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Blankets and quality assurance

Jun 1, 2002 12:00 AM

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Printers should choose blankets based on print quality and dot-gain characteristics. Document the effectiveness of new blankets during a specified period of time to keep track of performance for future purchasing. These data will also help determine the origins of poor print quality, blanket problems and potential machine deficiencies.

Blanket specifications should include the following:

  • Manufacturer and brand name

  • Blanket type: conventional or compressible

  • Thickness: three-, four- or five-ply, with variance of no more than 0.0001 inch across the entire surface of each blanket

  • Size and squareness. Many printers specify a different size than the manufacturer recommends to better fit the needs of the press

  • Blanket-bar specifications: hole-punched, non-hole-punched or premounted aluminum bars

  • Delivery date and destination

  • Shipping instructions: same day, overnight or freight

Thickness tolerance specifications are important and should be developed when consulting with the supplier. Blanket thickness should be measured with a deadweight bench micrometer in at least nine points across the blanket. Reject any blanket out of tolerance and return it to the supplier for replacement.

Blankets should always be stored in cool, dark areas that are unaffected by heat. Always be sure that the storage area is free from ozone, which emits from sparking electric motors. These emissions oxidize the blanket, and in turn, cause streaking on press. Because of the environmental factors affecting blanket quality, blankets should remain in the tube until they are ready to be used. If blanket bars are mounted for blanket staging, they should still be protected from environmental effects.

Source: "Total Production Maintenance," by Ken Rizzo (GATFPress).