Machine Direction Stiffness

Conversion Performance

High-speed packaging lines require a substrate that remains flat and resists bowing under the weight of the contents. Adequate machine direction stiffness ensures that the carton panels do not bulge when the product is inserted at high velocity. If the board is too soft, boxes collapse.

Converting equipment is designed to take advantage of this directional strength by orienting the vertical panels of the box with the strongest axis of the material.

Measurement Standards

Laboratory technicians use a Taber or L&W tester to apply a specific bending force to a standardized strip of the material. The result of this test provides the machine direction stiffness value used by engineers to calculate the theoretical stacking strength of a design. Factors such as fiber type, refining intensity, chemical additives and moisture levels influence the final reading.

Achieving the correct balance of stiffness and flexibility is necessary to prevent the board from cracking at the score lines.