WH Outline

Web Handling Table of Contents
Tensioning Webs	Rollers + Traction	Guide-Spread-Wrinkle	Winding + Winders

Tensioning Webs

Introduction to Tensioning What is web tension? Why tension a web? Web Mechanics What tension will break or deform a web? What are stress and strain? The Poisson's ratio? What is the right tension? What is the right tension for a laminated product? What are typical web tensions by product? What is elasticity? Viscoelasticity? What is web modulus? Strain, The Key to Web Handling   Why is strain important to speed control? Why is strain important to roller machining? Why is strain important to wound roll tightness? Why is strain important to laminating? Why is strain important to nipped rollers? Why is strain important to slitting? Why is strain important to roller alignment? Why is strain important to wrinkling? Why is strain important to spreading? Tensioning Basics How is tension created? Why is measuring tension a good idea? How is tension measured? How does a dancer roller set the web tension? How does an air pressure gauge set web tension? Tension Zones   What is a tension zone? What are pacers? What is a follower? How is the pacer selected? How many tension zones are needed?  Tension Control Basics How does closed-loop tension control work? What are pacers and followers? How is the pacer selected? How many tension zones are needed? Torque Control Basics What is open-loop tension control? Why use motors vs. brakes or clutches? How much torque is needed? Why is diameter feedback used with torque control? How is diameter measured? Speed Control Basics How is web speed or length measured? How are speeds controlled? How accurate is motor speed control? How does speed control affect tension? How are speed variations reduced? Draw Control Basics What is draw control? What determines draw in a machine? What is the relationship between draw and strain? How does draw control create tension? How are draw zones time dependent? Where and why is draw control used? What creates tension variations within draw zones? Tension Feedback How does a transducer roller work? What is a dancer roller? How does it work? What makes a good dancer roller system? What is an accumulator? Motors and Drives What is a drive? How is motor size determined? What types of motors are used in web handling? Should motor speed or torque be controlled? How fast does a tension loop respond? How is a tension control loop tuned? Tension Variations Over Time What causes tension upsets? (too low or high) What causes tension transients? (over time) What causes tension variations within a zone? What causes crossweb tension variations? Bending and Twisting What is a minimum bending radius? How far can you bend a web? How far can you twist a web? How much diameter change is significant? Baggy Webs What is a baggy or deformed web? What causes web bagginess? How is crossweb tension or bagginess measured? Where does web bagginess contribute to waste? How can you compensate for web bagginess? Tension in Laminates What is curl? What causes curl? How is curl measured? How can laminating tension create curl? How do you match laminating strains? Why balance the tension across a laminator? What is the effective modulus of a multi-layer web? Registration What is registration? Where is registration used? What causes registration errors? What is typical registration accuracy? What are mechanical and electronic line shafts? How is registration adjusted?

Rollers + Traction

Traction Basics What is traction? What causes scratching? How is scratching measured or quantified? What is coefficient of friction (COF)? How is COF measured? What is micro-slip? What is the friction circle? Traction Limits How much traction is needed on a idler roller? What are typical bearing drag torques? What bearings are used for idler rollers? How much traction is needed on a driven roller? When will the web slip on a wrapped (unnipped) roller? When will the web slip through nipped rollers? How is vacuum used to increase traction? Lubrication What is air lubrication? Can a nip roller eliminate the boundary air layer? What is the coefficient of traction (COT)? How is COT measured? How does roughness or grooving affect COT? What are the best groove patterns? Roller Basics How far should rollers be spaced? How is an idler roller specified? What is a cantilevered roller? How big should a roller be? Alignment What is level and tram? How is roller alignment measured? How should a roller be mounted to the equipment? How often should equipment be re-aligned? When should a equipment and rollers be manually adjustable? How do you keep a moving roller aligned, such as a nipping or dancer roller? Nipped Roller Basics  What is the pressure between a tensioned web and roller? What is the pressure between nipped rollers? Why do nips usually include a compliant roller? How should nip load be controlled? How does nip load affect rubber and web speed? What is the best web path to enter a nip? Rubber Covered Rollers What is Durometer? What durometer used by application? What are the most common rubber compounds? Nip Pressure Variations What cause pressure variations in nipped rollers? How are nip pressure variations measured? How can nip pressure variations be corrected? How does Durometer affect nip pressure variations? Air Flotation and Drag Bars How is forced air used to handle a web? What is a web turn bar? Why are turn bars used? What is air flotation? Why is air flotation used?

Guide-Spread-Wrinkle

Introduction to Web Tracking What are your lateral position needs? What is the most accurate web positioning system? Tracking Rules What is the parallel entry rule? How much will a misaligned roller shift the web? How do roller diameter variations shift the web? How does web bagginess shift the web? How is traction important to web tracking? What passive ways are used to guide a web? Automatic Guide Basics Where are web guides used? What are the components of an automatic web guide? How is web edge, center, or pattern detected? What is the best location for the web position sensor? How is a web guide actuated? What determines a web guide's accuracy? What are the limits of a web guide? How can a web guide be used proactively? Automatic Guide Mechanics How does a sidelay unwind guide work? How does a sidelay rewind chaser work? How does a displacement guide work? How does a steering guide work? What is understeering? Oversteering? Wrinkling Basics What is a trough? A wrinkle? A crease? What causes a shear wrinkle? What causes a tracking wrinkle? What causes an expansion wrinkle? What causes an accumulation wrinkle? Wrinkling Remedies Why is traction important to wrinkling? How do span length and wrap angle affect wrinkling? What is a kiss roller? How are wrinkles measured or detected? Spreading and Anti-Wrinkle Rollers What is a spreader roller? What is an anti-wrinkle roller? How much spreading is required to prevent wrinkling? Can you spread too much? What the best way to spread slit strands? What is the best anti-wrinkle roller? More on Anti-Wrinkle Rollers How does a bowed roller work? How does an expanding surface roller work? How do biased edge nips work? How does a flex expander work? How does a concave roller work? How does a hyper crowned roller work? Do spiral tape bands, grooves, or ridges spread a web?

Winding + Winders

Introduction to Winding What is the purpose of winding? What is a good roll? What is a roll's buildup ratio? How can I calculate roll size or length? What are the torque requirements of winding? The Winding Process What are the key process variables of winding? What is center winding? (and center unwinding?) What is surface winding? (and surface unwinding?) What is taper tension? What is nip-induced tension? Nip and Gap Rollers What are the advantages of using a gap roller? What are the advantages of using a winding nip? Does a nip roller exclude air from a winding roll? How do web roughness and porosity affect winding? What is the best geometry for wrapping a winding nip roller? Wound Roll Pressure How does pressure build up as roll size increases? What are the key web and roll properties of winding? What is the stack or radial modulus of a roll? How is stack modulus measured? How is internal roll pressure measured? How much pressure is needed in a roll? How does core stiffness affect internal roll pressure? Winder Design What are the most common winder designs? When is center winding used? When is surface winding used? When are winding shafts vs. chucks used? What is the best way to load or unload a roll? Why is winding two rolls on one axis difficult? What is differential winding? What should be included in a winder specification? Splicing and Roll Transfers How are automatic roll transfer completed? What is a zero speed splicer? What is a flying knife or stationary knife transfer system? Cinching and Telescoping What is torque capacity and how much is needed? How is torque transmitted though the layers of a winding or unwinding roll? What causes cinching in a roll? How is torque capacity improved? What causes shifted layers in winding? More Winding Defects What causes starring or spoking in a roll? What causes dimples in a roll? What causes knots in a roll? What causes roll dishing? What cause MD lines or ridges in a roll? Winding and Thickness Variation What is roll hardness? How and why is roll hardness measured? How do crossweb thickness variations affect a roll? What is oscillation winding? Why do it? What makes winding difficult?