DIY Exposure Unit: What light source?

[mr. illiteracy]

So I've been looking at building my own exposure unit, as that is the most expensive single item I need to start printing. I've looked at several diagrams, and the main difference between all of them is the light source.

Some use a single 1000w metal halide bulb placed about 24" away from the glass, some use 2 500w halide, and some multiple 8-10 UV tubes placed about 6" from the glass. There are tons of people that swear by each one of these designs, but from what I've read the multiple tube method puts you at risk of losing a lot of fine details in the image, and that a single 1000w or two 500w lights are the way to go. However when I look at professional units that can be found at legit print shops, theyre all using multiple blacklight tubes.

To me it seems like thats a better design, as it's more compact, runs cooler, and seems to have shorter exposure times. At the same time I tend towards the very detailed, fine-line type stuff and wouldn't want to lose that with an inferior set up. So to those of you who have built your own exposure unit, which design did you use and why?

[lil_tuffy]

I'm building mine currently based on these designs:
Exposure Units
http://unblinkingeye.com/Articles/UVBox/uvbox.html

YouTube - How to make a light table

YouTube - How to make a light table

It's probably going to cost me about $500 when it's all said and done but that's better than the $2k it would cost to buy that new with tax/shipping.

The first problem I've run into is that 36" tubes are non standard and I should have made it big enough to accommodate 48" fixtures (or 24" if you ain't gonna print that big).

Next, the tubes are hard to find. I've been to 3 industrial/commercial lighting supplies places in SF and all of them would have to special order it.

This the cheapest price I could find for the bulbs:
F30T8-350BL Black Light Fluorescent $12.95

I have heard rumors of fluorescents undercutting but no one on this site that has applied the method has reported any instance of that.

I'm off to pick-up my neoprene today!

[necro]

Originally Posted by lil_tuffy

I'm building mine currently based on these designs:
Exposure Units
UV Light Box
YouTube - How to make a light table

It's probably going to cost me about $500 when it's all said and done but that's better than the $2k it would cost to buy that new with tax/shipping.

The first problem I've run into is that 36" tubes are non standard and I should have made it big enough to accommodate 48" fixtures (or 24" if you ain't gonna print that big).

Next, the tubes are hard to find. I've been to 3 industrial/commercial lighting supplies places in SF and all of them would have to special order it.

This the cheapest price I could find for the bulbs:
F30T8-350BL Black Light Fluorescent $12.95

I have heard rumors of fluorescents undercutting but no one on this site that has applied the method has reported any instance of that.

I'm off to pick-up my neoprene today!

my first one i made with 36inch bulbs. total nightmare. Sometimes they work, sometimes they dont. 36"ers are not made to run wired in a series. 48" is the way to go.

[Andymac]

most 'professional' small format shops use fluorescent UV units, for the reasons you describe - fast, cheaper (cost to buy, cost to run, and replacement bulbs), efficient. CHEAP being the most prominent item.

any units using halogen bulbs are mostly homemade, becuase halogen doesn't give off high amounts of UV - UV being the 'active ingredient' in light that makes the stencil harden.

larger PRO units are almost all Metal Halide point light sources, because (a) they have the highest UV output, and (b) a point light source, properly set up, will give slightly finer and more controlled edge definition than fluorescent UV bulbs.

For home made, and (not to insult your desire to print 'very detailed, fine line stuff' but the difference in quality is in the last 10% of detail, and unless you are running imagesetter posi's and automatic presses with a squeegee grinder close by, your exposures will be the least of your worries regarding printing extreme fine detail...) I think you can put together a fluorescent unit that will fulfill all your needs. By the time you start running into limitations caused by ezposures, you will either be able to step up to a pro unit, or realize it's easier to let someone else print.

Thanks for going premium, and congratulations on your rapid mastery of language.

[milesstegall]

I have used Halogen bulbs for awhile and get fantastic detail but the exposure time is like 30 minutes.. which drives me insane.. but last week I found a 1000W metal halide ballast on craigslist for CHEAP!! So I am in the process of setting that up once my bulb arrives in the mail. From all of the research I have done this seems to be the best way to go. As Tuffy said I have heard about undercutting as well but not ever having used fluorescents I can't say.. but tons of people use those and they seem to work just fine.

[lil_tuffy]

Originally Posted by necro

my first one i made with 36inch bulbs. total nightmare. Sometimes they work, sometimes they dont. 36"ers are not made to run wired in a series. 48" is the way to go.

Yeah. I'll be running individual ballasts, adding to the overall costs.

[boatdreams]

Here's a breakdown of my exposure unit:
Two 500 watt halogen work lamps @ $14 each - $28
Wood and L-brackets - $10-15
Found glass - $0
Power strip - $10
------------
$58

Works like a charm, too.
My exposure time is between 5 and 6 and a half minutes, and I get really fine details.

[Andymac]

swing over a few from Tuffy's video to the Roger Jennings 'Screenprinting's best exposure unit (I think) on U tube. that gives a good explanationf of the factors involved.

the $150 1000w halogen grow lamp set up is an option too. Tuffy, you making this with a vacuum top? I've seen a number of homemade vacuum tops with neoprene wet suit material and an old vacuum cleaner, they work great.

[milesstegall]

boatdreams what emulsion do you use? and are your times for yellow or white mesh?

[lil_tuffy]

Originally Posted by Andymac

swing over a few from Tuffy's video to the Roger Jennings 'Screenprinting's best exposure unit (I think) on U tube. that gives a good explanationf of the factors involved.

the $150 1000w halogen grow lamp set up is an option too. Tuffy, you making this with a vacuum top? I've seen a number of homemade vacuum tops with neoprene wet suit material and an old vacuum cleaner, they work great.

Yes. Making a vacuum lid for it for multiple reasons -- to prevent the possibility of undercutting, to save space and time (foam pad and weights) and to protect the glass from dust/damage.

I've considered going the fast/easy route but I think spending the time to do it right will pay-off in the end.