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Questions about Projectors for Resin-Based Printers

Posted: Mon Aug 11, 2014 1:21 pm
by JohnStack
Ok, Jim's Geetar and JohnOly have given us some good basics - now, I'd love to know the details.

DLP instead of LED because of pixels (here's an article that explains why)

http://envisiontec.com/professional-gra ... -printers/

Now, does resolution matter?

Contrast (since you can basically shift to b/w)?

Do you get better/faster cures with higher lumens?

What's the minimum?

And 10K lumens are impractical and very costly for the results...

Re: Questions

Posted: Mon Aug 11, 2014 1:38 pm
by brent
I'll answer the Q's on resolution based off of John's interview answers with the 3d printing podcast. Resolution does matter. A 720p projector will produce less quality prints opposed to a 1080p projector. However, due to the small area you're printing in, 720p is fine for this purpose. You can absolutely go out and buy a 1080p DLP projector if you allocate the money for it. Since nobody has tested the droplit with both a 720p and a 1080p then compared the two, we really have no data to go by at this point.

Re: Questions about Projectors for Resin-Based Printers

Posted: Mon Aug 11, 2014 3:22 pm
by JohnStack
Another question:

Are there any physical size limitations for the projector?

Re: Questions about Projectors for Resin-Based Printers

Posted: Mon Aug 11, 2014 3:50 pm
by brent
JohnStack wrote:Another question:

Are there any physical size limitations for the projector?


I'm not positive, that's a question for John to answer. However if you look at the DXF file for the baseplate, you can get a sense of it (https://github.com/seemecnc/Droplit/tre ... LC%20Files

Re: Questions about Projectors for Resin-Based Printers

Posted: Mon Aug 11, 2014 8:46 pm
by Polygonhell
DLP instead of LED because of pixels (here's an article that explains why


Assuming you mean LCD rather than LED here.
For the resin to cure you need sufficient light at the right wavelength, usually 395-420 ish depending on the resin. LCD panels in LCD projectors happen to block this wavelength, so they won't cure the resin. On the off chance you were asking about LED based DLP projectors, those don't work because the blue LED is closer to 470nm wavelength so again they won't cure the resin.

It's not about total light output, but about how much output you are getting at the right wavelength, people have demonstrated very fast cure times with <10W LED based projectors by replacing the existing LED's with UV LED's.

The UV output being important is why you remove the UV filters from the bulb and the light path, BUT, be aware that doing so can greatly shorten the life of the DLP system. The filters remove both UV and IR and the latter leads to a lot of extra heat the projector isn't designed to deal with. Some of the higher output projectors already leak enough light in the near UV range that you don't have to remove the filter, unfortunately the only way to know is to try it, or buy a projector someone else suggests.

The other big issue you'll run into if you buy a random projector is that many/most projectors won't focus close enough, they are simply not designed to produce 5in images. Some can be modified by removing the focus stop, others require an additional lens.

Re: Questions about Projectors for Resin-Based Printers

Posted: Tue Aug 12, 2014 11:53 pm
by JohnStack
Polygonhell wrote:
DLP instead of LED because of pixels (here's an article that explains why



The UV output being important is why you remove the UV filters from the bulb and the light path, BUT, be aware that doing so can greatly shorten the life of the DLP system. The filters remove both UV and IR and the latter leads to a lot of extra heat the projector isn't designed to deal with. Some of the higher output projectors already leak enough light in the near UV range that you don't have to remove the filter, unfortunately the only way to know is to try it, or buy a projector someone else suggests.

The other big issue you'll run into if you buy a random projector is that many/most projectors won't focus close enough, they are simply not designed to produce 5in images. Some can be modified by removing the focus stop, others require an additional lens.


As usual, you eliminate more mystery! Thanks!

So - let's say a brand name, then take Droplit existing tests and beat it - plus find something that's HDMI....I guess. Because VGA.

Re: Questions about Projectors for Resin-Based Printers

Posted: Tue Aug 19, 2014 1:06 pm
by johnoly99
LOL,

Stack, i've been running the P1283 on HDMI or VGA, either one seems fine. Polygonhell is as always a wealth of knowledge. The extra heat generated seems to be minimal, I havn't noticed any issues with any of ours yet. The focus issue can ALSO be solved by spacing out the focal ring if you can't mod the stop to allow it to be focused further in