Silk Screen process printing

[Mikie]

Greetings!


We have a 6 color carousel press and are trying to increase the line screen. We currently run at 59 line and all is well. I have nill experience determining the correct angles/mesh count/line screen combinations to prevent moire. I have done research online and all the suggestions etc come out horrible. If anyone has any leads on how to determine the correct angles for the linescreen/mesh count etc it would be much appreciated. if there is any information i can give to help you help me just let me know. We image direct to screen using a CST imager, no film involved. Thanks in advance for any help.


and i already tried to set the thing on fire, didnt work.... stooopid sprinklers :p

[Possum]

If your're talking about garment printing, the rule of thumb is that the screen mesh should be at least four times the line screen. Most printers start at a 29.5 angle, but we use 61 degrees pretty well. Nothing, but nothing works all the time, though.

[Mikie]

Thanks Possum, it isn't garment printing, just regular old drinktilyadie' printing. we got the 59 line to work pretty good a couple of years ago, but this is driving me crazy. i have tried various LS/angle combinations and all i get are disturbing disturbing images lol...

[Grimace]

Nice old thread to resurect...

Well, this depends upon a lot of variables.
How much higher are you wanting to go?-you may have to increase your screen mesh accordingly.

What are printing on?-sounds like cardboard, but I have heard that 83dpi is more consistant with cardboard

What mesh count are you currently using?- not only what threadcount, but thread diameter, and weave type. I have had a 300 thread Plain Weave work great, then had the same files on Twill run like garbarge. Generally Plain Weave is more common. Now you can also get 300 thread Plain Weave with 28 -30 micron thread diameter, and yes, it does matter. Mostly with the amount of ink going down---larger diameter=more emulsion-more ink!

Common dot angle are just like offset, 15 degrees apart. But one thing I noticed was that we would get less moire by starting at like 7-C  22-M  37-Y 52-K and depending upon mesh induced moire, I would adjust to 1/2 degree less each.

The old garage shop method is to start with 0-15-30-45 and hold film up to the screen to see where the moire was active, then to adjust the film by rotating it till no moire showed, but you have to do this for each CMYK, and then split the difference, cause not all of the colors will always line up.

Now that's a little harder with a direct to screen device.  Possum's advice is not one I had heard before, but sounds right in line with what I have printed on CDs and DVDs. We typically used 420 to 460 mesh when printing 110-133 lpi CMYK.
What is wierd is that we had similar issues trying to fine tune our images, and for some reason(competition?) nobody wanted to come clean about what set-up they used. I even tried having our screen supplier tell me what to use, but they didn't seem to have an opinion...other shops were really evasive about their setups also.

Good luck, I hope you find a method that works. Remember, only change one thing at a time, or you'll be chasing shadows!