Actually, a flat spot on a Morgan Expansion truck would merely have the roller ride harder on the form. A flat spot on a roller (caused by leaving the rollers on the ink disk) will cause complete non-inking that does move around. I changed out a roller with a flat spot and it vastly improved things–now to get rid of the other roller that has a pit in it (old rollers).
NEVER leave rollers on the platen when the press is idle. If you are worried and like the have the platen closed (so fingers stay out) remove the rollers first. BTW this applies to Heidelbergs too (just flip the roller tracks up on the top if you leave the platen closed during non-use).
I’m having a similar issue. I’ve tried un-taping and re-tapting the rails, everything is even, the impression is good and consisten, the rollers are brand new (no flat spots) and I’ve conditioned them recently. there’s just a blank spot that moves around the image.
Below is an image of several scraps where the blank spot appears, then affects different areas, then is gone and everything prints fine for several runs, then it reappears again …
So mine looked like that… where it changed the areas of disappearance.
What I found as the problem was that I left the rollers on my press all the time (they are SO hard to take on and off). So then flat spots would occur on the taped trucks/rails. Do you leave yours on the press?
If not, it could be a myriad of things: uneven rollers, bent rollers, dented rails…
Thanks for the tip! I do leave my rollers on the after I clean up, BUT we were still having the same issue right after we re-taped the rails. But I’ll give re-taping a try. also maybe chalk in case they’re sliding?
I’d make sure your rollers were perfectly clean and dry as well, with no leftover solvent, crisco, or grease from the press on them–that can wreak havoc and make for unpredictable ink coverage on press.
I’ve had this exact issue. Also, I’ve had ink disappear in random places if the rollers get too dirty from picking up too much fiber off the lettra. I can usually see on the ink disk how dirty everything is getting.