Printing Units Troubleshooting - Register

Description:  Register is the alignment of colors that are printed in successive print units.  Problems can relate to software or printing unit prolblems.

Problems with register are broken down into two categories:

Transversal (Across the web)

Problem:  Web growth or fan out.
Description:  As the web travels from unit to unit, the size of the web width grows slightly.  This web growth or fan out causes the images not to register one on top of the other properly.
Solution:  Compensate with bustle wheels behind each unit. Additionally, some prepress software will allow you to compensate by manipulating the size of the image.

Problem:  Web wander.
Description:  When the web is wandering from side to side, automatic registrations systems work too hard to compensate.  
Solution:  Manipulate tension at your splicer to hold the wander steady.

Circumferential (In the direction of the web)

Problem:  Plates not mounted properly.
Description:  Perhaps the cylinder gap is not clean or perhaps it is mounted poorly.  Whatever the case, the plate may be cocked on the cylinder causing the problem.
Solution:  Clean the cylinder gap well as well as the cylinder itself to ensure the plate mounts uniformly.  

Problem:  Poor web tension.
Description:  Tension is too low, allowing the printing nips to have more control of tension than they should.
Solution:  Increase web tension.

Problem:  Rolls are imbalanced.
Description:  Rolls are not uniform and provide slight tension variations from end to end as they wobble.
Solution:  Since it is a tension issue, increase the tension at the splicer or infeed.  You may also want to try increasing the distance to the first printing unit by utilizing more idler rollers if you have any.  If all else fails, try a new roll.

Problem:  Blankets packed unevenly.
Description:  More often than not, this creates a tension issue.  If there is an uneven pull between printing units, it will show in the register.
Solution:  Pack all blankets evenly and check blanket heights for uniformity.  Also check that blankets are mounted and torqued properly.

Transversal and Circumferential Problems

Problem:  The camera on the automatic registration system cannot read the registration marks.
Solution:  Clean the camera or calibrate the software to see it properly.

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