Before You Went LED, What Were You Using?

[jvanick]

No problems here with sp1400 and our led unit... we've only done a few discharge runs with it at 1000 and 1500 .  Plastisol we've done 10k on a screen with no issues.  Good enough for us.

[ebscreen]

Have you noticed any degradation in image quality/complete exposure? And "Before You Went LED, What Were You Using?"

[ScreenFoo]

Stay tuned.  We're about to make this comparison,  in as scientific a manner as possible.  5kw halide,  dialed in with the highest quality bulb, new photocell and good integrator shooting 2up v starlight led shooting 1up.  High d max,  good d min film.  Exposure time,  exposure quality,  power consumption,  resolution will be the main points of comparison.  If anyone wants me to add another item to the testing or has suggestions please let me know.   I'm hoping to get an accurate handle on of this tech is ready for prime time.

Sent from my SM-G900V using Tapatalk

Not to give you crap for impending interesting free info, but why MH 2-up and LED 1-up?

Sounds like it would be a little 'off' from an apples to apples type comparison.

[3Deep]

Pretty good thread so far and amazingly has stay on the same topic , but to toss one in the companies that make the LED units, I would think these guys put millions of dollars into it and use some of the best equipment they could possible have to make sure this thing worked like they advertised, now my question is how many of our shops are going to hold up to the standards they used to R&D these units?  I know whats going on here is real world testing that we all do in our shops day in and day out which is going to be different...I know some of you have some pretty nice shops with top notch equipment, this is going to be a good tread for people looking into a LED unit.

darryl

[alan802]

Under a scope I can see slightly less quality with the LED but for the most part it's relatively the same between the two light sources.  I do have issues with getting a full exposure according to the expo calculator versus how the screen holds up on press.  I've said it a few times here but we've NEVER had screens break down at the squeegee blade edges until we started using the LED unit and now it's an issue even with over-exposing screens.  That tells me it's simply not cross-linking the entire layer of emulsion.  It passes the calculator test with flying colors but on-press it doesn't pass the test.  It's frustrating and I know with a big discharge job we will have problems.  Interestingly enough we haven't had hardly any DC jobs since buying the LED.  I'm ok with that though.

[Frog]

Stay tuned.  We're about to make this comparison,  in as scientific a manner as possible.  5kw halide,  dialed in with the highest quality bulb, new photocell and good integrator shooting 2up v starlight led shooting 1up.  High d max,  good d min film.  Exposure time,  exposure quality,  power consumption,  resolution will be the main points of comparison.  If anyone wants me to add another item to the testing or has suggestions please let me know.   I'm hoping to get an accurate handle on of this tech is ready for prime time.

Sent from my SM-G900V using Tapatalk

Not to give you crap for impending interesting free info, but why MH 2-up and LED 1-up?

Sounds like it would be a little 'off' from an apples to apples type comparison.

I'm guessing that is is a unit size issue, but nonetheless, could still each be done 1-up to even the playing field if needed.

[islandtees]

D- my starlight builds up heat if you burn 10 or so in a row....fyi



we didn't purchase our starlight for speed, we bought it to eliminate a variable. we now have a constant for exposure. a 180 S mesh, 1/1 with HXT is 70 seconds. all the time. every time. forever.

Even with the 2 fans going in the back?

[Sbrem]

Still on the fence with LED, there are other things to spend money on first here. But, we've always had Violux 5000S metal halide, would never have considered a lesser source, though when I started, it was for a good sized company that bought good equipment, so later on anything smaller and less expensive was just not considered, not trying to be snooty or anything. I do like the drop in electricity though, and the lack of heat, and of course I keep up with everyone's writings...

Steve

[Homer]

eb, we HXT with Diazo....it's s hybrid of sorts....yay.... I'll buy a gallon of the 1400 and see what happens. again, I don't give two sh*ts and a f*k about speed so I'm not going to toot the horn of speed....

[ZooCity]

Emulsions to be tested are Xenon Nova with Diazo and Murakami Aquasol HVP.  This is what we know and use and while the Nova is a photopolymer, it behaves much like a dual cure when sensitized.

Shooting 1up on Starlight (largest model) because the unit will not shoot 23x31 2up.  If it was simply 6" wider it would.

We could reposition the halide to the glass optimize for 1up shooting.  However, the SW reflector we're using while it is optimized to shoot closer to glass may have inferior resolution if placed that close to glass.  The Olec reflectors are engineered to shoot their most collimated/collinear light on a somewhat larger area than 1up 23x31 according to my understanding so this might still not be apples to apples if we optimize the Olec for 1up as it's resolution could potentially get thrown off.  Please correct me if I'm wrong on that. 

Also, give me all the crap you can sling!  Challenge every assumption and consider every angle of this with me.  After all, if we aren't as thorough as possible, what's the point?  We have an opportunity in our shop to give these two methods a quality comparison, something that appears to not have been done so far.  The bulk of the info on LED that we have is not empirical.  That's not to say there isn't harder data to back up the claims but aside from "very fast", "lots of LEDs" and "high output LEDS", etc. we're missing critical information from the manufacturers at this point some of it very notably absent, such as the attached for our current halide bulb.

This might take up to a month to see all the results because we're busy and I want to take time to do it right. 

[ebscreen]

Can I send you a gallon of 1400 to compare on the two units?

While I appreciate your testing as well Homer, I don't know that you'd notice much
difference unless you have a MH unit to compare it to.

[ZooCity]

Can I send you a gallon of 1400 to compare on the two units?

While I appreciate your testing as well Homer, I don't know that you'd notice much
difference unless you have a MH unit to compare it to.

Have one on hand.  It's a little under a year old but not sensitized.  We may be able to sneak this in.  I'm open to getting 1400 in the mix to round out the spectrum of emulsions though since we'll then have a pure photopolymer, a dual cure diazo (essentially that's what the nova is or behaves like when sensitized) and a straight diazo. 

[244]

We're currently using two 1200 watt MH units to keep up with screen production. We use SP-1400 diazo emulsion,
probably one of the more difficult emulsions to fully expose. I'd start exposing with a candle before I switched
emulsions, I like the stuff that much.

Our exposure times are long, 4-600 LTUs, probably roughly five minutes, never timed one though.
Obviously it would be a no brainer if we could significantly reduce that time. Not to mention heat, power
consumption, bulb replacement, etc.

I am absolutely unwilling to sacrifice image quality and complete exposure for the above mentioned benefits however.
I'd sooner buy a couple 8K Olec's and to hell with the bulbs and power costs.

So far I have been unable to get a straight answer, from either manufacturer or user, as to whether or not
I'd have to accept a degradation in screen quality from a LED unit for diazo emulsions. Every time I ask for
quantifiable information all I get back is "it's so fast". I hear whispers from trusted sources that my assumptions are
correct though, this post being yet another one.

It seems the majority of LED units are being used with photopolymer emulsions, which is kind of confusing as
exposure times with most MH units are going to be in the sub-minute range already, and going from 50 seconds
to 10 with the possibility for less complete control seems like a losing game. I guess if you were coming from
fluorescent it would make sense. Indeed, Workhorse's LED user manual states that the machine is intended for
use with photopolymer emulsions.

That one MFG has a generous return policy, but I'd honestly feel bad about sending the thing packing right back if it
doesn't cut the mustard. I'd rather know the straight dope beforehand.


So, really, honestly, diazo and LED, yay or nay?

You are more than welcome to try our unit and I assure you your diazo will not be an issue. Try the Starlight and you won't have to feel bad about returning it, because you wont!!!!

[ZooCity]

And that Rich is why we're trying it.  Nobody else is backing their unit with that kind of confidence.  ebscreen and also myself just feel bad about the potential of returning something like this, the thought of it just makes my stomach turn given all the hassles with our particular shipment issues.   I'm rooting hard for the starlight.

Also, I have an email in to Patrick requesting graphs on the UV output which would be immensely helpful in comparing what our halide bulb is outputting to the LED array's spectral output. 

There's a lot of talk going around regarding developments in multi spectral LEDs.  Multi spectrum rich exposure light in the correct range is a proven benefit to stencil durability.  It seems that most are reporting good imaging but mixed reports on stencil durability.  Does M&R plan to look into more spectral rich LEDs and if so, will it be available as an upgrade on existing units?

[RonH]

Over my many years with NuArc I have serviced and sold many different light sources that have been used in Litho and Screen Print, so I am very familiar with testing and comparing different light sources.  In reading thru this and other similar posts concerning the comparison of LED units to MH and other units I feel a couple of important things are being overlooked. 

The first is that many of the comments about LED exposure units are treating them like they were all the same thing.  That is not true, there are a number of different LED units that are available today and they should not be lumped into one category.  So keep in mind that there are a number of differences in LED Exposure Units when comparing units or using someone else's comparisons.  The best way to compare or judge is to do a live demo on a unit with your artwork on your screen, then you can judge the results.

The second thing I have found from going into a lot of shops doing demos is that there are also a lot of variables beyond just the brand or type of emulsion.  The way the screens are coated, handled and stored can affect the outcome.  What one shop considers a good exposure might be unacceptable in another shop.  When we began designing our LED units speed was not our main goal; but when our engineering came up with the type of LED's we should use, and the distance between the LED's to give the best overall coverage it was found to be a rather fast exposure unit.  In reading the comments about SBQ being the primary emulsion for LED's, I do not feel that is an accurate portrayal of what I see in the field.  One shop may be very happy with a particular emulsion and another shop using the same emulsion finds it too fast.  So yes, some are using SBQ with our Starlight units, while others have changed to Dual Cures and Diazos to get the results they are looking for.  In fact some shops found the SBQ emulsions were too fast and have switched for that reason.

Ron Hopkins
NuArc Sales Mgr.
M&R Sales and Service co.