registration issues

[jvanick]

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.

[Ryan]

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 

[Grumpy Ole Artist]

Is your exposure vacuum drawing down to the level it was when you weren't having problems? Leaky blanket= all kind of wierdness....

[mooseman]

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

[Screened Gear]

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.