Print it, Cut it, Fold it--Now Unfold it

I work in a print shop, doing the digital printing, but also in the bindery. A lot of bindery work is fairly boring, because it is repetitive hand-work. But I like using the folder most of the time (except for hours on end, because it is loud).

It is really an amazing machine. It's made by Stahl, I presume, in or around the mid-70s. All solid-state electronics, but mostly mechanical. There are a zillion things to adjust in order to make it work right. I'm only now, after using it for a year and a half, starting to get the hang of it. Still, folding pieces of paper, relatively easy with fingers, is kind of a hard task at high speed. There are more modern folders on the market, but even this machine is better designed than a lot modern bindery equipment. If our tape-spine printer breaks, there is nothing for it but to send it back to the factory, because all the electronics are sealed in plastic. But this folder, if something breaks, you can rig it back together with flashlights, duct tape, wire, and rubber bands (seriously). It's all designed in-line. By this, I mean the paper takes a straight path, and the machinery comes to meet it. My digital press is filled with crap, because the designer felt the need to flip the paper around all crazy like one of those moving ball machines that used to be in airports. (Whatever happened to those?) That means there are thousands of parts to break. It's like they built it one piece at a time. Okay, now the papers comes out of here... what do we do now? Uhh, train a penguin to carry it up a hill, put it on the roller skate, and then let it fly through the ring of fire to set the toner. Good idea! Not Stahl. This is good, German engineering.

Because I am the sort of nerd who finds this stuff facinating, I will give you a guided tour of how to fold a piece of paper, 6000 times an hour. If you don't find this stuff fascinating, you might want to skip to the gift shop now.

The paper begins here, in a giant stack. Each sheet must go through the folder separately, to get a clean fold. Compressed air is used both to blow air through the stack to seperate the sheets, and as suction to pull each sheet off. The compressor is on the floor to the right. As the paper goes through, the table raises automatically. There is a mechanical lever resting on the top sheet to tell the table when it is as the right height.

Each hose is carrying a flow of air to different sides of the sheet. Each one is adjusted individually to get the right amount of air to lift the top sheet, and only the top sheet. This is a tough part to balance. The metal wheel is suction, and it rotates to pull the top sheet off to the feeder belt, which begins at the top left of the picture. The suction starts and stops rapidly, to pull the sheet forward but not suck it up around the wheel. This timing and suction are also adjusted manually.

Here we are from the other direction. The belt pulls the paper forward, straightening it as it goes. The thing suspended near the gold piece of christmas garland is the counter. It's an old electronic eye, wired to a counter unit, which you'll see in a minute. Every person that sees the machine asks if the chirstmas garland is necessary. It is. It is exactly the right weight to keep the paper from popping up in that gap. The gray cord not connected to the counter, leading off to the bottom right, is the double detector. It is a flap of metal set (manually, of course) at a certain height to let only one piece of paper through. If two go through, the flap lifts, activating a switch to stop the machine. Two sheets will sometimes go through, and just get a messed up fold. Other times it will jam. The florescent light is because the bulb in the electric eye unit burnt out. No problem! Bring in a desk lamp.

The paper goes through the feed belt towards the folding panels. I don't know what they're actually called. Racks, panels, I don't know. They are the diagonal pieces extending upward and downward, which you saw in the first view. Wait, let me give you a closer look:

Yes, that. There are two there, parallel to each other, and another two extending downward below. In between them all are the rollers, about where the big shiny wheel is. The blue bar extending across the panel is the stop bar. You pull it up or down the panel, depending on where you want the fold. If you want it six inches in from the leading edge of the sheet, you set it six inches up. The leading sheet with shoot into the panel from the feed belt, and bounce against the stop bar. The bounce will cause the sheet to bend where it is not supported, which because of the panel and the feed belt, will be exactly six inches in from the edge of the sheet, and also right at the:

Rollers! It's a bit difficult to see, but there are a mess of rollers, very close together. They have small grooves, parallel to the axis of the roller. After the sheet bounces in the fold panel (which is pulled back to the left in this view), the bend in the sheet catches in these interlocking grooves, and is creased, nice and clean. In this action the rollers catch the sheet and drag it back out of the panel, taking it on its way.

The rollers are set up in a pattern like this, each spinning an opposite way, very much like gears. Since there are total of four panels, there can be up to four folds per sheet. After the first fold, the sheet can be pulled into the next panel, where it is folded again, just as if the first fold never occurred. You have to set the stop bars correctly to get the pattern you want. Or, if you only want one fold, you can fold down deflector bars to keep the sheet from entering the panel, and just continuing on its merry way through the rollers. The first fold would actually be creased by the rollers marked (2) and the unmarked roller between it and (1), in this diagram. Then it would go into the second panel, and the next crease would be made between rollers (2) and (3). Get it? No? Me neither, not for awhile.

These are the bottom panels. The job I was folding while I took these pictures was a pamphlet with a letter fold, which opened with two overlapping flaps, like a mini booklet. After the first fold, I had to send it down to the bottom panels to give it a second fold in the same direction. If it was a Z-fold, it would've gone to another top panel. That's why this machine is so crazy--the piece of paper never flips over. It is shuffling up and down, with the last fold becoming the new leading edge.

Here's a crude diagram. All the same sheet of paper, at different stages. Red is the first fold, blue is the second, green is finished. It's still complicated, I know. I think there should be a whole branch of publishing geometry, handling everything from N-up pages on a sheet, to rotation for binding, to folding (I don't even understand a gate fold, really), to dividing up parent sheets, to proper rotation for cutting and face trimming. The who I work with, who taught me this stuff, most of them have never taken calculus, or advanced algebra or trig. But they can convert fractions to decimal so fast, and when I couldn't understand the difference between a tumble and a work-and-turn, they just shrugged. Hell, I can explain the four fundamental principles of Kantian space, but I still have to draw a diagram before I start cutting a sheet of 8-up letterhead. It's a lot of spirals, let me just say that.

Anyway, back to folding. I love this diagram, and stare into it's magical gnostic lines while I'm hypnotized by the rhythmic clacking of the sheets hitting the stop bars. I just reminds you to set the stopper to keep the panel from catching on the rollers when the deflector plate is in place. You can also see two knobs for adjusting the gaps between the rollers (the purpose of the back diagram shown earlier). These also have to be adjusted manually. If you have them set wide, like for a thick stock, and then try to run something thin through it, the rollers won't catch it and it will just get stuck in the panel.

This is the counter. It is supposed to have a break (the LED screen) that will pause the flow of sheets every hundred, or two hundred, or whatever it is set at. This doesn't work right now, so I just watch the main counter, and stop the flow every hundred, so I can pull them off and rubber band them, or whatever. This counter unit is as big as my head. I've never been so fortunate as to look inside, but I bet there are some pretty awesome components inside: tubes and such. We inquired, and a new one costs $2500. I don't know if that's for a brand new solid state counter system, or if that's just how much replacement manufacturing equipment costs these days. They always try and get you on stuff like that.

This is the control panel... displaying sideways, for some reason I don't understand. Anyway, from the top we have air flow, feeder table controls, start/stop the flow of the feeder, and then the flow control (the two silver knobs) and table up or down. These buttons are a lot of fun to push.

And, here we are at the end. All the folded sheets come off on a conveyor belt, also manually operated. Finished, folded product!

You might notice the other piece behind the folder, that looks a lot like it. That is the right angle, which can replace the conveyor at the end. It goes on at a... right angle! It is for folding... right angles! After the initial four possible folds, you can send the sheet through for ANOTHER four folds, at ninety degrees. You have to replace the exit rollers with score bars, because by that point the folded sheets will be getting pretty thick, and you need to score it a bit to get it to fold again. Especially since the grain of the sheet was probably heading the direction for the first set of folds, and folding across the grain can get ugly. I can't really think of any typical project in which you'd want to do eight folds, because it is not a map fold--it would end up looking like an accordion folded again the other way. Sometimes we fold 11 x 17 sheets in half, and then letter fold those (so one fold, and then an additional two at the right angle). But that's just about it.

Anyway, if you're still with me, thanks for getting to know the Stahl folder! Being the nerd that I am, I really enjoyed learning how to use it, because such an interesting and amazingly simply yet complex mechanical process never occurred to me, despite all the folded paper I have seen in my life. Maybe you also derived a similar bit of perverse bindery pleasure out of it. I like paper products a lot (why I enjoy printing and bindery work more than the average manufacturing experience) and this is why. It's working with your hands, using your head, and in the end if you do it right, you actually end up with a useable product with quite a bit of craftsmanship imparted to it.

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