How do I determine what size of Shreiner Matrix I will need?
The 1.75 calculation has been adopted by more than one matrix supplier over the past few years. Many companies now use this as their primary calculation for determining matrix sizes. This calculation works well for most of the substrates we encounter, including recycled and coated stock. By using the 1.75 you keep the channel tight and force the substrate to delaminate. Delamination is the internal separation of the paper. The more delamination you can create the more air/space you create, which in turn will give you a better crease. Matrix contains the delamination into one area forcing the crease to form.
Most time when we run into thicker boards (.024 and up) we will determine the matrix size using the 2 x board thickness calculation and then immediately go to the next wider channel width. This is especially true when dealing with clay coated recycled stock. The reason for this is that using a narrow channel on this type of stock will not allow the crease to fold over smoothly. One may have a “good looking” score with a narrow channel, but once they try to fold the stock there will be a good deal of memory and it will not fold over nicely. The inside bead becomes too wide and the material can not fold over itself. Once you start to force the fold you are at a large risk of creating cracking and mis-alignment of the glue flaps, etc. By widening out the score you give the stock more room to fold properly, eliminating the memory issue. It is important to not get over zealous with widening your scores, you don’t want to create too much stretch across your sheet causing other headaches.
Corrugated creasing is a perfect example of an instance where a wider score is better. There are a few things to remember when creasing corrugated material. First, the thickness one should use when determining matrix is the crush thickness. Second, whenever possible try to cut from the outside of the sheet. I know that this is not always possible, especially with B and C flute, but if one is cutting corrugated with a mounted sheet of any kind this will substantially reduce checking. It has been our experience when dealing with E and F flute most times one can use the same set-up as a paperboard job and end up with excellent results. One thing that we will often suggest is to keep the channel wide and raise the channel height when with the flute. This in effect gives similar results to reduced bead by trapping more of the corrugation into one area and giving the material a more defined score.
1.75 x board caliper “a” + rule width “b” = channel width “w”
Board caliper “a” = channel depth
ShreinerProfile, Shreiner Fiberboard
1.75 x board caliper “a” + rule width “b” = “x”
Divide “x” by .0394 to determine the metric measurement for the channel width “w”.
Board Caliper = “a”
Divide “a” by .0394 to determine the metric measurement for the channel height.
Make it easy on yourself and use our Automatic Matrix Calculator.