Method of working out how much vinyl on a roll…

[Derek Heron]

work out what you need for the job
and its always just short by approx 700mm
:lol1:

derek

[Peter Normington]

Easy 😀

The area of cross-section of the roll can be expressed in two ways.
When stretched out in a straight line it is a rectangle of area L*T
where L is the length in inches, and T the thickness viewed edge on.
When rolled on the drum, this same cross-section will be pi*R^2 – pi*
r^2 where R = outer radius =(D/2), and r = inner radius (=C/2)

So we have L*T = pi{D^2/4 – C^2/4}

L = pi/(4T){D^2 – C^2} inches

Length = pi/(48T){D^2 – C^2} feet

= (0.06545/T){D^2 – C^2) feet (T,D and C in inches)

Try this in real life. It will be sensitive to the value of T you
use, so measure that carefully.

Peter

[Phill Fenton]

How do you work it out in cm 😕

[Harry Cleary]

Would be very very handy John….how hard would it be to mark the back of a full roll in increments? One of those stamp thingys they use for best before dates would do it.
I see an appearance on Dragons Den! 😀

[Peter Dee]

I have an Excel spreadsheet made up with formulas to calculate the length for 400/500/610 rolls.
It takes in to account the tube weight and is based on an average weight of vinyl per metre.
It flags up red when there is less than 5 metres on the roll.
I just weigh the roll on some old kitchen scales (max 5 Kg), enter the weight in to the spreadsheet and immediately get the length.
I have set it to be a bit over rather than 100% accurate.
The vinyls can be sorted by brand/type/colour.
In practice it works really well.

[John Dorling]

Peter D. I like that idea. Might be a lot easier. How accurate do you find it? I was mainly thinking about a method using the measurements as I don’t have any scales here and I’m too tight to go and buy some if it can be calculated with only a tape measure and a calculator!

Peter N. most of that formula makes sense but I’m not sure what the ^ symbol denotes? Or, the brackets { and }.

John

[Jeffrey Cross]

You might try something like this.
http://www.handymath.com/cgi-bin/rollen … bmit=Entry

[Peter Dee]

John, if I have a job needing even just 9 metres, it would be a right pain to measure it all out. Usually whatever is left on a roll, there will be a bit over on this method and it’s so quick to do.
I can know what’s on a roll inside 30 seconds.

[John Dorling]

Jeffrey that’s ideal! I’ll try it out and let you know how I get on. This will save hours when stock taking.

Thanks

John

[Peter Dee]

That calculator looks good. Just need to find a micrometer to measure the thickness.
Brilliant, good link thanks Jeffrey.
I have .21 mill thick for Mactac and .5 mil thick for Hexis digi banner material.
Results dead on.

[Gert du Preez]

Stop guestimating.

Build up a decent stock level. One roll "on the go" and at least one roll "in the store room" – more if it’s a mover like your "house brand" print vinyl. I always carry at least 3 rolls, and when I anticipate busy times, I increase the stock level. A good time (for us) to buy LOTS of stock is just before tax returns are due at the end of March…..let the taxman carry some of the risk for the next financial year !!

That way the 9m job will have the 8,3m on the roll, as well as the 50m in the store to get it through…..

It does not cost that much to build up decent stock levels over a couple of years. The only downside – especially when you are far away from your suppliers – is that other sign shops in the area forever rock up wanting to buy a metre of this or a sheet of that.

I like to help, but sometimes it feels that I have to compensate for their lack of planning…..

OR,

You can just guess how much is left. You get good at it after a few years…..

[Jeffrey Cross]

John:
I also found this one. For you people with the crazy measuring system…Ha
http://www.cutsmart.com/pages/length_on … lator.html

[David Rowland]

quote Jeffrey Cross:

John:
I also found this one. For you people with the crazy measuring system…Ha
http://www.cutsmart.com/pages/length_on … lator.html

code :outdiameterSquared = outdiameter*outdiameter;
indiameterSquared = indiameter*indiameter;
thisnumber = outdiameterSquared-indiameterSquared;
thatnumber = 0.06545/thickness;
leftfeet = Math.round(thisnumber*thatnumber*10000)/10000;
leftmeters = Math.round(leftfeet*0.3048*10000)/10000;

This is the code behind the website, I am confused?

[Jason Xuereb]

quote Dave Rowland:

quote Jeffrey Cross:

John:
I also found this one. For you people with the crazy measuring system…Ha
http://www.cutsmart.com/pages/length_on … lator.html

code :outdiameterSquared = outdiameter*outdiameter;
indiameterSquared = indiameter*indiameter;
thisnumber = outdiameterSquared-indiameterSquared;
thatnumber = 0.06545/thickness;
leftfeet = Math.round(thisnumber*thatnumber*10000)/10000;
leftmeters = Math.round(leftfeet*0.3048*10000)/10000;

This is the code behind the website, I am confused?

http://mathforum.org/library/drmath/view/51723.html

[Gareth Hankinson]

All sounds a bit mad and confusing to me (then again im a Geordie so….!) but when i buy a new role say 25m when i cut a job i know exactly what ive used so when i finish with it i put a bit of masking tape on it with the code for the vinyl and roughly how much is left working on the caution that its shorter than what ive actually written give or take a meter.

May be wrong but it works for me, in time id like to think ive got used to whats on rolls and never really seem to be to far out (just watch me mess it up tomorrow haha)

[Matty Goodwin]

Same with us Gareth!

A few years ago I worked for a company who in there ‘down time’ measured vinyl left on a core. Then when the diameter was found it was routed out of 3mm foamex.

At the end of the month we’d have 30+ square bits of foamex with circles cut out of them with vinyl lengths on them.

Bloody waste of time to me!

Run a feed check and if short, buy more!

Are you still modeling Gareth?!!!

Matt

[Gareth Hankinson]

I agree all sounds abit time consuming to me.

I’ve never modelled mate haha that photo is off a shoot with my missus and my new daughter Olivia I’ve just cropped it for on here.

[Derek Heron]

quote Gareth Hankinson:

I agree all sounds abit time consuming to me.

I’ve never modelled mate haha that photo is off a shoot with my missus and my new daughter Olivia I’ve just cropped it for on here.

gareth you couldnt model for airfix

derek

[Gareth Hankinson]

The state of your legs looks like airfix has put them together haha you want sue them.