Combine storage types for better space utilization, productivity, and safety
(Previously published in Material Handling Management- www.MHMonline.com)
Many companies take vanilla, unimaginative approach to selecting storage equipment. Quick decisions are made without an analytical approach, and distribution centers are filled with basic pallet rack and perhaps some bin shelving. If some analysis is done to determine appropriate choices of storage equipment types for various groups of products, then they often locate the different types in distinct areas of the DC. For broken-case picking, bin shelving might be positioned in one area of the pick area, case flow in another, and storage drawers in yet another. Select rack might be in one area of pallet storage, pallet flow in another, and push-back or drive-in rack in a third area.
While on the surface this may seem to make sense, there is often a lost opportunity to better utilize the cube space in the DC, which would reduce the square footage requirement and the related cost of building or leasing a facility. Also, there is a lost opportunity to reduce travel, labor costs, and even alleviate safety concerns. Consider some of the following examples of combining storage types when determining how to design your distribution center.
Racking options above case flow rack
Often case flow rack is in its own corner of the world within the warehouse and the space above is not utilized. Also the case flow rack sections are compressed together and replenishing the case flow requires a fair number of employees with significant travel and the hand-off of replenishment product that has been transferred to pallet rack. The alternatives presented below utilize the overhead space but keep lift truck traffic out of the pick aisles.
One alternative is to position case flow underneath the push-back rack. The case flow can be built into the push-back rack structure. Not only will you utilize space more effectively, but now replenishment can be a one-step process within the same aisle with much less labor required. Space utilization in this scenario can be enhanced even further. With additional structural support, the push-back rack can extend out over the pick aisle, gaining additional storage capacity.
Similar to the push-back over case flow scenario above, case flow can be installed within a double-deep pallet rack system with a double-deep Reach Truck selecting and locating pallets above the case flow from the replenishment aisle. The pick-aisle side of the double-deep rack can have some protection added to prevent accidental falling of product in the pick aisle. This is normally a less expensive design than the push-back option, although there are some trade-offs.
Push back over pallet flow
In a case-pick operation, some of your fastest movers are well-suited to be picked from a pallet flow rack. If your picking can be limited to the floor level, install push-back rack over the pallet flow. This will allow fast replenishment, and once again, lift truck activity is kept out of the pick aisle.
Bin shelving over storage drawers
Storage drawers with dividers within each drawer are a good application for very small parts and better utilize space than the normal bin shelving alternative. However, typical storage drawer units are only chest high, and the space above is not utilized. To overcome this limitation, position a couple of levels of bin shelving on top of the storage drawer units to store additional product. This will reduce your requirement for other bin shelving in your facility.
Bins under wire decking
Similar to how case flow is normally positioned in a warehouse, bin shelving often is in its own area with all the space above typical 7' high bin shelving unutilized. Bin shelving can be positioned at the bottom level of the pallet rack. However, bin shelving is only 24"-36" deep with an 8"-12" spacer between rows. Wire decking over the bin shelving in many cases might prove to be the best use of space. The wire decking could be installed with back-to-back 30"-36" uprights or with one single deep 48"-60" upright. The positions over the bin shelving could be used for reserved storage of SKUs located in the bin shelving or as pick locations for slow-moving products that require more cube than the items in bin shelving.
Wire decking within pallet rack
In many DCs, managers will state that they are out of room and need more space and rack to put additional pallets of product. But after closer examination, a considerable percentage of pallet locations may be discovered to be only partially full with significant underutilization of space within pallet positions (honeycombing loss). A number of pallet positions could be subdivided into additional levels with wire decking used to support half-pallets or cases stacked directly on the wire decking. At one client's DC, 25% additional locations are being created by adding wire decking to store products that take up less cube than a half of a normal pallet.
Multifloor picking on mezzanines with pallet flow or case flow
The best situation to be in is to be able to have picking on the floor level. However because of the large number of SKUs within many distribution centers, the number of pick faces required dictate picking from multiple levels. Two- or three-level mezzanines with picking to conveyor from case flow rack or pallet flow rack can be an efficient solution. To either side of this pick area can be additional pallet flow (or push-back or drive-in) for reserve pallets, depending on the number of apllets of each SKU normally stored in reserve.