A detailed analysis is made in this problem solving guide for common problems faced in Packaging Flexo press room. A brief description is given of each dilemma alongwith the possible causes and remedies. If you still have more questions , please use our Enquiry section to ask our experts.

Streaks ?    Uneven Ink ? Anilox Wear?
 Excessive Ink Film Thickness ?  Leaking Chamber ?

Streaks?

CAUSE

REMEDY

1. Foreign Particle under blade
  • Reduce blade pressure under blade
  • Install ink filters in ink system
  • Install magnets in ink system
  • Change the doctor blade
2. Cut in doctor blade
  • Install ink filters
  • Change doctor the blade
  • Check roughness of anilox roller
  • Check new blade tip for damage (if small, polish with #600 emery paper)
3.Abrasive ink and/or solvents
  • Use STAINLESS STEEL doctor blade
  • Use different  pigments
  • Check pH balance of ink (water-based)

Uneven Ink Metering ?

CAUSE REMEDY
1. Blades is wavy
  • Clean the doctor blade holder and remount blade
  • Check blade holder for damage
  • Tighten bolts from center out alternating sides
  • Replace missing bolts if any
  • Provide even tensioning of bolts on holder by using a torque wrench
  • Make sure blade is not too long for holder
  • Check end seal placement
2. Alignment
  • ensure centerline of chamber is parallel to center line of anilox roller
  • Make sure both the blades in the chamber contact the anilox roller at the same time
  • Ensure uniform extension from holder
3. Vibration
  • Blade chatter- blade angle too steep
  • Gear vibration from press
  • Bounce from printing plate, fix the plate uniformly

Excessive Anilox Wear ?

CAUSE REMEDY
1. Extra pressure on doctor blade
  • Look for the reasons why excessive  pressure is needed and correct
  • Install mechanical units  to ensure the chamber does not contact anilox roller
  • Metal fillings (silvers) from the blade tip. (Excessive pressure causes wiping by back of blade rather than the tip. The blade tip becomes thin and wears through, releasing silvers in inking system. This can damage the anilox.)
2. Contact area too large
  • Use correct width doctor  blade (check with holder manufacturer for correct size)
  • Use reduced thickness blade tip
  • Reduced blade thickness if using straight steel
  • Check blade angles
3. Poor steel quality
  • Analyse steel  for purity
  • Check for excessive roughness on blade tip ( use fine polishing paper to correct)
  • Try alternative blade materials (check with SUREPRINT to correctly match  blade to application)

Excessive Ink Film Thickness ?

CAUSE REMEDY
1.Contact area too large for cell  count

 
  • Use pre-ground lamella blade to reduce contact area
  • Incorrect blade angle
  • Use thinner blades
2.Cell volume or cell count of anilox not matched to line screen count of plate
  • Guideline: Cell count should be  4-5 times that of plate

Leaking Chamber ?

CAUSE REMEDY
1. Incorrect chamber alignment
  • Ensure chamber is parallel to anilox roller and both top and bottom blades are contacting anilox roller at the same time
2.Incorrect end seals or incorrect setting
  • Check with holder manufacturer for  correct material and dimensions
  • Check blade settings (ensure blade extension is correct to match cut on end seal)
3.Blade is wavy
  • Improper seating of blade in holder allows ink to escape holder
  • Poor condition of holder
  • Missing or worn bolts in holder assembly
4.Re-doctoring of ink from containment blade
  • Reduce excessive blade pressure
  • Correct ink viscosity
  • Incorrect containment blade for press holder or anilox