"He who marches out of step hears another drum." ~ Ken Kesey
Alan if I were in your shoes I would send these results over to vastex and ask them what they would recommend for emulsion for there unit? I would also test the voltage on your unit to see if you are losing power when the LEDs turn on but I doubt it. Green Galaxy did make a emulsion for LED use but I don't know how it will work on your unit. We got a free sample a week or so back that we our testing this week. At 60 secs on a 305 you shouldn't be getting these results since LEDs are suppose to burning faster than a 6k lamp. What emulsion are you using? It seems like the LED philosophy is that you burn the screen and than post harden it with light but with diazo emulsion you only get one chance to create this link. So it seems like post exposure is what your missing. I am against post exposure with diazo but it does work with pure photopolymers.
I'm a process guy (everyone here knows me well enough to know I like to break things down and know how each part makes up the whole), but I also understand that the goal/results are what matters when it's all said and done. The end results are where I simply can't separate LED with MH because I'm putting some of the most finely coated screens anyone on this forum has ever seen (seriously, my guy makes better screens than I do, EOM is within 2 microns across the entire printing area), and regardless of the type of bulb is producing the UV I'm after, the RESULTS are poor with one unit and superb on the other. So, I spend virtually an entire year, testing emulsions, moving our EOM all across the board, checking every part of the process to eliminate the exposure unit as the issue because I'm married to it at this point. And how I come to the conclusion that it is the problem has more to do with me being able to roll up our old MH unit next to it, put the exact same screen on it and our issues are solved. By saying that that is irrelevant and LED and MH are apples and oranges doesn't work for me. I may very well be in the minority on that subject, and I'm not saying they aren't different, obviously they are, but the FINAL RESULT, the developed stencil doesn't give a damn about any of that. I'm not against making some adjustments here and there, obviously, we've been doing it for a year, but there wasn't any built in reasons or instructions that said anything about shortcomings or to put in different terms, a different animal with LED. For example, every single screen that goes to press has an additional 36" of screen tape on the shirt side that never had to be done before. The stencil begins to break down anywhere from 70-150 shirts but it eventually happens even though there are few shops that use less pressure than we do, few shops that use such a large variety of squeegee blade edges and durometer. Because of the breakdown of the emulsion from the squeegee blade, that's one of the tricks we've had to put in place. To get a more durable stencil (which you can see, burned 5 times longer didn't yield much better crosslinking on the squeegee side) we can post expose or just slap some tape on the screens, but post exposure hasn't worked as well as I would have thought. I haven't done a lot of testing with post exposure and stencil durability due to the ease and speed of just putting some tape on a screen. I just shot a halftone test of 50lpi, one side was shot for 12 seconds, the other 65 seconds. The pic shows the white shirt that I rubbed on the squeegee side, very lightly, and only 3-4 swipes. This particular screen is a 305, 5-6 micron EOM, under 10% EOMR. The 12 sec exposure yielded decent halftones from 10%-90% but the 90 was sketchy and the 85% was solid. The 65 sec side was good from 28%-90%. I'm trying to get the pics from my microscope camera into my computer but the software isn't working properly so I can only post the phone pic right now. So, I just don't understand where else I'm supposed to go with this. Are we to jump through more hoops, continue to look for a different emulsion, increase the length of my tin foil hat antenna, even less EOM, be happy with what we're getting? So if LED is the apple, MH is the orange, what more do I need to do to get what I think is a quality stencil?
Here we go.When we tested the Aquasol with the Chromaline exposure calculator got a 15-20 second exposure. Then we used a Chromaline 10 step Stouffer scale, it gave us a full #6 at 15 seconds and #7 at 20 seconds. We shot the Kiwo (fine 85 LPI) and Chromaline calculator at 15 seconds and again got a solid #6. The instructions show 6-8 being a proper exposure. We held good detail, clear #4 text and good line and halftone detail. Paul can post detail photos tomorrow if needed. But, we think the best detail and durability still comes from dual cure emulsions.Bottom line is we tested this machine thoroughly. We sent it to the Kiwo lab in Texas and got a very favorable review (actually that is Alan's machine). Pierre tested one and was impressed, as he has posted on this and other Vastex bashing posts before. We had our Chromaline rep come in and do tests with us, all good. We brought screens and a digital microscope to every trade show for the last three years. Charlie Taublieb has many customers using them, all good getting fine detail and great speed. We have sold countless units all over the world with little to no issues.This thread, and a few others, has been hammering us with two customers unhappy with our LED machine, and one is using it below 50degF. Although we tested it outside at 30 degrees and it worked fine. We have hundreds of customers using these LED's not posting on this thread, not calling us with exposure problems. As a result of these two unhappy users we made many calls to many customers using our LED's, all very happy with their results. Not that we are not in touch with many on a regular basis, but we called the ones we never hear from. What we didn’t do is ask them to go online and post it, this forum is not for that kind of cheap tactics. We still stand at two not happy, hundreds happy, or at least quiet.We’ve had some trouble with bulbs going out, I admit it. I think it is the chips or its connections to blame, when this happens we replace them completely free of charge.Alan, if you’re so unhappy with your machine, move on. Contact River City and let him take it back, we will make you whole. I am sure we offered this over a year ago after your first or second thread, as we offered the pump upgrade over a year ago, but regardless, I will offer it again. The time spent writing about it could be better spent making money or enjoying life.In our 56 year history, Vastex has almost never had to take a machine back for an unhappy customer. But in the LED case, I can take a score of hundreds happy, one or two not.As for my friend in Japan, I wish you purchased through our dealer, they would have assisted you. But you insisted in purchasing directly. We contacted them, who has sold many machines; all their customers are very happy.One of my competitors has taken this opportunity to chime in on this one, very very classy. I have not responded to most of this or that because I always felt this was a place for people share ideas, not make sales pitches or stick it to the competition. And honestly we didn’t spend our time monitoring this or any other forum. I don’t believe either of these two customers was treated poorly, or ignored, requiring this and the other pages of reading for the world.Mark Vasilantone
If one of the manufactures did this please state that other than use this as forum to promote their equipment as perfect under the same scenario. (Yes I know you can over power the device to over compensate, but the UV output will not be the same at both temps either way) I have competed with Vastex for nearly 15 years and have the utmost respect for Mark and their team. Though we are competitors, I have seen how hard Vastex works to carry a solid reputation, and in every instance stand behind there equipment. As always good luck Vastex, I look forward to the fair competition for years to come! Steve Harpold The Brown Manufacturing Family!
I don't understand all this. The company offered to take back the machine. Why doesn't Allan return it and buy the machine he wants.I own a Starlight and Rich told me try it and if you don't like it return it.Needless to say the Starlight is still in my shop.
HA! In PA, the weather forecast was "Partly cloudy in the Allegheny county. (EVERY DAY). Er was it Partly Sunny. 50.50.
I have typed the science behind LED's and UV output at lower and higher temperatures a few times and deleted based on this thread. I am very confident in saying that none of the manufactures myself included have used a spectroradiograph to compare the UV output at differing temps, say 50 degrees - 100 degrees. To go one step further I am also very confident that none of the manufactures wrote software or (One possible idea) used a temperature sensor with a compensation circuit to drive the power differently when temps are lower compared when they are higher. Panasonic does this (Pretty cool) (not sure why we would as inks, emulsions, don't do well at 50 degrees either) or a light integrator would work as well. (Assuming all LED's performed exactly the same) If one of the manufactures did this please state that other than use this as forum to promote their equipment as perfect under the same scenario. (Yes I know you can over power the device to over compensate, but the UV output will not be the same at both temps either way) I have competed with Vastex for nearly 15 years and have the utmost respect for Mark and their team. Though we are competitors, I have seen how hard Vastex works to carry a solid reputation, and in every instance stand behind there equipment. As always good luck Vastex, I look forward to the fair competition for years to come! Steve Harpold The Brown Manufacturing Family!