Flexographic Plates Troubleshooting: Problems, Causes and Solution. – Part 2

This is a continuation to the series of article part 1 on flexo plates troubleshooting.

If you have not read the first article to flexo plates troubleshooting, we link it here :
Flexographic Plates Troubleshooting : Problems, causes and solution – Part 1

Curling

• Problem: Plate starts to curl and potentially causes “plate lifting“ issues.

• Causes: Different shrinkage behavior of polymer and polyester carrier film on the back of the plate; main exposure too short; plate processing time too long.

• Solutions: All plate making parameters should be reviewed and optimized

Insufficient plate hardness

• Problem: Insufficient plate hardness resulting in reduced print quality, high dot gain and reduced longevity.

• Causes: Long washout time; Short dry time or low drying temperature; low UVA intensity during main- or post exposure.

• Solutions: Confirm correct plate making parameters.

Dirty Plate Surface

• Problem: Dirty plate surface; Remaining slip sheet layer on plate surface.

• Causes: Polymer residue redepositing onto the plate surface from the processor; dried solvent drops; lint from cleaning towel.

• Solutions: Solvent saturation; condition of washout processor should be checked (especially the last wiping brushes); use lint-free cleaning towels or soft brushes for cleaning the plate surface.

Insufficient solid ink density

• Problem: Low solid ink density on the print sample.

• Causes: Condition of the ink; condition and specification of the anilox roller; plate and tape hardness combination.

• Solutions: Confirm and adjust ink viscosity and overall ink condition; confirm condition and specification of anilox roller; consider to use a different plate type and tape; consider to use a surface pattern.

Pin holing

• Problem: Image 1: Pin holing Image 2: Good ink lay down 

• Causes: Anilox specification; rheology and viscosity of ink; quality of the white printing; preconditioning of the substrate.

• Solutions: Confirm anilox condition and specification; consider to test different plate and tape combinations; consider to use a surface screening .

Dirty printing

• Problem: Print result is dirty in some colours and with high dot gain.

• Causes: Ink condition not ideal, especially the dry speed should be confirmed, wrong anilox specification; missing dots on the plate.

• Solutions: Confirmation of the condition of the ink; confirm anilox specification.

Slurring

• Causes: High impression settings; problems in cylinder rolling conditions; different surface speeds of the cylinders.

• Solutions: Confirm and correct all printing and press parameters.

Read next Flexographic plates troubleshooting – Problems, Causes and Solutions Part 3.