Hello! I have a 8x12 C&P that I just recently managed to get in working order. But I can’t figure out my current printing issue.
I’m printing with photopolymer plates, and I’m trying to isolate the issue. Before I started printing, I checked roller height and it looked fine. I’ve changed the placement and rotation of the plate on the boxcar base and still it prints unevenly. (see pictures) I’ve backed off on the ink, applied new rail tape, tried a different plate, reduced and increased packing, and in frustration swapped the rollers to a different roller hook each time, but the ribbon image always appears with a darker inner drop shadow.
I should also note my rollers have some weird lines on it, and I’ve been informed by the manufacturer that unless it actually feels raised, it’s most likely a discoloration.
I’m going to test the plates on my tabletop press to make sure it isn’t a plate issue (all were ordered at the same time), but short of that, I’m stumped and unsure of what to do.
Please help point me in the right direction?
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Ok, the image didn’t attach. (And the word is “fruitcake.” My relatives hate receiving Xmas fruitcake.)
Looks like ghosting to me. This printing defect is common enough so that there is a name for it.
In your print, note that it appears there are little dark spots (or ghost images) above the letters, as well as the dark stripe at the bottom of the banner..
The following explains it fairly well, even though they are using a different press:
Your picture shows two rollers. Are you using two or three. Three should help, as it would improve ink distribution.
Try double or triple rolling the plate (with the impression off) before making a print and see if it that helps.
If you still have questions, let us know and we will keep trying to help.
Have you tried double inking (trip impression, ink twice, place piece, re-apply impression lever, print, repeat)?
Or double impression? (place piece, Ink twice, print twice, remove piece, place next piece)
Either of these, while applying a heavier application of ink, might solve your problem. If the ink is too dark for your taste you can adjust the color to compensate or run with less ink.
May solve your problem or make it less noticeable.
I was having some similar issues with my windmill but obtained a rider roller and that really sorted them out actually, but I don’t think that’d be a thing easy to retrofit to your press. (sorry, this aside isn’t helpful to you; but the printing industry solved the problem you’re having with extra rollers that ‘ride’ the form rollers, and thus eliminate ghosting by providing a bit of extra oscillation/ink distribution)
Geoffrey-Just received a third roller today. Going to give that a shot this weekend. Even if it doesn’t solve it, I had been meaning to pick up a third eventually.
Haven-yes, I did try double inking and double impression. Sadly it only darkened the impression rather than even it out. (And rider rollers sound wonderful.)
I’ll update if I have a fix or other things that come up. Thanks, I appreciate the help!
I got the third roller, still having issues, then I noticed the disc lever paw is worn. I tested it—it takes twelve cycles before the disc fully rotates. While I don’t remember what a normal rotation number is, twelve sounds high.
How would I go about fixing this? Or is this a bring it to a welder problem? Thanks.
A couple of thoughts…
I’d try a few pulls with the plate oriented 90 degrees each set (eg. 5 pulls, turn plate 90, 5 pulls, turn 90, etc.)… mark each print with the roller direction… does the issue follow the plate or maintain consistency with roller direction?
Is the plate type-high? Any possibility the plate material is deep-relief thickness, but the base is standard?
Is roller height checked with lollipop gauge?
Any tests with higher/lower roller height?
Are the trucks and rails clean and gripping, or can the rollers slide on the rails at all?
WRT the disk turning, does the disk turn freely enough to coast a little bit after the pawl pulls it? Is the shaft getting oiled daily?
Ok, so I tried the pulls with the plate oriented […] All the prints are exactly alike with the same ghosting issue.
Plate is type high. I measured it against other plates that were ordered in previous batches, the thickness is the same.
Yep, checked the roller height. Fat nickel. Also tried printing it as a extremely fat nickel out of madness/desperation. If I go anything less than a fat nickel and only parts of the image prints.
Checked the trucks and rails (put up new tape on the rails and trucks for a fresh start.) I found that the new roller’s trucks bumps right up to the roller saddles and seems on the stiff side to turn. I can only get the roller to fit into the top roller saddle—the roller hook is out of the question as the trucks won’t allow it to even maneuver into place. Should I sand down the delrin trucks on the outside edge for a better fit?
As for the disc turning, if I turn it by my hand, it coasts. If the pawl turns it, it stops as soon as the pawl is off of it.
As for oiling, I only have time to print once a week or so, so the oiling gets done the evening before and the morning of. I pulled the disc out and put more oil on the shaft yesterday when I ran the tests—still same results.
Make sure that both roller tracks and trucks are oil free. Set both forme rollers so they leave about a 3 mm strip on a type high roller setting gauge. If your press can be fitted with a rider roller, fit this. Looks like roller ghosting to me, but some times a frisket can be used to help strip the stock from the plate. Try not to reduce ink as this tends to increase both mechanical ghosting and ink mottle. As suggested try double rolling if it is a short run and changing rolling direction.
then is there a mismatch between ink and paper?
how’s about just slightly roughening up surface of polymer with say pumice powder….. try on a scrap piece…….don”t know why I said that just a feeling…………slightly slacken off the ink with reducer?