Converting Industry Terminology Glossary

Term Definition
Air Entrainment

The forcing of air between a web and roller or between layers of a winding roll on nonporous webs run at higher speeds. Air entrainment on rollers can cause loss of traction. Air entrainment in rolls can cause a variety of defects.

Air Flotation

The reduction of contact between a web and roller due to air entrainment.

Air Shaft

A device used for handling winding reels in the processing of web-fed materials, such as continuous-process printing presses.

Air Shear Burst

An MD shear tear roll defect caused by a nonuniform air buildup beneath the outer layer in front of a nip.


A material whose stress-strain relations vary with time or other factors. Anelastic materials are prone to creep.


A material whose properties vary with direction. For example, the MD is stronger than the CD. Even isotropic materials such as metal are anisotropic in a roll because the ZD stack modulus is less than the metal’s nominal modulus.


In the direction of a roll’s core.


Slang for an unwind.

Backtender’s Friend

An online CD hardness profile measurement instrument.

Baggy Web

A web with an uneven natural length or residual stress profile.

Basis Weight

The mass per unit area of a web. Common metric units are (g/m2). English units for the paper industry are often (lb/3000ft2).


An operator’s control console containing switches, lights, dials, meters, and other electronics.

Biaxial Stress

A state of stress with two nonzero principle stresses. Webs (MD and CD) and rolls (MD and ZD) are usually in a biaxial stress state.

Billy Club

A stick which is used to strike and sound out the hardness of a roll.


The layers in a blocked roll are stuck together due to interlayer pressure, nip, adhesives, etc. A blocked roll will not unwind well because the web will jump or tear at the unwinding tangent.


Paper industry slang for nonsalable paper.

Butt Roll

A narrow roll on the ends of a winding set that will be discarded. Butt rolls result when the total width of an order results in a trim that is too wide to be handled by the trim conveying system. Also called a cookie.


To run a web between nipped rollers.


The thickness of a web expressed in micrometers in the metric system and mils (0.001″) in the English system.


A disc brake pad.

Cameron Gap

A roll structure measurement test that determines the winding strain by severing the outer layer and measuring the resulting gap.

Capstan Wrap

The physics of a change of web tension from the ingoing to outgoing tangents as described by the band/brake or belt equation.


Abbreviation for Cross (machine) Direction, sometimes also abbreviated as XMD, which is the direction perpendicular to the material flow and material plane in a machine.


An imaginary MD line equidistant from both edges of a machine roller.


A winder whose roll is driven solely by torque through the core or mandrel.

Center-Surface Winder

A winder that drives the roll through torque at the core and through a nipping roller.


A term for metals in a wound roll form. However, this can also be used to differentiate the concentric hoop approximation of winding models from the spiral or coil of real wound rolls.

Combining Winder

A winder equipped with two or more unwinds whose webs are laminated together prior to winding.


The statistical probability that a conclusion is correct.


The processing of a web material from one form to another. Converting processes include calendaring, coating, die cutting, embossing, laminating, printing, punching, sheeting, slitting, treating, winding, and unwinding.


A narrow roll on the ends of a winding set that will be discarded. Butt rolls result when the total width of an order results in a trim that is too wide to be handled by the trim conveying system. Also called a butt roll.


A hollow tube upon which a roll is wound.

Core Box

Paper industry slang for core chuck or core shaft slides.

Core Burst

An unwinding defect near a core caused by nonuniform nip-induced slippage between a core and a heavy roll. The core burst tear starts on the edge of a roll in the CD as a tensile tear and will often bend toward the MD as a shear tear.

Core Chuck

A winder component that is inserted into a core to guide the edge position of a winding or unwind roll.

Core Slides

Linear ways or bearings that guide core chucks or core shafts during winding from moving sideways and causing roll offsets.

Core Shaft

A mandrel upon which rolls are wound.

Core Torque

A roll structure test that determines the radial pressure between a roll and its core.


A nip-induced defect, often caused by excessive CD caliper profile gradients, which results in a narrow circumferential band of diagonal wrinkles. Also referred to as rope mark and a host of other names.


A fold over of a web going over a roller or onto a roll.


The permanent deformation of a body with time subjected to constant load. Creep moves stresses toward zero while elongating tensioned material and shortening compressed material.

Crepe Wrinkle

A nip-induced defect that is a series of one or more buckles of MD compression in a roll that had an accordion-like appearance.

Critical Speed

A resonant speed of a roller or winder that results in high-vibration amplitudes.

Cross Direction

Direction perpendicular to the material flow and material plan in a machine often abbreviated CD or XMD.

Crushed Core

A core that has collapsed into a non-circular shape due to radial pressures between the roll and core.


To set aside a wound roll that doesn’t appear to meet quality specifications for either rewinding or scraping.


A sensor used for feedback control of web tension.


The small band spanning a control se tpoint within which a controller can neither sense nor react.


The small band spanning a control set point within which a controller can neither sense nor react.


The change of length, width or shape or a material subjected to loads or stresses.


Weight per unit volume. In English units density is expressed as (lb/in3) and in Metric Units is expressed as (kg/in3). Density can refer to either a web or a roll.

Density Analyzer

A computerized roll structure instrument that measures roll density a function of diameter.

Diameter, Current

The outside diameter of a winding roll at an instant in the winding cycle. The TNTs of winding are often programmed as a function of current diameter.

Diameter, Finish

The outside diameter of a wound roll when the winding cycle has been completed. Finish diameter is very often a product specification.

Dished Roll

A roll that is wound with a progressive edge misalignment that results in a convex shape on one roll edge and a concave shape on the other.


To salvage rewind on a roll on a brand of center winder called the Roll Doctor.


The percent increase (or decrease) of a roller’s speed with respect to an upstream roller.

Draw Control

An indirect method of control tension by controlling the speed of driven rollers.

Dress a Coreshaft

To lip cores onto a core shaft and lock them in place prior to winding.


Slang for an electric motor and controller.


A specialized roller often having a heavier wall, higher precisions, and specialized surfaces.

Duplex Winder

A winder that has rolls wound in a staggered fashion on two sides of a drum.


Short for emergency stop. This is a maximum deceleration of a machine to protect an operator, product, or machine from further damage after an accident.

Edge Guide

A sensor and controller for positioning one edge or centering both edges of a web or roller to a set point.


Materials that return to the same size and shape when loads are removed (e.g., doesn’t creep).


A branch of engineering mechanics that describes the elastic behavior of materials subject to loads.


Output from a sensor that is input to a controller for maintaining a control set point.


A thin polymer (plastic) web such as found in stretch wrap or garbage bags.


A final process in base web manufacturing such as calendaring.


The ZD vibration of a web that acts much like a plucked string.

Flying splice

A machine feature that cuts and splices a web onto a new unwind or windup roll without stopping.


Slang for nip width or nip pressure profile.


A force-resisting motion. Friction between webs and rolls is important because it determines whether the web will track or lose traction. Friction between web and web is important because it determines how stable a stack or wound roll will be. Friction on machines is important because it may compromise the sensitivity of measurement or control.


The distance between the drums on a two-drum winder.


Short for Cameron Gap. A roll structure measurement test that determines the winding strain by severing the outer layer and measuring the resulting gap.


Paper industry slang for interlayer slippage.


A specific web material. This term may be used broadly as a subclass of a basic material, such as bond is a grade of paper, or much more specifically as a set of process settings and acceptable test results with its own unique ID number.


Regular-spaced, ansular grooves cut into a roller on a lathe during manufacturing for purposes of reducing air entrainment.


Short for edge guide.

Guide Roller

A roller with one end that can be moved to tighten the front side of a web versus the back and vice versa.

Hard Edges

Paper industry slang for a high-caliper band on the edges of a web.


A circular disc of heavy cardboard that protects the ends of a wrapped roll during shipping and handling.


A material whose properties are uniform at any position. Porous or laminated materials are non-homogenous on a fine scale, but may be treated as homogenous on a large scale for many analyses.

Hook’s Law

A law that states that stresses equal the product of a material constant called modulus (or Young’s modulus) and strains.


A materials that tends to absorb or absorb water or humidity. Most paper is hydrophilic.


The behavior of a hydrophilic material in the presence of water or humidity.

Idler Roller

A roller that is driven by the web rather than by an electric motor, belt, or other external means.

Inertia Compensation

An automatic adjustment of the gain of a winder/unwind drive controller to avoid sluggish performance at large roll diameters and instability at small roll diameters.

Interlayer Slippage

The MD shear slip between two adjacent layers in a roll due to a nip.


A control safety permissive that must be met before a function is allowed. For example, the roll ejector button will not activate the roll ejector unless the cradle is sensed up to keep from dumping rolls on the floor.


The overlap of two adjacent webs in a set as they wind. The result is two rolls that are stuck together.


A measurement of nip-induced interlayer slippage during winding or unwinding.


To briefly run a machine at low (thread) speed to position a web or rollers.


A particular exponential curve fit factor for ZD modulus.

Lay-On Roller

Slang or a rider roller.

Load Cell

An electronic sensor that measures force. On a winder, load cells under the ends of an undriven roller are often used to measure web tension.


A large roll of paper wound as the end of a paper machine on a reel.

Loose Core

A roll with insufficient radial pressure between the roll and its core to withstand subsequent unwinding.

Lowering cradle or table

A winder component used to lower a roll from winding height to the floor.

Machine Direction

Direction of the material flow through a machine.


The process of producing a base web material.


Typical web materials include: paper, plastic film, metal foil, nonwovens and textiles.


Abbreviation for Machine Direction, which is the direction of material flow through a machine.


A body whose thickness is much smaller than its length and width. Most webs are modeled as membranes so that the negligible bending stresses can be ignored.


A roller or machine component that is not level and square with a reference.


A material property measure of spring rate, expressed in kN/m2 or MPa in the metric system, and PSI in the English system. It is commonly given the symbol E with subscripts 1,2, and 3 for the MD, CD, and ZD, respectively. Sometimes test results for modulus are improperly given in units of force/length (web physical property) instead of force/length2 (material property).

Moisture Welts

Regularly spaced bands of soft circumferential buckles in the outer layers of a roll caused by paper taking on moisture from humidity in the air. The result looks like a corrugated culvert pipe.


The (usually elastic) reduction of web width due to changes in MD tension.


To load two parallel roller(s) together. A nip between two rollers is used in calendaring, laminating, and printing. A nip between a wound roll and a roller (or drum) is one of the three TNTs of winding, which control how hard the rolls are wound.

Nip-Induced Defects

A variety of wound roll or unwinding roll defects that are precipitated by a roll external nip such as a drum or internal nip such as at a core.


An abrupt change of a wound roll layer edge position.


A material that has three mutually perpendicular directions of elastic symmetry. Most webs are orthotropic with distinct properties in the MD, CD, and ZD.


To cycle an unwind axially back and forth a short distance to avoid piling high-caliper areas of a web on top of each other to form roll ridges and other roll defects.

Paro Roll Tester

A brand of handheld roll hardness measuring equipment.


To drive an unwind very slowly to allow manual threading.

Poisson’s Ratio

The ratio of deformation in the transverse direction divided by the axial direction where a body is subjected to a uniaxial (one direction ) load. Poisson’s ratio describes necking and width changes.

Poor Start

Slang for when the winding near the core isn’t tight enough.


The rate of change of energy with time expressed as horsepower in English units and kilowatts in metric units. The power rating of drives and unwind brakes is determined by thermal limitations.


The variation of some web or machine property, usually with respect to the CD.

Pull Tab

A roll structure test that determines the radial pressure between layers in a roll.


In a direction perpendicular to a roll’s core

Reclaim Winder

An offline rewinder that attempts to rescue rolls that may have a variety of defects.


A large single drum surface (or center/surface) winder at the end of a paper machine.

Regenerative Drive

An electric motor drive, often found on unwinds, that is able to return roll or roller braking energy back to the power lines.


An intermediate winding machine for large rolls in the paper industry.


A winding machine typically composed of an unwind, slitters, and windup.


A unit of roll hardness used by the Rhometer.


A brand of handheld roll hardness measuring equipment.

Rider Roller

A nipping roller on a winding roll. Also called a lay-on roller.


A roll defect caused by high caliper bands that cause circumferential bands of a slightly larger diameter than the rest of the roll.


A web in wound roll form. This term is also used in the industry for rollers. However, in this text the use of rolls will be exclusively for wound forms to avoid ambiguity.

Roll Ejector

A roller or beam used to push a wound roll set out of a winder on to a cradle, table, or floor.

Roll Structure

The programming of the TNTs of winding to achieve a hard start near the core, a softer finish at the outside of the roll, and a smooth transition between.


A rotating cylinder used for web transport. Aliases include drums and rolls.

Rope Marks

A nip-induced defect, often caused by excessive CD caliper profile gradients, which results in a narrow circumferential band of diagonal wrinkles. Also referred to a corrugation and a host of other names.


A small, 1-5 second curve section between steady-state speed and an acceleration/deceleration ramp.


Abbreviation for the rotational speed of a roll(er) in Revolutions Per Minute.


A measure of the mean distance between web breaks on a winder or other converting machine.


The deviation of circularity of a roll or roller measured as TIR.

S Curve

A linear acceleration/deceleration ramp with a small amount of rounding on each end.

Salvage Winder

An offline rewinder that attempts to rescue rolls which may have a variety of defects.

Schmidt (Concrete) Hammer

A brand of handheld roll hardness measuring equipment.

Segmented Roller

A series of two or more coaxially located rollers. By segmenting rollers, smaller diameters can be used to avoid the requirement of a drive.


The ability to discriminate, measure, or control with great precision.


Several narrow rolls wound simultaneously.


A control setting (dial position, etc.) for a single process control variable.

Setpoint function

A control setting that is programmed to automatically vary as a function of current wound roll diameter.


To wind a roll on a mandrel as opposed to core chucks.


To wind a roll with chuck end support instead of on a mandrel.

Shear stress

A stress component that changes angles in a body. Shear stresses in webs are important because they may result in wrinkles. Shear stresses between layers in a wound roll caused by nips is important because slippage may result in roll defects.


To move an unwind sideways for purposes of aligning a web with downstream components.


Slang for linear ways or bearings that guide core chucks or coreshafts during winding from moving sideways and causing roll offsets.


To cut a web lengthwise.


A device used to cut the web lengthwise, often composed of two rotating cutting wheels.


A winder equipped with an unwind and slitter.

Slitter Rings

A geometrical pattern of tiny web offsets in a roll caused by runout slitter bands.

Smith Needle

A brand of handheld interlayer pressure measuring equipment.

Soft Edge

Slang for a low caliper area on the edges of a roll.

Speed Differential

The (controlled) difference in surface speed between two rollers, often expressed as a % difference. 


To join two webs together, usually with adhesive tape.


A device used to remove wrinkles in a web or separate slit webs.

Stack Modulus

The nonlinear ZD modulus of a stack that is used in the radial direction of winding models. This is sometimes referred to as the K2 factor used in a particular curve fit.


A defect, often caused by poor roll structuring, where the wound roll collapses and buckles internally. The visible result might appear as a single radial spoke caused by a handling impact, or as a series of evenly spaced radial spokes.


The change in length, width, or angle of a material subjected to stresses. Commonly expressed in units of 8length/length or %.

Strain Gage

A thin, flat electrical transducer for measuring strain that is bonded to a body of interest.


Force divided by area expressed in psi in English units and kPa in metric units. Pressure is one type of stress.


The ultimate strain of a material expressed in %.

Surface Winder

A winder that drives the roll through a torque nipping roll or drum.

Tangent Modulus

A measure of material stiffness that is the slope of the stress strain curve at a specified stress or strain.

Time Cycle

A procedure for analyzing the productivity of a winder.


A defect whereby the inner layers slip or break loose on an unwinding roll, allowing the roll to shift axially.


Stresses or forces that pull on the material, usually in its MD. Lineal tension for webs is expressed in lb/in in English units and kN/m in metric units. Stress tension for materials is expressed as psi in English units and kPa in metric units.


To manually pass a web through a machine prior to starting.


The axial push of a surface wound roll against a core chuck or core shaft.


Abbreviation for Total Indicated Runout, which is the change of radius as a function of rotational position on a roll or roller.

Torque Differential

The sharing of drive torque between a driven winding roll and a driven nipped roller or between two driven drums upon which is nipped a winding roll. Torque (or speed) differential is one of the three TNTs of winding. Often torque differential is referred to as merely torque.


No relative moment between a web and roller or between a roll and roller.


The width of a web.


A narrow slit on the edges of a web that will be discarded.

Trim Chute

A vacuum inlet for removing a trim strip from the edges of a web.

Tungsten Carbide

A thin flame deposition of a very hard material on a drum or roller. It can be used to enhance wear resistance, or in varying surface roughness, to increase web/roller or roll/roller traction.

Turret Winder

A center or center surface winder with two or more winding positions that are rotated into position for continuous winding.

Two Drum Winder

A winder arrangement where the winding roll set sits on top of two drum rollers, and may often be loaded from the top by a rider roller.

Ultimate Strain

The maximum elongation (m/m) of a material in uniaxial loading. This is called stretch in web tests and expressed in %. The ultimate strain is usually less in the CD than in the MD.


A web is a long, thin, and flexible structure. Common web materials include paper, film, foil, nonwovens, and textiles.


Short for basis weight.


Abbreviation for Wound-In-Tension.


Short for a Wound-In-Tension, Wound-Off-Tension lab winder for measuring roll tensions.


Sometimes abbreviated as WIT, this is the single outer boundary condition that results from the TNTs of winding. It is the tension on the current outer layer of the winding roll.

Wrap Angle

The angle between the incoming and outgoing tangent of a web on a roller, or equivalently, the angle the web defects as it goes over a roller.


A machine that applies a film or paper wrapping on a roll to protect it from surface damage during shipping and handling.


A generic term for a variety of out-of-plane web buckling defects. Wrinkles oriented in the MD are caused by CD strain, and wrinkles at a slight angle are caused by shear stresses.

Young’s modulus

A measure of material stiffness, which is the slope of the stress-strain curve.


Abbreviation for the Z Direction of a material. In a web, it is normal to the plane of the web. In a roll, this is the radial direction.