Successful Folding

All materials of 150 g/m2 and above, particularly coated stock should be pre-creased. Where a cylinder machine is used there will be a difference in the characteristics between creases formed around and those across the width of the cylinder. For this reason it may be necessary to use different rule heights in each direction; for example, reduction of the creasing rule height in the direction of sheet travel. Creasing with a platen machine requires common ruling.
There are a number of characteristics that will affect fold ability, i.e. bulk, grain direction and rigidity. In some instances boards as low as 200 g/m2 can be of a laminated construction which will dramatically alter rigidity compared to non-laminated board. It is therefore essential that the former supplier is made aware of the type of product to be processed, supplying him with samples for testing.

 

Do’s and Don’ts

  • In order to produce constant crack-free folds we suggest a platen approach using a creasing rule and matrix system. Always fold into the bead. Folding around the bead is likely to produce cracking.
  • Check the quality of fold during production on a regular basis. If cracking is evident, stop. An adjustment may well rectify the problem.
  • Take care at guillotine stage. Use minimum clamp pressure to avoid damaging the bead.
  • Ensure a minimum distance of 4-6 mm between parallel folds.
  • Do not attempt to rotary crease or score. There is little if any adjustment with this method; it is ineffective and damaging to the surface.
  • Do not use UV varnish in areas to be pre-creased.
  • Do not subject the printed material to dry conditions. Folding quality deteriorates as the moisture content of the substrate decreases.

Hints and Tips

Problem

Likely cause

Solution

Crease cracks in centre fold

Creasing rule too high

Lower rule required

Crease cracks at one edge of fold

Creasing rule not in correct alignment with centre of matrix

  1. If hand cut m/r, trim edge
  2. If matrix strip, replace
  3. If counter die, reposition, use wider channel or replace

Crease cracks at two edges of fold

Channel too narrow

Use wider channel

Poor definition of crease

Creasing rule too low or chnnel too wide

Increase height of rule, using shim tape if appropiate, or use narrower channel

Head colapses at back of crease

Creasing rule too low

Increase heigth of rule, using shim tape if appropiate

Poor definition of crease in poor quality board

Channel depth may be too shallow

Use deeper matrix

Bruising at end of creases

Too much pressure

Rub down or chamfer ends of matrix

 

 

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