1A – Dealing with Imperfect Webs

All webs are imperfect, but with worsening magnitude of imperfections waste increases, productivity decreases, and profits suffer.

This set of recommendations does not reduce the camber, bagginess, or curl in your product but aims to improve handling the imperfect webs with reduced waste.

Primary Problems:

  • Baggy web without sufficient tension will wrinkle at most nipped rollers and winding
  • Baggy lanes will more easily wrinkle or fold over in long spans
  • Lateral shifting in air flotation ovens and air turns
  • Wound roll tightness variations for wide rolls
  • Slit roll tension and tightness variations in lock shaft winding
  • Lay-flat or laminate curl complaints from customers
  • Curled web may fold over in handling, especially in long spans.
  • Curled web will fail customer flatness requirements.

Secondary Problems:

  • Coating variations in tension dependent coating methods
  • Backside corona treatment
  • Post-slitting lateral motion of slit strands
  • Crossweb registration errors
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1B – Baggy & Cambered Webs

Webs have do not lay flat or roll out straight due to variations in length versus CD position.

Primary Problems:

  • Wrinkling at most nipped rollers and winding
  • Wrinkles of lateral shifting in long spans
  • Lateral shifting in air flotation ovens and air turns
  • Wound roll tightness variations
  • Lay-flat or laminate curl complaints from customers

Secondary Problems:

  • Coating variations in tension dependent coating methods
  • Backside corona treatment
  • Post-slitting lateral motion of slit strands
  • Crossweb registration errors

There are many methods to qualify or quantify bagginess.

  • Most are difficult, expensive, or time-consuming.
  • Cambered webs are rated by rolling them out and measuring deviation from a straight line.
  • A manual pull out and 1-to-5 grading may be the simplest.
  • For some films and papers, roll hardness profile can be a useful predictor of bagginess.
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1C – Curled Webs

A web has length or width variations through the thickness of the product and does not lay flat without the help of gravity or tension.

Curl can be predominantly in the MD, CD, but can also be strongest at an angle or seek to curl in all directions.

  • Curled web may fold over in handling, especially in long spans.
  • Fails to meet customer requirement for untensioned flatness in their end use.
  • Curled web may create problems in web line threading and roll transfers.
  • Curl is best measured in narrow strip samples.
  • Cut an ‘X” in the web and see which direction the MD and CD triangular cutout curl.
  • Strip samples are usually cut in the machine or crossweb direction, but may be cut at any angle.
  • Curl can be quantified by radius of curvature.
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