High-Bay Warehouse with Stacker Crane
About this app
Stacker cranes run single, dual and relocation cycles live with real travel and hoist profiles. FEM 9.851 test cycle versus 20,000 simulated cycles, number of aisles from positions and throughput, beam check with ℓ/200 and the check point. Case DC Neckar.
With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.
How the cycle time of a stacker crane is determined
A stacker crane travels along the aisle and hoists at the same time. Each axis follows a trapezoidal profile of acceleration, travel at top speed and braking; the axis that takes longer decides. FEM 9.851 defines test points at which a mean single command cycle (storage or retrieval) and a dual command cycle (storage and retrieval on one trip) are calculated. Fork cycles and dead times are added. The cycle times give the throughput limit per aisle. The number of aisles follows from the larger of two requirements: pallet positions and throughput in the peak hour.
What the app shows
For the fictional distribution centre DL Neckar a high-bay pallet warehouse with pre-zone, check point and roller conveyors stands in 3D. Aisle 1 is cut open, and its crane shows a live clock with travel, fork and dead time. With the default values the FEM 9.851 test cycle gives a single cycle of 56.6 s and a dual cycle of 93.3 s. A simulation of 20,000 random cycles gives 59.3 s and 93.3 s for comparison. For 21,497 pallet positions the warehouse needs 6 aisles; throughput alone would require 3. The simplified beam check shows a deflection of 7.0 mm against a permissible 9.5 mm (ℓ/200).
What you can try
Change levels, bays, speeds, accelerations, fork and dead time and follow how cycle time, histogram and number of aisles respond. Switch to double-deep storage: positions per aisle rise, relocation moves cost performance, and throughput now decides the number of aisles. Increase the weight of the unit load until the beam no longer passes the check to EN 15512. The calculation panel shows every formula with the numbers used. Crane and rack values are disclosed teaching assumptions.
Frequently asked questions
- What is a dual command cycle of a stacker crane?
- A cycle in which the crane stores one pallet and retrieves another on the same trip. In the app it takes 93.3 s per FEM 9.851, while two single cycles take 113.2 s together.
- How is the cycle time calculated per FEM 9.851?
- The single cycle is the mean of the trips from the transfer station P0 to the test points P1 (0.2·L | ⅔·H) and P2 (⅔·L | 0.2·H) and back, plus two fork cycles and dead times. In the dual cycle the crane travels from P0 via P1 and P2 back to P0.
- Is distance divided by speed enough for the cycle time?
- No. Each axis has to accelerate and brake, and travel and hoist run at the same time. The longer of the two axis times counts, plus fork cycle and dead time.
- How is the deflection of a rack beam checked?
- The app treats the beam in simplified form as a simply supported member under distributed load and compares its deflection with ℓ/200 per EN 15512. At 1,000 kg per unit load it is 7.0 mm against a permissible 9.5 mm.
Subject: Warehouse and factory planning
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