Doctor Blades Troubleshooting

1. Streaks

a. Foreign particle trapped

  • Reduce blade pressure under blade
  • Install ink filters in ink system
  • Install magnets in ink system
  • Change doctor blade

b. Nick in doctor blade

  • Install ink filters in ink system
  • Install magnets in ink system
  • Change doctor blade
  • Check anilox for damage and/or excessive roughness. High or uneven areas from laser engraving
  • Send worn doctor blade to us for evaluation
  • Use LONGLIFE doctor blade
  • Check new blade tip for damage (if small, polish with fine polishing paper)

c. Abrasive inks and/or solvents

  • Use LONGLIFE doctor blade
  • Use DURA or STAINLESS STEEL doctor blade
  • Check with ink supplier for alternative pigments
  • Check PH balance of ink (water-based)

2. Uneven Ink

a. Metering Wavy blades

  • Clean doctor blade holder and reset blade
  • Check blade holder for damage and repair
  • Tighten bolts from center out alternating sides
  • Replace missing bolts
  • 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

b. Alignment

  • Make sure centerline of chamber is parallel to center line of anilox roller
  • Make sure both blades, top and bottom, contact the anilox roller at the same time
  • Check blade extension from holder (should be the same through the entire length)

c. Vibration

  • Blade chatter—blade angle too steep
  • Gear vibration from press
  • Bounce from printing plate

3. Anilox Wear

a. Over-pressuring doctor blade

  • Look for the reasons why excessive pressure is needed and correct
  • Install stops to limit adjustment to insure the chamber does not contact anilox roller
  • Metal filings (slivers) 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
    slivers in inking system. This can cause score lines.)

b. Contact area too large

  • Reduce contact area
  • Use correct width doctor blade (check with holder manufacturer for correct size)
  • Use reduced thickness blade tip
  • Reduce blade thickness if using straight steel
  • Check blade angles (send worn blades samples to us for evaluation)

c. Incorrect blade material

  • Have steel analyzed for purity
  • Check for excessive roughness on blade tip (use fine polishing paper to correct)
  • Try alternative blade materials (check with us to correctly match blade materials to application)

4. Excessive Ink Film Thickness

a. Contact area too large for cell count

  • Use some form of pre-ground blade to reduce contact area
  • Incorrect blade angle
  • Blade material too thick (applied to straight steel or non-metallic)

b. Cell volume or cell count of anilox not matched to line screen count of plate

  • Guideline: Cell count should be 4-6 times larger than count of plate

5. Leaking Chamber

a. Incorrect chamber alignment

  • Verify that chamber is parallel to anilox roller and both top and bottom blades are
    contacting anilox roller at the same time (check empty chamber with a machinist
    level and a feeler gauge without end seals in place)

b. 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)

c. Wavy blades

  • Improper seating of blade in holder allows ink to escape holder
  • Bad holder condition
  • Missing or worn bolts

d. Re-doctoring of ink from containment blade

  • Reduce excessive blade pressure
  • Correct ink viscosity
  • Incorrect containment blade for press, holder or anilox (use a thinner alternative
    material such as mylar, polyester, or non-metallic)

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