Warehousing and Materials Handling
This domain tests warehouse flow design, slotting logic, picking method selection, handling technology and the KPIs that expose warehouse performance.
Functions and flow
A warehouse receives, put-aways, stores, picks, packs, ships and handles returns. Layouts follow I-flow (straight through) or U-flow, which shares docks and suits cross-docking and returns. Cross-docking moves goods from receiving to shipping with little or no storage, so it needs reliable inbound timing. Slotting places high-velocity items in golden-zone locations nearest the dispatch point; slot by pick frequency, not by unit volume. Honeycombing is wasted location space from partial pallet occupancy.
Picking methods and handling technology
Discrete picking takes one order at a time. Batch picking gathers several orders in one pass. Zone picking splits an order by area, wave picking releases work by schedule. Pick-to-light, voice and RF raise accuracy and throughput. Storage options span selective pallet rack (best access, lowest density), drive-in and push-back (density, poor access), pallet flow (FIFO), cantilever for long goods, AS/RS for high density and cube, goods-to-person pods driven by AMR, and conveyors for sortation.
KPIs
Dock-to-stock cycle time, lines and units per labour hour, order accuracy, inventory record accuracy, space and cube utilisation, on-time shipment, cost per order and per line, dock dwell time, and safety incident rate.
Worked example: does batch picking pay?
A shift handles 3,000 order lines. Discrete picking takes 30 seconds travel plus 20 seconds pick per line: 50 seconds x 3,000 = 150,000 seconds = 41.7 labour hours. At 7.5 productive hours per picker, that is 5.6, so 6 pickers. With batch picking of 6 orders per pass, travel is amortised to 5 seconds per line: 25 seconds x 3,000 = 75,000 seconds = 20.8 hours, requiring 2.8, so 3 pickers. The saving is three pickers per shift. The counter-argument is accuracy risk and sortation effort at the batch-breaking station, so the example justifies the change only if the batch station and verification are included in the cost.
Traps that cost marks
Slotting by SKU sales value rather than pick frequency. Maximising cube utilisation until accessibility and picking time degrade. Treating cross-docking as a storage strategy. Ignoring reverse logistics in layout design. Reporting pick rates without the accuracy and rework that accompany them. Forgetting that automation is justified by throughput, SKU count, accuracy need and labour availability together, not by technology appeal.