Of the 847 things that can go wrong when operating your folding machine, here’s another one you might not have thought about. It may never come to your attention until you run into mysterious problems with sheets misbehaving in the right angle folding sections.
The components we're talking about are on certain models of many popular machines such as MBO and Stahl folders, among others. They are small plastic holders for the steel and plastic balls (marbles) used in the right angle sections. Some folders don’t have separate ball cups; instead the balls ride within the side guide itself. They are variously referred to as ball cups, ball cradles, marble cups, marble holders, etc. (Shown in top right photo.)
Unless you run a variety of paper, you might not have to fiddle much with the ball cups. But if the stock is curled, or you are running at very high speeds, you might need to pay closer attention to them. Here are 5 things to look at when you run into right angle feeding problems.
1) Use the minimum weight and number of balls needed to get good register. Less is more when it comes to moving paper through a folding machine. Find the minimum weight and combination of plastic and steel balls to make the job register. This prevents marking, wrinkling, paper jams, and other problems.
Most folder manufacturers have basic recommendations for starting out. In the end you’ll have to experiment until you find the right combination for each type of paper on each machine.
2) Make sure that ball cups are positioned in the right direction. This applies to MBO folders. It’s a little detail many operators don’t know about.
Both the adjustable cups as shown here and the non-adjustable cups (no screw at the top) have small tabs at the bottom of the cup to secure them into the side guide. You can see them in the photo, top right. You can also see in the second photo, top right, how these clips can interfere with a passing sheet if they aren’t positioned correctly.
On the top of each cup are directional indicators (red arrows) to show which way they are to be inserted in the side guide. It’s important to note that they are NOT supposed to face the same way along the full length of the side guide.
The photos at right will illustrate that point more clearly. Where the sheet enters the side guide, the cup indicators should be facing the direction as shown. The remainder of cups should be 90 degrees to that as shown in the two photos at right. The yellow arrows below show which direction the indicators should face.
This prevents the edge of the folded paper from catching on the plastic clips. If they aren’t set correctly, you increase the odds of an edge catching the clip. When positioned correctly, the tapered edges of the clips help to properly guide the sheet.
3) Beware of missing ball cups. (Photo at right.) We often remove a cup to fix a problem and forget to replace it when the job is done. The open spot can snag a passing sheet on a subsequent job if the paper is a different size.
Cup holders on Stahl folders are slightly different. When a ball is not needed they have special ball cradles to insert to prevent edge of sheet from catching.
4) Check for cups that are unseated. It’s easy to unseat the cups, especially those with the adjustment screw on top. The cup looks like it is in place but the clip isn’t fully snapped into position. It has been done countless times and isn't usually noticed until a sheet snagged the loose cup on the way through.
5) Don’t forget about the adjustment screws (If you have them). If they’re set tight for one job, they could be too tight for a thicker paper. This in turn will cause sheets to slow too much or to jam altogether.
For the most part you won’t have to do a lot of work with ball cups in the right angle sections. Just keep them in mind when you run into a problem.
This is by no means a comprehensive guide to right angle sections on all models of folders. Newer MBO’s have high speed guides that work differently than the ball cups.