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screen printing => General Screen Printing => Topic started by: Ryan on June 30, 2014, 06:29:04 PM
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Did not know which category to put it in, but over the last few weeks, I've been having jobs being out on both sides of the design. Quite a few have been repeat jobs with the same films that were used before without issue. I honestly don't know where to look to figure out why this is the case. Anybody have this problem and can point me to where I should look? Amergraph 300/350 exposure (don't know the number), shurloc frames with fairly good tension. Don't know what other info would be pertinent, but any suggestions would be helpful
~Ryan
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What press?
Is the out of registration consistant?
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Hey Ryan, are you able to dial them in, or are they just plain out of wack once on the screens? Maybe the screen is shifting after imaging? I'd say if it was new film, maybe film is slipping in your printer but if you've used the same films before something is going on between exposing and loading on the press. I had to get after my guy today taping screens, my wife told me she saw him lifting screens up putting a ton of un-necessary pressure on the mesh with his thumb to the point where she thought his hand was going to go through the mesh, thankfully nothing popped and nothing moved to be noticeable. But I wonder if mesh shifting after an image in burned in can be happening.
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Its out both ways when I get to press, so if i move left its worse on the right and vice versa. Sometimes its been top and bottom. Its like the image was "shrunk" in of both sides so there is no getting it in register. I just don't know where to be looking to figure it out. I feel like when its getting exposed that some how the vacuum is pulling something that is causing to be out, but I just can't see how that would be possible. When I look at films, they are fine
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No experience with the Shurloc frames, but does the mesh sit flat against the glass before pulling
the vacuum? Or does the vacuum pull the mesh down?
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it sits pretty flat. Its like using a static. There may be just a little space, but Its never had any effect on registration before
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Are you running a flash in between the two colors? If so, there's a slight possibility that the shirt could be shrinking on press. Otherwise you may want to check your off contact on all heads/pallets as that can definitely throw things off.
I've had these type of bizarro screens pop up from time to time and usually after a reburn of one or both, all is well. If not, and the films line up, its more than likely something on press.
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Flashing was my other thought as the guy I work with runs the flashes hotter than I do and he's had more issues than I have when he's running his stuff do that could very well be the culprit more so than anything prepress. I will have to check tomorrow if screens are still up. Thanks
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1, Even tho they are the same films from previous runs, (Check the films) to assure that they line up. If they are out of alignment (and used to be good), then somehow, they were set near or on excessive heat that caused them to shrink/distort.
2, Check that all screens have the same tension. 5-10 newtons difference may cause misalignment.
3, Check that they align on press (in the frame holders registered) when you start on one platen.
4, Like someone else said, check the level (consistency) of your platens. If one or two are now out of synchronization, that will cause miss registration (in the print).
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X2 what Dan said
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Also:
Are you using a different squeegee blade/blade type than you normally do?
Off contact the same?
Squeegee pressure any different?
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Excessive and/or wildly varying off contact can cause this. Check for parallel on all heads/platens and keep that off contact reasonable ≈1/8" depending on mesh selection and tension of course.
Over flashing is always bad and will cause more issues than just registration...then again so will under flashing.
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My guess is high humidity is causing your film to stick to the screen during exposure not allowing the film to lay flat and distorting the image. We experience this for time to time.
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have you sacrificed a virgin to the screen print gods recently? i always start there
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So that's where they all went
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How are you drying your screens?
we just had this problem a few weeks ago and it was due to the space heater in our drying cabinet slipping out of position and heating the screen up too much.
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Films sticking have been a problem, especially the more I do in a row, the end ones seem to stick to the screen and the screen is stuck to the glass. No heater in my drying room right now, I typically turn on the AC and the dehumidifier when I get in this time of year. Off contact is pretty low, I don't go higher than 3mm except the rare occasion I get to about 4mm, though I did not check to see what everything was on this particular job as I did not run it. From what I could tell the underbase screen was the culprit. That was the last screen I burned for this job, which did stick to glass/screen, so maybe that has something to do with it. I only have 12 squeegees that I could use so they are really only 75 or 65/90/65, same squeegees i've used for the past 1 1/2 years. Boards are good, though one is slightly bowed front to back, but really isn't noticeable at all. Heads were re- paralleled about 3 months ago, so i'm guessing that isn't it. I am chocking it up to humidity/sticking screens. thats the only thing that makes any sense to me though I will have to pay better attention to whats going on through out the steps so that I can back track if/when it happens again.
I am currently looking for some Virgins too just in case...man are they hard to find :)
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Is your exposure vacuum drawing down to the level it was when you weren't having problems? Leaky blanket= all kind of wierdness....
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my guess and it is a pure guess is that your screens, (mesh) are not sitting flat on the glass.
When you draw a vacuum the mesh is distorted as it is pulled to the glass and exposed to the film.
When the vacuum is broken the mesh returns to original position thus distorting the image.
When you place the screen on the glass IF you can press on the mesh with you finger and move it down to the glass ANYWHERE over the surface of the screen it is not sitting flat in static mode. Under vacuum it will distort...my guess is your frames are not parallel and or flat.
mooseman
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There is some tests that can answer this.
Does the film line up. Take the film to your light table and see. If they do then its not the film.
Moving on to testing the screens.
Is the print off consistently. If you change the speed and pressure of the print does the registration get worse? If so its your tension most likely. Could also be other on press items, like printing too hard, too thick of ink, off contact too high. Most of this is because of tension.
If it stays the same when adding speed and pressure and the film is fine then it could be how the screens are burned. This one is a stretch unless you doing something funny.