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Web Press Troubleshooting Guide - Superstructure



Definition:  The web press superstructure is responsible for performing various functions which include the following:
  • Slitting
  • Tension control
  • Web guidance
  • Cutoff control / compensation
  • Moving web position by angle bars
Problem:  Web breaks
Description:  If the web breaks in the superstructure only, it is likely a tension  or alignment issue.  Read first this guide on how to troubleshoot web breaks.
Solutions:
1.) Check that all web alignment devices are centered to put minimal stress on ribbons or web.
2.)  Use correct tension.  There should be a nip before and after the angle bars.  Generally tension is reduced slightly just before the angle bars and increased slightly just after.  This reduces tension slightly as the web slides around the angle bars.
3.)  Check that slitters are not dull and not not have any nicks in them.


Problem:  Web wanders around angle bars.
Description:  Web moves uncontrollably when going around air bars.
Solutions:  
1.)  Run the air that flow through the angle bars at a minimum, but not too much that set-off occurs.  
2.)  Tension can also be adjusted, but most likely increased to get more control. 
3.)  Ensure that devices reading the web alignment are doing so on a side of the web that is slit.  Edges of the roll tend to to change as roll sizes can marginally fluctuate.
4.)  Check the setting of the nip points.  Tension can vary if they are too light.


Problem:  Setoff on superstructure
Description:  This is a drying problem, or at the very least a silicone issue.  First, ensure you have a good understanding of what setoff is.
Solution:  
1.)  Ensure the dryer temp is set at optimum temperature.  A precaution to take is to not set the temperature too high as setoff will occur because of chalking.   
2.)  Increase amount of silicone being applied.
3.)  Change ink formulation.  Though this would be a last resort, there is much an ink manufacturer can do in reducing setoff.  The flashpoint can be changed as well as anti-setoff ingredients in the ink like wax.


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