Posts are the main load-bearing members when stacking cages; tube diameter and wall thickness directly determine how many layers the bottom cage can support without bending or crushing. When cages are stacked, the upper load is almost entirely transmitted downward through the posts, while the bottom frame is not the primary load path.
Common post specs are square or round tubes: standard cages mostly use 20×20×1.5mm or 25×25×1.5mm square tubes, medium cages step up to 30×30×1.5mm or 40×40×2.0mm, and heavy cages use 40×40×2.5mm or thicker. Tube diameter determines overall bending cross-section, and wall thickness determines local compression resistance—consider both together.
Rule of thumb for stacking: at about 500kg full load per cage, 25×25 square tubes generally stack 2 layers stably; above 800kg, start at 30×30 and stack 3 layers; for heavy cages above 1.2 tons, you must use thickened 40×40 tubes combined with stacking-foot sockets, otherwise the bottom posts are prone to bulging.
On acceptance, measure actual post wall thickness with a vernier caliper and watch for negative tolerance; check whether the post-to-base-frame joints are fully welded, with weld leg height no less than 1.5mm. Stack empty cages to the agreed number of layers and observe for 24 hours; if visible bending appears at the post bottoms, the spec is undersized.
Selection advice: report single-cage load and planned stacking layers together to the manufacturer, and let them calculate the post cross-section. Since its founding in 2013, Nanjing Tongnuo Warehouse Equipment Manufacturing Co., Ltd. has sized tubes by load tier, and supports delivering in bulk only after on-site stacking tests.