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Image area piling is a result of poor ink transfer, which is typically composed of a build-up of ink and/or paper components on the blanket.
Image area piling is a result of poor ink transfer, which is typically composed of a build-up of ink and/or paper components on the blanket. This build-up of material can increase in tack and may appear as mottle in screens and solids while progressively losing detail in tones.
Another form of piling is tail-edge pick or snap-outs occuring at the trailing edge of solid images. When this condition remains unchecked, the increasing tack build can pick the blanket apart or cause paper delamination. Piling usually suggests a systems incompatibility with fountain solution, ink, and paper. Lubrication at the point of blanket release in both image and non-image areas is vital in minimizing this concern by preventing the blanket from becoming too tacky.

 

Press
Conditions affecting ink transfer:

  • Cold press start-up;
  • Incorrect roller durometer or settings;
  • Low or over-packed blanket;
  • Excessive or light impression cylinder pressure;
  • Ink train running too hot or too cold;
  • Ink film running too thin on rollers;
  • Emulsified ink causing pigment separation;
  • Lack of lubrication from running too dry on the plate;
  • Optimize press speed for job and coverage.
  • Determining and maintaining an optimum ink train temperature with chilled oscillator rolls (if so equipped) is an excellent opportunity to control an adverse variable directly affecting ink stability and eliminating the potential for piling.

Ink

Ink too cold — not acclimated to preferred run temperature;

  • Tack of ink too high — Piling will usually be more evident in same unit of print;
  • “Speed” of ink too fast — Piling in subsequent units as ink tack builds;
  • Poor ink grind containing a coarse pigment;
  • Over-pigmented formulation or pigment separation — High pigmented ink could also be too strong and running too thin on the rollers;

•    Exceptionally high or low water pickup — Ink formulation incompatible with fountain solution.

Blanket
Blanket wash or solvent is causing excessive tack or swelling of the blanket. Check compatibility of blanket compound and solvent.

  • “Fast” inks demand quick release blankets.
  • Blanket variables offer a variety of surface finishes which carry more or less water. Increased moisture will supply additional lubrication at the point of blanket release. Consult supplier.

Plate
Plate must successfully carry and transfer an optimum ink/water balance to the blanket for effective lubrication in image and non-image areas.

  • Plate needs a water film thick enough to keep ink out of the non-image grain of the plate.
  • Different plate surfaces and grains offer different capabilities in carrying and transferring moisture.

Fountain Solution
Assuming ink is not emulsified or washed out, the plate could be running too dry with lack of lubrication.

  • Fountain solution and alcohol substitute should have adequate lubrication (glycols) that will help the blanket carry water and facilitate a favorable release.
  • Excessive or overly acidic amounts of plate moisture can break down critical ink properties and paper surface.
  • Fountain solution is too cold or too warm. The recommended temperature setting for the refrigeration unit is 55°F with a slight temperature increase to the fountain pan.
  • Maintaining appropriate and consistent conductivity levels is vital in minimizing piling. Opportunities for eliminating conductivity variables at the tap source with a water treatment system specific for the lithographic process is a important.

Paper
Low pick strength of paper surface;

  • Excessive linting (uncoated paper);
  • Surface slope of paper (set rate) incompatible with speed of ink — Tack builds too quickly through subsequent units causing stressful blanket release exceeding the pick strength of paper.
  • Analyze the composition of material at the point-of-pick for either paper or ink related components. Paper that is otherwise running clean may benefit from an ink reformulation.
  • Compare side to side performance of the paper along with a competitive sheet of equal grade, basis weight, and surface. If the problem appears to be an isolated concern, try a different grade run of the same paper.

Pressroom
Monitor relative humidity and temperature;

  • Ideal climate control is 45% (±5%) Rh and 72°(±5°)F;
  • Allow paper to acclimate to pressroom environment;
  • Paper will acclimate in skid and carton packs. Do not open until going to press;
  • Paper acclimation time is relative to environmental extremes and volume of paper;
  • Properly conditioned paper runs with a broader operating window on press.
Our Address:
2672 Hickory Grove Rd.
Acworth, GA, USA 30101
+1.800.241.7970
Hours of Operation:
Mon. to Fri. 8 a.m. to 6 p.m. EST

In-House Machine Shop

Full service machine shop complete with in house CNC/Lathes. We have blueprints for over 1000 different cores.We can repair, rebuild or manufacture to OEM specs.

Our capabilities include:

  • New Core Fabrication
  • Journal Repairs
  • Center Hole Repairs
  • Custom Welding

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