Screen Tensions....???

[Printficient]

Also flipping the screen so that the next pass of the coater is going the "opposite" direction from the previous pass is beneficial for "Bridging" which is the 1st goal of coating.

[alan802]

That's impressive that you can get those types of numbers with just a 1/1.  A 1/1 coating with Saati PHW red on a 110/81 at our shop yields about 10 microns EOM which is about half of the % that we are shooting for.  I'd like to see 30-40 microns on a 110/81.  I still think stencil thickness plays a large role in ink deposit thickness just not as much as I used to in that once you get to a certain EOM you stop seeing the benefits and the further away from the stencil edge on those larger designs the benefits are lost.  I do think we get better results out further from the stencil edge than many shops because of our tension levels, squeegee blades, pressure and squeegee speed. It's all about perceived opacity and the fact that we get a more opaque print from a 123/55 than we do a 123/71 is proof of that even though the 123/71 should have deposited more ink.  Maybe it does but is more of that ink inside the fibers of the shirt because you had to use more pressure and less print speed?  I say yes because I see it everyday and that's why we prefer printing white ink through thinner thread mesh.

There was a time when I thought 60-70% EOM was better than 25-30% but now I know that we are wasting emulsion because much of what we print can't take advantage of the stencil thickness as much for ink deposit thickness.  I think the line for underbase and screens used for printing white ink perform better in the 25-30% range in the long run yet most other mesh counts and colors get by with 20%.  High mesh and halftones work best at our shop with 12-15% EOM.  I do think more now days that those really thick stencils we used to make we're wasting emulsion for the most part. There were some designs that it worked great with the thick stencil but most of them do not need it. 

Though I technically agree with Greg on most things he said I do think that there is a lot more that goes into those statements and things are different from shop to shop obviously. They can achieve better EOM with 1/1 coatings than we can at our shop with the emulsion we use.  The numbers I posted were fresh and with a calibrated thickness gauge so I know my numbers are correct but there are so many other factors that go into it that I can't use Greg's numbers as a goal at my shop.  I coated a few mid mesh screens like 195/55 with he Saati PHW red and I had to coat 3/2 to get 10 microns EOM, which is only about 12-15% EOM, chromablue gave me barely 5-8 microns at a 2/1.  I use the glisten method for everything and most of the time on mid to high mesh it yields a thinner stencil than I want but adding another coat will bump the stencil thickness up too high and we are wasting emulsion. I could find that perfect speed and pressure that will give us exactly the EOM we're looking for but there is too much variation with humans that I'm afraid I'd be chasing my tail trying to get everyone that coats screens to use exactly 2"/sec speed and exactly 5lbs pressure on the scoop coater.

And to Sonny's point, I've measure screens that I have flipped between coats to screens I didn't and I got no measurable difference in EOM.  There were only a few microns difference between them which many other variables can make a bigger impact than flipping them.   That's not to say it doesn't do something to increase the stencils quality, but it does nothing to change EOM.  Maybe it helps rz or the stencil edge after exposure but I haven't been able to measure those variables to see if its worth flipping the screen. I know the shops out there that have the best stencils probably use an automatic scoop coater and I don't think many of them flip the screen between coats but I could be wrong.   

Another good discussion here at TSB.

[Homer]

you just blew my mind Mr. K....keep it coming guys.

[Rocfrog]

Wow! That is a lot of great info from Alan (as always) and Kitson, thank you!!

I know there is a billion variables from shop to shop and I have now way to actually measure anything here other than screen tensions because we don't have any fancy tools here. So everything I go off of is either based what you guys or someone else has told me or what I see or think here in the shop, but that is iffy at best because I know next to nothing and have been learning a ton along the way! Like I have no idea what that second number is that you guys keep posting after the screen mesh #....example "123/55"....

We coat all our screens with the same emulsion and they are all coated the exact same way......2:1 and all currently with the KIWO ONE-COAT. Then they sit in our "dark room" (basically a small closet, no dryers or climate control of any sort)  for at least two hours before use. Then all our screens are exposed for 43sec which was determined by achieving a clean wash out to #7 on the SAATIprint 21 step gauge.

Nick

[Printficient]

Wow! That is a lot of great info from Alan (as always) and Kitson, thank you!!

I know there is a billion variables from shop to shop and I have now way to actually measure anything here other than screen tensions because we don't have any fancy tools here. So everything I go off of is either based what you guys or someone else has told me or what I see or think here in the shop, but that is iffy at best because I know next to nothing and have been learning a ton along the way! Like I have no idea what that second number is that you guys keep posting after the screen mesh #....example "123/55"....

We coat all our screens with the same emulsion and they are all coated the exact same way......2:1 and all currently with the KIWO ONE-COAT. Then they sit in our "dark room" (basically a small closet, no dryers or climate control of any sort)  for at least two hours before use. Then all our screens are exposed for 43sec which was determined by achieving a clean wash out to #7 on the SAATIprint 21 step gauge.

The second number is the thread micron size (Thickness)
Nick

[inkman996]

Alan Sonnys point doesn't do anything for EOM it is done to help the emulsion reach all corners of the thread knuckles. I spent many many years coating that way because it is what I was taught by a guy that specialized in extremely high mesh screens for a different industry. I learned that in that case making sure you have good penetration of the knuckles is important but after seeing so many auto coaters being sold and obviously they do not flip the screen I realized there is no real point to flipping a screen for t-shirt printing.

[Rocfrog]

Kind of back on topic since Printficient said that second number is the thread size, the new supplier sent me the "chart" they use to base screen tensions on and it has that number listed but how do I know what we have....?

Here is the chart he sent me.



Is this chart pretty standard? Is this what I should b looking for? I thought that anything lower than 160m should be 20n-25n and 160m and up should be 25n-35n.....

Nick

[alan802]

Those are the standard mesh counts that most suppliers force upon you.  Those mesh counts will simply get the job done, but if you really want to print with the highest quality and do it as fast as possible with very little pressure then those mesh counts will hold you back compared to what's out there.  If you bought a 110 from these guys then you have a 110/80.

The tension level is very mesh count specific and can vary from manufacturer.  A 156/64 can go up to a much higher tension level than a 150/48. 

[alan802]

Whoops, didn't mean to do that.  But there is a dot on a 135/48 if anyone is interested.

[Rockers]

Those are the standard mesh counts that most suppliers force upon you.  Those mesh counts will simply get the job done, but if you really want to print with the highest quality and do it as fast as possible with very little pressure then those mesh counts will hold you back compared to what's out there.  If you bought a 110 from these guys then you have a 110/80.

The tension level is very mesh count specific and can vary from manufacturer.  A 156/64 can go up to a much higher tension level than a 150/48.

Alan, what tension levels do you achieve on your 150-S smartmesh? I just did some Murakamis Smartmesh but it`s a 150-T got it up to 35N without a problem but I assume the 150-S is thinner then the 150-T.

[IntegrityShirts]

I'm sure Alan will reply as well, but I tension my 150S up to 30 and I don't go any higher.  Once in production it relaxes down to around 23-24 and periodically I'll pull a bunch of clean screens and retension back up to 28-29N.  The S mesh is fragile, and you have to have your corners softened perfectly absolutely no burrs on the channels.

[abchung]

I have several questions here.

1. What is the magnification on the loupe?

2. DO NOT RETENTION RETENTIONABLE SCREENS? Did I read it correctly?
I read a Halftone Article in the mid march printwearmag.com issue. On page 37 (or there about), the author states we should not retention our frames.

Does anyone here have problems with retentioning issues with their halftone dots?
I have the wood grain moire as he stated.

Thanks
Anthony

[Admiral]

I suggest reading this:
http://murakamiscreen.com/wp-content/uploads/2012/07/Stretching-S-and-LX-Meshes.pdf

and following this for tension:
http://www.murakamiscreen.com/documents/MeshGuidefromCatalogweb.pdf

I hi-lighted all of the mesh counts we use to follow the tension.  I keep it at the highest recommended for a couple hours(after doing a couple lower tension stretches) on the roller table then lower down to where I will be tightening the bolts and leave it there for 10-15 min.

I have had bad luck with stretching the 135S though, so instead of going all the way to the high end I will be settling with 22N when bolts are tightened.

[alan802]

I take the 150/48 up to 28 newtons and then run it through production once then retension at least once.  The S thread is better at reaching a work hardened stage than other mesh that I have used.  I'm not sure why but it doesn't drop as far after the initial tension and I don't have to retension 3-4 times like I do other mesh.

[ZooCity]

Agree with Alan, the S is very stable compared to every other mesh I've used. 

Use the recommended max tensions on Murakami's chart, they're legit.  You can get away with higher but you will shorten the lifespan of the mesh relative to how much over max recommended you go.

The 135/48 and the 310/30 are the most delicate of the bunch that we've used.  Great, no, amazing mesh counts but difficult to maintain even in a shop like ours where screens are never outside a mesh safe space.