. Fast-moving items should be stored in places where they are easiest to handle, and where they can be moved with minimal risk of injury. By avoiding the need to stoop or stretch, the order picker can operate with greater speed and less fatigue. The "golden zone" is rack or bins that are between knee and shoulder level.
While many of these ideas may seem elementary, a surprising number of warehouse managers neglect some, if not all, of them. A continuous storage-planning process pays dividends in improving both storage and handling productivity. The process starts with a plan, and the plan should consider picking methods, materials-handling equipment, information technology, product velocity and ergonomics.
Furthermore, the plans must be reviewed regularly to adjust to changing conditions. Maintaining and adjusting your storage strategy is one of the best ways to improve the productivity of your warehouse.
