EUROSCANTRADING

In the past we were all happy to classify board sheets in respect of warp as flat sheets, warped sheets and too warped sheets. Today we have to measure the warp in numbers, report it and in line with ISO 9000 also give a guaranteed maximum warp of the sheets or blanks delivered. 

How shall we measure the warp in a correct and scientific way? In the USA there is since long a system for measuring the warp
(H = height) over a suitable width (cord), most often over 12 inches, over 24" or over 48". 

In order to avoid the disadvantage with reporting also the width for each warp reported, the Scandinavian Group for Corrugated Board Development (SUW) introduced the use of Warp = 1/R where R is the radius of the circle following the curvature of the warped sheets. With that definition of warp we can measure over any suitable width and report an exactly defined warp. 

This SUW-definition gives the warp in inverse meter, i.e. m-1 , and it is today often mentioned the European unit for warp, or just EU-warp. Consequently the American unit inch/24" ought to be called US-warp. 

The transforming of US-warp (h) into EU-warp (w) of course depends of the width used in USA, but if we stick to a cord of 24" we get H = 1.83W. 

To simplify the metering of warp, you can use a small, handy warp meter.