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August 04, 2005
Differential Bars, Part 1 - What Torque? Tension?
When people look at differential bars, they often focus on their main function and benefit - the ability to allow many individual rolls on a common shaft to turn independent, finding their appropriate rpms to compensation for variations in roll-to-roll diameter differences and lane-to-lane length variations.
OK, this is great, but let's move from this function onto other specification that will make or break your winding yield.
#1 The right winding tension
What is the right winding tension for your product, including the initial tension, the final tension, and any wacky tapering or profile you may want to run.
Winding and handling tension are usually in the same ballpark, but unusual wound roll characteristics many mean winding tension needs special considerations.
Slippery or thick products may need more tension (and pack). Thin and pressure sensitive (thick adhesives and other special coatings) product many need quite low tension.
#2 Torque creates tension
More...
#2 Torque creates tension
Once you have an idea of the right tension for your product, you need to find a differential shaft that has the operates in that range. All differential shafts use clutching, either pneumatic or magnetic, to apply a torque to the core and through the roll's radius, create tension. Any clutch will tend to have a 20-to-1 range. So look at your tension x radius needs, figure the torque, and compare that to the shaft's specification. If your need is outside the 0.3-3.0 lbs/in range, you may find it difficult to get a differential shaft to fit your product.
Other factors to consider:
Core and roll wobble.
Core dust and wear.
Lateral shifting.
Ease of setup, loading, and unloading.
Ease and cost of maintenance.
Initial costs.
Core tolerance.
Core dependency.
Control of differential torque, considering gravity and inertia.
My last question? If winding tension is so important to roll quality, how come there are so few slitter-rewinders with tension measurement of winding tension? Are we just that cheap?
tjw
Posted by Tim Walker at August 4, 2005 10:55 AM
Comments
I do appreciate to be able to read this kind of educational information about converting process technology.
Posted by: Yukuo Yamamoto at August 5, 2005 06:35 PM
It was really a nice article for Differential winding. I would appreciate if you can provide us the Exact data of Rewind Tension required for winding on a slitter Rewinder.
Substrate would be : 12 Micron Polyster films, BOPP , PVC Shrink film, Laminates(3 Ply , 2 Ply ), LD , LLDP
Max. width of the Substrate : 1200 mm
Max. Speed : 450 m/min
Please guide me in this regard.
Posted by: NILESH PATEL at August 5, 2005 11:37 PM
THANK YOU..
Posted by: sangjae at August 6, 2005 02:31 AM
The articles are really interesting and very informative. Thank you
Posted by: Elias Mokgonyana at August 7, 2005 10:53 PM
Please keep me in the loop this kind of information is very important for understanding winding
Posted by: wim van de Camp at August 8, 2005 05:08 AM
Is there a system that has a large enough window (starting tension/finish tension) to rewind large coils (60" OD) without the operator making any adjustments? We run steel .010 - .032, and aluminum .015 - .060.
Thank you.
Tony Heath
562-699-4550
Posted by: Tony Heath at August 8, 2005 05:11 AM
Very interesting and informative. Thank you & please keep me in the loop for slitting and winding.
Posted by: Thomas Heyn at August 8, 2005 08:49 AM
Very useful information. Thanks.
Posted by: Francisco at August 9, 2005 08:51 AM
We process polyester films with heat transferable coating applied to the web. The coating thickness can be up to two mil with a coat weight of 24lbs / ream. Can any one recomend a system that will wind reels 5/16" - 50" @ 5000'?
Posted by: Bill Lambert at June 29, 2007 05:36 AM
