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Four of six units struggle with solid ink coverage ...
May 20, 2008

Question: Why can't our 6-color, eight-year-old sheetfed press print good solids on units three through six? The second unit prints a good solid. Per manufacturer recommendation, the plate is +.006 over bearer and blanket is exactly at zero. (We're sending you samples.)

Answer: Keep in mind that the printing of a good solid is paramont to printing good dots. Because you have packed the press correctly and (I presume) you have a packing gage to use, then we have to progress to the next step: to pull breakaway dry solids.

Breaking Away

Set the paper thickness for the press to the actual paper thickness of the stock being used. Using cyan ink at a density of 1.40, then pull a dry solid. What you should see is a great solid with no more than .06D difference around the cylinder.

Mechanic Needed

Now, reduce the pressure between blanket and impression cylinder by .002” by setting the paper thickeness for .002” thicker stock. What should happen is nothing. When you reduce pressure by another .002, you should see a good break in the solid. On the sheets you sent to me, the break occurred when the paper thickness was set correctly. There is definitely a pressure issue, and a press mechanic should be brought in.

Readers, please e-mail your questions to Ray. 

Posted by Raymond Prince on May 20, 2008 | Comments (1)