Matching Thickness to Duty Cycle
PP sheet ranges from 2 to 10 mm and the right choice depends on what the box carries and how it is handled in service by the people and the machines that move it through the plant. Light totes for 5 kg parts use 3 mm; heavy bulk bins for 50 kg use 5 to 7 mm. Rulowin maps thickness to load with a simple rule: add 1 mm of wall for every 15 kg of rated content, capped by the base design and adjusted for any drop or stack condition that the standard duty cycle does not cover in the field where the box actually lives.
The rule is a starting point, not a substitute for testing, because the load shape matters as much as the mass does for the wall that carries it. A 15 kg point load on a small foot prints more stress than a 15 kg distributed load on a flat base, so the engineer should consider where the weight sits before finalizing the thickness. Rulowin’s application team walks the customer through this so the spec is right the first time and the box does not fail in service and generate a claim that the thicker wall would have prevented cheaply at the design stage of the program.
Compression and Drop Performance
Edge crush rises roughly with the square of thickness, so small changes matter a lot at the top end of the load range where the stack gets tall on the rack. A 4 mm wall holds 180 kg column; a 6 mm wall holds 340 kg. For drop survival, thicker walls absorb more energy, but foam or honeycomb lining can substitute for mass on fragile goods, letting you stay light and protect the product at the same time without adding the freight weight that a uniformly thick wall would impose on the lane.
The trick is to put the material where the stress is rather than uniformly thickening the whole part and paying freight on resin you do not actually need to carry the load safely through the journey. A targeted reinforcement at the corner and the base, with a thinner wall elsewhere, often meets the spec at a lower total weight, which is the kind of optimization that Rulowin’s engineering service provides to the customer who wants the cheapest compliant box rather than the heaviest safe one that overshoots the requirement and costs more to ship.
Weight and Freight Trade-off
| Thickness | Weight m2 | Rated load |
| 3 mm | 900 g | 15 kg |
| 5 mm | 1,500 g | 35 kg |
| 7 mm | 2,100 g | 60 kg |
| 10 mm | 3,000 g | 120 kg |
When to Upgrade the Base Instead
If load exceeds the wall limit, reinforce the base with a honeycomb footbed before thickening all walls uniformly across the box, because the base is where most failures start under a fork tine or a stacked column that presses down through the floor of the tote. That targets strength where stress concentrates, saving 20 percent resin versus a uniform thick wall that adds weight everywhere including the sides that do not need it for the load that the base actually carries in service during the trip.