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screen printing => General Screen Printing => Topic started by: 3Deep on September 10, 2013, 05:39:18 PM
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We did a print last week, sim process and it printed great all but keeping it from getting to dark during the run..using 280 and 230 mesh ct. The first few prints are just what we ordered then it tends to get a little darker, so I dial back the squeegee pressure, I'm at the point now where I only need one print stroke to clear the screens. So if you've had this problem what do you do besides wipe the bottoms of your screens every so many rounds.
Darryl
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Sounds like the screen tension might be less that adequate.
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Darryl,
how many prints is so often? You should be able to go several hundred without touching anything.
pierre
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Excessive dot gain? Usually from low tension screens. Too much squeegee pressure can lead to excessive dot gain as well. If your tension is solid, 20 newtons or better, use a more upright angle, harder & sharp squeegee blade, off contact according to screen tension and those little things will help with the dot gain.
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We did a print last week, sim process and it printed great all but keeping it from getting to dark during the run..using 280 and 230 mesh ct. The first few prints are just what we ordered then it tends to get a little darker, so I dial back the squeegee pressure, I'm at the point now where I only need one print stroke to clear the screens. So if you've had this problem what do you do besides wipe the bottoms of your screens every so many rounds.
Darryl
Are you using WOW ink?
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All that stuff that everyone said and once you've exhausted all that and have good tension, angle, blade, speed, flood, off contact running on a paralleled press and can do no more it comes down to the ink. For me, good WOW ink is the difference between being pumped about doing sim process and being totally bummed out from wiping down screens every fifty prints.
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@ Blue Moon the other day about every 30 shirts which is not cool, it could be the screen tension, I bought these screens from Sonny! lol. No I'm not using WOW inks even though I have some, just not the colors I needed to use, the next batch of screens I buy are going to be what I want in tension or they are going back. @ Alan you could be right low tension screens and off contact could very well be my problem.
Darryl
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Dot gain could also not have been compensated for in the art.
We like to see the first few prints as "too light" and then then things start to fill in
and we're good to go. If you've made all of your adjustments on press but still have
to wipe screens I'd be going back to the art.
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That very well could be a point also, I tend to try and sep to look like what I will print, but you know I know this stuff but have brain farts or just have to much going on. Thank guys
D
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We like to see the first few prints as "too light"
That's def ideal. It's a strange thing how we're not building the screens/stencils to print correctly as is, we're making them to print correctly with buildup over a run.
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D,
I'll just restate what was already said . . .
If printing WOW, the inks have to build up on the bottom of the screens. This takes about 20 prints for us before everything settles in and stays the same for a while. Red in particular takes longer to build up then the others.
Inks not designed for WOW use will continue to build up and without additives might not even settle in. The WOW inks have additives that prevent the buildup already in them. Union Ink actually sells a product called Buildup Buster, but I think it is designed for the Maxo series of inks specifically.
So for the next run, find a better ink and if it is still too dark compensate in the seps. This will make the first few shirts too light, but should settle in after a little bit.
pierre
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Hey Darryl, Ditto what everyone else is saying. Re-working seps is a time honored tradition, we're looking at tweaking a 7 color that's already been approved for crying out loud. Crazy work we do in this biz...
Steve
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I've did seps like that before, but for some reason I was thinking going with a higher mesh count would help, will be taking all y'alls advice on next sim sep job.
Darryl
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Why not change your mesh counts to 305-355? Smaller mesh openings yield smaller deposits of ink. We seldom run sim process on anything but 355's, even if we run 55 lpi halftones. The other comments regarding tensions, and artwork should be considered as well. Sharp 70/90/70 squeegees will also make a huge difference over a softer squeegee to prevent dot gain. Lastly, level pallets and off contacts will prevent heavier deposits of ink on some pallets and lighter on others. Control the variables and you will control the print.
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I'll say ditto to what CastleKing said about the 70/90/70 triples.
I've been having the same issues recently (screen tensions are not the issue - old overused squeegees are) and after seeing the prints that they put out I went out and bought 144" of brand new Pleiger triple durometer squeegee rubber. I ran 2 jobs today with the new squeegees both about 400 pcs. Art was all solid filled areas and 2-3 colors front and back. They were run with no flash and at the end of both jobs very little build up on the back of the screens. Mesh counts varied from 180 - 305.