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Prinergy web growth

Started by mantman, December 12, 2017, 05:18:34 PM

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mantman

Soo asides printing i managed to throw myself into the beautiful -or not?- world of prepress.

I have register issues on the press, i have succeded -i hope- in getting the hang of stretch in various ways except this one...the inverted smile.

Allow me to explain...i ran a KCMY config and at M i have loss of pressure in the middle of the cylinder. This does not concern me -i lose 0.10 of density and 2-3% of dot i can live with it- but my register is off in the middle of the sheet by 0.05 towards gripper while at 4 corners are in place.

The commands at my disposal are xpansion xy,xyshear,rotation,xyshift,excludemargin no fanout sadly

So is there a way i can distort the image of magenta OR cky to match this...smile? or i am bound to print in a machine that tend to say "have a nice day you will never see rosette!"

Thank you in advance

(Corrected title of post ~ Joe)

DigiCorn

I imagine you have a RIP for platesetting. You could create a color curve on the M plate through your midtones that reduces output density to match.... THIS does NOTHING for registration; merely for color. If you are using paper/poly plates in which you refer to "stretch," then no... you can't reproduce a *glitch.* Without knowing how to operate a press even in the slightest, I would attribute it to a roller/packing issue.
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mantman

Quote from: DigiCorn on December 12, 2017, 05:35:49 PMI imagine you have a RIP for platesetting. You could create a color curve on the M plate through your midtones that reduces output density to match.... THIS does NOTHING for registration; merely for color. If you are using paper/poly plates in which you refer to "stretch," then no... you can't reproduce a *glitch.* Without knowing how to operate a press even in the slightest, I would attribute it to a roller/packing issue.

Fast reply  :hello:
Roller/packing/blanket/impression jacket all checked, plates are regular aluminum 0.15mm -though negative with an extra silicon coating- here is a pic how it prints a solid breakaway.
I presume you cant make middle of separated tiff file print "heavier" -meaning at gripper/tail dot say 68% middle 64% so bump 4% only at middle of sheet-.
What i meant stretch is the expansion/shrinkage of separated 1-bit tiff file -or web growth-

Joe

Take a look in the Prinergy help for Web Growth. Here are a couple of examples that might send you down the right path. Or maybe not. We use web growth compensation a lot on web press but pretty much across the web from the center.
Mac OS Sonoma 14.2.1 (c) | (retired)

The seven ages of man: spills, drills, thrills, bills, ills, pills and wills.

mantman

UPDATE

Tried today with double separations -CYK and exclude margin command in separation of magenta- it looked okish but thing is, if there is a line it could go like -----_ _ _------ made a grid and will try to print and register

Joe

Yeah you shouldn't have any harsh breaks like that.
Mac OS Sonoma 14.2.1 (c) | (retired)

The seven ages of man: spills, drills, thrills, bills, ills, pills and wills.

Ear

Stretch is an odd one to chase, since it can change based on the paper. I see it more on web uncoated than sheetfed but I have seen it on sheetfed too, in poor climate/paper conditions. Also see web forms grow after the face trim, in perfect bound books... we decided the heatset locked moisture in and swelled as it cured after trimming, but it's just a theory.

I run a Sierra and use web stretch compensation, per ink station, as a companion to the dot gain compensation curve. I believe mine works by just scaling the tiff separation slightly. 
"... profile says he's a seven-foot tall ex-basketball pro, Hindu guru drag queen alien." ~Jet Black

Joe

Web growth changes with humidity, temperature, kind of paper, manufacturer of paper, width of web, mood of pressman, etc....

We have different web growth profiles for each press, web size, type of paper with winter and summer profiles for all of them. And we still have to make changes in the middle of a press run at times because all of a sudden it will do drastic different things than the ordinary. Of course it is never a press or pressman issue.

But only for the web presses. Never use it on our sheetfed presses.
Mac OS Sonoma 14.2.1 (c) | (retired)

The seven ages of man: spills, drills, thrills, bills, ills, pills and wills.

Ear

I've seen it making multiple passes on a 2 color, 40" sheetfed... but not on the smaller Speedmaster 4up, 4 color sheetfeds
"... profile says he's a seven-foot tall ex-basketball pro, Hindu guru drag queen alien." ~Jet Black

Joe

I'm not saying we don't have the issue on our sheetfed (s). It is just the guy in charge of sheetfed never wants anything changed. By God they ran it that way 50 years ago and they can run it that way now.

We have a new (to us) ManRoland Rotoman that can deliver folded sigs or sheets like a sheetfed. We use web growth on the stuff runs as folded sigs but not on the stuff that comes out as sheets. All from the same roll of paper. Go figure.
Mac OS Sonoma 14.2.1 (c) | (retired)

The seven ages of man: spills, drills, thrills, bills, ills, pills and wills.

Ear

 :lmao:  Yeah, same here. We saw it but the pressman just centered the marks to split the dif and called it good.
"... profile says he's a seven-foot tall ex-basketball pro, Hindu guru drag queen alien." ~Jet Black

Farabomb

I've been in sheetfed for 15+ years, about 5 of them in a web shop and this is the only place I've ever heard of web growth. I honestly have no idea what it is and I'm pretty damn sure the web place we were in didn't know either.
Speed doesn't kill, rapidly becoming stationary is the problem

I'd rather have stories told than be telling stories of what I could have done.

Quote from: Ear on April 06, 2016, 11:54:16 AM
Quote from: Farabomb on April 06, 2016, 11:39:41 AMIt's more like grip, grip, grip, noise, then spin and 2 feet in and feel shame.
I once knew a plus-sized girl and this pretty much describes teh secks. :rotf:
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
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My other job

Joe

The web sheet actually grow a little across the web as it goes through each unit of the press. We print in KCMY order in the press. Our web growth profiles enlarge the cyan one-bit tiff a tiny amount, the magenta a little bit more and the yellow the most but only across the web. A typical profile runs the black at 100%, the cyan at 100.03%, the magenta at 100.7%, and the yellow at 100.11%. It really does help
Mac OS Sonoma 14.2.1 (c) | (retired)

The seven ages of man: spills, drills, thrills, bills, ills, pills and wills.

Farabomb

I know printing is a game of minute numbers, that's part of the reason I liked it. That's why I don't understand why the boss thinks everything can be fixed by a hammer. The minute measurements we use are the difference between success and failure.
Speed doesn't kill, rapidly becoming stationary is the problem

I'd rather have stories told than be telling stories of what I could have done.

Quote from: Ear on April 06, 2016, 11:54:16 AM
Quote from: Farabomb on April 06, 2016, 11:39:41 AMIt's more like grip, grip, grip, noise, then spin and 2 feet in and feel shame.
I once knew a plus-sized girl and this pretty much describes teh secks. :rotf:
They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.
         —Benjamin Franklin

My other job

zox

Same situation here as with Joe,

Sheetfed is fine, however webs need web growth compensation.
At the moment they use only bustle wheels but on really think and crappy stocks bustle breaks the web so I am looking into web growth software right now. I demoed Agfa software for about 3 months, it was really good, now I am looking at Heidelberg tool, it seems more capable but we'll see.