Husbandry-Derived Loading and Multi-Criteria Lightweight Design of an Industrialised Three-Tier Breeding Rack for Whitmania pigra and Hirudo nipponia

Rearing Whitmania pigra and Hirudo nipponia relieves the hirudin feedstock shortage, and the rack sets its cost and the animals’ environment; earlier designs were judgement-based. Six husbandry requirements become load and geometric inputs; limits (SFy ≥ 2, SFb ≥ 2, and δ ≤ L/200) screen 36 tube and rank 17 bar schemes. The machine is three tiers of one pan, sized by the credible accident (pans full to their rims, 1417 L each, 47.1 kN), not by the 20–60 mm operating depth, where nothing approaches a limit. The three-ring frame is 74.9% of the baseline, so tubes and bars can save at most 25.1%; the tube number governs the mass (61.26%) and stress (74.32%), and strength governs 34 of 36 schemes. Three 30 × 30 × 2.5 mm tubes with eight 5 mm bars weigh 101.34 kg, 18.4% below baseline, at SFy = 2.09 and SFb = 3.35 on the 235 MPa minimum for Q235; the lightest section breaks at 315 mm and this one at 481 mm. The 1.1% lighter 25 × 25 mm section clears the criterion only where the capacity and scaling both favour it; the ±8.3% band on the connection factor exceeds the 4.6% margin, its lower end falling below 2.0; one measurement closes it.