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Blogmaster: Dr. David Roisum

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Entries for 'David Roisum'

01

Mandrel/Spool/Roller Journal Safety

Posted by David Roisum on October 1, 2011
Thankfully, journal failures are rare.  However, when it does occur it is often catastrophic; things come loose; things that have mass and speed; things that clearly pose a safety hazard when they come loose. Most journal failures are due to fatigue at stress risers at the journal fillets; eve...

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Posted in: Design, History, Maintenance, Rollers, Safety, Winding
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29

Really Thick Webs

Posted by David Roisum on September 29, 2011
Are really thick webs subject to web handling laws? Of course. You can not break any laws of physics. However, the question is better posed as “are our current web-handling laws predictive for thick webs?” Here we are not so lucky as we were with strings. Thick webs are not necessarily a subset...

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27

String Theory

Posted by David Roisum on September 27, 2011
Is a string a web? In other words, does web-handling theory predict how a string will behave? The answer is yes in almost all cases. The reason is that a string is a subset of a web in the sense that the width or width to length span is effectively zero. Thus, any equation where zero (or at leas...

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22

The Wide-Shallow or Burping Groove

Posted by David Roisum on September 22, 2011
The Wide-Shallow or Burping Groove
The solution for the air bubble behind the winding nip described in the previous post was independently discovered in both the film and paper industries. A wide-shallow grooving had long been used in paper for reasons the designers could not articulate, but it prevented a problem we now know the me...

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Posted in: Rollers, Winding
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20

An (Air) Bubble in Front of a Winding Nip

Posted by David Roisum on September 20, 2011
An (Air) Bubble in Front of a Winding Nip
Air bubbles can accumulate behind a winding nip as seen below. The mechanics of air entrainment modeling taught us that the air entrainment increases with: increasing speed, decreasing WIT (web tension and especially nip), increasing web smoothness and decreasing web caliper. What modeling did not...

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Posted in: Nips, Winding
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16

Can you see air in a wound roll?

Posted by David Roisum on September 16, 2011
Sometimes. If you have a mostly clear web, such as many films, you can infer the amount of air in the roll by looking at how transparent the roll is. If the roll has very little air (wound tight), the roll looks relatively clear and if it has a lot of air it will look more cloudy or translucent. ...

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15

The Test for Air

Posted by David Roisum on September 15, 2011
How do you know air is involved in any particular problem? Simple, change speeds and note a response. Compare half speed with full speed. If you see a (web handling) difference, that difference is almost certainly due to air. (Vibration is about the only other speed dependent web handling respon...

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14

Air Escape from Wound Rolls

Posted by David Roisum on September 14, 2011
Aside from air getting into a roll and causing it to wind looser, is there any other trouble you can get into when winding smooth webs? Yes, air can and will escape from the ends. It will do this slowly, over the course of a few hours. If you don’t believe this, drop your roll in a tank. It wil...

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13

Air Entrainment in Winding

Posted by David Roisum on September 13, 2011
Air is entrained into wound rolls. You may not even notice the effects at low speeds or if you have rough or porous webs because the air just passively fills voids. On smooth products, however, such as glossy paper and especially film, the air loosens the wind. In fact, there is a direct correlat...

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11

Winder Safety per Metso

Posted by David Roisum on September 11, 2011
According to the US Bureau of Labor Statistics, many more people are killed in the workplace every year in the US than were killed on 9/11 (and nearly 10X that number die on the highways according to the US National Highway Traffic Safety Administration).  In our web industries, nips and winder...

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Posted in: Nips, Safety, Winding
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Blogmaster

David Roisum photo

Dr. David Roisum

Dr. Roisum is a well-known authority in the area of web handling and converting. He has authored seven books, including Winding, Rollers and Web-Handling and has coauthored or edited several others. He was a technical editor for Converting Magazine with a monthly column entitled "Web Works." An accomplished professional speaker and instructor, Roisum has been praised for his skill at translating highly technical information into a common sense practical reference. Dave has been honored by TAPPI with their Finishing & Converting Division Award, Thomas W. Busch Prize and Finest Faculty awards and is a TAPPI Fellow. Dave received his Ph.D. from the Web Handling Research Center where he later became an Industrial Advisory Board member.

Dave has worked for the Beloit Corporation as a designer of winding machinery and later as a manager of research, and for Kimberly-Clark as a converting expert serving all business units. He is now a principal of Finishing Technologies Inc., providing consulting services to more than 300 clients who convert or manufacture: paper, film, foil, nonwovens, textiles and many other materials. He has accumulated much practical experience working in nearly 1,000 plants over the course of more than three decades.