Before You Went LED, What Were You Using?

[alan802]

We have also seen issues with ink not clearing, and we've had a bunch of screens lock up on us if we used screen opener in them to do a color change or change inks in a screen, it's frustrating having issues that you've never had before.  You start to second guess yourself, start to buy into all the great reviews which I'm not casting doubt on, but you have to take some with a grain of salt.  There are plenty of guys who post here that when they type something, I treat it as gospel, I don't have to second guess it or wonder if they really did their due diligence.  But the reason I say this stuff is one day we're cruising along without any screen making issues, next day strange things start happening and if EVERY fantastic LED review on the forum were completely factual, the issues wouldn't have started happening the very first day you put a new exposure unit into production.  I do feel there is a difference in LED output among the different brands, but I've seen conflicting information as well regarding the UV output from competing units.  Some are going to shake their heads in disagreement when I say this, some are going to say amen, but I feel very strongly that the best MH units will outperform the best LED units when it comes to fully cross-linking MOST emulsions and it's not that close of a comparison.  Now I will admit, we don't have the unit that I consider to be the best LED unit on the market so I can't be 100% sure of this.  I have seen and heard a lot from other LED users that came from really good MH units that have had similar experiences to what we've had and they didn't all have the same brand LED.

This is going to sound harsh, but I've had some trust issues with a manufacturer or two with equipment and some of the mistrust is absolutely warranted in my opinion.  How could a manufacturer put out an exposure unit that had outrageously long vacuum draw downs?  Seems like if something that simple was messed up, the more difficult aspects of building an exposure unit could very well be wrong.  One could argue that maybe they spent so much time fine tuning the more important parts of the unit that they overlooked the simple things, but if LED units are being sold with speed being one of the most important variables, isn't vacuum draw down a HUGE part of how fast a unit can expose screens? 

[T Shirt Farmer]

Alan,

does your screen loop allow you to expose, soak, rinse, place in drying rack and tape up two more screens in less time than the draw down of the exposure... if not I am not seeing the issues. I have the same unit as you and was disappointed at first with he 45 second draw down but soon realized it was of little significance in real time screen making for my shop.

[GraphicDisorder]

I think like many things out there as soon as someone builds a X then others build it as well, its assumed they are all equal or similar.  I think its clear that's not the case with most things. Now I don't assume we have the BEST LED out there, but I do know we aren't having screens lock up on ink changes. We do ink change overs almost daily.

[Frog]

Success on press notwithstanding, I am now interested in quantitative readings of comparative EOM with all things other than light source being equal.

[ebscreen]

Success on press notwithstanding, I am now interested in quantitative readings of comparative EOM with all things other than light source being equal.

Very interested in this as well, simple enough test to perform for those with the tools....

I feel I should mention the reason for us sticking with MH for now is largely because we use diazo emulsion
only. I think (know from experience) that you can underexpose photopolymers to retain detail, baby it through
developing, and post expose in the sun and get a pretty well usable screen. Not ideal in the slightest but probably
pretty common practice.

With diazo we expose for an inordinate amount of time, retain excellent detail, blast with reclaim pressure washer
to develop, and don't post expose. We then beat the brakes off our stencils on press, we're about to print across 600 zips
with discharge. I got 99 problems but a properly exposed screen ain't one.

It would be cool if people mentioned what emulsion(s) they're using as that's the make or break with LED.

[Frog]

Success on press notwithstanding, I am now interested in quantitative readings of comparative EOM with all things other than light source being equal.

Very interested in this as well, simple enough test to perform for those with the tools....

I feel I should mention the reason for us sticking with MH for now is largely because we use diazo emulsion
only. I think (know from experience) that you can underexpose photopolymers to retain detail, baby it through
developing, and post expose in the sun and get a pretty well usable screen. Not ideal in the slightest but probably
pretty common practice.

With diazo we expose for an inordinate amount of time, retain excellent detail, blast with reclaim pressure washer
to develop, and don't post expose. We then beat the brakes off our stencils on press, we're about to print across 600 zips
with discharge. I got 99 problems but a properly exposed screen ain't one.

It would be cool if people mentioned what emulsion(s) they're using as that's the make or break with LED.

When all other factors are correct, this should not be necessary. For as long as I can remember, even before Photopolymer emulsions were used, underexposure was the most common issue/problem when it came to making screens.

[GraphicDisorder]

We use Diazo, never tried anything else on our LED. Never had a reason to yet I guess.

[ebscreen]

Indeed. I will say that for a long time with photopolymer we struggled between developing low range halftones and not blasting out the mids.
It was always a delicate dance at the development sink. So much so, that, I don't mean to be rude, but for any kind of serious detail
work I can't see how people aren't using diazo. It was that much of a game changer here that I'm putting up with extensively long exposure
times. The diazo is in the details.

It would also be cool if people would mention what LED unit they are/were using, particularly the fella that conjured this thread from
the grave. While I'm certain not all units/lights are the same, they still are all using LED's. Just like a Chevy is different than a Toyota,
they're both still trucks, and neither is an airplane.

[jvanick]

SP1400 and SP1400W here... Diazo emulsion...
Starlight 2331

no problems with halftones...

SP1400W exposure times on a 160S are at 40 sec... 225S around 22 seconds...
solid 7 step on the stouffer strip.

now that we're going back to standard SP1400 I'll have to redo our exposure times... last year we were around 34 or so for our 160S screens.  I'll post up later once I re-dial the SP1400 with our good bucket of emulsion.

no problems on long runs.

[alan802]

Alan,

does your screen loop allow you to expose, soak, rinse, place in drying rack and tape up two more screens in less time than the draw down of the exposure... if not I am not seeing the issues. I have the same unit as you and was disappointed at first with he 45 second draw down but soon realized it was of little significance in real time screen making for my shop.

I see what you're saying, but I don't want to judge something's speed based on what I can get done in the meantime while it's doing it's thing.  Sure, I can tape up film, be on the pressure washer developing another screen while I'm waiting for 65 seconds for the vacuum, but what about all the times when I'm just burning one screen, or there is 2 of us running the developing loop?  I can always fill the space with something, but if I had a unit that drew down in 15 seconds I'm saving 50 seconds per shot, times 25-40 shots per day...that's how I am looking at it.  You make a damn good point, and I could do things in a way that the extra 50 seconds could be filled doing something else, but I argue that there shouldn't be an exposure unit in the world that takes longer to draw down than it does to burn the image.  I'm not right, you're not wrong, it's different perspectives from different people trying to accomplish the same task. 

We use pure photopolymer almost exclusively and the Richmond unit spoiled us I guess.  We could shoot 55-65 line halftones and develop those halftones well into the difficult ranges on both sides, now it's a lot more difficult.  I'm not trying to put this shop on a pedestal, but shooting sim process screens was extremely easy with the Richmond, if we needed to hold dots below the 5% mark sure we'd underexpose a little bit, but if I want to hold those same dots with the LED, I'm going 50% less than I should be, and you all know what's happening with that screen after that.  Emulsion locking up during reclaim, weak stencil, yes, we can post expose but that all goes back to the precedent that was set with the MH and not having to do all the extra work to get a 280/34 with 55lpi halftones on it to hold up to 1000 imprints.  I'm not liking having to do the "dance", I'd rather just get to the bedroom if you know what I'm saying .  Our whole production philosophy is based off of squeezing every second we can out of every process.  When we go CTS I won't have to complain about vacuum times but for the near future I have to deal with it, and also with underexposed screens, weak stencils, on-press breakdown, pinholes, 10 screens per hour being reclaimed, etc.  I don't know that CTS will fix all those issues, but I'm sure it will a few.   

[T Shirt Farmer]

I get what you are saying Alan... trying to have the perfect anything in an un-perfect world can be very taxing on ones energy.

[GraphicDisorder]

You've already located your fix Alan, CTS!

[ebscreen]

We use Diazo, never tried anything else on our LED. Never had a reason to yet I guess.

What brand Brandt?

[GraphicDisorder]

We use Diazo, never tried anything else on our LED. Never had a reason to yet I guess.

What brand Brandt?

Chromaline

[ebscreen]

Any particular flavor of Chromaline?