What emulsion do you use with a LED exposure unit?

[Northland]

currently using chroma lime. Works for me, though I am getting an auto in a few weeks (Yay!) so I might start testing other options if we get more into sim process. Will be watching this thread.

I use ChromoLIME too. I just ran a price check and found online prices that range from $59 to $95 per gallon

I can't vouch for it's ability to hold detail (I don't get many halftone jobs).... but it exposes in 13 seconds on my DYI LED unit and reclaims well.

I coat 1X1 on S-mesh and can easily do 120 screens/gallon.


Also, it is fairly transparent after drying... which aids in registration, if your regi-system is not top-notch (mine is still a work in progress... homemade).

May I ask what mesh count that is. We do only S-mesh here and don`t get anything like 13 sec. on our Vastex LED with the Chroma Lime coated 1/1 with sharp edge. If we would do 13 sec. reclaiming would be a nightmare.

Rockers.... I'm using mostly 180S & 225S mesh... occasionally 135S (which I burn at 15 seconds).
My LED field is about 300 watts of 5050-SMD diodes (1500 total)... that are mounted 2" below the glass

I think the key to quick exposure time is the distance between the field and the glass.
The one characteristic that I enjoy the most, with LED, is the instant ON.
My old MH needed about 5 Min of warm-up time and around 10 min if it got shut OFF and then needed to be re-lit.
The 13 second exposure time doesn't really move the needle for me (anything under a minute would be acceptable for my operation)

[ABuffington]

In my seminars I discuss 'baking the cake'.  It's not how fast you expose, it's how well you expose a screen that matters.  If your shop is along a foggy coast like it is in So Cal in spring you will need more time than someone who is Phoenix AZ.  Really dry screens expose faster.  Really dry cannot be determined by just touching the screen.  A moisture meter is the tool to determine how dry the emulsion is on the inside, you know the part that actually binds itself to the mesh.  I am sure many have experienced the stencil completely falling off the screen with discharge.  Typically this is an underexposure issue, but rush a screen through the process without drying it completely after coating and it will do the same.

Image vs Exposure.  You can get just about any emulsion to get an image with short amounts of exposure time.  I can't tell you how many times a screen room worker will underexpose to try to get all the details he can.  This makes him happy, but uses up rolls of tape and drives the production manager nuts with pinholes appearing all the time in the print, or needing a new discharge screen in the first hundred prints.

In the case of LED exposure the shorter the exposure time the more narrow the exposure latitude is available for optimum exposures.  So comparing times between different print companies doesn't take into account humidity, screen moisture, temperature of the emulsion, film or CTS?, or image density of either.  The exposure latitude of any emulsion on an LED is narrow.  That's why they have tenths of a second on some units to really dial in the best exposure possible.  (And the best stencil is never the shortest time you can get an image.) So if someone in the desert is exposing HVP at 14, the coastal foggy conditions may need 16 seconds.  2 seconds difference is a 12% difference.  That's a lot of change for another shop who's screen room conditions may be way different. 

So back to bake the cake.  Any baker will always, and I mean always, bake the bread or cake for a precise amount of time.  The same holds true for emulsions.  We need to give the emulsion as much light energy as it can take and expose right up to the point that more time will result in over exposure.  90-95% of the emulsion strength comes from the exposure.  Everything else is a band aid to make it stronger, from post exposure to hardeners.

In today's print world we mix plastisol, wb, discharge, and HSA inks in many shops and without complete exposure you will see breakdown, press stoppage and rejects increase.  Shops run better when the press doesn't stop and start to fix pinholes, blow outs or de-lamination of the stencil.  If you calibrate your exposure times and base it on  your film/cts image/image dmax, humidity, coating technique, you will have a recipe that allows you to print with less pinholes, less break down, sharper line work, better halftone dot gain control.  Without exposure calibration your shop is missing the quality it bought in the emulsion to begin with. 

Al

[Dottonedan]

 Some emulsions fully bake much faster than others.   With some emulsions you can get a full cure in a third of the time as a few others. As you know, speaking specifically about a fully cured stencil, one emulsion can be fully cured in one minute  and at the opposite end of that another of emulsion can be fully cured in five minutes. Both will do a specific job.  Depending on your specific job needs, the one minute can be perfect for you or the five-minute can be perfect for you.

[Steve Harpold]

The simple answer in today's world is just about any emulsions typically used in screen printing will work with the LED systems. Yes this includes Diazos and photopolymers. It will not be long before all you can buy is an led system, the wave lengths and the power needed at those wave lengths are readily available. If you are intrested in the Brown LED system:

LEDS - 4" away from the glass to (remove heat issues, as well as properly burn halftones)
Total LEDS - 30 to burn 23x31 screen

Photopolymer: 3-12 seconds
Diazo - 20-35 seconds (can make it faster if you really want to challenge it)

[Orion]

We use KIWO Multitex.

I still have not seen any comprehensive spectral output data on any manufacturers LED system. I find it interesting to see that tonypep still relies on a multi-spectral lamp for stencils that will be used for dc inks.

[Dottonedan]

We use KIWO Multitex.

I still have not seen any comprehensive spectral output data on any manufacturers LED system. I find it interesting to see that tonypep still relies on a multi-spectral lamp for stencils that will be used for dc inks.

I don't know that answer. Apparently, you could assume that he either doesn't feel it is a full and complete cure all the way to the back and durable to hold up to the water breakdown for (all) types of quantities. That could be a factor.

As for me, I've been in shops/installed in shops and back at shops 2 years later that are all discharge/waterbase using nothing but LED. The typical quantity for these shops were in the area of 48-500 typical orders.   (How much quantity) or length of time exposed to potential breakdown seems like it would be the only answer.

I'm a First hand witness that it does work in some DC shops (and I don't even work for a company that sells LED anymore). Why those shops and not another?  I don't know that answer. Preference maybe.


What I find interesting is that while DC is on the rise, it makes up a small percentage of the industry.
So lets say that number is 15% of the industry (I don't know) but it feels close. LED apparently works for some or a percentage of those....and works for 100% of the rest of the apparel screen printing industry.

You can safely say that LED is a more than viable option in the industry for the vast majority.

That's also what scares some or at least one emulsion manufacturer that sells an emulsion that requires a long exposure time to fully cure for traditional light (to begin with). So that emulsion exposes (faster) on LED....but still, for LED it's a VERY long exposure time....and for those who have invested in an LED exp. and especially a DTS machine with LED exp on it, well, you could see why that emulsion Co. would tell people it's not a viable option. Let me explain this for some.

It would take away A LOT of sales. An emulsion that takes 1.5-3 min to expose on an LED would sound as if that emulsion is not as time efficient to use (since a shop may have bought the machine for the purpose of obtaining these well known 30 second exposure times of many many others emulsions. So they want their machine...and can easily change to another emulsion that does the same thing with far less time.


Since a (long exposing emulsion) had a market share of plastisol printers and DC printers, One like this, would want you to believe that LED is not good enough.

[Mr Tees!!]

I use CCI WR-14 with my Starlight. I still use inkjet film, and I have crept my exposure time up to 50 sec for durability and easier reclaim. for art that may have really fine detail, I cut my exposure time down to as low as 32 sec.

[tonypep]

Curious as how light units are not discussed here. Thats what integrators are for

[ZooCity]

Curious as how light units are not discussed here. Thats what integrators are for

No photocell/integrator on most LED units as far as I know.  I found that very strange but the claim is that the LEDs don't degrade, I guess we'll see.

I'm equally surprised that there are not low output options for the LED units, ours is built with dimmable LEDs but doesn't take advantage of that.  Would be good for PP emulsions that are shooting too fast- no benefit that I can see to a sub 20s exposure time except perhaps reduced undercutting but that's prob negligible. 

[Colin]

A reminder that LED units do not like thicker stencils.....

They lack the power necessary to really kick through thicker coatings.

I do wish that a high power option was available if I wanted to do a high density/capillary film.

[ABuffington]

Just a general observation on speed of emulsions.

Pure Photopolymers = fast
Dual Cures = Slower
Diazos slowest.

Coating and resulting EOM have a lot to do with times.  A 2:2 coat for a spot color on a 160 will be different than a 1:1 on a 160T due to emulsion thicknesses.  This change in times gets magnified on LED, but LED's ease of use, exposure speed and consistent lamp strength, and quality are more than acceptable for any print job.

LED's definitely help if you have lots of screens to burn in a short amount of time.  Multi Spectral has more wavelengths and amplitude in the wavelengths emulsion is sensitive to.  LED's used to be single wavelength with some bleed in nearby area.  These too will be moving to multi spectral, some have already.  With good calibration you can get either LED or MH to work.  My main point is time of exposure should be looked at as exposure quality first, whatever time that may be for the unit and screen room you are in.  Film imagery, ink jet, wax, image setter also have a stake in the quality of exposure.   

[Dottonedan]

A reminder that LED units do not like thicker stencils.....

They lack the power necessary to really kick through thicker coatings.

I do wish that a high power option was available if I wanted to do a high density/capillary film.

The only thing I can say about an LED and thickness is based off my experience with M&R's LED's. That said, we resolved up to 400 micron thickness with the LED. Could be thicker, but that is the limit for what will be allowed past the height sensors on an I-Image.  What emulsion can be used for that, I don't remember.

[alan802]

Most of you know our experience with exposure units, but I'll briefly put in my .02 because I feel like it.  I read above that only LED will be available in the future and I guess you can't stop progress.  I'll only say that in the world of LED there are good ones and bad ones.  We had both.  But I'll argue with anyone, sales person or engineer that a strong MH bulb is still unbeatable when it comes to detail and durability.  If we were doing a ton of process work, and long runs I might refurb our Solarbeam.  But the Starlight has been able to do a lot of things I didn't think LED was capable of after our first go around with it.  No LED likes a stencil over about 20% EOMR, and even at 20 you'll likely get screen breakdown at the squeegee edge after a few hundred impressions, but with the right mesh count, "thin is in".  If you can keep your edge definition and keep dot gain down with a 10% EOMR then that's the target in my opinion for most LED shops.  It's taken a bit of time to get our Starlight dialed in to get results comparable to a good MH unit, but it's 90% there.  I'm sure with time the manufacturers will continue to perfect things so that you'll never see a screen breakdown on press and you won't have to do much legwork to get a 5%, 60lpi from an LED unit.  Our LED unit can almost do what the Richmond MH unit did, the only difference is the MH was easy.  When I was a pup in this game I was putting out amazingly detailed halftone screens on our MH unit, and for years I really didn't know why so many people had issues developing stencils.  Then I was humbled when we put the Richmond in the corner for about a year and I quickly learned how spoiled and easy it was to get a 65lpi 5% dot with a good MH bulb. 

We've used so many different emulsions over the last few years, I can't name them all.  And our burn times can be anywhere from 5 seconds up to 60 seconds on the same screen, it just depends on how long I want the stencil to last before the squeegee edge breaks it down.  I can literally burn the same mesh count and image for as little as 5 and as long as a minute and the image washes out fine, that's pretty good exposure latitude.  I like Chroma-Prototype from Kevin at River City and Ulano QXO currently.  Most others simply won't dry sufficiently enough to keep film from sticking, even in a 30% humidity dark room for a week at a time.  I've recently tried the Multitex and T9 but they are way too tacky and no matter how dry our dark room is it doesn't help.

[Dottonedan]

A good detail resolving emulsion "I liked" for film was ChromaLine Blue , BUT, it seemed to have a stickiness to it. A rubber sticky if you will.


I've said it before, and I'll say it again, If it were my shop (and just for testing and playing to win awards, push myself and the envelope of what can be done, etc.) I'd go with MH for that. Like you said, with that, you can hold 3% dots from good film (true imagesetter films) in a 65-75 -85 lpi.
From that standpoint, like Zoo once said MH is superior. It does work extremely well for sp. but with that said, it's also...(overkill for screen printing) for most. THen added cost of bulbs etc. It's for that reason alone, (now obviously an unnecessary overkill) for the vast majority that I say MH would not fall into the "superior choice" category. It's a superior method of exposing, but not a superior choice (for the majority) of shops.


In essence, for the vast majority literally thousands of shops who are not even close to even wanting to print awards or high end sim process or process, or discharge/waterbase, (and there are far, far more of them ....then a MH is NOT superior. It's not a superior choice as it pertains to production efficiency and cost of getting your more than average and your average job out the door fast. People WITH led are even winning awards, so that's not a factor. For the purposes of production, LED and LED (ON AN I-IMAGE) ...and any NEW EXPOSURE TECHNOLOGY that is or will be better coming out behind LED...is currently a superior production choice. There are hundreds of shops now, if not into the thousands that can support that claim. Take it to extremes and exposing 4 up on a MH compared to an LED I-IMAGE will only "equal" the exposure time output, but I-Image wins over film (at any level) in terms of the process to get it there more efficiently over the 4up MH.

Many shops just don't have things in place to expose "properly" on their MH to keep the efficiency of the MH at 4up.  Like I've said, I've been around now, both from being a Tech and all of the years before and after. I love all shops and what they do in their shop is up to them. They have proven to me far too many times to discount their credibility in the business... but you guys here (the majority of the contributors) are far above on efficiency than most "ever think about" let alone actually do. Here, in our little world, "Our group on this forum", is but a smidgen, a speck of sand on a vast shoreline of sand...where you are 100 fold greatly outnumbered by the printers who can't, won't or don't feel they need to...do more than what they are.


Durability is better?  I'm sure it is. BUT, there are shops out there, (many) cuz there are a lot of these LED's sold who are using LED exclusively for these orders, using DTS that "supposedly" can't give you durable cures all the way thru for long production runs...who are doing 10, 50, 100,000 piece orders. Why is that?  How is that?  Do they just find that it's more efficient to burn two sets, three sets of screens?  I've asked that question while I was watching the order being printed. I've been told no. Same screens on a 50k peace order front and back. Same screens. Hmmmph. Another shop, a contact printer. MHM presses. LED exp. I-Image DTS, with an average order of 5000 units. Big order is 200,000 units using several times a month exclusively LED. HOW?  I donno. Somehow, they make it work.

The mass numbers of people who will easily be improving their business by using LED and DTS, greatly outweigh those few that prefer a "superior MH" over LED.  Granted, there is NOTHING wrong about the exposure quality you get out of a MH and you can still get great production out of them for those who know their stuff. So for those who do use them and will keep using them, I'm with ya. No issues. It's a good method depending on your needs in your shop.

LED is here, it's staying, and MH is more than likely going to be a thing of the past soon, like true imagesetter films. (I prefer them). I think they are superior to inkjet. I know they are. They are better quality but it's no longer a viable option for production. Still, some (very few) hold onto it.

[Stinkhorn Press]

To drift further from the question asked....

the difference between MH going away and imagesetters is in the quantity available on the used market.
there are, and will be, for quite some time, decent (usable of fixable) MH units for sale at decent prices.

when you can get a good MH (NOT NEW) system up and running for less than the cost of a NEW LED (not really much available on the used market)
it throws off my measure of Dan's "superior choice" description. there is more latitude in an decent MH setup at this time, in my opinion. more latitude and currently cheaper (up front)? no questions here.