Exposure Units

[adman1986]

Wondering if someone could tell me the difference in screen quality outcomes when it comes to using a Amerigraph or Nuarc metal-halide vs a Vastex E-2331 multi light source. I know where I worked before we had a Nuarc 3140 because of all the half tones screens we were shooting. I am making my equipment purchases and don't want to make the wrong choice. Brandt you may be able to answer this question since I noticed you had both in your pics of your shop.

[Denis Kolar]

I do not have much experience, but from my research when I was buying, I have learned that if you think about printing halftones buy the single point exposure. With multi light exposure, you will have lights coming at multiple angles to light up a single dot which will result in undercutting on stencil.
I ended up with a used single point Nuarc 40-1K with a Mercury bulb for $350. Not as good as MH exposure units, but it does pretty good work with halftones.

[Orion]

Agree with DK, single point light source.

[ZooCity]

+1 for a single point light source.

Aside from good 'ol sunshine in the very early days, single point is all I've used.  And I've used everything from a low-bay warehouse MH lamp to the Olec we run now, all of it homebrewed and jerry rigged to some degree and have been quite happy with our exposures pretty much all the way.

Off the top of my head, three things you really want in an expo unit:

• Vacuum top
• Single point light source
• Integrator

You don't absolutely need any of that but if you want to really move through the screens, resolve fine lines and halftones with confidence and not have a high rate of failure I would start there.  I would never go without these in a production environment again.

I also like a shuttered bulb rather than an "instant-on" type, it seems to extend bulb life.  And, I don't really see the point (oh ho! accidental pun!) in blacklight units that are built so well mechanically but are still using diffuse, UV-weak light to do the exposin'.  Nevertheless, printers expose great screens, halftones and all on them every day I'm sure.   Last thing I'll say is get a 5k watt unit if you can swing it, even more is better.  It's less about having 10 second exposures (which we do with our 5k and that's certainly nice) and more about getting a solid exposure all the way through the stencil.  The extra watts seem to really help out in that department but I find a post exposure to be necessary on any of our thicker stencils and anything destined for waterbased ink. 

Hope that helps.  There's probably a whole slew of articles on this out there in the interwebs. 

[adman1986]

Thanks for the replies guys

[blue moon]

there are used 3140's on the market every so often. Several of them in last few months in the mid $2k prices. I paid $825 for mine!

at those prices, skip the multibulb setups . . .

pierre

[shellyky]

Hey sorry i didnt catch this-yes we started with the vastex 2331..it lasted us "in the beginning" and yes it would burn halftones,even did a pretty great 4CP job with it, but the burntimes, man that was too long LOL...upgraded to the amergraph 150 and it went from 25 MINUTES to like 1-2ish and it would also do 2 at a time if you use small screens...i love the unit, i havent had any problems and everyone who comes in here 'in the know' says its a great unit and they dont see many of them...im sure the 3140 is awesome as well and i think it has a couple more features.

as far as screen burn quality, the edges/lines are sharper, more distinct on the amergraph unit, and it will expose a piece of dust on the glass.  I regret not going metal halide from the get go---we dont even use the vastex unit, im not sure why we havent sold it lol

[Sbrem]

Metal Halide, point source, nuff said. Fortunately, I've never used anything but a point source, starting with a carbon arc lamp. Damn, that made the best screens, but the poison smoke...

Steve

[tonypep]

Shelly do not overlook the emulsion when looking at halftone quality. Pure photopolymers were developed for those who need speed and have less demand for detail for instance. Its the proper combination of light source and stencil (emulsion is only one factor in determining stencil quality) that will yield the best results. And yes a light integrater is a must if you demand the best and most consistent results.
best tp

[sportsshoppe]

I picked up a Plate Maker 1000k for less than $100 and then took the top off fliped it over where the source is at the bottom, made a glass holder out of 2'' x 2'' wood and made my top with wet suit material and 1'' x 1.5'' light weight tube steel and it works great. I have less than $150 in everything and it comes with a light Integrator. Sure beats the price of a 2K one

[Evo]

I've used everything from a very small fleuro tube unit up to to a 6' x 8' vacuum table with a 6k lamp. I now have a MSP 3140 and it's a dream. Most any good point source unit with a metal-halide lamp and an integrator will make things faster and easier. The difference in stencil resolution is like going from an old black and white tube TV to a new 1080P plasma with a Blueray player.


Other things to consider whether buying new or used:


PARTS. Are the blanket, controls, lamp, hinges, springs etc all good quality and easy to get parts for?

Is the lamp easy to change?

Does the unit have a memory feature to program different exposures?

Will it fit my current frame sizes that I commonly use AND the maximum frame size I can fit in my press?

[Fresh Baked Printing]

Metal Halide, point source, nuff said. Fortunately, I've never used anything but a point source, starting with a carbon arc lamp. Damn, that made the best screens, but the poison smoke...

Steve

I used to use carbon arc in the film projectors as a film projectionist back in the day. Brighter than a million suns. I can retire someday with all of the movie posters I have from the 60's-mid 80's (I'm not that old btw)

Tidbit. Does anybody realize that a typical film is about 6 reels long? That little black dot in the top right hand corner means it time to fire up the other projector. The second dot a few seconds later means it's time to switch over. Then we reload the projector all over again with the next reel. The audience never knows it.
Too this day, that dot stands out like the size of the moon to me when I see a movie.

[squeezee]

Haven't they gone digital now?

[squeezee]

http://www.norwb.com/index.php?topic=84.0 explains all.

[Fresh Baked Printing]

Haven't they gone digital now?

This is waaay off topic but I haven't had a chance to talk about this forever

We knew when to start looking for the dots when a bell on an arm against the film reel dropped when the reel diameter got to a certain size as the film ran through. Very low tech but brilliantly simple.
Film was loaded just like teachers used to load class films before the video machine came out. Projectors were about 6 feet tall.
Some theaters had a platter system where the individual reels were all spliced together to form one big reel that layed horizontally. Then separated into reels again for the next theater.
I'm not sure how they do it these days. Must be digital.