WHQuiz Answer #9 - Nip Uniformity

Published: March 07, 2012, By Timothy J. Walker

WebHandlersQuiz 9: Nipped Rollers - What is a simple measurement to determine if two nip rollers are pressing together uniformly?

Footprint. Measure the machine direction contact length vs. cross-roller position. There are many options to measure footprint. One of the simplest is to lay down a piece of colored sticky tape with bubbles intentionally left trapped in the adhesive, then close the nip, open the nip, and measure the machine direction length where the bubbles have been pressed out. Alternately, stick a series of Post-It™ notes in pairs across from each other on eitehr side of a closed nip, tacking them to one of the nipped roller, then open the nip and measure the space between the note where the nip footprint starts and stops.

Gap. For extreme nip variations, shine a flashlight on one side and see if light appears on the other side. Alternately, use a thin feeler gauge or paper strip and see if there is a measureable gap anywhere across the nip footprint.

More on this topic was covered in this archived Web Lines column: 

Mission: Detect Nip Variations Sep. 2010 

If you missed it, here are all 20 questions in my Web Handler's Quiz.