Walls look simple and are not. A wall on a returnable box takes stack load, lateral load from the part shifting, impact from the outside, and it has to do all of that while staying light enough that the box is worth moving. Those four requirements pull in different directions, which is why wall construction is where most of the cost sits.
Thickness is not the same as stiffness
A thicker panel is stiffer, but so is a thinner panel with a better-supported edge. Because the panels on a box are short-span, edge support matters more than in a long unsupported sheet. That is why a well-designed box often uses a thinner wall than people expect and wins its stiffness at the corners and the base. It is also why a box that rattles is usually an edge problem rather than a panel problem.
Skin and core are doing different jobs
The core resists shear and holds the skins apart. The skins carry the bending. In a box wall the loads are rarely pure bending, so a heavy skin on a light core is not automatically the right answer. For a wall that takes repeated impact, a more forgiving core and a modest skin frequently outlasts a stiff, brittle alternative, and it dents rather than cracks. Which is better depends on whether the wall is knocked from outside or loaded from inside.
Edges are where walls are decided
An exposed honeycomb edge is an open invitation to a folded corner. The edge has to be closed, and it has to be closed in a way that does not introduce a hard, brittle line where the panel wants to hinge. Sealed edges, bound edges and capped edges all behave differently under impact, and the failure mode is usually a delamination that starts at the edge and creeps inwards over a few months.
Vented or solid walls
Solid is the default and is right for most parts. Vented walls matter for anything that can hold condensation, for parts that must not trap moisture, and for boxes that are washed and need to dry. The trade-off is stiffness and dirt: a vented wall is weaker and the holes collect debris. If a box is going to be washed weekly, ventilation or drainage at the base matters more than wall vents.
Wall joints and the hinge problem
Every wall on a returnable box has a joint, and every joint is a hinge unless it is restrained. Riveted, stitched, welded and pin-and-socket joints all exist for good reasons, and the choice follows from whether the box is permanently assembled or knocks down. A permanently assembled box with a weak joint will wobble for a year and then fail at the joint rather than the panel. This is the same structural question that appears on corner reinforcement.
Impact from outside is the harder case
A box in a plant gets hit by other boxes, by forklift tines, by trolleys and by whatever is on the other side of the aisle. External impact is rarely in the design brief and it is the single biggest cause of cosmetic retirement. Where impact is expected, the answer is usually a sacrificial component, an outer rail or a replaceable lower band, rather than a heavier wall. Making one cheap part absorb the damage is nearly always better than making the whole box heavier.
Thickness in practice
For a box up to about 600 mm internal height carrying a few hundred kilograms, a moderate wall with well-sealed edges and a reinforced lower band covers most applications. Above that, the walls stop being the governing part and the base and the stacked corner posts take over. If a supplier is quoting one thickness for every size in a range, the range is a catalogue rather than a design.
What we can do
We make PP honeycomb board boxes wall by wall rather than size by size, so the thickness follows the load case and the wear points are replaceable. Send the part and the loop; we will tell you where the wall has to be strong and where it does not.