I have a friend with a Universal III. It had the power drive, but he had a handcrank put on instead.He is a knowledgeable printer with solid skills.
He was printing something this past week (two colums of text) and every other one would bounce back and forth about 5 points.Nothing looked odd to me and I looked over his III carefully.
I came back and looked at mine (I have the automatic kind) and I couldn’t see anything that would lead me to believe the misregistration was possible.
He believes it was tightly locked in.
Anyone have any thoughts at all.
I have used heavy brown wrapping paper as frisket. It can be used in place of the tapes, or in conjunction with them. If masking out inked portions of the form or background marks, poly-coated butcher’s paper does well, and doesn’t allow the ink to eventually seep through. I printed on very thin paper one time, and the frisket saved the paper from sagging laterally during the impression as Eric describes.
Gear backlash came to my mind, too. The motor drive keeps constant pressure on the cylinder whereas a hand crank can have varying pressures, which, can cause the gears to back apart a bit if the form were particularly heavy in coverage or required pressure.
Like most things, if you don’t notice it happening at the time, you just have to eliminate the potentials, and watch very closely the next time something is run. Perhaps printing the next image on a clear sheet and laying it over the just printed sheet throughout the run in alignment would give some security that the image is not moving aorund on the sheet.
Even with tapes I can imagine circumstances where a problem sheet might rise in between the tapes, and possibly give a lateral misregister. (If you used the string method I just suggested and tied the strings closer at the rear then it might force the sheet to bow at the tail, maybe even shift to the side.) The Vandecook tower system was originally designed to hold a frisket sheet between the tapes, for use in proofing multicolor photoengravings before the dead area was routed. Today a frisket could insure absolute contact against the cylinder. I think the material Vandercook sold as frisket was a thin tympan with a barrier coating.
Mechanically, the Universals have a flange that mates with a recess between gear racks that prevents any lateral motion of the cylinder. Front-to-back there shouldn’t be any misregister but not sure about the design of this manual drive retrofit. Any possibility of gear backlash? That could result in a specific front-to-back misregister. But if the misregister has any lateral or diagonal misregister I’d think it has to be a feeding problem. Vandercooks have an inherant flaw, in that the format feeds to the narrow edge of the sheet. That is always less stable than feeding to the broad edge, as on any production cylinder press. Feeding a large sheet on a Vandercook is not easy, and all it takes is a temperature/humidity change during a run, and then static is changing the way the sheet moves. Problems will be worse at the tail, so if the misregister is toward the head then something is REALLY wrong.
His press has the tower and he was using the tapes to hold the paper tight against the cylinder. So, there wasn’t the problem of the paper sagging into the blank areas.
Paper was approximately 20″ long x 15″ wide.
My friend has printed hundreds and hundreds of pieces with very, very tight registration. It was just this time. He had printed two columns of type (again he thinks ‘locked’ in) with a gap for an illustration between them.
When we got to his studio he was complaining that he couldn’t keep the illustration in register. After some looking and measuring it became obvious that the problem wasn’t with the illustration but with the first run of type.
I looked at our Universal III (essentially the same as his but his is about 6 years newer) and I just didn’t see anything that might throw things off that far.
Thanks for the note.
How big a sheet, how big the form, how much head margin? Grain direction? Does the whole block shifft position or is it fish-tailing? If it is shifting at the head that is troubling.
The biggest problem I have is the sheet sagging into blank areas of the form which makes the tail element go long (and slur). The sheet supports on the press don’t help with this especially in large sheets. My only solution is to use high furniture or low bearers or put layers on scrap binders’s board into the gaps, all high enough to support the sheet but too low to ink. Note that I am not talking about use of a large photopolymer base, just type and individually-mounted plates.
You might try tying string or bands from front to back cross-rods of the cylinder carriage in the margins of the sheet, to hold the sheet firm against the cylinder through the print stroke, but not tight enough to mark the sheet. I’ve never done this, just recalled it as a method of getting heavy cover stock through a Heidelberg cylinder, might be applied here.