Xerox DocuColor 8000 - Manual (Page 4)

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Coat ed Papers
Coated papers have binders, adhesives, and pigments applied to their surfaces on one or both sides.
As compared to Xerox Digital Color Xpressions + 24 lb, coated papers will provide improved image
quality and gloss.
Coated papers are susceptible to humidity. Image mottle (light patches in solid area) or light images
overall will occur if paper is not kept packaged in environments with more than 40% humidity. To
avoid this, keep packages sealed and store unused paper in a resealable bag.
The surface of coated paper is susceptible to scratches and fingerprints. Handle all coated stocks
carefully and avoid excessive handling. Keep all work areas clean, as dust or dirt can scratch the
surface of coated papers.
Side t o Side Regist rat ion Considerat ions- Paper St ret c h
When running two sided printing applications side to side registration may be affected by the inherent
paper stretch that occurs as the paper passes through the high pressure and temperature nip.
Typical paper stretch for light uncoated materials is between 0.2% and 0.6% of the paper size in the
process direction. For coated materials the effect can be as high as 0.9% of the paper size in the
process direction.
As a summary, the following observations are relevant to the stretch of paper in belt-nip fusing:
1) The paper stretch problem is most apparent with coated papers. Most coated papers stretch
significantly more than uncoated papers due to the larger frictional stresses experienced by
coated stocks and softening of the paper.
2) The direction of feed with respect to the orientation of paper fibers also determines the amount of
stretch. Papers fed in the CD (grain perpendicular to process direction) stretch significantly more
than papers fed in the MD (grain parallel to process direction).
3) Increasing the basis weight decreases the stretch since less stress is experienced due to the
increased thickness.
4) The synthetic material tested (DuraPaper 10 pt) actually contracts as it passes through the fuser.
Paper stretch correction can be done using the “tools” mode registration adjustment, but front-to-back
trim mark registration may not always be possible. This is because the side-1 image expands by the
same amount that the paper stretches, thus making it necessary to expand the side-2 image by the
same distortion amount. In order to compensate for this you can use the Alignment Adjustment tool
(refer to the System Administration Guide Tools Mode Chapter). The tool will allow you to create up
to 20 custom profiles for individual paper stocks. Lead / Side registration, Perpendicularity, Skew,
and Image Magnification (Process and Cross-Process directions) parameters can be adjusted for
optimum registration performance.