Touché® FC Scoring & Bending Guidelines
FiberMark’s Touche FC is dense and stiff compared to traditional boards of equivalent caliper. It may be scored and bent to make very satisfactory hinged products required for a number of applications, providing the operation is within the limits required for this particular material. General guidelines provided by the Recycled Paperboard Technical Association (RPTA) may be used to assist the proper decisions for rule and channel dimensions, while taking the non-traditional density of the material into account.
Some fundamentals of scoring and bending Touche FC are as follows:
1. To fold and bend these materials, the stiffness of the sheet at the bending line needs to be lowered and a flexible “hinge” formed within the sheet itself. This is achieved by scoring.
2. A satisfactory score must reduce the bonding strength between the individual plies of the sheet, so the plies will experience localized delamination when the board is folded on the score line. In addition, the width of this delaminated portion must be great enough to allow the stock to squeeze down into the bead on the inside of the bend. If this is not accomplished, a fulcrum will be formed near the surface of the sheet, which will rupture the outside ply (or plies) when the bend is made.
3. Touche FC scores and bends much better when processed at the normal moisture content (as manufactured). However, if this is not practical, it is essential that the board be left in the shipping packages or kept in covered piles until scored and bent if best results are to be obtained. Material, which has lost its normal moisture content by exposure to low humidity atmospheres, is more likely to crack when scored and bent due to the dry condition of the sheet. This is most likely to occur in the fall and winter when outside temperatures are low and inside relative humidity is reduced when the air is heated.
Scoring Rule Selection:
Two major considerations define the conditions that direct the choice of scoring rules for a job. First, the female channel width should be slightly or to twice the board caliper plus the thickness of the rule. Second, female channel width must be between 3.5 and 4 times the board caliper for CD scores, and about 3.5 times the caliper for MD scores.
Touche FC is denser than traditional boxboard, and the fiber construction gives it greater stiffness and plybond than equal caliper boards of lower density. Therefore, the board needs to be treated as if it were slightly higher in caliper than it actually is.
12 point (300 gsm) for Packaging Applications: When applying the same density factor to 0.012”, the “effective board caliper” would be 0.0138”. The application indicates the use of a 2-point rule (0.028” rule thickness). The male rule depth of penetration can be adjusted between 0.003” and 0.006” to achieve sufficient delamination of the plies, when appropriate channel widths are used.
18 point (470 gsm) for Packaging Applications: For 0.018", an “effective board caliper” of 0.021” is generated, indicating the use of a 3-point rule (0.042” rule thickness). The male rule depth of penetration can be varied between 0.005” and 0.010” to achieve sufficient delamination of the plies, when appropriate channel widths are used.
26 point (660 gsm) for Packaging Applications: Application of the density factor to 0.026" indicates an “effective board caliper” of 0.0299”, indicating that a 4-point rule (0.056” thickness) is the proper choice. The male rule depth of penetration can be varied between 0.008” and 0.013” to achieve sufficient delamination of the plies, when appropriate channel widths are used.
For packaging applications, wider score lines are necessary to handle the additional stress demands of a box hinge where the score may be folded 90 the opposite way.
Scoring rules should be rounded to prevent cutting the board (we suggest rounding to 0.005” radius).
1. Rule width: In die cutting terminology, rule width is characterized by the term “point”. One “point” is equal to 0.014”. A 2-point rule is 0.028”, a 3-point rule is 0.042”, and so on.
2. Rule selection: Two criteria need to be met simultaneously in order to indicate an appropriate rule choice for a given caliper board (see Scoring Rule Selection - page 1). The selection of a 4-point rule for 0.026” Touche FC can be verified by applying its width and the “effective board caliper” (0.0299”) to the criteria.
2-1. Female channel width 2*board caliper + rule thickness
Female channel width 2*0.0299” + 0.056” = 0.116”
2-2. Female channel width between 3.5 and 4 times board caliper for CD scores.
3.5*0.0299” = 0.105” and 4.0*0.0299” = 0.120”
A 4-point rule is the first rule width that fully satisfies both criteria for this caliper. This scoring rule could be used with good results when matched with appropriate female channel widths.