Norms and Standards
For the specification of paper honeycomb core products, Axxor adheres to the Technical Standards as defined by the European Manufacturers of Paper Honeycomb Association (EMPHA).
Paper properties (including paper type and paper grammage – basis weight) strongly influence the overall honeycomb properties.
Axxor makes a conscious decision to work with paper suppliers who can provide a high quality product at high volumes, with tight tolerances.
To measure the height of paper honeycomb, the EMPHA recommends the Gauge C shape height meter. The honeycomb must be 75% expanded when measuring the height. Then the height is measured at 10 intersections (see image) located in the production length of the paper honeycomb.
Cell Geometry according to EMPHA is a combination of the pitch and glue line width. Leveraging these definitions allows for transparent and objective comparisons between different cell geometries and anticipated material usage.
Glue Line width
The average width of the glue lines (joints where two sheets of paper are bonded together).
The glue line width can be determined by measurement of 10 glue lines and taking the average width.
The distance between the center of a glue line and the center of the second next glue line measured across unexpanded honeycomb.
There are several definitions of width that are regularly used in the honeycomb industry. Below, an overview is presented of the width parameters most commonly referenced.
Paper reel width
Different paper reel widths are used for the production of honeycomb. The paper reel width is generally indicated in cm or inches.
The width of the paper reel does not have to correspond to the width of the paper honeycomb.
Our products are produced and shipped in their compressed, unexpanded form, then expanded on-site at the customer location. This means that there are two widths that can be used when describing honeycomb width:
Unexpanded (measured when cells are closed)
Expanded (measured when cells are open).
The expanded honeycomb width is determined by multipying the unexpanded honeycomb width with the expansion rate:
Expanded honeycomb width = Unexpanded honeycomb width x Expansion rate
The relative width of the expanded HC when compared to its width in the unexpanded state, expressed as a percentage, is known as the Expansion Ratio. The calculation is as follows:
Expansion Ratio = Expanded Width / Unexpanded Width
This ratio helps ensure that cells are opened properly in your application. Many of the EMPHA tests must conducted when the honeycomb is at a 75% expansion ratio.
The Cell Indicator is the distance between two following glue lines in the machine direction (at a 75% expansion ratio) and is a relative indicator for the area weight (kg/m2 or lb/ft2) of the honeycomb.