Caring for your plates

A guide to handling, cleaning and storing photopolymer printing plates

The proper care of photopolymer printing plates will optimise plate life and minimise problems in the pressroom, as well as reducing replacement costs and costs associated with press downtime.

bevelCutting and trimming plates

Cutting and trimming plates with a bevel and having no sharp corners helps to  reduce lifting of plates while on press. Use a sharp blade to cut or trim plates. Change blades often to ensure a clean cut.

Preparing the plates for mounting

  • Clean the base polymer of the plate with a 50/50 micture of NP Alcohol and Meths.
  • If needed, varnish the base and the plate with a micture of 80/20 NP Alcohol and Ink Extender.
  • Using 100% NP Alcohol, remove any varnish at the leading and trailing edges of the plate.

Preparing cylinders or sleeves

  • Clean the mounting surface with a 50/50 micture of NP Alcohol and NP Acetate to remove all dirt, grease and dried ink.
  • Make sure the cylinder is free from nicks and burrs.
  • Check TIR (+/- 4um) for cylinders and outer diameter of sleeves.
  • Load and remove sleeves using lowest air setting possible.
  • NEVER sand sleeves

Mounting plates

  • Do not mount plates where the seams of the plate and tape are positioned over each other.
  • If possible, place tape seam under a non-critical printing area and far from the leading or trailing edges of the plate.
  • Leave 10mm of tape around plate when trimming tape.
  • Wrap cylinder in thin, UV-blocking poly until ready to load into press.

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demount2

Demounting plates

Proper demounting is important to ensure the plates are in good condition for future use.

If you use your fingers for leverage, you run the risk of stretching the Mylar backing, creating ripples along the edge of the plate. Instead, use a demounting tool such as a blunt stainless steel spatula. Do not use knives or other sharp objects.

It is important not to use the demounting tool as a pry bar to remove the plate from a sleeve or cylinder. If this happens, the edge of the plate will have a wrinkled, wavy appearance and will be nearly impossible to hold down when it is remounted.

  • Hold the tool at a 45° andgle. Insert the corner under the base and run along the edge until the plate realeases from the tape.
  • Run the tool smoothly along to top of the plate to give a free flap to grasp. Gently peel the plate from the cylinder making sure you are not stretching it.
  • Do not yank on the plate or fold it back on itself.
  • Remove the plate from the tape first, then the tape from the cylinder.

Plate cleaning

After printing, plates should be cleaned thoroughly of ink immediately .

Use a soft brush with natural bristles and a compatible cleaner. Once you are satisfied all the ink has been removed, blot the plates dry with a lint-free cloth, or blow them dry. Do not rub. Plates should be completely dry before storage.

If ink is allowed to dry on the surface of the plate, it becomes difficult to remove without harsh scrubbing. This could lead to surface damage.

Aggressive solvents such as acetates, heptane or naptha should not be used flor cleaning plates.

For solvent inks, use:

  • Undiluted alcohol
  • Solvent blends compatible with the plate

For water-based inks, use:

  • Alkaline water with a small amount of mild liquid detergent or handsoap
  • Flexo Super Cleaner

For ultraviolet inks, use:

  • Undiluted alcohol
  • Solvent blends compatible with the plate

To test whether a solvent is compatible with plate material, soak the material in the solvent for 24 hours and then measure its thickness.

Storing plates and sleeves

  • Clean and dry plates thoroughly.
  • Store plates away from white light, ozone and heat sources (max 40°C).
  • User foam separator sheets of storing flat plates on top of each other in boxes.
  • Ensure plates stay flat during storage.
  • Wrap sleeves in black poly for storage.
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Any questions?

If you would like any more information about caring for your plates, or any aspect of flexo, use our contact page to send us a message.
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