Hi Guys I need to calculate the diameter of a butt roll. I do not know the caliper and the diameter can't be measured (I have no access to the physical roll) I know: Basis Weight Basic Area (Sq inches) Roll width Original Weight Original Diameter Core Diameter New Weight For example, The roll is 50-inches in diameter and weighed 4,000lbs when full It now weighs 1,000lb. I need to calculate the diameter (I actually need the outer circumference, but can get that from easily from diameter) It doesn't have to be spot on. I found many calculators like this: http://www.internationalpaper.com/US/EN/Products/RollWeight.html but they all use some mysterious "factor". I could probably fudge some lookup of "factor" based on basis area, but would prefer to do it based on attributes I have. TIA Mark

most papers come with an m-weight. which means the weight per 1000 sheets, for example a 25x38 sheet of 50 # offset is 100# per thousand, and a 23x35 sheet of 50 # offset has an m-weight of 85#. you can subtract the core weight from the total weight and divide the remaining weight by the m-weight and that will give you an approximate amount of sheets left on any particular roll. The key is knowing the m-weight.

rolls of paper sometimes have linier footage on them. if you have a new roll with 32,000 linier feet you can divide that by the cuttoff length an calculate how many impressions you can get from that roll. if your running an old press,with multiple rolls and have to shut down to splice you want to match roll lengths so both rolls run out close to each other that way you dont have alot of cores with excess on them. You can guess a close caliper, say 50# offset is .004 and then use this app at apps.fasson.com/roll_od.asp if its a 35" roll of 50# offset its about 37" diameter. If its a 35" roll of 80# cover at a caliperof .008 its diameter is about 31".

Thanks, but doesn't help at all. As I mentioned: I know basis weight and basic area so can calculate M-weight easily, but knowing the length or "no of sheets" (bizarre concept for roll stock) doesn't help me figure out diameter, which is the attribute I need

As I don't know caliper, i was hoping not to have to guess (or have some massive lookup table - we have a LOT of weight, grades, brands, etc.).

what type of paper is it an how wide is the roll? As far as number of sheets per roll, presses have a cutoff length,this is the amount of paper a press pulls through in one revolution. Our press is 22.750" first it goes over a former that folds it in half and then through a series of cylinders that fold it into a 16 pg. signiture that is 11.375x8.75 then the bindery cuts it into 8.5x11 book. i guess this is bizarre if you have never seen a machine that prints rolls.

We currently have 19 web presses with different max widths and cut-offs. The digital web presses have variable cut-off. the cut-off has nothing to do with the diameter of the roll. I'm intimately familiar with web printing

if you have 19 web presses why are you fretting over the circumference of a butt roll? it was a good math test but you'll never be able to get your answer without the factors you need to complete the equation. x=?

I need to calculate it in a piece of software. I have what I have. I don't accept that there's no way to do it with the attributes I have, just gonna be a bit trickier

if you give me the type of paper and the width of the roll I'll tell you the approximate diameter. As the caliper gives you the final diameter according to the length of the paper wrapped on a core.