Paper core crush strength, explained
Radial vs axial crush, what actually causes core failure, and how to spec a paper core against your roll weight and winding tension. A working guide for converters.
Core crush is the failure converters meet most and understand least. The two loads are different animals: radial crush presses inward around the circumference — winding tension and stacked rolls cause it — while axial crush loads the tube end-to-end, the way a clamp truck or vertical storage does. A core specified for one can still fail in the other.
What moves the number: wall thickness (the dominant factor), ply count and paper grade, adhesive coverage, winding angle, and humidity — moisture softens fiber, and a core that measured fine in January can flat-spot an August roll. Diameter matters too: at equal wall, a larger ID resists radial load less.
How to spec against it: give your supplier the finished roll weight, web tension, chuck type, storage orientation, and worst-case humidity. A good tube engineer specs the wall and construction from the load — not from a catalog page. That conversation is free here, and it comes with samples to prove on your own winder.
// RELATED: paper cores · tape & label cores · slitting & rewinding cores
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FAQ
What is the difference between radial and axial crush?
Radial crush is inward pressure around the core circumference (winding tension, stacking); axial crush is end-to-end loading (clamping, vertical storage). Cores must be specified for both loads they will actually see.
What causes paper cores to crush?
Under-specified wall thickness for the roll weight, humidity softening the fiber, point loads from chucks or clamp trucks, and long storage under stacked weight.
How do I increase core crush strength?
Increase wall thickness or ply count, upgrade paper grade, and control storage humidity. Send your roll specs and we will engineer the wall with you.