PFFC Archives
Web Lines Archive: Links to Paper, Film, and Foil Converter
I've written over 80 columns for the converting industry trade journal Paper, Film, and Foil Converter. All are archived at www.pffc-online.com in reverse chronological order.
Most people are searching for an answer, so I have organized the links to my PFFC columns by topic with description of each below.
| Topics/Titles | Date, and Description |
| Web Properties | |
The Long & the Short of Web Bending |
Sep03: How much force is required to bend a web? How does the force to bend the web change with span length (the distance between rollers)? |
Bending: Don't Get Bent Out of Shape
|
Feb07: How far can you bend a web until an edge goes slack? How much force does it take? |
Twisting: Twist & Shout
|
Jan07: How far can you twist a web before the center goes slack? Why is this common twisting specification not conservative enough? |
Who Likes Film?
|
Jan05: Why do customers like products made with films? What are the advantages and disadvantages from a process engineering viewpoint? |
| Traction | |
Optimizing Traction: Goldilocks and the Three Bears Deal with Traction Problems |
Aug02: A high level of web-roller traction will prevent slip and scratch problems. A low level of web-roller traction may prevent web wrinkles from forming? Is there a window between high and low traction where both wrinkles and scratches are prevented? |
A Slippery Answer to Web Scratching |
Jul03: How much slippage is required to scratch a web? |
Five Questions and Answers on Lubrication |
Oct02: A short Q&A session to help understand web-roller air entrainment, lubrication, and loss of traction. |
Roughness and Grooving to Prevent Lubrication:Are You Rough Enough?If Not Rough, How About Groovy?
|
Feb06: What roller roughness is required to prevent air lubrication (and slippage) as a function of roller radius, speed, and tension? Mar06: What common roller groove patterns are used to prevent air lubrication? Which ones work the best? |
Friction Circles on a Winter's Day
|
Jan04: What can you learn from driving around in a snowy parking lot that will help you understand some odd web handling friction effects? How does the concept of friction available for machine and crossweb direction demand help explain strange steering, wrinkling, and winding behavior? |
Get a Grip: Driving Your Web |
Jan08: Design all driven rollers with traction sufficient to support your apparent or actual tension differential between tension zones. If your driven pacer roller slips, you lose control of line speed. If your driven follower rollers slip, you lose tension control. |
In Search of Tension Isolation |
Oct07: Though the sufficient drive roller friction prevents slip, it is incorrect to say the non-slipping pull roller provides tension isolation where the tension in one zone is totally independent of another. 'Tension isolation' is often defined as a drive roller with available friction higher than the tension differential of the two zones it separates; however, tension isolation is a myth. How does strain transport bust the myth of tension isolation? |
| Roller Design | |
Idler Roller Bearings: Living the Good Long Life?
|
Jun08: Idler roller bearings can have extremely long life expectancies if you consider a few real-world factors. |
Support Your Rollers |
Sep07: How should a roller be supported or attached to your equipment? |
The Spin on Idler Roller Testing
|
Jun08: Three tests I recommend for measuring idler roller performance: break-away drag, at-speed, and spin-down testing. |
| Air Floatation | |
Whatever Floats Your Web
|
Jul06: How and why can a cushion of air be used in place of a roller? |
| Tension Control | |
Do You Have a Need for Speed?
|
Oct08: Here is a checklist of what to consider as you think about moving to higher process speeds. |
A Wealth of Accumulators
|
Sep08: A web accumulator is a safe place to keep extra web in a buffer between two sections of a web line running temporarily at differing speeds. Most accumulators are found at either end of a web line, buffering between the main constant speed process, such as coating or printing, and the stop-start processes of splicing at the winders. |
Dancer Rollers: Trust But Verify
|
Nov06: Dancer rollers are an excellent way to close the loop in a tension zone, but they do not provide a good indication actual magnitude and variations of tension. Why not? How do you verify, then trust the tension in a dancer regulated zone? |
Web Tension: A Pop Quiz
|
Oct06: A short quiz to determine if you tension control plan passes the grade. |
Drawing Conclusions: Part 1, Part 2 |
May-Jun05: How is the tension created in an open-loop speed ratio zone? What are the advantages and disadvantages of using open-loop speed ratios to control tension? |
Why Tension?
|
Feb05: What are the benefits of tensioning a web in any converting process? |
Well Done Tension
|
Sep02: Why is a load cell or tension transducer roller a great idea for any converting process? How is using a load cell in tension control like using a thermometer in an oven? |
Mapping Your Way to Better Tension Control
|
Apr02: How do you determine the tension control plan for any converting process? How many tension zones do you have? Where is the pacer? Are the zones closed or open loop? |
| Lateral Position Control / Guiding |
|
Going with the Parallel Flow |
Aug03: How do well-aligned, non-slipping rollers promote centerline tracking? |
Your Guide to the Right Web Guide |
Apr08: There are four types of web guides: Unwind sidelay guides, rewind chaser guides, displacement guides, and steering guides. Which is the right one your unwinding, intermediate, or winding alignment need? |
Steering Directions Made Simple |
Jul04: Steering guides appear simpler, since they are often a single actuating roller. Don't be fooled. Thinking a single-roller steering guide is simpler than a two-roller displacement guide is like thinking a unicycle is easier to ride than a bicycle. Simple in design does not always mean simple in use. |
Strand Tracking Problems on Your Slitter/Rewinder
|
May02: Good side wall alignment after slitting usually relies on maintaining the lateral registration from slitting. What slitter designs promote or degrade slit to wind tracking and alignment? |
| Nips & Laminating | |
Under Pressure (Revisited...and Revised) |
Mar-Apr07: What is the pressure in your nip? How does one set of nips compare to another? What if you change roller diameters, rubber hardness, or covering thickness? If you want to double the pressure in the nip, how much do you need to turn up the load? |
Who's Driving This Nip? |
Dec08: What is the best way to drive a set of nipped rollers? Two rollers and two drive options (driven or not) lead to four options. |
Shifty Answers to Nip-Induced Tracking |
Nov08: Imperfect nips, where the load is uneven, can create process variations, but they also may induce a lateral shifting of your web, leading to misalignment or wrinkling. |
Deflecting Nip Roller Problems?
|
Apr06: Can roller deflection be compensated for by intentionally misaligning nip rollers? If so, whether intentionally or unintentionally, how much will crossing rollers compensate for deflection? |
Get Out of the Scroll Business
|
Mar05: What causes curl in laminates and webs? How is curl avoided or minimized? |
Can This Lamination Be Saved? |
Sep04: How can you avoid delamination in handling your laminate? |
Reduce Web Nip Problems
|
Feb04: Nipped rollers are used in many web processes. What are common nip-related problems and how are they minimized or eliminated? |
| Wrinkling & Spreading |
|
How Much Misalignment Is Trouble?: Part 1, Part 2
|
Jan-Feb09: Some products gain more from precise alignment, while other products quite likely are insensitive to misalignment. How do we know what the alignment specification goal should be for a specific product? How does web width change the answer? |
Converting Rx for Bowed RollersConverting Rx: Bowed Roller Dosage |
Nov-Dec05: A two-part column on bowed rollers. Part 1: Where are bowed rollers appropriately used? What are their advantages and disadvantages? Part 2: How much bow is required for spreading slit strands? For fighting wrinkles? What is the disadvantage of too much bow? |
Ten Tips on Antiwrinkle Rollers
|
Oct04: If you want to try an anti-wrinkle roller, here are ten tips to help correctly apply them. |
Tracking Wrinkles: Part 1, Part 2
|
May-Jun04: Tracking wrinkles are a family of wrinkle cause grouped together due to their common mechanism of the left and right sides of the web tracking towards the center, meeting in the middle with compressive stresses to form a wrinkle. Understand the mechanisms and common places tracking wrinkles occur. |
The Signs of Shear Wrinkle
|
Aug04: Web bending is almost always accompanied by out-of-plane buckling in the bending span. The bending lateral shift may be difficult to see with the unaided eye, but the buckling or troughing in the span will tell you which way the web is bending. |
Small Flexing, Big Benefits
|
Nov03: A flexible spreader is a roller with a thick, soft rubber covering with biased grooves cut in the rubber angled inward from either side. How a flexible spreader works is commonly misunderstood. Learn why the web may move laterally more than the rubber flexes. |
Where Does a Spreader Spread?
|
Oct03: Spreader rollers are used to separate slit strands or to pull out web bagginess and troughing to prevent wrinkles. Understanding the mechanism of where a spreader tries to move the web laterally will help apply them correctly. |
| Tale of the Tape (PDF) | Mar01: (written for Flexible Packaging) Guidelines to creating a concave (a.k.a. reverse crowned) roller with bands of masking tape. |
Concave Rollers Pros & Cons |
Jul05: Concave rollers and taped collars on rollers are a great and effective anti-wrinkles / spreading technique that works on many products. This article covers how they work and the pros and cons of their use. |
| Winding Process | |
Winding Better Rolls |
Jun03: My feature article (longer than my columns) on the advantages of controlled gap and nipped winding. |
Winding: What We Know & What We Don't Know
|
Aug08: Our understanding of winding can be broken into three areas: the winding process, winder design, and wound roll quality. For each of these three areas, there are some things that are well or generally understood. There are also some mysteries for which we still need enlightenment. |
How to Drive a Winding Roll
|
Dec06: What is center winding? What is surface winding? What other choices are there to drive a winding roll? |
Difficult Winding: Part 1, Part 2
|
Jul-Aug06: What makes winding difficult? Three main factors: Isotropic elasticity in the radial and tangential directions (learn what that means), large buildup ratios (learn what that means), and unusual frictional properties. |
The Pressure of Winding Rolls
|
May06: How much pressure is within the wound roll? What determines whether pressures increase greatly as roll diameters increase or not? |
The Converting Relay Race: Part 1, Part 2 |
Aug-Sep05: When an unwinding supply roll runs out, your process will shut down until you can get a new supply roll spliced in. What are the key points to minimizing downtime at unwind splicing? |
Cinching Belt Tightening Gone Bad: Part 1, Part 2 |
Feb-Mar03: Cinching is motion of tightening a belt. Cinching in rolls leads to scratching and telescoping. How do the applied torques and internal roll friction determine when cinching occurs? |
Pyramids and Wound Rolls: Long-Lasting Quality
|
Mar02: A roll's structure is like a pyramid. The core and initial layers should be sufficiently stiff to support the outer layers in a roll. Taper tension is one of the key variables to make your rolls stable like a pyramid. |
| Winding Equipment | |
Differential Rewinding: Part 1, Part 2, Part 3 |
Nov02-Dec02-Jan03: A three-part column on how differential winding shafts work and help to remedy common post-slitting winding problems. |
Differential Winding Limits: Part 1, Part 2 |
Nov-Dec07: How do different differential winding shafts control torque and tensions? How do roll weight, inertia, and nip loads change differential shaft tensioning? What other limitations are their to different differential shaft designs? |
Support Your Rollers |
Sep07: How should rollers be mounted to your equipment for ease of maintenance and alignment? |
The Case for Automatic Splicing
|
Oct05: When is automatic splicing justified? When are zero-speed splicers used vs. at-speed splicers? |
| Web Bagginess | |
Baggy Webs:
|
Apr-May-Jul-Aug07: A four-part series on baggy webs. Part 1: What problems do baggy web cause? Part 2: How do you measure web bagginess? Part 3: What are the common cause of web bagginess? Part 4: How can you minimize problems with baggy webs? |
| Slitting & Cleanliness | |
Slitting Debris: Cracking the Case |
Nov04: What are the common causes of debris from slitting? How do razor, crush, and shear slitting compare? Where does slitting debris go? |
Stripe Slitting: The Challenge of Staying within the Lines |
Jun02: Why is slit-to-stripe registration likely to be seven times less accurate than your stripe-less slit width tolerances? What are the factors that make stripe slitting challenging? |
Why Isn't Your Slitter Running? |
Jan06: What determines the productivity of a slitter-rewinder operation? How important is slitter speed? How important is the order characteristics like roll width, length, and order size? Why is the title of this article the wrong question to ask? |
Clean Thinking |
Apr05: What can you do to clean up your converting operation? |
| Clean Up Your Act (PDF) | Mar01: (written for Flexible Packaging) How does web handling contribute to product cleanliness? |
| Process Integration | |
The Harms of Harmony |
Dec04: How do you find the origin of a repeating defect? |
Web Line Knowledge Offers a Competitive Advantage |
Feb02: Web handling is a process technology that is often overlooked since it isn't considered a value-adding process. However, web handling can definitely be a value-subtracting process as you run challenging materials or processes. |
| Miscellaneous | |
Understanding Stress: Linebackers, Leashes, & Superman: A Look at Stress |
Dec03: Most people don't think about tension in terms of stress (in units of force over area). This column puts some numbers on engineering stresses in our life. What stress are commonly at 1 psi, 10 psi, 100 psi, 1000, psi, 10,000 psi and above? |
Outsourcing Is Trendy, But Is It Right for Process Expertise? |
Jul02: Making the case for a dedicated web handling expert at your company. |
Web Lines: Thinking About New Equipment? |
Feb08: Here are some tips on what to consider when ordering new converting equipment for any web handling process. |
Fun with Force Gauges |
Mar04: A simple 0-50 lbf range force gauge is a useful tool for understanding web handling processes. Learn how to use one to help measure frictions, torques, and roll pressures. |
Can't Touch This (Web): Part 1, Part 2, Part 3 |
Apr-May-Jun03: What are the tricks of web handling used when you can't touch one or both sides of your web? Limited or no contact handling has many cases, including can't touch both sides, one side, center of the web (edges OK), web side A to side B, and others. |
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