Screen Tension

[eliteinkprinting]

What's everyone's takes on screen tension. We've made it a routine to check our screens as soon as they are dry. What's usually a good number to either toss them or strictly use them for black ink? We seem to be having some issues lately with bleeding on simple 2 color jobs. Today's job was a simple white/black print and the black lines didn't seem to be as crisp as I like. Messed around with squeeze pressure and angle, but nothing seemed to help. White was on a 156, black on a 230. Both screens around 20-newton meters.

[screenxpress]

I have rollers, but since you asked about tension numbers, I like to have set mine about 24-26 range.  I don't bother trying to get into the stratosphere on tension. 

That being said, I have printed halftone prints using 4 old wooden screens that later (after got a meter) I found to be in the 18-20 range.

20 should work.  Not great, but usually "good enough".

By "bleeding" do you mean the two colors are interfering and bleeding between them?  If so, could the "Bleeding" be from too high off-contact letting excess ink flow?  Or not enough choke and images overlap on their edges?  Can you post a picture of the "bleeding"?

[cbjamel]

too much flood pressure or dull blades?
Shane

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[BP]

If you have low tension you may look at your off contact.

[mooseman]

Tension ( we find) is a hub with many spokes. To simplify the tighter your screens are the more flexible you can be or get away with on other elements that influence your print quality such as flooding, off contact, print speed , ink viscosity , EOM, the characteristics of the actual image, screen mesh etc. Some may disagree but managing screen tension can prevent a bunch of variables entering into your print process.
mooseman

[Sbrem]

When I started, there were no tension meters, except in the high end shops, and mesh was stapled to wooden frames that deflected. Measuring one later on when we did finally have a meter, they wouldn't register at all. So, at 20, it's not so bad as some would have you think. We printed tens of thousands of shirts with those woefully inadequate screens, and the work looked good, halftones and all. I am not advocating low tension and stapled mesh, of course. As someone else mentioned, high tension will solve a lot of ills, but the other variables also still need to be looked after. It's good if all of your frames are close to or the same tension. If the tension is too low, then the print stroke stretches the image, and that can drag over the wet ink beneath it, causing the bleeding you're seeing possibly. You'll get it...

Steve

[StinkyDaddy]

I mostly use 156 and 230's, tighten to 25 and retention at 20.