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screen printing => Screen Making => Topic started by: alan802 on October 30, 2015, 10:35:50 AM
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Since buying the Vastex LED we haven't had much need to do any discharge work so I was excited this past week to see 3 new discharge jobs come in but I was apprehensive at the same time with our poor results with most every aspect of our LED unit. I had this really detailed review of what we've seen, the whole routine we used to make the screens, the emulsions tried, etc, but I just deleted it all and I can sum it all up in one word: SUCK. It's my own fault, how in the hell could I have thought that I'd get anything other than poor results? I still can't believe I thought it would be fine. So not only can we not produce a good sim process screen above 50lpi, we can't seriously do any waterbased or discharge printing until I jump through so many hoops, do a lot of back flips, hold my finger in the air just right while wearing a tin foil hat, AND PRAY the screen holds up. I don't like those options. This shop has steadily progressed over the years into something we're all proud of, and to think that we've had to take a step backwards in our quest to be one of the best doesn't sit right with me. I know some will think I'm an insane person, that what I'm asking of a piece of equipment isn't reasonable, I need to get over myself and deal with it's capabilities like everyone else because we're not special...I don't see it that way. Anything less than our best isn't good enough, and over the last year I've tried so hard to keep moving this shop in the right direction and I've finally hit a plateau (actually we've digressed) due to something that did not come with any fine print or disclosures like what we've had to deal with. It's very bothersome to me. How could I be the 1st person (that I know of) to have something negative to say publicly about an LED exposure unit? Were we the first to actually put an exposure calculator on one? Were we the 1st to fun a few hundred impressions on a screen and have the stencil fail? Surely not. Now were we the 1st of active forum members to do those things I asked? Again, I seriously doubt it.
I can say that if you're seriously looking into this particular LED for your next exposure unit, you still could love the product depending on what you ask it to do. If you want to do high-end sim process work, it's not for you. If you want to do virtually any WB or DC work on an auto...probably not for you. If you use thicker stencils, not for you. Low mesh counts (thicker stencils)...again, not for you.
What is it good at? Doesn't use much energy, the bulbs don't weaken much over time, it doesn't put out much heat, it will do the basic, run of the mill spot color stuff all day long without much problem until you get the screens on press for longer runs, then it really isn't very good at all.
I went further with these DC screens than I thought would be necessary so I wouldn't have to worry much about the screens breaking down on press. I used a very good water resistant emulsion, a dual cure, tripled the recommended exposure time, blockout, hardener, 10 minute post exposure on the expo unit, sat it out in the sun for an hour, then let them sit for 24 hours before we used them. The only thing I haven't done with regards to DC screens is test a ton of different emulsions. I feel confident though since our results were on par with what we're seeing with our plastisol screens and at least 15 different emulsions, I think I'd be wasting my time testing out a bunch of DC emulsions. And everyone that knows me knows that I didn't just put some emulsion on a screen and shoot them and call it "tested", and to do all of that again for DC ink isn't going to happen any time soon.
Am I out of line to expect this expo unit to be able to consistently produce single digit % halftones of even 50lpi? What would everyone here expect to be able to get on a standard exposure calculator as far as halftones go? 10% at 65lpi? 5% at 50lpi? Or am I shooting too high?
So with ALL of that being said, who wants to buy a used Vastex LED unit?
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Time to move on to something else, you've spent almost what it cost in monkeying with it I would suspect.
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Yep its time to get that thing out of there the Richmond solarbeam you have is an excellent exposure unit. Fix it up and get back to work, and sanity.
Sent from my SM-G900V using Tapatalk
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I don't know much about the vastex unit but I love my star light and would never go back to a halide unit
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Have you tired a Star Light Alan? Isn't M&R sending a guy around with one to try out?
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Alan the Starlight that Ron Hopkins brought to our shop did very good job on exposure even on some old high detail film I got from Scott Fresner many years ago, so I'll have to say the starlight would be a good option even thought we don't have one and happy with my old unit right now.
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if you had the screens in the sun for an hour and are still having problems, it is not the exposure unit! Anything not crosslinked by the LED unit would be finished by the sun. If the sunlight is not completely crosslinking your screens, the issue should be somewhere else.
For comparison, we are now using an entry level SAATI LED unit at 50 second exposure time. Aquasol HV is giving us about 100-200 discharge prints straight out of bucket. If we put it out in the sun, we are getting 500+, even up to 1,000. We are also testing the SAATI PHU and are getting about twice as much on the discharge runs. All of these are without hardener.
pierre
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I still think 6k lamp or higher is the way to go with large vacuum table. So you can burn 2 screens a time and get the proper cross link. We recently up dated our film systems and that helped a lot in being able to hold half tones that were 50lpi or higher. I wondering if your old unit could be repaired. Did you have a tech ever look at it? Or call Richmond to trouble shoot the problem. The last time our nuarc went down a hour later with M&R we had parts ordered and fixed it the next day.
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I agree with P we don't have the best exposure unit in the world so when we do expose for discharge I sit our screens out back after washout in the sun to dry and they are rock solid using HXT emulsion.
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I agree that even ten minutes in the sun should fully crosslink any photopolymer or dual cure emulsion.
That old sun is one giant mutha' of a single point UV light source!
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As I understand it:
Dual Cures get little to no benefit from sitting in the sun/post exposure. Something about how the molecules position themselves. I think it was a Saati article? Or maybe Al posted some of his great wisdom about it....
It's the emulsions like Murakami's Aquasol and Saati's PHU that do benefit from post exposure. The SBQ's if I remember right. Someone please correct me if I am wrong.
If the bulbs are not emitting light in the correct frequencies for a dual cure, then the screen is doomed from the beginning.
Even using a chemical hardener will not give you the life expectancy (and detail) you desire.
Sorry to say Alan, yep you need a better light source.
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I'm not 100% convinced that the starlight puts out the optimum light for these emulsions either.
Diazo is 360nm
SBQ is 405nm
Starlight is 385nm
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As I understand it:
Dual Cures get little to no benefit from sitting in the sun/post exposure. Something about how the molecules position themselves. I think it was a Saati article? Or maybe Al posted some of his great wisdom about it....
It's the emulsions like Murakami's Aquasol and Saati's PHU that do benefit from post exposure. The SBQ's if I remember right. Someone please correct me if I am wrong.
If the bulbs are not emitting light in the correct frequencies for a dual cure, then the screen is doomed from the beginning.
Even using a chemical hardener will not give you the life expectancy (and detail) you desire.
Sorry to say Alan, yep you need a better light source.
I thought that as well, but was corrected that the diazo does not negate the positive effect that the photopolymer receives.
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I believe you are correct, Colin, about the post exposure benefits being only for pure photopolymers.
Another, very important, consideration is pre-exposure moisture content of emulsion coating.
As jvanick pointed out he, I and others perhaps, are not totally convinced that LED can fully expose emulsions because of the lack of broad spectrum emission.
Alan if you have not yet tried the Kiwo multitex SBQ get Bill Warren to get you a sample. We switched to it from SP1400 and are very happy with it.
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Digitsmith that turd and get that starlight bro. Guys using it and a good emulsion are rockin some serious discharge prints trouble free. We are getting one here soon as soon as I have a buyer for my tri light. The Trilight exposes awesome trouble free discharge screens no problem, I just want to free up a bit of room in my imaging room using the star light. If you had CTS, you could always just walk those imaged screens out in the sun. I've done it when waiting on a new bulb to come in. I taped a peice of cardboard to the inside of the screen, set it on the roof of the car, went in to take a piss, came out rinsed it out, and that puppy was exposed like steel. full detail because of the cts. Great back up plan!!!
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As I understand it:
Dual Cures get little to no benefit from sitting in the sun/post exposure. Something about how the molecules position themselves. I think it was a Saati article? Or maybe Al posted some of his great wisdom about it....
It's the emulsions like Murakami's Aquasol and Saati's PHU that do benefit from post exposure. The SBQ's if I remember right. Someone please correct me if I am wrong.
If the bulbs are not emitting light in the correct frequencies for a dual cure, then the screen is doomed from the beginning.
Even using a chemical hardener will not give you the life expectancy (and detail) you desire.
Sorry to say Alan, yep you need a better light source.
I think you are right! dual cure supposedly does not benefit from post exposure as much. So it might be the light source after all.
pierre
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I'm not 100% convinced that the starlight puts out the optimum light for these emulsions either.
Diazo is 360nm
SBQ is 405nm
Starlight is 385nm
Speak with Diggler, he's running discharge screen using CCI-Green? some new dual cure of theirs, on his Starlight bullet proof. Someone else here, maybe Homer? Runs CCI HXT on their starlight bullet proof.
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I'll correct my correction. I wondered if the addition of Diazo for hardening a Photopolymer emulsion, reduced the effect of post exposure, and was told by Murakami, no.
I, perhaps incorrectly, carried this over to dual cures.
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I'll correct my correction. I wondered if the addition of Diazo for hardening a Photopolymer emulsion, reduced the effect of post exposure, and was told by Murakami, no.
I, perhaps incorrectly, carried this over to dual cures.
Isn't adding diazo to a photopolymer the definition of a dual cure? :)
Yep its time to get that thing out of there the Richmond solarbeam you have is an excellent exposure unit. Fix it up and get back to work, and sanity.
This is what I've been thinking for some time on this subject...
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we use CCI HXT with 1/2 bottle of diazo added - don't need a whole bottle, shot with a starlight, DTS - our screens are bullet proof too...we do DC/WB every single day, not one single issue.
Thanks to Mike for the heads up on the HXT, been over a year now, can't find anything better.
Al, man, you gotta move on from this issue. You suspected a faulty expo for a while now, time to make a move. see my tag line ;)
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we use CCI HXT with 1/2 bottle of diazo added - don't need a whole bottle, shot with a starlight, DTS - our screens are bullet proof too...we do DC/WB every single day, not one single issue.
Thanks to Mike for the heads up on the HXT, been over a year now, can't find anything better.
Al, man, you gotta move on from this issue. You suspected a faulty expo for a while now, time to make a move. see my tag line ;)
Glad it works for you too Jay! I think we are hitting almost 4 years of rocking HXT. I don't even use the diazo. Our discharge orders aren't over 2,000 peices, most of them are below 1,000, but Some times an order may call for a double stroke so I count those strokes as total use on the screen. I have some Discharge underbases that have gone past 3,000 strokes of use and are still like new. The only reason I don't add the Diazo right now is because our discharge orders dropped. When we get the starlight, because of the speed, I think we may go 100% HXT for everything and then it won't be an issue dosing a bucket with Diazo because I know it will be gone in less than a week, but right now I'll coat say 30 screens with HXT when I have a fresh discharge order, then what ever screens weren't used in that order are racked until next order, so It might go a few weeks before I open the bucket again. You get where I'm going. HXT can sit without diazo for a long time in the bucket and still be good. I had a bucket that got hidden behind a rack, 6 months later I found it, it had already been opened, gave it a whirl and it was like new. That might not have been so with diazo, but I can see diazo will make them last even longer as the very first testing we did with HXT was a half gal with and a half without. The diazo added a few more minutes to the exposure. The BIG FACTOR people miss with this emulsion is they try to RUSH the time. Let it cook and it will last like steel. Under expose it and watch it fail. Not bad for 45 bucks a gal either, =).
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I'll correct my correction. I wondered if the addition of Diazo for hardening a Photopolymer emulsion, reduced the effect of post exposure, and was told by Murakami, no.
I, perhaps incorrectly, carried this over to dual cures.
Isn't adding diazo to a photopolymer the definition of a dual cure? :)
Well, at this point, we need someone who really knows to chime in.
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when adding Diazo to a SBQ and since the Diazo has a optimum light sensitivity of 360NM, and the SBQ is up in the 405NM range, and my light source is around 385-390, what happens when the SBQ cures long before the Diazo cures? Just wondering how the chemistry works? I can totally understand the mixing in a MH/multi-spectral light source as the light is putting out both of those spectrums, but in a LED source, what's actually happening?
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Vastex unit in my shop... on the fence with this topic as we have had hit and miss experiences with stencils.
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@ Mike - we use Diazo on everything. DTS w/ Starlight on average, 30seconds to 1 min max, everything for 110 to 305, S MEsh and all.
We double stroke every DC print. 24 units to 1k pieces. always double stroke. I was taught a few tricks by some fellas at New Buffalo, so we double up....
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This is yet another instance of that the manufacturers of these units HAVE to start informing the buyers of what wavelength the LED's are putting out.
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the emulsion manufacturers HAVE to start informing the buyers of what wavelength the emulsions are most senstive at.
Playing this game because "it's a competitive advantage" is not in our best interest, and we shouldn't be letting them get away with it.
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My understanding is that diazo or diazo added emulsions need complete exposure at initial exposure. Could they benefit from post expo? Probably somewhat but they won't be as strong as a correct initial exposure. Somebody correct me if need be and/or put the science in there.
5k and up MH is superior to LED when we're solely discussing exposure strength as it relates to imaging using the current emulsions on the market. Now, match an emulsion to a specific LED wavelength and this will change. LED benefits are less power consumption, consumables, floor space, they do not, really cannot at this time, offer superior imaging.
I agree jvanick, the fact that nobody will offer a histrogram of their output is just off. I need to qualify that however, if it so happens that revealing the output range would allow a competing mfg to determine the proprietary LEDs being used and ape the other's product without putting in the R&D than that's fair enough.
Nevertheless, a quality, high powered LED unit like the Starlight works well (or well enough to feel good about the other benefits) and is our shop's current choice of exposure method.
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Alan isn't ignoreing the replies here. He's chained to a manual press. I'm sure he'll respond when he is free.
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For comparison, we are now using an entry level SAATI LED unit at 50 second exposure time. Aquasol HV is giving us about 100-200 discharge prints straight out of bucket. If we put it out in the sun, we are getting 500+, even up to 1,000. We are also testing the SAATI PHU and are getting about twice as much on the discharge runs. All of these are without hardener.
pierre
Off topic, but I have had similar results as it relates to aquasol and saati phu. The PHU lasts MUCH longer than aquasol did with DC or WB runs.
Alan, time to punt. Fix the 8k, or was it 10k, light source and don't look back. I've said it before and I'll say it again, the quality of these units solely rides on where they source their LED's from. M&R either contracted the company that makes theirs to have them made in a specific wavelength, or just bought their 395nm units that are EXPONENTIALLY more expensive than what you can find online or on aliexpress.
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Sorry I have been out for a while and I skimmed through the replies best I could.
I have demo'd the Starlight and with the few screens we did I liked what I saw. I didn't get to run a long plastisol job on the screens to see if they'd hold up and definitely didn't do a discharge run.
And on the subject of whether or not it's the expo unit, I immediately thought it was the problem simply because on Wednesday we were shooting screens with a Richmond and over the course of 7 or 8 years we never had a problem. Thursday afternoon we are shooting screens with a Vastex LED and you all know what we've been dealing with since then. I know that sounds way too simple and there is no way the answer lies in that theory, but those are the facts and as basic as we can get them.
As far as the screens being dry, dry as a bone within about 2 hours after a coat job. Joe C measured a batch of screens that my guy had coated about 2 hours prior, and used his fancy moisture meter and they were "superb" I believe were Joe's words.
I'll take a better look at the replies over the weekend and try to address everything. Trust me, I wouldn't have fought through all of this for almost a year if I thought it was the exposure unit only. I tried my best to make sure I didn't call something a loser if it really wasn't. I feel like I gave this thing a better shot at proving itself than anyone else would have given the circumstances. I've been doubting my abilities and my knowledge the entire time we've had this unit and have actually learned a hell of a lot more from all the failures than I ever would have running the Richmond this past year. For that I am grateful. Yall have a good weekend and those who can't stay away from this place over Saturday and Sunday we can continue this.
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Alan -- what kind of emulsion thicknesses are you guys getting, and how consistent is it?
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Richard Greaves will be in my shop all day Monday going over these very issues! Will post my findings!
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For comparison, we are now using an entry level SAATI LED unit at 50 second exposure time. Aquasol HV is giving us about 100-200 discharge prints straight out of bucket. If we put it out in the sun, we are getting 500+, even up to 1,000. We are also testing the SAATI PHU and are getting about twice as much on the discharge runs. All of these are without hardener.
pierre
Yup, Saati PHU all the way
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Different question; what does Vastex have to say about this? They seem to have a pretty good reputation for putting out a solid product. Can they offer you information on why their exposure unit does not work for anything in your shop (one which sounds like you really know what you are doing)?
I went to a trade show a couple years ago intent on buying an LED exposure unit as they just hit the market, I wanted to sell my MSP3140 before it dropped in resale value. A person in this industry (who shall remain nameless) whose opinion on equipment I really respect told me not to. His opinion was all the manufacturers were in such a rush to get their LED to market before/in pace with their competitors that they were still fine tuning and a year later they would more than likely have made a lot of improvements to the product. So I saved my money and have no regrets.
So what this bring me to wonder is you bought the Vastex unit right around when they first came out. Is this an early issue that Vastex has addressed and changed in their unit over the past couple of years? If so it sounds like they should offer a replacement or send the upgraded part(s) for you to swap out. Did you get a lemon from the early batch? If I was in your shoes I'd be looking at Vastex to come up with the solution. You invested your money in their technology as opposed to a competitor's.
I think Vastex is a great company. I'd love to hear their take/resolution on this.
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Since buying the Vastex LED we haven't had much need to do any discharge work so I was excited this past week to see 3 new discharge jobs come in but I was apprehensive at the same time with our poor results with most every aspect of our LED unit. I had this really detailed review of what we've seen, the whole routine we used to make the screens, the emulsions tried, etc, but I just deleted it all and I can sum it all up in one word: SUCK. It's my own fault, how in the hell could I have thought that I'd get anything other than poor results? I still can't believe I thought it would be fine. So not only can we not produce a good sim process screen above 50lpi, we can't seriously do any waterbased or discharge printing until I jump through so many hoops, do a lot of back flips, hold my finger in the air just right while wearing a tin foil hat, AND PRAY the screen holds up. I don't like those options. This shop has steadily progressed over the years into something we're all proud of, and to think that we've had to take a step backwards in our quest to be one of the best doesn't sit right with me. I know some will think I'm an insane person, that what I'm asking of a piece of equipment isn't reasonable, I need to get over myself and deal with it's capabilities like everyone else because we're not special...I don't see it that way. Anything less than our best isn't good enough, and over the last year I've tried so hard to keep moving this shop in the right direction and I've finally hit a plateau (actually we've digressed) due to something that did not come with any fine print or disclosures like what we've had to deal with. It's very bothersome to me. How could I be the 1st person (that I know of) to have something negative to say publicly about an LED exposure unit? Were we the first to actually put an exposure calculator on one? Were we the 1st to fun a few hundred impressions on a screen and have the stencil fail? Surely not. Now were we the 1st of active forum members to do those things I asked? Again, I seriously doubt it.
I can say that if you're seriously looking into this particular LED for your next exposure unit, you still could love the product depending on what you ask it to do. If you want to do high-end sim process work, it's not for you. If you want to do virtually any WB or DC work on an auto...probably not for you. If you use thicker stencils, not for you. Low mesh counts (thicker stencils)...again, not for you.
What is it good at? Doesn't use much energy, the bulbs don't weaken much over time, it doesn't put out much heat, it will do the basic, run of the mill spot color stuff all day long without much problem until you get the screens on press for longer runs, then it really isn't very good at all.
I went further with these DC screens than I thought would be necessary so I wouldn't have to worry much about the screens breaking down on press. I used a very good water resistant emulsion, a dual cure, tripled the recommended exposure time, blockout, hardener, 10 minute post exposure on the expo unit, sat it out in the sun for an hour, then let them sit for 24 hours before we used them. The only thing I haven't done with regards to DC screens is test a ton of different emulsions. I feel confident though since our results were on par with what we're seeing with our plastisol screens and at least 15 different emulsions, I think I'd be wasting my time testing out a bunch of DC emulsions. And everyone that knows me knows that I didn't just put some emulsion on a screen and shoot them and call it "tested", and to do all of that again for DC ink isn't going to happen any time soon.
Am I out of line to expect this expo unit to be able to consistently produce single digit % halftones of even 50lpi? What would everyone here expect to be able to get on a standard exposure calculator as far as halftones go? 10% at 65lpi? 5% at 50lpi? Or am I shooting too high?
So with ALL of that being said, who wants to buy a used Vastex LED unit?
Totally agree with everything you`ve said. Between not being able to get good sim process screens and extreme undercutting of the image I would not be able to say which is worse. Before we bought the unit we asked the guys at Vastex about exposure times for different emulsions and how halftones hold up, got a .pdf with all the info from Vastex. Based on that we decided to purchase the unit and of course as well the fact that they were able to deliver at the date we needed it while M&R told us they would be 3-4 weeks out before the Starlight could be shipped. In hindsight I really should have waited those 4 weeks and got the better unit instead of wasting a lot of cash on that Vastex tank, build tough but slow as hell.
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We have tried both the Workhorse led unit and the Saati one, ended up returning both. In Saati's defence the original one they shipped us had a massive hole in it. But neither of them were good. The Workhorse MH 1k unit we had for years worked better.
All ours were on Murakami SP-1400. I refuse to post expose or harden, and I know we probably print with too much pressure in general. So my experiences may be extreme.
We use a MH 5K unit now and don't have issues, it's hard for me to think about switching. Suppose that may change when I need a new bulb though! ;D
The LightSpeed led guy is based up here and is always wanting us to try his, I may have to take him up on it some day and report back!
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I will tell you that I'm having issues with the starlight exposing Saati PHU-2 emulsion. The guys from Saati are involved and I'll be testing their 300w light next week.
I believe that part of our issue is that we've been getting almost 40% EOM and that it just may be too thick for the starlight to completely penetrate without over cooking the shirt side of the screen. I've got a batch of screens that are more around 18-20% EOM that we'll be trying next week as well to see if that's it.
But, between the edge breakdown issues as well as the emulsion softening on longish discharge runs even when exposed to a 7+ on the stouffer strip, I'm not super happy right now. (This is following all the steps and instructions from Saati)
I can say that halftone detail has been awesome, and that for plastisol jobs, I'd likely be perfectly happy...
SP1400 and the Starlight is not a fun combination... in order to get solid 7's, we were exposing at nearly 2 minutes!
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I didn't like phu2 or sp1400 with my starlight, to many issues. Right now for us, CCI DC plus is giving best results with the starlight. This may change Monday after I spend the day with Richard Greaves.
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Just some general LED thoughts and opinions. I believe LED is the wave of the future but just not there yet.
LED UV spectrum is a narrow band width. So if your emulsion exposes best at 390nm and the LED puts out 400-420 your not in an optimal UV range.
The LED units expose the bottom layer of emulsion so quickly it may block some of the UV energy from reaching the ink side of the screen acting like a UV filter causing a under exposed condition through the rest of the emulsion.
I do not think LED has for lack of better words enough ass to fully penetrate a thick coating of emulsion.
Eventually I think emulsion mfg will narrow the optimal exposure band with to match a LED standard band width.
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Brian nailed it on the emulsion / wavelength sensitivity.
This is one reason why I'm excited to test out Saati's light next week. They claim their SBQ's are most sensitive at 405nm, and that's what their light is tuned to.
I'm pretty sure there won't be an 'optimal' 'standard' bandwidth for quite some time (if ever).
Another thought that I had is that ALL led sources are a compromise... in order to expose both SBQ's and Diazo emulsions, the manufacturers have to engineer the wavelength so it sits right in the middle. My bet is that if I put a diazo screen in front of a 405 nm light source, it would take forever to expose (and probably not expose all the way)... same with a SBQ in front of a 360nm light source.
A dual wavelength LED unit of say 360/405 seems like it could be perfect (no idea how to engineer that).
Dirk: What kind of exposure times are you running for the CCI DC plus? -AND- how is the reclaim? We moved away from Dual Cures due to the hard(er) reclaim than the SBQs.
Alan: When calling Vastex, what do they say that the UV wavelength is of their LED's..
Anybody know what kind of unit we may be able to find to test the ACTUAL wavelength of light being generated from these units? I'd love to get one and bring it to ISS and do some real testing.
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CCI DC Plus 55 sec. on the Starlight, SUPER easy reclaim, CCI micro wash in my dip tank.
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in case anyone is wondering i've been apart of an email thread about LED and PHU2, with a shop in Chicago, and a couple people from Saati. It's way over my head, but i'll share the details.
I'm not sure what wavelength the STEII/Starlight is, but i do know, we have virtually no screen breakdowns in the shop anymore, with HSA or DC. Here is what they've suggested for PHU 2, adding a Diazo:
Regarding Diazo 11, it's main function is just to sharpen the image detail, as an 'anti-halation additive'. It's a very light dose of diazo and doesn't contribute a whole lot to cross-linking for added durability. That said, the sharpening effect does allow for longer exposure without closing out fine details. The longer exposure results in more curing and thus better durability (encapsulation). We normally don't recommend adding diazo to SBQ, but for multi-point, or scanning bar, exposure systems that kill resolution it becomes necessary to ensure that finest details can be reproduced in the stencil. Diazo is more tolerant of light wavelength than SBQ but in any case 405nm is best choice for both. 395nm is ok, but 365nm (UV) is a bust.
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I will tell you that I'm having issues with the starlight exposing Saati PHU-2 emulsion. The guys from Saati are involved and I'll be testing their 300w light next week.
I believe that part of our issue is that we've been getting almost 40% EOM and that it just may be too thick for the starlight to completely penetrate without over cooking the shirt side of the screen. I've got a batch of screens that are more around 18-20% EOM that we'll be trying next week as well to see if that's it.
But, between the edge breakdown issues as well as the emulsion softening on longish discharge runs even when exposed to a 7+ on the stouffer strip, I'm not super happy right now. (This is following all the steps and instructions from Saati)
I can say that halftone detail has been awesome, and that for plastisol jobs, I'd likely be perfectly happy...
SP1400 and the Starlight is not a fun combination... in order to get solid 7's, we were exposing at nearly 2 minutes!
there are a ton of very good emulsions that work extremely well with the Starlight and provide exceptional screens both in durability and halftones. You are close by. Take the time to see the options in Niles or check with our technical staff.
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A dual wavelength LED unit of say 360/405 seems like it could be perfect (no idea how to engineer that).
That's what the LightSpeed unit has a patent on from what I understand.
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I never claim to be an expert in emulsion and I can't give any educated information on the wavelength on others or even ours in great detail that would explain any differences. I can only say that the proof is in the pudding. The largest I know of for a fact is 50k while I was there. Another shop does nothing but larger orders of 5k to 30k regularly using LED and dual cure. I personally have customers using dual cure that do the following,
A, Holds great detail. 7pt times roman (serif font) on 305 mesh for example. 55-65lpi easily down to 3% dots. I haven't looked at edge definition under a high powered mag but the printed results seem able to win awards.
B, Holds long term production runs of 50,000 units in one run with no screen breakdown.
How you get to B, may require a different recipe for different emulsions. Maybe not all dual cures will be able to yield 50k shirts without breaking down but I can tell you it is a fact that there are emulsions out in the market that are doing this. For many shops "is it fully cured?" is not an issue. For anyone having any kind of issues, I would look at the recipe,
Thickness aka EOM. As with any case of curing stencils, there is an optimum EOM ratio (for each mesh) provided by the emulsion manufacturers. Use them. Most overlook this as inconsequential.
Dryness of the emulsion. Have enough screens that you are not starving for dried screens and may use them before they are fully dried.ftp://
So to me there is no question that LED can be well above just "good enough" but it may be true that even the best on the market is not (as strong) as a 5-10k MH. Does it need to be? I say obviously not. It's more than capable of handling everythibg we need it to do.
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99% of our jobs are discharge. Never had a stencil breakdown. We use this combo: Aquasol HV with diazo. 1/1 coat with sharp edge, 6-10 sec blast with 10K single metal halide in 25 year old Richmond Graphics Solar Beam. S and LX mesh, counts from 135 to 225. Works like a charm.
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A couple of notes here:
SBQ pure photopolymers can be post exposed. Dual Cures and Diazos don't benefit the same as SBQ from post exposure. The initial light strength and exposure determines a lot more of the durability than post exposure or hardening which are band aids to fix exposure. We never used hardener on most jobs using Aquasol TS, high res SBQ, since an 8K metal halide with true film maximizes the exposure. That is a pet peeve I have about LED. It's not how short you can expose for it's how well you expose the screen. Our tests show SBQ in the sub 10 second range, its the tenths of a second that can make the difference.
LED is applicable to many companies. However as noted it can have a hard exposure on print side and soft on squeegee side, so SBQ is better on LED for post exposure to harden the squeegee side. Halftones on MH have better cure and side wall formation, but LED is fast, easy and convenient and works for most shops. Once I hit huge volume though metal halide has stencil exposure advantages. Like many pieces of equipment available what works for one shop may not work for another.
Al
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Damn, what a day. After a few weeks of being able to manage instead of putting out fires, I'm now back to running around playing a fireman.
Our stencils are VERY consistent and over the years it's been one of the things we've excelled at and I've wanted to show off our screens against an auto coater if given the chance. We've consistently been able to be within 2-3 microns from like mesh counts from screen to screen and also within 1-3 microns from top to bottom of all mesh counts. So with all that bragging out of the way, our 150's are either 45 or 48 micron thread thickness are around 15% EOMR and right around 12 micron EOM. There is the occasional 15 micron EOM on the 150's but I spend a stupid amount of time measuring our screens so I feel good about where our stencils are.
Now I do not feel good about going even lower on our stencils for the sake of our LED. I feel like we've already sacrificed enough and I don't feel that there is much more to do but move on.