Intolerant about tolerances

Designing print projects on-screen comes with a false sense of precision. It is easy to assume that whatever is designed on-screen will accurately reproduce – without flaws – into a real-world finished product. This is reinforced by the ability to place objects on precise coordinates and align and distribute with similar precision.

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

Such examples are

  • Variables in the substrate. Paper stocks can stretch, distort and swell based on humidity, storage conditions, temperature and ink density, just to name some variables.
  • Creep (aka shingling, pushout or thrust). This is covered in an earlier article, but it is the phenomenon of artwork in a book moving towards the foredges of pages due to the gathering of folded sections.
  • Registration between inks and Embellishments.
  • Precision of the paper folding.
  • What your computer says vs what the output device prepares.

Some tolerances are hardly noticeable and imperceptible without magnification, while other tolerances are large in comparison. This article will examine several print phenomenon and the tolerances associated with each phenomenon.

Tolerances in ink registration

This is an example where tolerances are quite tight, and best shown when printing several colours in one pass, such as full colour 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, demonstrating tolerances in microns.

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

  • Using a printing method where misregistration is a larger concern, such as flexography or screen printing;
  • Printing additional colours on a second pass, meaning the sheets have to dry first and add the variable of paper distortion to trying to register the additional inks to the previously printed inks.

Embellishment registration

From here, tolerances begin to get worse. Take for example a full colour plus one spot colour print that has an additional spot UV clear varnish applied over the lettering.

Note that while the inks are in register, the spot UV is off by half a millimetre to the top right. This is because two separate processes were used – a five colour press to print the inks onto the paper; then the spot UV was applied using a screen printed stencil that was made using an imagesetter that was different to the platesetter that produced the images for the plates.

Another example is how a design translates from screen to embellishment. Take this complicated foil, and notice how the fine detail in the foil is lost.

Fold registration

This is where tolerances can be out by several millimetres. A simple exercise that demonstrates this issue 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 issue occurs when taking an imposed sheet and folding it into a signature to combine with other gathered signatures for burst binding.

Take the following example that has a running header in InDesign where the sidebars bleed off of the foredge. Note the difference between the highest point vs the lowest point.

What can be done?

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

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

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