Well, after 25 years of printing on Vandercooks, I encountered a new problem today. There is a 1/2″ strip across the whole sheet that is not printing with the correct impression. It is illogical, but it seems that the carriage raises up just for that line of type and then goes back down.
The press is inking fine, but not making an impression in that area. Impression is fine before and after that line.
I was printing a 12×18 sheet of paper with a photopolymer plate. The area in question is about 17″ inches into the carriage run.
Is there anything that could cause the carriage to jump up and then back down randomly? One print will be fine and then 6 will be bad. 10 will be good and 2 will be bad.
I watched the rails on the opposite side of the press as one of my staff turned the carriage back. Didn’t see anything unusual.
Bottom print has impression, Top prints do not.
Ink is picked up from the area with impression, but not off the line in question.
Any thoughts?
Any chance that the time from the MOMENT the rollers return to the press and start to refresh and you insert your paper and start printing again is so quick that the form roller to not rotate a full revolution allowing the ink to refresh so it is not getting completely re-inked. Might you be getting a bit of ghosting when it finally gets to that problem line in the image?
You might try taking the plate off the base, build up the base until it prints and see what that image shows you. Might be clearer if you see the same general inking problem, but also to show you how abrupt if is and its exact placement.
Mylar on cylinder tight and straight.
Something in gear track for either the inking roller or cylinder.
Something where the rollers are locked to the side rails (not sure the technical term).
Allison, while I know you are a seasoned printer, let’s run through the possibilities for the benefit of others as well:
– Can you get better results by printing slower?
– Loose and/or dented cylinder packing. Tail of drawsheet may not be fixed to the reel rod and/or the pawl is not locking to the ratchet.
– Nonstandard form (height to paper).
I see that you have a standard Boxcar base and standard depth, polyester-backed plate, but is the plate adhesive standard and is it evenly applied?
– Press bed: standard (0.918″), galley height (0.968″) or adjustable?
If a galley bed, there should be a bed plate (0.050″), but it could be warped/sprung, or a non uniformed caliper, e.g. made of galvanized steel and not the originally specified cold-rolled steel. Perhaps card stock is substituted or there is multiple underlay sheets.
If an adjustable height bed it may be unbalanced do to long term grime/lack of lubrication and needs to be disassembled, clean and lubrication.
– Worn under rails. is there noticeable wear or roughness at the point of interest?
– Carriage bearings out of adjustment. Loose lock nuts? Were they previously adjusted to compensate for under rail wear.
– This Universal I (#22601) was built in 1962 and most likely has the original design, thin-wall cylinder trip rack on the backside of the press, which can become warped. A redesigned replacement can be fabricated by NA Graphics.