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Registration woes from a new guy

Posted: Sun Mar 30, 2014 11:46 am
by RiderFan
Hello.

As this is my first post I thought I'd give a bit about who I am then get to my question. I am back in the screen printing world after about 30 years. Back then I was in a high school Graphics Arts class that had a simple manual screen board and we ran off a couple of simple posters every other Friday for one semester. After a couple of non-related careers I decided to invest heavily in my own screen printing shop. I have a semi-automatic press with vacuum table, high quality vacuum exposure cabinet, film based image setter, and other goodies. An exceptionally large investment in good quality equipment because all of the work I do is extremely fine detail, for example, I need to print legible text that is only 0.5 mm high. My screens are typically 420 mesh although I do have a couple of 305 for less detailed work.

I have been getting good ink lay down using Nazdar ink and about 10% retarder. Even the finest text comes out great.

The problem I'm running into, and my question, is registration. I spend quite a while getting the registration perfect on the machine. All the registration marks line up exactly correct. The machine is clamped down tight (the micro-adjusters are on the table, not the frame). And after a couple of tests I've proven to myself there is no movement of the frame.

However as soon as I print anything the registration is way out of wack. I mean by a lot. I take the screen and lay the film back down and everything is perfect. I lay the film down on the printed item and things are squashed. If I align the far left hand side of the print with the film, the print on the far right will be out of register with the film by as much as 3 or 4 mm. (my squeegee prints right to left)

I'm arriving at the conclusion that for some reason the screen is deforming when the squeegee is run over it but the screens are very tight (the company that stretches my screens for me has been doing it 35 years). I tried reducing the squeegee pressure but then my print quality suffers quite a lot (especially for small detailed items). My off-contact is very small, about 2 mm or so.

I'm wondering if anyone has had this happen to them before and if anyone has any suggestions? Do I need more retarder and make the ink thinner? Will that not cause bleeding under the screen? Has anyone tried stainless still mesh? Would that solve this problem?

Hoping someone has some advice. I'm burning through a lot of expensive materials and getting useless results right now.

thanks
David