Paperboard Grain Orientation Effects on High Speed Vacuum Cartoner Extraction
Aligning paperboard machine direction perpendicular to the pull axis maintains panel flatness under suction, preventing extraction jams at high machine speeds.
Air Permeability
Structural Porosity
Measurement of the rate at which gas passes through a fibrous structure under a constant pressure differential establishes the primary standard for openness in packaging substrates. Standard test procedures for air permeability utilize a clamped specimen area subjected to a fixed pressure gradient to gauge the density of the sheet. It determines the migration of coatings and the drying speed of print inks during high-speed converting runs.
Measurement Protocol
Testing instruments apply a known volumetric flow through the paper matrix and monitor the resulting backpressure to calculate the resistance of the material. Low values for air permeability often indicate highly calendared or heavily coated surfaces that resist moisture absorption. The calculation typically uses Gurley seconds or Bendtsen millilitres per minute to express the time required for a specific volume of air to pass through the sheet.
Production Impact
Converting equipment relies on consistent porous behaviour to prevent vacuum feed failures on automated cartoning lines. When air permeability fluctuates widely, it disrupts the suction cups that pull flat carton blanks from the feeding hopper. Adjusting the refining intensity of the pulp slurry during stock preparation provides the primary control mechanism for this physical property before the web enters the forming section of the paper machine.
Proper monitoring ensures that subsequent coating steps do not cause blistering or uneven ink lay during multi-colour offset lithography. Operators modify the starch application at the size press to seal open pores and establish a uniform barrier.