Here’s a question we hear frequently, especially from folder operators new to running cover stocks on their folding machines… “Even though I’ve scored it, the cover stock I’m running still cracks when I run it through the folder. What can I do?”
First, check the score. Make sure you are using the Tech-Ni-Fold Tri-Creaser. Play with different settings until satisfied with the hand fold. If it was scored off-line or with another tool, this tip will still help! If you can fold it hand and it looks good, we believe you can get it through the folding machine without making it look worse. Yes, many digital or heat—set web-jobs, and certain paper stocks will crack if you just look at them. In some cases even the best die score doesn’t eliminate fibre-cracking. Even so, this technique will minimise the damage and can turn a reject-quality job into an acceptable one.
WE’LL USE A 4PP, 1-FOLD PIECE AS AN EXAMPLE:
The common way to fold this is in fold plate no.1; that’s how we were all trained. Fold roller calliper 1 has one sheet of stock; callipers 2 to 5 have 2 sheets. All well and good for text stock. As shown in Figure 1, the sheet is driven into plate no.1, it buckles (folds) then travels through the remaining rollers with the fold plates closed off. This means you have 4 pinch points where pressure and bending forces are applied to the folded spine after it is folded – that means 4 opportunities to make it crack.
A FOLDING SOLUTION:
Use fold plate no.4 to make the fold as shown in Figure 2. Then reset the calipers like this — 1 sheet in callipers 1 to 4 and 3 sheets in calliper 5 instead of the normal 2. Remember that folding machine rollers drive the sheet, so we don’t really need any pressure on fold roller no.5.
The end result is that we’ve reduced the pinch points from 4 to 0, and you now stand a much better chance of getting that delicate cover stock folded without any cracking. You can use the same principle when folding a 6pp on cover stock. Use the “bottom” fold plates 2 and 4 or 3 and 4 to make your 2 folds. Then remove all pressure from fold roller no.5 with an extra sheet and use minimum pressure on all other fold rollers.