The introduction of aqueous coatings in the late 70’s was a plus for a few reasons, one of which was that aqueous coated jobs could be sent to the bindery for cutting and folding within minutes. But that great looking high-gloss finish often makes the folding machine operator’s job more difficult. The fold rollers simply have a tougher time gripping the super slick surface.
Although fold rollers are infinitely better than they were in the 70’s, we still get the occasional question about how to fold print jobs or other substrates with especially slick surfaces. In most instances folder operators with relatively new equipment are able to fold aqueous jobs as easily as any other ‘normal’ folding job. Those of you with older folding machines might struggle.
There are quite a few ways to address problems with folding aqueous jobs which can be categorized under Equipment , Emergency Cures or Environment.
The fact that most people can fold aqueous jobs without doing anything out of the ordinary highlights the complexity of printing and finishing. If you follow the recommendations of paper suppliers, press manufacturers and ink suppliers, you can hit the right combination of paper, ink, coating and machines to run without a hitch.
But if you haven’t hit that perfect combination and you are having problems, let’s take a look. This week we’ll look at Equipment and Emergency 'Cures'. Next week we’ll review Environment.
1) Most operators we queried have a simple remedy: use more fold roller pressure. Adjust fold roller pressure manually or use thinner sheets in the calipers. That little bit of extra grip might be just enough to do the trick. Remember to reset the pressure when you're done.
2) Check the register belt (or belts) on the in-feed table. It might be too worn and smooth to handle a slick, coated stock yet it could work just fine on regular folding jobs. A simple test: wet the belt slightly. If the register problem goes away, you've found the culprit.
Next, give the belt a good cleaning according to the manufacturer’s suggestions. Usually a solution of warm water with mild soap will remove any glaze or ink and paper residues. Be wary of using chemicals unless you know with certainty that it won’t cause damage.
If cleaning doesn’t solve the problem then your belt may be worn. Until you can replace it, you might want to periodically dampen it (lightly) or use a light touch of glycerin to give it a temporary grip.
3) Check the register marble combinations. Usually the heavier steel marbles will be required to consistently pull a slick sheet. Gradually add steel marbles until it starts to register.
4) Clean your fold rollers. They may look clean yet be glazed just enough to affect folding performance on the slick paper.
5) If none of these fixes helps, it may be time to call in your folder mechanic. In the meantime, there are some ‘desperation cures’ that could get the job out the door. These won’t be endorsed by any manufacturer because they can damage the machine, hence the ‘desperation’ tag. Do these at your own risk!
6) One surprisingly common tactic is to spray a very fine water-alcohol mist directly on the fold section. Obviously this will promote rust on metal parts! Water and metal simply do not mix. (WD40 or Pledge polish lightly applied can help prevent rust.) Be sure to dry equipment when the job is done.
7) Another frequent suggestion: use Shower to Shower body powder on the fold rollers. As with water, fine powder and moving machine parts do not mix. We suspect this works because the powder gives the rollers a fine grit similar to sandpaper.
Again, these are desperation tactics to get a critical folding job out the door on time and are not something to do on a regular basis. If you find yourself running aqueous folding jobs frequently and your current folding equipment is struggling, there are sensible mechanical solutions.
USA Roller & Supply, a manufacturer of post-press specialty items and folding machine rollers has a High Density fold roller which uses a rubber-to-rubber overlap (right side of photo) versus the conventional steel-to-steel overlap. (left side of photo) These fold rollers can also be made with either foam or urethane, and are said to decrease marking in addition to providing superior grip on aqueous stocks.