Tray design decides half the protection — and half the cost
For the same product, a different thermoforming tray design can change transport damage several-fold and material cost by more than 20%. Good structural design is not “make it thicker”; it is balancing cavity fit, rib layout and stacking loads. Here is how to get those three right.
Cavity design: fit well, release easily
Cavities should be slightly larger than the product — typically 1-3 mm clearance for handling. Too tight and parts stick; too loose and they rattle in transit. For precision parts, support the load-bearing points instead of letting the part float. For long, slender parts, locating both ends is more stable than clamping the middle. Consider demoulding and manual picking too: undercuts and side recesses complicate tooling — use split structures or pick notches where needed.
Ribs and wall thickness: structure instead of material
Stiffness in thermoformed parts comes mainly from geometry, not raw thickness. Well-placed ribs — domed, corrugated or grid patterns — deliver the same bending resistance from thinner sheet, while shortening cooling time and lowering unit cost. Rules: run ribs along the main load direction; fillet the rib-to-wall junctions to avoid stress concentration; and keep ribs from becoming too tall and narrow (a height of roughly 2-3× width is a practical limit) or they form poorly.
Stacking strength: think beyond a single tray
In warehouses and containers, trays are stacked, so the bottom tray usually carries the greatest load. Estimate the bottom-layer load from the real stacking height and per-layer weight, then verify with a stacking test — ideally at ambient and elevated temperature to reflect transport. Stacking strength depends on wall thickness, rib layout, sheet material and how the product's weight is distributed. Where needed, reinforce corners or load paths locally instead of thickening the whole tray.
Material and thickness work together
PET/PETG offers good stiffness and clarity for display packaging; PP is tough and heat-resistant for heavier parts and recyclable applications; PS forms easily and costs little but is brittle and may crack under stacking; HIPS sits in between. Changing material means re-evaluating thickness and rib layout — never carry parameters over from the previous project unchanged.
Balancing cost: tooling, material and yield
The more complex the structure, the higher the tooling cost, the longer the cycle and the greater the yield risk. A pragmatic sequence: meet protection with the simplest structure, reinforce with ribs, and only then consider split or folded designs. High-volume parts justify optimising structure to use thinner sheet — the saving is ongoing material cost; low-volume parts should keep tooling simple to avoid heavy one-off investment.
Common design mistakes
(1) Cavities too tight — parts stick or get scratched on removal. (2) Thickening without ribs — cost rises but stiffness barely improves. (3) Skipping stacking tests — bottom layers collapse in real shipments. (4) Radii too small — sheet tears during forming or cracks at stress points. (5) Reusing structural parameters across materials — poor forming. All of these surface at the sampling stage if samples are tested with the real product weight and stacking pattern.
Summary
Thermoforming tray design is a balancing act: cavity fit, rib layout, stacking strength, material, thickness and cost all constrain one another. Tell us the product's weight distribution, shipping method and stacking height, and Jiushun can advise on structure at the sampling stage and verify it with stacking tests — avoiding rework after mass production.