Web201.41a Web Extremes – Slow v High Speed
***201.41a – Web Extremes – Slow v High Speed
04 Slides Duration 03.39 v 15.03.11
201.41a.01 – Title Slide
Welcome to Web-Handling. My name is Dave Roisum. I am very excited to begin a new series on some extremes of the web-handling world. In this first clip we will explore speed.
201.41a.02 – Inspirations
I must confess the inspiration for this series came from a list generated a decade ago when my friend and colleague Tim Walker and I first started our blogs. I unabashedly copy many of the great ideas on that long lost list and flesh them out.
The inspiration for this particular clip comes from many of my clients who run slower processes who are prone to a couple of misunderstandings about speed.
The first is that if you run at a slower speed that somehow the system is a lot more forgiving. This, as we will see, may be overstated from a web handling point of view.
The second is that running faster is much harder. This again may be overstated as the paper industry has clearly shown by designing and operating winders in excess of 3000 mpm or 10,000 fpm.
201.41a.03 – Speed Comparison
To get started we need to make a somewhat artificial black and white division between low and high speed when the situation is obviously gray. Here we will call high speed anything above 100 mpm or 300 fpm.
What might surprise some is that by far the biggest difference with speed does not have anything to do with web-handling. It has to do with marketing. Fast or wide machines require a large market to ‘feed the beast’ as they say.
If we focus on web handling, we will note the primary difference is that higher speeds require attention to air handling such as grooving on idler rollers and nips for winding rolls. We covered these topics in great detail in the web and winding sections of Web101 respectively.
The mechanical design challenges include vibration whose imbalance forcing function goes as the square of speed. The big drive control challenge is that large gear reductions actually make slow speeds more challenging as the tension into torque control method is not a good option anymore.
Also what may surprise some who have not had my Web101 class is that wrinkling challenges could in fact be slightly worse at lower speeds.
Where high speed clearly poses challenges is process upsets such as jams or breaks. The time-cycle and economics of high speed also demands high reliability.
Last but not least is safety. While slow machines can be hazardous, especially if the web is thick or the web is wide, high speeds are potentially life threatening under nearly every situation where humans are in close proximity to the machine.
201.41a.04 – Questions?
Thank you so very much for watching this module in my plant practical video clips. Stay tuned for the next clip as we explore more web handling extremes.