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screen printing => General Screen Printing => Topic started by: T Shirt Farmer on March 14, 2012, 07:57:37 PM
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What the heck is going on here?? These are about 5% dots 55 lpi... I have never seen a moire pattern like this. I have burned this on a 330 and 355 and get pretty much the same result. If I loop the areas that are printing they look good... why am I completely missing areas of dots? any input is much appreciated.
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If the screen looks good (washed out completely) I would say fabric interference.
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Yep, what EB says.
If you can print the halftones clean and clear on paper, then you are getting a pattern interference from the shirt weave itself.
Doesn't happen often, but it does happen.
Simple solution is to print a clear or white under the halftones to "seal" the shirt and the weave that is causing the problems.
Or get a different lot # of shirts.
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When you used a loupe what are you examining? The screen? the film?
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Check the film first.
Then check the stencil, you may have impartial washout in that area.
But it's highly likely fabric weave issues like eb and colin said. If so, try changing the angle of your dots. Upping your tpi isn't going to change the size, angle or frequency of the dots and that's the issue with the weave teaming up with those parameters to make moire and/or dots falling into a void or having nowhere to adhere.
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Son of a cracker jack. I just posted a nice few paragraphs and hit post. Never showed up so it's not getting it tonight! I hate when that happens!!
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Frog: I was looking at both film and shirt,the film has all the dots in the proper places and when I examine the shirt the areas that are printing have nice dots, it is not the fabric I am sure as it repeats the same issue on multiple prints. it is defiantly in the stencil.
Zoo: I am thinking wash out as well, I do use an exposure strip and thoroughly wash out the stencil with mild pressure as to not blast out any dots. I think some of the dots are washing out and some are not, but the reason why is a mystery. My epson 1400 is about 4 years old and I am wondering if the density of the dots is not uniform. I can see all the dots on the film but have no way of knowing how dense they are The emulsion looks nice and even after coating , good mesh tension, vacuum and light source on amerigraph 150 unit. When I have had moiré issues in the past hey generally show as thin closely spaced lines and not as blobs as the image above shows.
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Well, you have to make sure that
1. the dots rinsed out when developing the screen
2. you had no scumming, especially possible if the screen was underexposed on purpose in an attempt to hold detail.
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Frog: I was looking at both film and shirt,the film has all the dots in the proper places and when I examine the shirt the areas that are printing have nice dots, it is not the fabric I am sure as it repeats the same issue on multiple prints. it is defiantly in the stencil.
Zoo: I am thinking wash out as well, I do use an exposure strip and thoroughly wash out the stencil with mild pressure as to not blast out any dots. I think some of the dots are washing out and some are not, but the reason why is a mystery. My epson 1400 is about 4 years old and I am wondering if the density of the dots is not uniform. I can see all the dots on the film but have no way of knowing how dense they are The emulsion looks nice and even after coating , good mesh tension, vacuum and light source on amerigraph 150 unit. When I have had moiré issues in the past hey generally show as thin closely spaced lines and not as blobs as the image above shows.
I'm going to shy away from "knocking dots off the screen". I think if that was happening, you would be laying down solid ink for missing dots, not void areas from missing ink. My vote goes for scum in the screen blocking the flow. Just my 2c.
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Son of a cracker jack. I just posted a nice few paragraphs and hit post. Never showed up so it's not getting it tonight! I hate when that happens!!
Yeah, the 500 errors on this site are a bit ridiculous.