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How to select a kiosk printer: Part 3

October 25, 2011 by Charles Levinski — Product Manager, Hengstler GmbH

In part 2 of my series on choosing a kiosk printer, we discussed selecting the right technology for your application. Now that we've chosen wisely, we'll go over some paper-related issues.

Paper width

Once you've chosen your technology, the paper width is arguably the next most important point. How wide do you want the printout to be? This will, in many cases, determine which printer models that you are able to consider. For example, you can't choose a printer for 60 mm wide paper if you plan to print 80 mm wide paper; unless, of course, the printer can handle both widths, usually by adjustable paper guides of some sort. When possible, use the narrowest, common-width paper that you can, because narrower is generally less expensive. Sometimes your application will mandate your width; for example, if you print railway tickets, you'll have to conform to the standards for such tickets.

Another factor is how easy the printout will be to read and how much information it will contain. It would be tough to put a large, detailed map of Manhattan on a 60 mm wide printout; for something like that, you'd want a full letter width (8½ inch) or A4 size printout. (Although... at this insistence, I once printed an entire report on a 60 mm wide printer in a tiny 8 x 16 font for a customer. The printout itself was very clear, but was only readable if you were under 25 years old!

Moral: just because you CAN do something doesn't necessarily mean that you SHOULD.

Paper weight or thickness

Different companies generally specify the paper that their printers will handle in one of two ways. The first is by density, usually measured in grams/square meter, or g/m². Typical receipt paper is usually around 55-60 g/m². The second way is by paper thickness, usually measured in mils (thousands of an inch) or micrometers. Paper manufacturers prefer to talk about thickness (which they may also refer to as "caliper") because that's what they can most accurately control in the manufacturing process. In fact, many thermal papers include the thickness in their model number. For example, Appleton Papers might refer to one of their thermal paper stocks as "Alpha 800-3.8". This paper is 3.8 mils, or .0038 inches thick. The same paper could also be referred to as 97 micrometers (µm) thick.

Since my goal is not to give you an education on thermal paper (others are much better qualified to do that), let me say only that thickness is usually about durability, cost and perceived value. If the printout needs to be durable, (for example, if the user will put it in their pocket to pull out and show later), it should be somewhat thicker. Exactly how thick depends upon how the printout will be handled. Thinner paper is generally less costly, but paper that is too thin tends to jam the printer more easily. Around 50-60 g/m² seems to be the norm for thinner paper.

Finally, certain types of printouts are perceived as having intrinsic value, and that value depends upon the "feel" of the paper. For example, if you give your spouse tickets to a long-anticipated play, do the tickets seem more valuable if they are printed on heavier paper (think manila folder) or on thin paper like a grocery receipt? In cases like this, thickness matters.

Media type

We've talked about paper above, but the printout could be other materials, as well. Ski lift tickets or water park passes are sometimes made from a plastic-like tag material to be resistant to water. Maybe your application needs to print labels; if so, how will the liner (the waxy backing on which they are mounted) be removed? Perhaps linerless label material is the preferred material; if so, make certain that the printer you select can print and cut it. Most printer companies will make a test print on your media to verify that the printer works with it at no charge.

Paper configuration

Should you select roll paper or fan-fold? Roll paper is continuous and less expensive, but the printer has to be able to pull the roll if it is large. When using fan-fold paper, the printer never has to pull more than a few ticket's worth, so it doesn't need to be as robust. However, due to the perforations usually present at the fold, the paper must be positioned within the printer to not print across the folds This requires the use of some type of positioning technique, like black mark sensing, to position the paper after each printout. A word of caution; if your printer must cut fan-fold paper, always cut slightly after the fold! Cutting before the fold causes a flap on the leading edge of the next printout that can cause paper jams. Cutting exactly on the fold is also problematic, since the fold itself softens the paper, making it more difficult to cut.

Paper roll size

As mentioned above, as the paper roll gets larger, it gets more difficult for the printer to pull. But once it reaches a certain size, there's an additional problem; inertia, also called momentum. The crux of the problem is this; there is generally some slack paper between the roll and the printer. Once printing begins, this slack is taken up and the paper becomes taut. At that instant, the paper roll must accelerate from not moving to matching the print speed. This can't happen, so the paper usually slips, causing characters that are vertically compressed and look like they're crushed. Once the paper gets up to speed, the problem goes away... until the next printout. What is needed is a way to accelerate the paper roll before the slack paper is printed. This is usually accomplished by a device called a "dancer bar" (named for the way it dances up and down during printing) or "inertia dampener."

The paper is threaded under a spring-loaded or weighted horizontal bar. As the printer takes up the slack paper, the bar pushes down, gradually applying more force to the paper roll and starting it moving. By the time the slack is gone, the paper roll is already turning at printing speed and there is no sudden jump in speed needed. The reverse problem also occurs when printing stops, (the paper roll keeps turning, producing slack paper like toilet paper pulled off the roll too fast), but it is easily addressed by adding a little friction to the spindle. If you are printing a paper roll over, say, five inches in diameter, you may need a dancer bar. Check with the printer manufacturer and be sure to allow room for it inside your kiosk.

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