screen printing > DIY - From master engineered marvels to cobbled together jury-rigged or Jerry-built junk!
DIY LED Exposure Unit
Pangea:
I'm in the process of rebuilding my LED exposure unit and figured I would document it here.
Through looking at some tech sheets it looked like most emulsion crosslinks at about 395 nm wavelength. I was surprised to find this wavelength was available in inexpensive strips and 2 density layouts. I opted to get the densest at 120/meter rather than 60/meter because more = better, right?
I ended up using 11 34" strips mounted on a piece of coroplast that was then stapled to a box made of 1"x4"s. It looks pretty janky and like a fire hazard which is the reason it's getting rebuilt.
The power supply is 120v AC in and has two 12v DC outputs that are rated at 10 amps. The time controller was purchased on eBay and pretty much interrupts the 12V DC circuit when the time is up, shutting off the LEDs. The switches on the laser cut control panel turn all the power on, start the timer and turn on safe lights (yellow LEDs). I intended to purchase glass at some point but it was never needed because I use a space saver vacuum bag for exposure. For the new build I'll probably end up adding glass and a proper vacuum lid in phase 2.
I plan on reusing the time controller/switches and the power supply but not the LED panel or box. This time around I ordered 4200 LEDs because I want the strips to be much closer together like the M&R Starlight/Workhorse Lumitron. The strips will be soldered this time instead of using the crappy snap connectors and will be done in parallel to avoid differences in brightness. If they're wired in series the end strip has voltage drop and the whole exposure would be uneven.
So now for the before pictures:
Wiring Diagram
Turned on
Janky Wiring
Control Panel Mock Up
Control Panel Finished
First Tests (WBP Emulsion)
Switched to Cryocoat with 18 second exposure
Final exposure time using a Stouffer 21 step is ~80 seconds. I'm curious (and I'm sure someone here can answer) when companies are advertising their exposure units can expose in 10 seconds, are they using the 21 step guide?
Anyway, I'll update this thread when I start the rebuild and make sure to add any updated documentation (wiring diagram). Until then, ask any questions if you have them!
UPDATE:
Redrew the schematic during my morning coffee
Prince Art:
Thanks for sharing. I built one similar to to this a couple of years ago. I need to go back & solder the connections - I do have a few places where brightness isn't consistent. The clips were a simple way to get the thing put together, but aren't great quality.
IntegrityShirts:
Looks good. I went down the same path a few years ago. Final results were ok, but finding a reliable quality LED source was the variable I ran into. The M&R LED's are not the same as the ones we can get off AliExpress or from Amazon. I built mine as an experiment, but it also can serve as a back up if my 5k Olec decides to die on me. I hope as technology progresses we might find a single point source LED in the 1000W range that is reasonably priced with enough wattage to REALLY replace a 5k traditional source.
Pangea:
Just finished putting together my updated version:
There are a few dead LEDs because I had to pull them from my old unit due to a math error on my part. Soldering took about 3 hours so I'll probably post a proper update tomorrow.
blue moon:
try to eliminate the gap between the sections. It causes the light field intensity drop in that area and potentially weaker exposure.
Also, see if you can get a current regulating power supply. This will stabilize your light output and prevent overheating.
there's more to think about, but all together looks like a pretty good start. Looking at the exposed screen images, they look pretty good!
pierre
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