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Apr 1, 2007 12:00 AM
Scratches on litho plates have been a problem for many years in printing plants. With the advent of more positive CTP plates, the problem has been increasing. In addition, buyers have increased quality expectations. No scratches are acceptable in work today. Scratches add dramatically to makeready time on press, because the press operator has to stop the makeready and use scratch remover or hone out each scratch.
Scratches come from many sources, including:
All areas can be controlled. The areas where I see the most problems are stacking, storage and transit. One of the simplest methods to prevent scratches is to apply an interleaf sheet of unprinted paper. The photo (above) shows a taped unprinted sheet that covers just about all of the plate except for the identification area, eliminating many scratches. This sheet should be applied when the plate comes out of the plate processor and after inspection.
For 60-inch or larger plates, we would roll and tape the plate as shown in the second photo (right). This makes it easy to transport and store the plate prior to press.
For plates 40 inches or smaller, we would hang the plate on a plate rack (left), making it easy for the press operator to locate the plates for a job.
Practices that cause or allow for scratches include:
Scratches on press usually are caused by rough handling, but might also be caused by sand or metal flakes in the press. Sand can come from incoming water, the floor or the ceiling. Metal flakes usually enter the press from rags that have been in a machine shop.
Ray Prince's “Tech Thoughts” run each month in New Products. Don't miss his new podcasts at www.napl.org.
Raymond J. Prince is a leading expert in pressroom technical and operational issues. He recently joined NAPL (Paramus, NJ) as vice president and senior consultant, operations management. During his tenure at PIA/GATF, Prince conducted nearly 1,000 Technical Plant Assessments (TPAs), in-plant analyses of a printer's production facility and capabilities. As a lecturer and trainer, he led numerous industry seminars on all phases of pressroom operations. Contact him at (605) 941-1492 or e-mail RaymondJPrince@aol.com.