Workhorse LED + Murakami T9

[rendered.co]

Hello all. We just got our Workhorse LED in today to replace our florescent. Of course it's one of the busiest times of the year for us so we are trying to mitigate the downtime as much as possible. Does anyone use a Workhorse LED with Murakami T9? If so, can you share what times you are getting for exposure/post expose? Also, we've been using diazo for stronger screens when using the fluorescent, but is that needed for the LED? Thanks in advance.

We're hoping to get this dialed in as soon as possible since our screens are taking about 30 minutes a piece right now with exposure+post expose on our fluorescent. I know, it's ridiculous.

[im_mcguire]

We used T9 for a bit with our workhorse LED, and we were in the 32-37 second range for most screen mesh.

We dont run WB/DC here, so we started going back to the Aquasol HVP, so we dont post expose anything. We just leave it in the sun to dry for a few minutes.

[Cole]

I'm not using a Workhorse LED, but I'm using a unit similar, also with Pure Photopolymer emulsion. My exposure time for spot color designs is 15 seconds (meshes 110-230). For halftones, 12 seconds (Meshes 158-230). I use almost all 180s mesh, so my exposure times don't vary much. The Workhorse LED is 5 amps I believe. The one I use is 8 amps, so my exposure times might be faster than yours.

A super useful tool I've found is this 21 step exposure calculator from Saati. Here is a link to it: https://www.totalinksolutions.com/saati-21-step-sensitivity-guide.html

I've used this whenever I've switched emulsion, thin to thick thread mesh, exposure units, etc. It takes the bulk of the guess work out. As far as post exposure goes, I just put the screens in the sun for at least 15 minutes. I do a lot of discharge and I see very little breakdown on orders below 300pcs. Haven't ever run a discharge job larger than that, so I have no idea how durable the screen is in the long run.

Hopefully this gives a little bit of insight. If you let the board know what coating method you are using and what kind of thread (s mesh or regular) your screens are, I'm sure someone will have a good answer for you!

[rendered.co]

Sweet. Thanks for the info guys. Murakami just reached out to me to give me some more insight, but this is a great start.

[Prince Art]

Here's a way that has worked for me, using a Saati 21-step Stouffer strip. It allows you to test several times on a single screen.

-measure the strip
-using black construction paper (or other opaque material), cut 8-10 pieces that are about 3" wider in each direction than the strip. (I actually cut 16-20 pieces, and double stack to ensure opacity.)
-Tape these to the film side of your screen so that they are hinged. Use a smaller piece of tape across from hinge to keep it "closed" when moving the screen.

Then
-fold back one of these "doors," and position the Stouffer strip in the area that the door normally covers.
-Expose the screen at your first test time.
-Pull the screen, removed the strip, close the "door."
-Open the next door, and repeat the process, using your next test time
Repeat until you've tried a different test time behind each door. Work in a pattern, and keep note of your times per door. (I make a sketch of the door layout, and write times on the sketch.)

All open area of your screen will of course be exposed every time - doesn't matter.  Wash out the screen, examine each test area, and note which test time got you closest to proper exposure. You may determine the correct time on this screen alone. If not, you should be able to use the closest times to set up a 2nd test to zero in on the proper time.

[screenxpress]

Andy....................WHERE IS STEP WEDGE MAN?

[Frog]

Andy....................WHERE IS STEP WEDGE MAN?

He was watching the A's!

[Frog]

And, here's a link to the pdf that Murakami has prepared about the step wedge exposure test.

http://murakamiscreen.com/wp-content/uploads/2012/07/Step-Test-Instructions.pdf

[screenxpress]

Ya, I had to snicker a bit. 

The Step Wedge process had been discussed for many many years (here and previous places) even though I had not seen mention of it recently until this post.  So had to call out for the Super Hero, lol.

[rendered.co]

All good info. Thanks everyone. I mainly wanted to see if anyone had a good recommendation of where to start our time for the step calculator. We got a lot of great tips from Al over at Murakami. We are primarily a waterbased shop so emulsion strength is a big factor. My main take aways from the conversation:

Use 4g Diazo for T9 (versus the 8g that usually comes packaged with ours)
Coat 1/1 sharp
Dry screens squeegee side down

With those considerations and all else taken in to account with screen room humidity, etc. we were able to get our 225s exposed at 84 seconds on the Workhorse LED + 50 second post expose. I know it's not as fast as a lot of shops claim, but using the Diazo slows it down a bit. On our fluorescent we were at 17 minute exposure with 15 minute post expose, so it's an amazing improvement. The halftones were really impressive on the LED as well, with almost zero drop out. I did a test run of an equivalent of 200 shirts on the press to make sure we didn't lose any halftones and the screen held up tremendously. Hopefully we're all dialed in for Monday when production starts up again.

Thanks again for all the input!

[Sbrem]

Ya, I had to snicker a bit. 

The Step Wedge process had been discussed for many many years (here and previous places) even though I had not seen mention of it recently until this post.  So had to call out for the Super Hero, lol.

If you're one of us that used a process camera and tray developed film, the Stouffer Step Wedge was an everyday tool. And it worked for screens too!

Steve

[screenxpress]

Naw, was kidding from the many posts for Step Wedge posted on the previous sites we used to visit.  I never used a camera for film.

However, my dad was a Lithographer and I remember the times he used to tray develop film from a really large camera and do the set up and taping to burn plates.

[Frog]

Naw, was kidding from the many posts for Step Wedge posted on the previous sites we used to visit.  I never used a camera for film.

However, my dad was a Lithographer and I remember the times he used to tray develop film from a really large camera and do the set up and taping to burn plates.

I ran offset for a short while in between real jobs. Little guys,  (the small presses were technically called duplicators I seem to recall. They were just starting to use a combo camera and plate maker. I think it was Itek.

[screenxpress]

This is what I remember my father running.  A Multilith 1250 with a T head to run 2 colors and a one color press.  He came from a background of the really big 4 color Harris (I think that was the name) presses before he opened a small Quick Copy 'style' mom and pop store.

[balloonguy]

This is what I remember my father running.  A Multilith 1250 with a T head to run 2 colors and a one color press.  He came from a background of the really big 4 color Harris (I think that was the name) presses before he opened a small Quick Copy 'style' mom and pop store.

I wish I had video. My dad used to print balloons on something like this with the offset roller fully exposed. We (even as kids) would have to time the print and manually spin a balloon at the same speed as roller to get a pretty crappy print. It was awesome at the time though. He started in the late 60's with a deconstructed AB Dick (I think).