"He who marches out of step hears another drum." ~ Ken Kesey
We are still in the evaluation process of LED exposure units. Our first tests were very promising and no doubt about it LED's are the future of curing. One point to note is that most LED systems are wavelength specific. They output at the same nanometer wavelength whereas a Metal Halide will have multiple spikes in the important wavelengths to cure all emulsions. Diazo emulsions tend to like 360nm whereas Pure Photopolymers like HVP fall in the 390-420nm range. For this reason Pure Photopolymers and Dual Cures expose well on the LED systems.There are some new players that popped up at SGIA. Light Speed which is repped by North West Graphics in MN has a patented multi-spectral light source with good focused lenses. The concept sounds great to an emulsion manufacturer since we know multi-spectral metal halides simply create stronger stencils. However in the US we don't see the 80k-90k print runs in water base and discharge that exist in large production shops off shore. For us the light has to be able to create a very strong screen for these longer runs. In the US however LEd's will work very well since we are lucky to see 10k runs here. The Starlight is incredible and exposure time is so short we worry a little about the lattitude of exposure, but initial tests show very strong positives. For us only very long runs will be needed to compare to MH lamps. The other new exposure unit is from Douthitt and designed by Olec. Their LED lights are quite strong by comparison to other units and need to be water cooled and we will test these as well, but for plastisol the LED systems are very good and the lamp life and 110V is a huge cost savings.Not to be overlooked, Sign Tronics and others have scanning laser exposure with incredible details, CST as well, and we will be testing these on long run wb, discharge for evaluation.
I was in the exact same spot as TCT. We have two complete Olec 5k systems, total redundancy save for our integrator and photocell. Just purchased a new photocell to boot and we have a 3 different reflector options. It seemed silly to move to anything else but what pushed me over was space and electrical. The Starlight we ordered takes up nothing compared to the giant Millington frame and lamphead on a cart setup. Most importantly I dropped 29a of draw from our electrical situation. The 5k Olec draws almost exactly 30a when running and we shoot a lot of diazo added, high EOM screens which means it's running a lot. Would I have done it if space/power were not an issue? Hard telling. I guess I'll let you know when the Starlight gets into production. I like buying anything we can from M&R. Only knock I have on the Starlight is it needs just 6 more inches of expo area to do (2) 23x31 screens at a time. Given the expo time reduction we'll see from shooting 2up with the halide 63" away from the glass I reckon it will be a non issue but it seems like a no brainer to add that additional space. Must be something to do with the parts that prevents it. We did run over 10k pc runs of discharge, wet on wet (which was the lone cause of breakdown for us), earlier in the year and we needed 2 sets of screens if I recall correctly, all hardened with "permanent" 2 part hardener, so if that job swings back around next Spring I can put the LEDs to that ultimate test.
You selling either 5k light zoo? my 1k is starting to wear on me as my screen volume increases...definitely don't have the funds for led right now unfortunately, not until I at least get an auto.
As noted in previous posts, you can get a strong screen with the new LED units out there. Our preference for multi spectral light stems from the need our offshore clients have when printing 80-120K runs. For runs under 10k the LED's are producing great screens when exposed well. We have shops testing on longer runs currently and will post the results. Emulsion is only part of the solution to avoiding breakdown on press with wb, discharge and HSA inks. Press set up, operator knowledge of how these inks print better, and how a wb and plastisol press set up differs from plastisol is also crucial to long runs with wb inks.My biggest tech challenge is getting customers to realize just obtaining an image may not be a good screen exposure. Durability of the stencil is directly related to how much light energy you are able to give the emulsion before it is over exposed. An image obtained by under exposure will never match the durability of a good exposure using as much time as possible.
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Topic: Exposure decision advice (Read 4638 times)
