Printing Units Troubleshooting - Nongear Streaks

Definition: Lateral streaks are not to be confused with gear streaks.  These streaks do not coincide with the teeth of the gear that drives the plate or blanket cylinder.  They do however occur laterally from the gear to operator side of the cylinder.

Problem:  Ink forms are set too heavy.
Solution:  When ink forms are set too heavy, they will often hit the gap too hard.  This will cause a bounce and hence a slightly noticeable line across the printed image.  Lighten the forms to the manufacturers specifications.

Problem:  Bad bearings in form rollers.
Solution:  Check each form roller bearing thoroughly.  A bearing that is starting to wear will cause skips across the plate.

Problem:  Main cylinder bearings.
Solution:  Much like the roller bearings, the worn cylinder bearings will cause the same problem.  Inspect and replace as necessary.

Problem:  Rollers are too hard.
Solution:  Change rollers to something softer according to the manufacturers specs.  Generally, form rollers, and particularly the water form, are softer than the others.  When they lose their hardness, plate wear and bounce will occur.  Use a durometer to check.

Problem:  Blanket is loose or smashed.
Solution:  Lines across the blanket can actually be smashes.  Additionally, the blanket should be torqued tight enough to not roll up on the cylinder.  It must be tight enough to not move on the cylinder, but not so tight as to lose blanket height.

I can't find my problem.

Start Over :Web Press Troubleshooting Guide

No comments:

Post a Comment