SUGGESTED TENSION LEVEL LIST FOR WEB PROCESSING
The following charts indicate suggested tension levels for various products commonly run in web or continuous strip form. This information has been gathered from prior experience. They generally run at 20% or less of the tensile strength of the products involved. The best general rule for selecting tension is, Use the minimum tension necessary to get the job done. The lower the tension levels in any given process, the less stress applied to the product, which leads to higher quality product and less wastage. Also, the lower the tension levels, the less energy consumed by motors driving the processing machine and the less wear and tear on the machinery. Again, these are only suggested levels; from experience, do not be surprised if you find radical deviations in practice from these norms. We occasionally vary from these standards when a customer knows better.
Also included are several related formulae, which will help in determining other factors related to web handling, such as total footage on a roll, inertia of a roll, unwinding time, etc.
The list of suggested tension levels is subject to revision at various times, so please, if out have any further additions to make to the list contact our office. The list can only improve and become more useful if we all contribute our field knowledge.
Generally, throughout Australia, New Zealand and most of South East Asia, Paper is specified in gsm (grammes per square meter), and Board in UMS (1,000 UMS per 1 mm Web Thickness).
Throughout the U.S.A., Paper is specified as Pound Paper (weigh in lbs. of a 3000 Square Foot Ream) and Board as Point rating (Point is equal to thickness of web thousandths of an inch).
For conversion from the European system to the American system, divide the gsm rating by 1.63 to give the approximate equivalent in Paper.
From field experience, we have found that the following Papers and Boards are the most commonly used throughout Australia, etc.
PAPER
| Suggested Centre Winding Tension Levels (Wind Up Clutch Applications) | Suggested Unwind Tension Levels (Unwind Brake Applications) | |||||
| PRODUCT | SIZE | TENSION | PRODUCT | SIZE | TENSION | |
| Brown Papers | 33gsm | 0.75 lb.pli | Brown Papers | 33gsm | 0.5 lb.pli | |
| 39gsm | 0.875 lb.pli | 39gsm | 0.6 lb.pli | |||
| 49gsm | 1.0 lb.pli | 49gsm | 0.75 lb.pli | |||
| 57gsm | 1.25 lb.pli | 57gsm | 0.9 lb.pli | |||
| White Papers | 60gsm | 1.4 lb.pli | White Papers | 60gsm | 0.9 lb.pli | |
| 70gsm | 1.75 lb.pli | 70gsm | 1.0 lb.pli | |||
| 80gsm | 2.0 lb.pli | 80gsm | 1.3 lb.pli | |||
| 90gsm | 2.25 lb.pli | 90gsm | 1.4 lb.pli | |||
| 95gsm | 2.4 lb.pli | 95gsm | 1.5 lb.pli | |||
| 100gsm | 2.5 lb.pli | 100gsm | 1.75 lb.pli | |||
Reference: 1,000 UMS = 1.00 mm Web Thickness
ADDITIONAL WEB HANDLING FORMULAE
Surface Winding: Horsepower = (Web tension x Velocity) / (33000)
(Effective Horsepower = Approx rated HP)
Total footage on a roll = 0.065 (OD2 - Core2) / Web Thickness
Total (un)winding time = Total Footage / Velocity (FPM)
Total number of revolutions = (OD - CORE) / 2 (Web Thickness)
Roll Inertia Calculations (WK2)
Volume (V) = 0.7854 (OD2 - Core2 )
Weight (W) = V (weight of material per inch3)
Mass (M) = W/g (g = gravitational acceleration = 32.16)
Inertia (I) = M(R2 - r2)/2 (R = OD/2; r = core/2 )
WK2 = I(g)
Paper Basis Weight: (South East Asia/Europe)
Generally expressed as grams per square metre
Paper Basis Weight: (U.S.A)
Generally expressed as pounds of weight per 3000 square feet. If expressed as pounds per 1000square feet, or any other system, simply convert to 3000 by multiplying. The following general rule will then apply:
Maximum Winding Tension = Basis Weight (lb. per 3000 square feet) / 20
Alternatively
Maximum Winding Tension = B
asis Weight (grams per square metre) / 33
Board: (USA)
Conversion to the above sq. ft. standard can be made by multiplying the point rating of the board (point is equal to the thickness in thousands of an inch) times for example, 10 point board is roughly equal to 80 pound paper. This equivalent basis weight can then be plugged into the above formula to determine rewind tension.
VARIOUS ADDITIONAL WEB MATERIALS
| Product | Tension Lib/mil/in |
| Acetate | 0.5 |
| Aluminium foil | 1.0 |
| Cellophane | 0.75 |
| Cellulose | 0.5 |
| Gryovac | 0.1 |
| Glassine | 1.5 |
| Mylar (Polyester) | 0.75 |
| Nylon | 0.25 |
| Polyethylene | 0.25 |
| Polypropylene | 0.25 |
| Polystyrene | 1.0 |
| Pliofilm | 0.1 |
| Saran | 0.1 |
| Vinyl | 0.1 |
Reference: mil = 0.001 inch
Example: Web ma
terial 0.003" Acetate, 36 inches wide.
Suggested tension level 0.5 lb/mil/in.
Therefore 0.5 x 3 = 1.5lb. tension per lineal inch of web width (1.5 lb.pli)
COPPER WIRE
| AWG | Tension lb. |
| 0.8 | 30 |
| 10 | 20 |
| 12 | 12 |
| 14 | 9 |
| 16 | 6 |
| 20 | 5 |
| 24 | 4.5 |
| 30 | 1.25 |
| 36 | 0.25 |
| 40 | 0.1 |
Run aluminium wire ar 1/2 to 2/3 of copper tension levels.
Multi strand cables are run at the sum of the tension of all strands.
Example: 6 conduct, all 20 AWG copper.
6 x 5 = 30 pounds.
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