When the short side of a rectangular sheet is running against a folding machine side guide, it’s generally called an ‘oblong’ sheet in reference to the oblong fold that might take place in the parallel folding section. It’s also referred to as landscape format. A common scenario is the 11x17” or 8.5x11” cover stock run in such a fashion in order to score and/or perforate the sheet before folding in a right angle section.
Problems can arise when running this way since it’s trickier to keep the sheet firmly against the side guide as it moves forward on the feed table. The bigger the difference between long and short side, the harder it is to maintain registration and even the smallest of errors are magnified.
But there are techniques to minimize problems when faced with this format. Here are some basic considerations along with an interesting tip submitted by a Bindery Success reader.
- One basic technique is to experiment with the marble arrangement, changing among steel, glass and plastic, or a combination of the three. The rule of thumb is to use the least amount of marble weight possible to get the sheet to register. Too much or too little pressure from the marbles can create register problems. Often the selection of marbles available is limited and it can be tough to fine tune the marbles for best oblong sheet register, especially when running lighter text stocks. If you can purchase an assortment of marbles, by all means add them to your toolbox.
- Another consideration is the position of the feed table register tapes (if any, depending on your model of machine) and the position of the marble holder in relation to the register tapes. This involves a little trial and error.
- Also important is the condition of the metal side guide itself. Believe it or not, the groove inside this piece can become unevenly worn or nicked and problems may not appear until an oblong job is running.
- The condition of the register belt under the marbles is also important. If it becomes saturated with ink, varnish, coating residue and dirt it will lose grip on the sheet. Again this will be more apparent when running an oblong sheet. The belt can also develop a curl with age and this too can affect registration.
- Folding machine speed is a factor. In any event you’ll need to slow it down considerably when running with a right angle section.
- Be sure that the sheets are trimmed squarely and consistently. No amount of folder technique will compensate for inconsistently trimmed sheets. If coming directly from a press, make sure the sheets that go to press are as close to perfect as you can make them.
- If curl is a problem, try turning the sheets over. Sometimes your register problem will disappear.
- This novel tip came to us a while ago from Bindery Success™ reader Anthony Dempsey, a folder operator from Illinois. Simply take a piece of 60# uncoated offset stock cut to the length of the marble holder in the first unit, fold it over 3 to 4 times so that it’s about 2 inches wide.
Then take the folded piece and insert it between the marbles and the marble hold-down bar. (see photos and diagram) The extra pressure is just enough to help the oblong sheet maintain register without causing the problems you might get with using too much marble weight. To adjust the pressure, simply change the number of panels of the insert.
You may not need paper the entire length of the side guide. In fact what often happens is that a slight curl, especially with cover stocks, causes the sheet to bounce ever so slightly as it enters the fold rollers. If that's the case, the folks at the MBO Folding School suggest using paper in the last 3-4 marlbles. You can also use tissue, napkins, or any other soft paper. You'll have to experiment to see what works best.
When the job is finished, don't forget to remove the paper, as mentioned below in the comments. If you leave it in you could wear out the register belt too quickly.
It’s clear that to get maximum productivity and profit from your folding machine these days you will need to master running the oblong format. If your folder is in reasonable mechanical condition, it’s not at all difficult. When you add the right creasing, perforating and cutting tools for your work flow, you add a significant level of productivity and profit to your bindery operation.