I have a 10x15 motorized C&P.

It has this on going issue where there’s a blank spot that doesn’t ink the image in one area, and then it moves and affects different areas.

I print primarily using polymer plates.

The rollers are new. There’s not flat spots, I clean them well and condition them regularly.

The rails are taped with UMHW tape. I’ve tried untaping and retaping them.

The impression is great. The rollers are even.

Everything else is fine, there’s just a blank spot that doesn’t print in some areas. (see image attached)

Any thoughts??

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you may deny it but your rollers are not contacting your plate properly go throught the plate to inker contacts again and bearer height (rails) ,it cant be oil as its moving its not the plate as that would not move so its your roller height/ roller bearers (trucks) or your ink rollers have a low point .
You could check that the tension springs on the roller arms are doing the job they should and that you have free return onthe arm when spring is pulled up and released .
A quick fix that may work for you is remove the thinnest packing sheet you have in the tympan packing and put that behind the form , it will tell you if you have weak springs on the arms and may stop the problem ,or create a different one .

Hey Shayna,
I have the same problem on my Colt’s and I suspect it’s the combination of worn and taped rails, worn trucks, and possibly looser springs like Peter mentioned. Funny, though, that I only have this problem on polymer and not with type or woodcuts. If I ever fix mine I’ll let you know what worked- I haven’t had time to rip it all apart and clean/fix/rework everything.
Sorry it’s not an answer, just a commiseration!
-val-

Hey Val,

Thanks for the tip.
We’re not the only ones!

I also found this thread on Ladies of Letterpress forum: http://ladiesofletterpress.ning.com/forum/topics/ink-disappears-and-reap...

She seems to think it’s dents in the rails. Or leaving the rollers on the rails putting pressure on the tape and making it uneven.

Anyway, seems to be a mystery to everyone. I’ll let you know if I figure anything out!!

~ shayna

If the light areas move around, then it isn’t the tracks. In my experience it is caused by trucks that are eccentric, IF rollers are true.
Photopolymer plates require a much lighter setting than does a metal form, and when you raise the level of the tracks and/or the diameter of the truck to suit photopolymer, and are not extremely precise, this problem is the result.
I would not use expansion trucks with photopolymer plates. Results improved dramatically for me when I switched to solid trucks and made sure they were concentric and accurately matched to roller diameter.

Try removing your ink rollers and turn them over so left goes to right and replace ,try again and see if its stopped or moved if it remains the same its your bed bearers (rails) ,if it moves to the other side of the press its your bearers(trucks ) on the rollers .

I have had this issue as well. I do think it is partly due to small divots in the taped rails. The spring thing makes sense too (have NO idea how to replace those…). A few things that gets me through jobs when this happens:

Clean rails with a degreaser
Powder rails slightly with that powder they sell in sporting goods stores for your hands in baseball (comes in a little push for a few dollars)
If those don’t work I put a very thin piece of paper behind the boxcar base where the ink isn’t hitting.
Hope that helps!

Love the lobster!

I think the ladies of letterpress solved this problem (dents in the tape on the rails) but my logical instinct is to be suspicious of the trucks because each time they went up the inking disk and back down the rails wouldn’t they start rotating at a different point on the truck? If there was a low spot, that would explain why it would move around because the rollers would be hitting the plate a different point in their rotation each time.

A dent in the rail tape would cause a light spot in the same place wouldn’t it? UNLESS, there were multiple dents or the tape was sort of soft. Then maybe as the trucks roll along the tape it would push the bumps around (like rolling out dough). In that case it would make sense because as long as there was one lump to start it could just squish it around through the whole run without ever getting perfectly flat again.

I’m just speculating and curious to know what really ended up being the issue.

I have 3 rollers on my 12x18. I use metal trucks on the 2 bottom ones and morgan’s on the top. My rails are not taped and look like a roller coaster. Putting the metal trucks on did wonders. I think because they don’t sink into the divots on the rails and stay more true and not eccentric. (think of roller skating on a washboard….the wheels would ride on the top of the ridges)

I have had the same problem and it was the morgan expansion trucks. I had to release the pressure and then tighten them back up so they expanded evenly. It seemed every so often they would line up just right and cycle together to pull the roller off of the form. Resetting the trucks helped. Never leave your rollers on the press after a job.

There is some play left and right with any roller. So check to see if your rails have wear. As the truck moves down the form it may pull to one side of the rail or the other. If the rails have worn lower on the insides closest to the form and the truck rolls into that or out of that path it may create a heavy spot or a light spot.

This is a somewhat related, and very basic question. Do people remove their rollers form the press between jobs, or is it sufficient to leave them on the rails, but of course, not on the ink disk? Thanks - Niel

If you have composition rollers, take them off - if you have rubber rollers, you don’t need to as long as the rollers are not left on the ink disc.

I take mine off to clean them thoroughly anyway, and just wait to put them back on before next using the press.

Yeah, don’t leave any rollers on the ink disk, OR on a form. But I wouldn’t leave expansion trucks on the tracks either. Or taped trucks. Or metal trucks on on taped tracks.
Metal on metal will not deform or compress at rest, but anything else may.
Remember, a shifting lack of ink is high spot on truck or low spot on roller. These relationships, of track to truck to roller to form, are far more critical with photopolymer plates. A metal form has more latitiude.

Thanks to all and hi to you Bill. Neil