1. Background of Data Analysis
3-3. Relationship with Schedule Charts
The fundamental principle of work time schedule design in a distribution center lies in "calculating backward from the shipping (departure) time of trucks, which is the final process, tracing back to upstream processes to specify work time slots and cargo volumes."
Assembling tasks in a forward direction starting from inbound receiving time or work start time creates risks of missing shipping deadlines or overwhelming equipment and labor due to work concentrating in specific time slots. Because absolute delivery deadlines exist in distribution centers to "have trucks depart by designated times," all work processes must be calculated along a pull-type (backward-calculated) time axis originating from shipping times.
2) Logic of Calculating Time and Cargo Volume Backwards from Shipping Time to Each Upstream Process
This is the specific calculation procedure that clarifies "at what time, in which process, and how much volume processing capacity is required" by calculating backward from shipping deadlines to upstream processes.
【Process 1】 Loading at Outbound Docks & Truck Departure Process (Benchmark Point)
- Time Identification: Set the loading completion target time (16:30) as the starting benchmark point, calculated backward from scheduled truck departure times (e.g., 17:00 departure) and the time required from arrival to loading completion (e.g., 30 minutes).
- Volume Calculation: Identify total case counts and total pallet counts to be loaded onto that flight, deriving the required number of outbound docks and loading staff processing speeds.
【Process 2】 Packing, Outbound Inspection, and Staging Process
- Time Identification (Tracing Back): All items must complete packing and inspection to be assembled at the outbound dock prior to loading commencement (16:30). Calculate backward through packing, inspection, and staging operational times to set target work completion times (e.g., 15:30 to 16:30).
- Volume Calculation: Calculate hourly packed shipping case counts and inspection scan counts. Estimate automated sealing machines, packing station counts, and outbound inspection staging buffer areas.
【Process 3】 Picking and Order Sorting Process
- Time Identification (Tracing Back): To supply products to the packing process, trace back further to set completion times for picking and sorting (e.g., 14:00 to 15:30).
- Volume Calculation: Identify case counts for case picking and line counts (pick frequencies)/piece counts for piece picking by time slot. Calculate required processing volume per peak hour to derive necessary DPS (Digital Picking System) locations and sorter (automated sorting machine) processing capacities (pieces/hour).
【Process 4】 Retrieval from Storage Area and Replenishment to Operational Racks
- Time Identification (Tracing Back): To prevent inventory in picking areas (flow racks or operational shelving) from running out, replenishment must be completed prior to or concurrently with picking commencement (e.g., 13:00 to 14:00, or previous day / early morning operations).
- Volume Calculation: Calculate retrieval and replenishment volumes from storage areas equal to picked case and pallet counts. Estimate AS/RS (automated warehouse) retrieval cycle counts and forklift numbers.
【Process 5】 Inbound Receiving, Inspection, and Put-away Storage Process (Upstream Endpoint)
- Time Identification (Tracing Back): To avoid interfering with replenishment or shipping tasks, set the time axis to complete receiving, inbound inspection, and put-away storage starting from inbound truck arrival times (e.g., morning 8:30 to 12:00).
- Volume Calculation: Calculate hourly inbound truck counts, inbound case counts, and inbound pallet counts. Derive required inbound berth numbers, inspection area sizes, and put-away forklift counts.
3) Advance Operations for Shipping Leveling and Peak Staffing Allocation (Dynamic Shift Design)
To absorb hourly peaks without excessive machine investment or securing vast areas, operational leveling measures and dynamic staffing allocations are implemented.
【Leveling via Advance Operations (Batch Pre-Picking)】
To prevent concentration of work (bottlenecks) during peak hours, work is dispersed forward along the time axis.
- Pre-Picking Fast-Moving Standard Items (A1 & A2 Ranks): Fast-moving items with confirmed demand and zero stockout risk are picked and primary-extracted in advance during morning or previous-day off-peak hours.
- Pre-Assembly of Value-Added Services & Kitted Items: Promotional items and specified kitted products are created in advance outside peak hours and temporarily stored (buffered) near the packing area.
- Wave Batch Processing: Orders are wave-batched 1 to 2 hours prior to shipping deadlines for batch picking, dispersing concentrated loads on conveyors and packing lines.
【Peak Staffing Allocation and Cross-Skilled Worker Deployment】
Staff is dynamically deployed according to work load waves shifting across processes by time slot.
- Inter-Process Cross Support (Job Rotation): Peak waves shift sequentially: "Morning: Inbound Receipt/Put-away (8:30–11:00)" → "Afternoon: Picking/Sorting (13:00–15:00)" → "Evening: Inspection/Packing/Loading (15:00–17:00)." Cross-training staff and reallocating them alongside wave movements suppresses total headcount requirements.
- Spot Deployment (Utilizing Part-Time & Temporary Staff): In addition to full-time core staff, short-term staff is intensively deployed limited to work peak hours (e.g., 4 hours from 13:00 to 17:00).
- Required Staff Calculation Formula Based on UPH (Units Per Hour):
Required Staff Count ＝ Hourly Peak Required Processing Volume ÷ Standard Hourly Processing Capacity Per Person (UPH)
