BOSPrint allows you to set-up the Flexographic printing Cylinders with its respective Presses, Plates and Distortion Ratios.

The flexographic printing process requires precise connections between the various aspects of the press. Plate cylinders are crucial to the flexographic printing process as the base component for consistent web performance. Plates attached to the plate cylinders transfer inked images directly to the substrate.

For more on Flexographic printing, click here.

Discover Cylinders (Flexo)

• Cylinders (Flexo) Data Grid
• How is Distortion Compensation Calculated?
• More About Cylinders in Flexo Printing

Cylinders (Flexo) Data Grid

Navigation

Main Menu > Setup > Cylinder (Flexo)

Cylinders are set-up directly in the Data Grid by selecting the Press and Type from the drop down lists; and entering data to the Size, Repeat, Plate, Ratio and Stock fields.

1. Press - This allows you to select which presses you want to view.
2. ID - This is a unique ID generated by BOSPrint for the cylinder.
3. Size - This is where you enter the size of the cylinder
4. Press - This is the press that the cylinder is used.
5. Type - This is the type of cylinder you can select from:

6. Repeat - This is the Repeat length of the plate. See Distortion Compensation below, to better understand point 6 to 8.

7. Plate - This is the Plate length. The plate length will be shorter than the Repeat length because of distortion.

8. Ratio (%) - This is the calculated distortion ratio percentage for the plate.

9. Stock - This shows how many cylinders are in stock.

How is Distortion Compensation Calculated?

The first step is to calculate the distortion compensation that is necessary to ensure that the final image is printed without being stretched vertically or horizontally. It is important that distortion calculations are precise, because even a small error can create problems in the final printed image. In most cases, flexographers prefer that graphic designers not compensate for distortion in their artwork files. Instead, the distortion compensation is typically performed by the flexographer onsite, at the printing or tradeshop facility.

Most flexographers use a standard formula to determine distortion compensation percentages. This formula can be expressed as follows:

• Distortion compensation % = (K x 100%)/R

where K = constant, and R = repeat length

Determining the "K" factor (constant)

The distortion produced relative to the plate thickness is known as the "K" factor (K). You can calculate the constant K factor using the following formula:

K = 2πt where π = 3.142, and t = plate thickness (minus the polyester adhesive/mylar/stickyback).

• Distortion Constant (K) = 2π(plate thickness - plate mylar thickness)

Example:

Most 0.067 inch plates are on a 0.005 inch mylar so:

Plate thickness is 0.067", polyester adhesive (stickyback/mylar) is 0.005"

K= 2π (plate thickness - thickness of the polyester adhesive)

= 2π(0.067 - 0.005)

= 2 x 3.142 x 0.062

= 0.3896

Determining the repeat length (R)

The repeat length (R) is normally specified with the print job. If repeat length is not known, you can determine it by measuring a printed sheet. If this is not possible, you can calculate it by adding the radius of the printing cylinder, the thickness of the polyester adhesive, and the plate thickness, then inserting the results into the following equation:

• R= 2πx

where π = 3.142, and x = (cylinder radius + adhesive + plate thickness)

Example :

Plate mounted on a 8" diameter cylinder (radius of 4"),

Polyester adhesive is 0.005", plate thickness is 0.067"

R= 2π(cylinder radius + adhesive + plate thickness)

= 2 x 3.142 x (4 + 0.005 + 0.067)

= 2 x 3.142 x 4.072

= 25.59"

Completing the calculation

With the K and R values known, you can calculate the distortion compensation percentage using the original formula.

Distortion compensation %= K/R x 100%

= 0.452/25.59 x 100%

= 0.0177 x 100%

= 1.77%

The entire calculation can be mathematically simplified to:

Distortion compensation % = t / x X 100

Once you calculate the distortion compensation percentage, subtract it from the original size (100%) to determine the actual output percentage.

= 100% - 1.77%

= 98.23% (Scale source image to this value). Enter this final output value in the Scale box of the output process template.

With correct compensation applied, layouts will print with their intended final dimensions.

Watch this video of a short lesson on calculating distortion compensation:

More about Cylinders in Flexo Printing

Flexography prints from a flexible printing plate that is wrapped around a rotating cylinder.

The plate is usually made of natural or synthetic rubber or a photosensitive plastic material called photopolymer. It is usually attached to the plate cylinder with double-sided sticky tape

Types of Flexo Plate Cylinders

There are different configurations of flexo plate cylinders, each of which can be swapped out for cylinders of varying diameters depending on the application. The attached plate is inked by an anilox roller and transfers images directly to a substrate passing between the plate cylinder and the impression cylinder.

• Integral plate cylinder –Every part of the cylinder, including shafts, body and end caps, are contained in a single unit.
• Demountable plate cylinder –Manufactured without pre-attached shafts, this type of plate cylinder can be mounted onto an existing shaft.
• Sleeve –The plate is mounted to a removable cylinder sleeve and slid onto the main plate cylinder. Air pressure expands the sleeves to allow for easy mounting and removal.