Build Your Own SLA/SLS

Hello,

I'm looking for some knowledge regarding LCD projectors. I have a Samsung SP-M250S, I have read all over that LCD projectors are no good for resin printers but cannot understand the reason why? This LCD projector is within the 2500 Lm needed and have good resolution. there is anything that I can do to it to make it useful? I already acquired a 100 watts 405nm LED system with driver, power supply and the lense for it (I know that I will have to create the tunnel to direct light). If I need to I will purchase a DLP projector, but if I can save the money for other items will be great.

Thank you in advance for any assistance.

Regards,

Gerardo

Good question, i would like to know as well.

haha, found the answer

http://www.lcd3dprinter.com/

What you found is using an LCD screen as a photomask, not the same as a LCD based projector.

LCD projectors are not ideal because it is not UV compatible. An LCD projector usually uses 3 LCDs for passing RGB colors to generate an image. Each of these have optics in place to filter out or reflect specific colors (dichroics). That's just the start of why its not very feasible. The composition of each LCD module also causes a significant amount of light loss. There are some good illustrations on how LCD projectors work if you want to look into it.

What you can look into is LED based projectors. You can remove some of the dichroics and replace with UV LEDs and that is not a problem.

Hope this helps clear things up a bit.

I read a paper which claimed only about 12% of 400nm light when through a color lcd. So your 100w light just became 12w or so, which is another way of saying you are wasting a lot of energy. It is being reflected away or absorbed into the lcd, causing damage and eventual failure of the LCD.

Read up about DLP tech. It is pretty cool, but basically it relies on reflecting light off lots of tiny mirrors, which dramatically increases the amount of light that "passes through" the projector.

That said, if you bought the right type of "visible light" resin it may actually work, but you may die of boredom first. But look at those resin absorption curves and you'll see most are still way more effective below the 400nm range. They require more light intensity as you increase up in to the violet/blue spectrum (less energy). And we've just decreased it massively by running it through a tiny lcd in the projector (12% or so goes through). And if it is a three LCD projector it may be worse than that, as the red and green light would pass 0% of the light you need, so you'd rely solely on the LCD passing through blue. I think.

All this is rough estimation. Many also point out the LCDs are simply not made to have UV pass through them, and the higher energy radiation will actually damage the LCD much faster than most expect. Even the DLPs do to some degree, but it seems the LCDs are quicker to fail. So even if you had enough light and didn't mind the wait, you're slowly destroying an otherwise good projector. I'm not sure anyone has figured out how quickly that would be. Many "bulbs" have a built in UV lens before the LCD to try and diminish the damage to the LCD.

Hope that helps a bit. I now realize AndersonTa said most of the same stuff in a less chaotic manner.

AndersonTa, it is unclear to me if the LED projector needs to be a DLP one, or if the other types are workable as well. I've never read anything about the longevity of LCOS, for example. Isn't that used in some small led projectors?

LCD projectors are fine for lithography. Some people are just trying to use the wrong resins.

See this thread for the hows and whys
viewtopic.php?f=12&t=84&start=210#p9616