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Strain Control Unwind Method

IP.com Disclosure Number: IPCOM000126496D
Publication Date: 2005-Jul-21
Document File: 2 page(s) / 16K

Publishing Venue

The IP.com Prior Art Database

Related People

Gregory Fromm: AUTHOR [+2]

Abstract

Some of the elastomeric raw materials used in the production of personal care areas have material properties such as stretch, basis weight and thickness that change from the outside of the roll to the core. Variation in such properties can affect material consumption, product dimensions and overall process control. Using a strain control unwind method can reduce material consumption, decrease the variability in roll circumference and decrease overall process variability.

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Strain Control Unwind Method

Gregory Fromm and Paul Weber Kimberly-Clark Corporation

Neenah, Wisconsin

Abstract

Some of the elastomeric raw materials used in the production of personal care areas have material properties such as stretch, basis weight and thickness that change from the outside of the roll to the core. Variation in such properties can affect material consumption, product dimensions and overall process control. Using a strain control unwind method can reduce material consumption, decrease the variability in roll circumference and decrease overall process variability.

Background

Conventional raw material unwind systems typically use a closed-loop process control system, an unwind spindle assembly and an air- or weight-loaded dancer bar or festoon carriage to control web tension from the top of the roll to the core. A position sensor (e.g., a Quik Stik linear position transducer manufactured by Gemco, Inc., Southington, Connecticut) determines dancer or festoon carriage position then adjusts unwind spindle speed to maintain consistent position and through-roll web tension levels. This control method works well for materials with consistent machine directional stretch, machine directional tension and thickness. Some of the elastomeric materials often used in production of disposable absorbent articles have material properties such as stretch, basis weight and thickness that change from the top of the roll to the core. Conventional unwinds will not compensate for changing elastomeric properties, resulting in increased raw material consumption, potential increases in machine cull waste, and products that may not conform to target product design criteria.

We describe a web control method for controlling material consumption by printing a set of marks or "eye spots" at known machine direction spacings on a moving web. The spacing between eye spots can be measured when the web is under minimal (normal elastomeric converting) tension and after the web is stretched to the desired length, prior to and maintained around the construction drum, during product construction. Unwind spindle speed, dancer tension or feed roll speed could be adjusted to control the amount of material that is introduced into the process.

Strain Control Unwind Method

Conventional raw material unwinds are designed to maintain consistent tension at the exit of the unwind regardless of the diameter of the unwinding roll. Conversely, the Strain Controlled Unwind Method described herein can be designed to minimize the effect of through-roll elastomeric web inconsistencies by automatically adjusting unwind spindle speed, dancer pressure, or feed roll speed to provide consistent material feed regardless of roll diameter. Elastomeric web feed inconsistencies are caused by changes in through-roll basis weight and elastomeric properties (stretch-to-stop, modulus of elasticity) and fundamental winding principles.

The method described herein can provide consistent t...