I ended up not calling Xerox customer service. Basically, I gave up on the thicker cardstock, and went with a thinner cardstock which did not exhibit smudging.
I see no one has responded to this post yet. So, at this point I would recommend contacting your local Xerox Support Department to speak with a Product Specialist for more assistance. Please call 1-800-821-2797 or 1-800-835-6100.
My goal: Print an image on an 8.5 X 11in cardstock, double sided, and then cut them out (ignore the double-sided aspect for now; that is an issue as I found out later from the Phaser® 6180MFP Multifunction Printer User Guide page 86, "Automatic 2-Sided Printing Guidelines" where it says that "Thick card stock" cannot be used for 2-sided printing, so I'll just have to manually reload the backside for this particular cardstock).
This is what I see when printing my image to "12pt Matte cardstock" (0.0120in thick, 281 g/m^2 laser printer paper): (See https://i.imgur.com/VR6zXLk.jpg if the forum moderator has yet to approve/release this attachment):
Notice the smudging or smearing or otherwise delaminating of the toner on the edges. Please ignore the "Censored" blocks which were digitally added to the photo.
The "12pt Matte cardstock" comes from the description from the person behind the print counter at the Office Depot (they could only sell me what they had behind the counter; they couldn't tell me other specs on this paper type).
The "0.0120in" sheet thickness value comes from my direct measurement with a digital micrometer.
The "281 g/m^2" value comes from my weighing a single sheet of this cardstock on a **bleep** scale, and doing some math to calculate its value (single sheet weight: 17g). I did so to see if the paper type is simply out of range of the specs on this printer, as given by Phaser® 6180MFP Multifunction Printer User Guide page 69:
Paper Type (Weight)
Plain (65 – 120 g/m2) (17 – 32 lb. Bond)
Thin Card Stock (100 – 163 g/m2) (37 – 60 lb. Cover)
Thick Card Stock (160 – 220 g/m2) (60 – 80 lb. Cover)
Glossy Paper (100 – 160 g/m2) (37 – 60 lb. Cover)
Thick Glossy Paper (160 – 200 g/m2) (60 – 80 lb. Cover)
So the largest it goes to is 220 g/m^2.
Is that the likely cause? Meaning, am I simply out of range of what this printer can support?
Note that I've tried changing the Tray 2 settings to both "Thin Card Stock" and "Thick Card Stock", but still see the smudging/smearing effects. Note that, in between those experiments, I switched the Tray 2 setting back to "Plain" and printed some other a page of random text (not the image) double-sided to clear out the smudging. I printed twice on plain paper and the smudging somehow transferred onto the first paper, but did not onto the second printing. My conclusion: The smudging was left upon some rollers or something. So, at this juncture, I have not tried How To Clean the Paper Tray Feed Rollers as recommended by cardstock feed mpt answer by CathyO-Xerox only because I think I might be already doing something that is not possible.
My previous question giving detailed specs on this printer and the current driver: https://forum.support.xerox.com/t5/Printing/Phaser-6180MFP-D-How-to-enable-2-sided-double-sided-prin...
Another person having issues with cardstock: https://forum.support.xerox.com/t5/Printing/cardstock-feed-mpt/m-p/235282
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