I had this happen a few weeks ago with a bad paper jam printing on curled hand made hemp paper. It was a very bad train wreck and I almost messed things up big time with the ribbon cable on the carrage assembly getting the torn up paper out. Afterward I was getting black marks on my roll prints. I saw ink on a couple of star wheels and one was bent. I cleaned them with alcohol and straightened one that was bent with needle nose pliers right in the printer ( with a good work light ) . Everything was fine after that, but scary. Don’t take chances with warped paper or paper with frayed organic edges that can get caught in the star wheels. Since the very beginning of the z series the star wheels are one of the weak points of the printer. But they did fix the scratching on gloss media that was epidemic on the first two years of the z3100. I’ve had very few problems since then, but I treat my printers like little babies and try to avoid warped media. If you are careless you can end up with a costly service bill because of those star wheels.
John
quote author=simplesimon link=topic=128393.msg1087261#msg1087261 date=1546712226]
Thank you. After losing seven prints to the scratching, I felt more comfortable in doing something from reading your post. I removed the two torx head screws holding the rail to the printer, and the spring clip retaining the wheel sections on the rail. I identified three sections that had a little tension when turning starwheels, and soaked them in isopropyl alcohol. After that, I popped out the spring axles, inspected the center of the wheels (which all looked clean at this point) and reinstalled the wheels. They all seem to be turning quite well now. Had I known it was such a simple operation, I would have done it much sooner. I was concerned I could throw something with the wheels or rubber rollers underneath, but nothing seems to be adjustable in what I did, as it's just held in by those two screws threaded into plastic bosses. If it still scratches, I will either completely remove the offending wheel, or take it off, grind down the very tips of the teeth on a diamond plate, and put it back with that reduced profile.
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