Flexographic Printing Tools

Flexo plate distortion calculator

Calculate the distortion factor and compensated image length for a mounted flexo plate, with every assumption visible.

A flat plate wrapped around a cylinder stretches on its printing surface. If the image is imaged at full size it prints longer than the repeat, so the file is shortened before imaging. That shortening is the distortion factor.

Different plate systems and workflows account for this slightly differently, so this calculator exposes the factor rather than hiding it. Use the value your plate supplier or CtP workflow specifies.

Calculator

How to use it

Enter Print repeat in mm. Cylinder repeat, the printed length of one revolution
Enter Plate thickness in mm. Total plate thickness as supplied
Enter Mounting tape in mm. Include only if your workflow counts tape in the distortion
Enter k factor. Neutral axis factor from your plate supplier. Many workflows use less than 1.

Formula

Effective thickness = (plate thickness + tape if counted) x k factor Reduction = 2 x pi x effective thickness Distortion % = reduction / repeat x 100 Imaged length = repeat - reduction

Worked example

A 1.14 mm plate on a 400 mm repeat with a k factor of 1 and no tape counted:

Reduction = 2 x pi x 1.14 = 7.163 mm
Distortion = 7.163 / 400 = 1.791%
Image at 392.837 mm instead of 400 mm

Assumptions

The image stretches around the neutral axis of the plate. The k factor is how your workflow expresses where that axis sits, and it is why the same plate can be given different distortion values by different suppliers.
Mounting tape is included only if you enter it. Some workflows count it, others treat the tape as compressible and exclude it.
Distortion applies along the repeat direction only. Across the web the image is not distorted.

Limitations

Every calculator on this site gives a planning figure, not a production guarantee. Check the result against your own records before committing material or money to it.

This is the classic geometric compensation. It does not model plate compressibility, relief depth, durometer, mounting tension or press behaviour.
Continuous sleeves and in the round imaging have no seam and no flat to wrap, so this compensation does not apply to them.
Your plate supplier and CtP workflow are the authority. If their figure differs from this one, use theirs.

Common mistakes

Applying distortion twice, once in the RIP and again in the artwork. It is the single most common cause of repeat errors.
Using total plate thickness with a k factor of 1 when the supplier specifies a lower factor, which over-compensates the image.
Carrying a distortion value across to a different plate gauge or repeat without recalculating.

Frequently asked questions

What is flexo plate distortion?

A flat plate wrapped around a cylinder stretches on its outer printing surface, so an image imaged at full size prints longer than the repeat. The file is shortened before imaging by the distortion factor to compensate.

What is the k factor?

It expresses where the neutral axis of the plate sits, meaning the depth at which the plate neither stretches nor compresses as it bends. Plate makers publish their own value, and it is the main reason two workflows can give different distortion figures for the same plate.

Does distortion apply to sleeves?

No. Continuous sleeves and in the round imaging have no flat plate being wrapped, so there is no stretch to compensate for.

Should mounting tape be included?

It depends on the workflow. Some include tape thickness in the calculation, others exclude it because the tape compresses. Follow whichever convention your plate room already uses, consistently.