Honeycomb Paper Core Size: 8, 10 and 15 mm Cells and What Each One Is For
Honeycomb paperboard is specified by thickness and by cell size, and buyers usually fixate on thickness. Cell size decides how the board behaves under a point load, how it crushes, how it cuts and how much paper it consumes. An 8 mm cell and a 15 mm cell can have the same thickness and the same edge crush value, and still be wrong for each other's application.
What Cell Size Changes
Cell size is the diameter of the hexagonal core. An 8 mm cell at 15 mm thickness gives about 55 cells per square metre; a 15 mm cell gives about 18. Smaller cells mean more wall material per unit area, a denser core, and a smoother top surface after lamination.
Density drives weight. A 15 mm board with 8 mm cells weighs 1.6 to 2.0 kilograms per square metre at 120 gsm liner; the same thickness with 15 mm cells weighs 1.1 to 1.4. That 30 percent weight difference is the main reason cell size appears on a specification at all.
Strength Numbers
Edge crush for a 15 mm board at 120 gsm liner runs 6 to 8 kilonewtons per metre with 8 mm cells and 4.5 to 6.0 with 15 mm cells. Flat crush runs 1.8 to 2.4 megapascals and 1.2 to 1.6 respectively. The smaller cell wins on both, because the unsupported span of liner between cell walls is shorter.
Under a point load, the difference is larger. A 100 mm by 100 mm pad loaded through a 25 mm indentor carries 900 to 1 200 newtons with 8 mm cells and 500 to 700 newtons with 15 mm cells before the top liner tears.
Cushioning Versus Strength
Larger cells give a longer crush stroke, which is better for cushioning a fragile product through a 1 metre drop. A 15 mm cell board compresses 8 to 10 mm before densification; an 8 mm cell board compresses 4 to 6 mm. For a 5 kilogram appliance, the longer stroke reduces peak G by 15 to 25 percent.
So the choice is not "smaller is stronger, therefore better". It is: small cells for stacking and point loads, large cells for drop energy and weight saving.
Paper Grammage and the Cell Wall
Core paper runs 100 to 140 grams per square metre. At 100 gsm the cell wall is thin enough that an 8 mm cell can buckle locally under 1.5 kilopascals of flat crush; at 140 gsm the same geometry holds to 2.4 kilopascals. Increasing grammage by 20 percent typically raises edge crush by 18 to 25 percent.
Do not mix grammage between lots without re-testing. A supplier switching from 110 to 100 gsm to protect margin will change the board's performance by 8 to 12 percent, and the change will not appear on the invoice.
Thickness and Cell Aspect Ratio
The ratio of thickness to cell size matters. Below 1.5 the cells are shallow and the board behaves like a thick paper; above 2.5 the cell walls become tall and prone to buckling. The practical window is 1.6 to 2.2, so a 15 mm thick board pairs with 7 to 9 mm cells, and a 30 mm board with 13 to 18 mm cells.
A 30 mm board with 8 mm cells is technically possible and rarely sensible: it uses 40 percent more paper than a 15 mm cell board of the same thickness for a 20 percent strength gain.
Matching Cell Size to Application
Furniture and appliance protection: 8 to 10 mm cells at 20 to 30 mm thickness, for point-load resistance and repeated stacking. Electronics cushioning: 10 to 12 mm cells, balancing stroke and strength. Pallet top decks and layer pads: 8 mm cells at 10 to 15 mm thickness, for flat crush. Lightweight dunnage and void fill: 15 mm cells, where weight and cost dominate.
Write the cell size, the core grammage and the liner grammage on the drawing. "Honeycomb board 15 mm" is not a specification; it is a category.
Cost per Square Metre
At 15 mm thickness, an 8 mm cell board costs 3.20 to 4.10 USD per square metre and a 15 mm cell board 2.40 to 3.10. The difference is paper consumption, not process. On a 20 000 square metre annual buy, that is 16 000 to 20 000 USD, which is real money and a reason to check whether the smaller cell is genuinely required.
Test both on the actual product before deciding. A drop test with an accelerometer costs a day and settles the question with data instead of instinct.