High-bay warehouse: how many rack aisles and stacker cranes are needed?
Enter the number of pallet positions, peak-hour throughput and building height — the calculator returns the number of aisles, aisle length, number of levels and whether a spare crane is needed. Below are five game levels comparing stacker cranes with shuttles.
What the model calculates, and what it doesn't
Stacker crane: double cycle (pick one pallet, store one pallet) calculated with the Bozer–White approximation for a rectangular rack: T = max(length/vngang, cao/vvertical), b = ratio of the two travel times, cycle ≈ T·(4/3 + b²/2 − b³/30) + 4 handling times. Each cycle completes 2 pallets.
Multi-level shuttle: one shuttle per level (cycle ≈ average travel of half an aisle out and back + 2 handling times); the lift serves the whole aisle with a fixed cycle per pallet. Aisle capacity = min(total shuttles, lift) — which is why the lift is often the bottleneck.
Level 4 — warehouse profile: keep 2,000 positions, one aisle, one crane (travel 2.5 m/s, lift 0.8 m/s); the number of levels determines height (1.5 m/level) and length (2,000 ÷ 2 sides ÷ number of levels × 1.2 m). Balance factor a = (H ÷ vlift) ÷ (L ÷ vtravel); rule: a ≈ 1, with 0.5–2 accepted per Mecalux (citing UNE 58912). The double-cycle model above peaks exactly at a ≈ 1.
Level 5 — real cranes: parameters of two stacker crane models taken from INFORM's product page (Panther TMHS-P1-1500-24, Lion SMHS-P1-1500-08): travel speed, loaded/unloaded lift speed, acceleration 0.5 m/s², fork speed. The cycle is calculated with acceleration (each axis t = d/v + v/a, or 2√(d/a) for short distances), with horizontal travel and lifting simultaneous; each pick/put = fork extension and retraction 1.25 m + 2 seconds positioning (assumed), averaged over 800 random position pairs. Results are 12–22% lower than the constant-speed formula.
Queue after 30 minutes = (demand − capacity) × 0.5 hours when demand is higher. Not calculated: frequency-based slotting (ABC), batch order sequencing, shared I/O, start-up and stopping times, congestion at the aisle-head conveyor. The figures are for comparing configurations, not for fixing CAPEX.
Frequently asked questions
Why does adding a shuttle not increase capacity?
When the lift is the bottleneck, every level must go through the same lift. Adding shuttles only increases capacity if the lift has spare capacity; otherwise, add a lift or shorten the lift cycle.
Does the stacker crane throughput the model produces match reality?
With a 60 m aisle, 24 m height, and speeds of 2.5 and 0.8 m/s, the model gives about 90 pallets/hour in dual cycle — in line with the figures suppliers publish for standard equipment. Higher-speed or lower-cost equipment will give different figures; enter your own parameters.
Have real project parameters? Send them to CGD and get feedback on the design scope
This simulation stops at the principle. For a specific project, CGD builds the model on real operating data and floor plan drawings.
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