Intolerant about tolerance – Kolikando!

Designing screen printing projects comes with a false sense of precision. It’s easy to assume that whatever is designed on screen will be reproduced accurately—without defects—into a final product in the real world. This is enhanced by the ability to place objects on precise coordinates and align and distribute them with similar precision.

Unfortunately, the practical application of computer design to a real-world product comes with a series of tolerances that are not taken into account in design software.

Such examples are

• Variables in the substrate. Paper stock can expand, warp, and swell based on humidity, storage conditions, temperature, and ink density, to name a few variables.
• Creeping (also known as planking, pushing or shoving). We discussed this in a previous article, but it is a phenomenon where artwork in a book moves towards the edges of the pages due to the gathering of folded sections.
• Registration between inks and decorations.
• Paper folding accuracy.
• What your computer says versus what the output device promises.

Some disparities are barely noticeable and imperceptible without magnification, while other disparities are significant by comparison. This article will discuss several printing phenomena and the tolerances associated with each phenomenon.

Ink registration tolerance

This is an example where tolerances are very tight, and are best displayed when printing multiple colors in one pass, such as full-color process offset printing, digital toner, or inkjet printing. Take, for example, the following headline.

At normal magnification, the inks appear to be in perfect registration. However, when zoomed in, it is possible to see that the registration of the inks is slightly off, showing tolerances in the microns.

However, it doesn’t take much to make the disparities worse, such as:

• Use a printing method where misregistration is a greater concern, such as flexographic or screen printing;
• Additional colors are printed in a second pass, which means the papers have to dry first and a paper warp variable is added to try to register the additional inks over the previously printed inks.

Registration of decorations

From here, tolerance begins to build. Take for example full color printing as well as spot color printing which has an additional transparent UV varnish applied to the letters.

Note that while recording the inks, the spot UV is off half a millimeter to the top right. This is because two separate processes were used – a five-color printing press to print the inks onto the paper; Spot UV was then applied using a screen-printed stencil made using an image separation device that was different from the plate separation device that produced the images for the plates.

Another example is how design translates from screen to decoration. Take this complex wafer, and notice how fine details are lost in the wafer.

Double the registration

This is where tolerances can exceed several millimeters. A simple exercise that illustrates this problem is to take a sheet of paper and fold it in half four times, then look at how the pages line up at the heads and feet of the folded pages. The same problem occurs when you take a forced sheet of paper and fold it into a signature to combine it with other combined signatures to connect the rush.

Take the following example which has a header running in InDesign where the sidebars bleed off the edge. Notice the difference between the highest point and the lowest point.

What can he do?

• Be aware that printing and binding are not as precise and subject to tolerances as any other manufacturing. What is important to know is where the maximum tolerances lie and how to design with them in mind.
• Talk to your printer or finisher and ask to see samples of previous work.

There is also page-to-page logging that needs to be discussed, but that will be covered in a future Colecandoo article.