Exposing phat films on a LED unit?

[Rockers]

Was kind of wondering if that will work. Are the LED lights strong enough to penetrate the full thickness of let`s say a Chromaline Super Phat Film 400 or 700 microns? Has anyone ever tried that, is there actually still a demand for this sort of application?

[jsheridan]

Great question!

so who's going to test this out....

[bimmridder]

We do thick stencils, 350-400 micron screens on ours. Direct emulsion. It takes us a lot of trips under the light bar to get exposure, but it works.

[Screen Dan]

An old co-worker of mine got a hold of me recently to let me know about his adventures with his new LED exposure unit, which has blown him away.  He wasn't using phat films, but he was using a ~600 micron buildup of Aquasol HS, which I've found to have similar exposure requirements to yield similar developing difficulty.

He thought he'd go a little bit over to make sure it was cured and apparently it produced a screen that was impossible to develop with all of the soaking and pressure they could throw at it.

This is obviously anecdotal and I've provided no hardware specs and even fewer specifics about every other detail.  But the takeaway should be that, yes, LED units can expose anything an MH light can do so far as I know.

I don't know what he had before he got this unit which I know nothing about, but I'm coming from a 5000w MH light, so, as excited as I am about maybe getting an LED unit in the future I have many reservations at the moment. 

[Dottonedan]

I don't know the results, (what the exposure times are) on something like that,  but I hear from Alex Mammoser that the media height sensors on the STE's can take no more than 400 micron stencils before passing/interfering with the head protection sensors. The fact that we are told it can take up to 400 micron thickness indicates that yes, you can indeed expose them (at some amount of time). I just don't have any idea what time that might be. Each emulsion type will produce different results. If using an M&R STE with the front bar, it may take two passes. If using the back panel aka STE2, it will be one consistent length of time but obviously longer than a normal thickness.
[/size]I did a dual cure the other day and had 38 seconds on a 60 mesh coated 2:2 with round edge. So, X that by 3 roughly I guess and you might be in the area. So maybe around 2 minutes for a 400 micron. Just guessing.I was at another shop where they were exposing 60 mesh two times using dual cure. Each time at 270 light unites that equated to 2.5 minutes each so they needed 5 minutes to expose a 60 mesh on a 5k metal halide. Apparently the light was weak maybe. We were exposing that same 60 mesh and emulsion in one shot at 25 seconds using the back panel.

If using a starlight, or any other LED exposure system, then the thickness isn't going to matter on those since there is no need for height sensors. So there again, yes, it can be done on ours, just don't have a good estimate on exp time. How well they are exposed, will there be any noticeable undercutting on that thick of a stencil, edge definition, etc. I also have no information on, but then again, you're probably not trying to hold .5 lines or halftones and yes, i'd imagine it will take a while to wash out, but I expect that you would have additional wash out time with any other exposure unit as well.

[GKitson]

We do thick stencils, 350-400 micron screens on ours. Direct emulsion. It takes us a lot of trips under the light bar to get exposure, but it works.

A Lot of trips.  What kind of answer is that, you would think we live and work in the back of a VW micro bus, traveling to Grateful Dead love ins selling tie dyed boot legged t-shirts that are 'smoked' rather than cured by a bunch of un bathed, tattooed, pony-tailed, free love political radicals.

Oops, I guess that does describe a bunch of us so I guess A Lot of Trips is a perfectly acceptable answer, kind of like " It Depends".   

~ Kitson

[bimmridder]

You got me , Greg

[markdhl]

Thickness will definitely adversely affect the quality since we have a multiple source of bulbs in the led systems.

Mark Diehl

[ABuffington]

The other key factor is how black is the image? With wax systems, it is super opaque.  With inkjet CTS I have seen both good and weak D max or opacity. The exposure time on a 5,000 watt MH is 1.5 minutes per 100 microns of Murakami Thick Film, or Aquasol HS.  Any transparency in the black image can cause burn through in the image area, especially at 6  minutes on a MH.   If some are achieving good exposures on LED units with these products are you seeing any slime at all on the inside during development or if you take a white rag do are you able to wipe off any emulsion, green One Pot C color for the Thick Film, or pink for Aquasol HS?

Both products still have light sensitivity when developed.  Throw them in the sun for added exposure strength.   No sun?  Use exposure unit, sold the MH?  oops.  I still like Metal Halides but see the cost and some speed benefits of the new LED units that will only get better.  In my travels the 20k/run plus printers are still using MH. 

Al

[jvanick]

I've done 400 micron films on our Starlight...

I believe the exposure time was around 3 minutes and 30 seconds...

as said before, make sure you have a REALLY dark stencil...

We cannot run them through the I-Image due to the head height and the laser, so when running them we have to put the glass back in the exposure unit.

[244]

I've done 400 micron films on our Starlight...

I believe the exposure time was around 3 minutes and 30 seconds...

as said before, make sure you have a REALLY dark stencil...

We cannot run them through the I-Image due to the head height and the laser, so when running them we have to put the glass back in the exposure unit.

not so. You can purchase a pusher bar to adjust for your films. Takes about 10 seconds to change out.

[Dottonedan]

Al,

I appreciate your knowledge and experience. Thanks for sharing.

I am only familiar with M&R DTS so I can't speak for all types, but if imagine the information below should apply to others as well.


For different shops, there can be different print modes geared to the majority of the type of work they do.
For that reason, you can find different levels of image density based on that shops needs. A shop may only have one print mode setting but others more complexed may have 4-8 different print modes set up to choose from.  Typically, we provide a 6 pass and a 12 pass and add to those depending on customer needs. With each of those, the user can then also choose to print BI directional or UNI directional. You can choose that on the fly and don't need any special calibration to switch. Each of those provides a different level of ink lay down and production speed. In short, this provides versatility.

To add to your information about the opacity of inks, you will find that the opacity can change based on your desires for the image. For example, a 4 or even 6 pass calibration may be more suitable for very high line counts such as 75-85lpi ( for those who might want to experiment) in those line counts. It holds finer shadow tones more accurately in high line counts, but does require a slightly different or slightly faster exposure time or speed than does another pass setting to compensate for the thinner lay down of ink.  That's probably an extreme example.  Another example might be if all of the images you produce are solid athletic type prints, you can and probably should choose a 12 pass for more opacity. Many shops prefer this setting because it's so opaque and allows for a week de latitude for exposure times. It relies more on your emulsion type where some will allow you to use the same exposure times for more screens. Let's say a 305, a 230 and a 200 may all be able to be exposed at the same speed. I'm not find of that technique but many order to streamline and have less options.

The "ink" types of DTS are as far as I have seen, more than able to produce the best opacity needed for screen print.

[244]

We do thick stencils, 350-400 micron screens on ours. Direct emulsion. It takes us a lot of trips under the light bar to get exposure, but it works.

A Lot of trips.  What kind of answer is that, you would think we live and work in the back of a VW micro bus, traveling to Grateful Dead love ins selling tie dyed boot legged t-shirts that are 'smoked' rather than cured by a bunch of un bathed, tattooed, pony-tailed, free love political radicals.

Oops, I guess that does describe a bunch of us so I guess A Lot of Trips is a perfectly acceptable answer, kind of like " It Depends".   

~ Kitson

The front bar on our STE II is designed for photopolymer emulsions and using for super thick emulsions is not it's designed function. The rear light is designed for diazo and thick films. Yes you can do the exposure on the front bar but it will take multiple passes where the rear unit should cure faster than a 5 K Mercury  and with no more or no less undercutting. This is specific to our unit. I cannot speak of the units with less LED's.