Flexographic Printing Blog

What Is Distortion in Flexo Printing? Plate Thickness is One Factor

Posted by Luminite on Mar 17, 2021 9:00:00 AM

 flexo print distortion

If you’ve ever seen a child play with Silly Putty and newspaper, then you’ve seen image distortion at work. When the putty is pressed to the newspaper, the ink and text are transferred. Then, when the child stretches the putty -- or even puts it around another object -- the image is also stretched.

Those in the flexo printing industry see this process in action every single day.

But, in flexo, image distortion is a lot less fun. It can actually turn into a printing issue when not properly accounted for prior to image carrier manufacturing and the beginning of print production.

About Flexo Print Distortion

Distortion in flexographic printing occurs when the (relatively) soft material of the printing plate is wrapped around the hard cylinder while being mounted on the press.

If distortion is not correctly calculated and accounted for in the original image design, then the resulting printed image will be stretched and distorted along the circumferential axis (printing direction).

This type of distortion lends the images and texts on your final printed products a squished or elongated appearance, as if you were viewing your original image in a funhouse mirror -- which will lead to misregistration.

Can Distortion in Flexo Printing Be Prevented?

The short answer is absolutely yes. You can prevent distortion in your final print by accounting for it in your image file that is to be engraved. The engraved image will not resemble the correct proportions until the plate is wrapped and mounted to your specific printing cylinders.

This process requires a calculation to determine the distortion factor for your specific flexographic printing plates. Calculating your distortion requires the knowledge and measurement of:

  • Print repeat

  • Plate mount base circumference

  • Plate thickness

  • Sticky back thickness

  • Gear tooth (if needed)

4 Steps to Calculate Distortion in Flexographic Printing

To determine exactly how drastically your flat image needs to be foreshortened to account for image distortion, follow these steps:

  1. You will first need to measure the repeated length of your print job.

  2. Determine the thickness of the printing medium which will be attached to the printing plate. This usually includes a polyester backing attached to a photopolymer coating.

  3. Calculate the plate thickness constant using the following equation:

    • Plate Thickness Constant = 2π (Photopolymer Thickness)

  4. Determine the distortion factor with the following equation:

    • Distortion Factor % = (Plate Thickness Constant / Repeat Length) (100)

If you find the math daunting, enter your measurements into an online distortion calculator, like the one available here.

Opt for 100% Distortion Free Image Carriers

Calculating for distortion is only necessary for printing plates.

Our sleeves and cylinders are created and print 100% distortion free. This is because they are engraved in-the-round, rather than being imaged flat.

This allows for a continuous, seamless print, that produces beautiful final products after every run.

Get Additional Help Directly from Luminite's Printing Experts

Luminite’s team can walk you through our distortion free image carrier options and capabilities, removing the headache caused by distortion.

Download this ebook guide to diagnose your printing problems and defects

Editor's Note: This blog post was originally published January 21, 2019 and was republished on March 18, 2021 to reflect updated information.

Tags: Flexographic Printing, print misregistration, printing defects, flexo printing defects

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