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screen printing => Screen Making => Topic started by: mooseman on February 20, 2012, 06:44:22 AM
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we have been working for some time on methods of depositing emulsion on mesh better, and with greater consistancy. Some things we tried didn't work very well or should I say as planned while other results are quite encouraging and going in the right direction.
Our target goal is reliable EOM with a 1/1 process, may be unrealistic but you gotta start somewhere......
I am wondering a couple of things relative to your methods in the coating process
we coat with one hand on an 18" coater and tilt the screen from nearly vertical at the start to nearly flat while coating across the screen and back to nearly vertical at the end of the stroke.
How do you coat your screen,
one hand, two hands on the coater?
screen position, vertical, 45 degrees, whatever works?????
what unique methods do you have
Please think through your technique carefully as i gurantee you are thinking one way and actually producing another way. Think i am kidding video yourself coating a screen..................you might be surprized ;)
mooseman
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The most important tip for a good coated screen is to flip the screen instead of turning the screen as you go from side to side. This will allow you to coat in the opposite direction allowing you to get better bridging.
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I generally coat 2 over 2, shirt side first, rotating the screen end to end, then flip over and do the squeegie side the same way. I coat one-handed, starting out with the screen straight up, then tipping maybe 15 degrees from vertical while I draw the coater up to the top, then tip forward straight up.
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Coating technique really depends on what emulsion you are using ,what kind of scoop coater, etc. with standard photopolymer emulsion i use a tetko scoop coater using the sharp side coating 1 slow stroke on each side with the print side last. Drying horizontal with the print side down is very important also..
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Maybe I'm doping smoke, but aren't some of the best screens made done on automatic coating machines? And if so, I'd say watch one in action and try to duplicate its actions. Just thinking out loud. I'm pretty sure they don't flip and/or rotate the screen either (sorry Sonny ;))
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I am no pro by any means but I use Imagemate PC701 with an unknown scoop coater, sharp side. The screen is at a 70 degree angle. Coat shirt side first then turn the screen(no flip) and coat the print side. Screen dries horizontally. This works for me. I don't have any issues with pinholes and I get good prints.
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Heh heh heh... Where's John?
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I am no pro by any means but I use Imagemate PC701 with an unknown scoop coater, sharp side. The screen is at a 70 degree angle. Coat shirt side first then turn the screen(no flip) and coat the print side. Screen dries horizontally. This works for me. I don't have any issues with pinholes and I get good prints.
As he said, no pro here. PC701 with AWT scoop coater, sharp side. Two coats on shirt side, one on the squeegee side. Two handed, no flipping, around 70 degree angle when coating. No issues so far with ChomaBlue before I switched, I just started using PC701 and I love it. Just did my first try at CMYK, 2/1 on 305 exposed on 40-1K (1000 mercury bulb) @ 16.3 light units. Washed out beautifully.
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I'm a one handed coater with the screen almost vertical, maybe 80 degrees. My speed is roughly around 4-5" per second, it takes me about 5 seconds to do one coat. I always use the round edge and use the glisten method on 95% of our screens and on some of our lower mesh counts I'll add another coat to the squeegee side to finish to add another 20-40 microns of stencil. I don't flip the screen anymore like Sonny mentioned. Since it was a pain to flip the screen every time and I had to put down the scoop coater, flip the screen then get my coater back in the right position, I looked at both techniques closely and came to a loose conclusion that I didn't need to flip. I took my techniques from one of my employees who is now our printer. I've never seen screens so close in thickness to one another than what he used to do. I'd measure our screens with our thickness gauge when he was coating and I swear that they were within 5 microns top to bottom and 5 microns from screen to screen, simply amazing and probably on par with automatic coating machines. My new screen guy is pretty good, but he uses two hands and leans the screen up against the wall and it sits on top of a table. I'd like to see him move to the one handed method because he is pretty slow. It takes him 45 minutes or more to coat a rack of 20 screens and it took Carlos 15 minutes to do 20.
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If your looking to get good EOM with a 1 and 1 use the rounded edge. We do that, also we flip the screen. We have a thickness gauge and get great results.
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Where do you guys get your thickness gauges?
I do mostly glisten method which ends up being 2/2, rounded edge with the AWT coater with Aquasol HV at about 80 degrees one handed from the floor.
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http://highlinemeter.com/ (http://highlinemeter.com/)
I have the 1Gen.
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I got my gauge from Bill but his store is offline I think. Ours is a Highline Meter II. highlinemeter.com It's a simple unit that is pretty accurate from what I can tell. I'm sure the $800 one from Kiwo or whoever sells that really high dollar one is better but I've found this one to be as accurate as you would need.
Dammit, you beat me to it.
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I doubt you can get a better one. This thing is damn accurate. And if it is more accurate, by how much? To be honest, a simple magnetic paint gauge would probably work fine. It doesn't have to be the most accurate thing in the world.
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Poor printer's thickness gauge (but only really works after screen is exposed and developed to offer an edge to feel)
(http://media.nowpublic.net/images//72/4/72445f95d9705e00383f043d67278ece.jpg)
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Where do you guys get your thickness gauges?
I do mostly glisten method which ends up being 2/2, rounded edge with the AWT coater with Aquasol HV at about 80 degrees one handed from the floor.
Pretty much identical here except I coat two handed. Like br suggested, I watched videos way back of the coating machines doing this and imitated them. I do flip the screen and would need sophisticated tools that I don't have to accurately say if this is needed in manual coating or not. So, I err on the side of flipping.
Another thing I do is have coating options on the mesh chart. Our chart has unique exposure values for a 150s coated 2/2 and for the same coated 2/1. I also use the round edge exclusively up to 180 s and then the thin edge up from there.
I've considered the one hand method since it makes good sense but my way works so I haven't tried it out yet.
I think it's all about operator skill in any case. Alan's man was doing perfect screens with that one hand method whereas I had a former employee try and convince me to go that way and the screens he built were unusable compared to mine.
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Maybe I'm doping smoke, but aren't some of the best screens made done on automatic coating machines? And if so, I'd say watch one in action and try to duplicate its actions. Just thinking out loud. I'm pretty sure they don't flip and/or rotate the screen either (sorry Sonny ;))
Main difference on an automatic coater is both sides are done at the same time. This wraps the emulsion around the mesh. No Problem Dave ::) ::)
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Was gonna say the same thing as Sonny, and also add that it says right there on the bucket of emulsion to flip the screen.
Even has a little internationally recognizable drawing for the act.
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Dave's a rebel!
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Dave has an automatic coater?
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I know where there is a used one for sale with very little miles and in excellent condition. Northern NE
yp