Build Your Own SLA/SLS

I followed the build steps for the LittleRP with a 7820hd (and focus modificaiton). I noticed that there isn't any mention of removing the UV filter (I believe that is what it is, based off of other tutorials) that sits after the lamp. I can imagine this helps protect the DLP chip as well, but I'd like to learn more and other people's opinion as this is my first SLA printer.

I would like some info on this too before I start taking apart my projector. I have a Viewsonic PJD7820HD.

I relocated the colorwheel from my PJD7820HD. I think that the filter in front of the bulb is also an IR filter and needs to be there for heat reasons.

It is an interesting question. I would like to think that the main issue with the filter removal is that the hot and is allowed to proceed into the light tunnel. The other issues may be increased uv reacting with the optics / dlp chipset and ir reacting with the optics / dlp chipset etc.

I have some borosilicate and quartz windows I will try and replace the included filter with. I would like to do some spectrum analysis of light through the filters to see just what it is filtering. There is definitely a large uv component it is filtering as curetimes without the window are easily 2.5 times quicker. It seems like newer projectors this filtering is becoming more aggressive as well.

That said longer cure times should give better results, there will be less resin shrink in addition and variation in the projected image length / intensity won't show up as dramatically.

Just relocating the color wheel dropped my exposure time from 9sec to 3 sec at 50 micron z layer (WaxCast) and
to 1.5sec at 30 micron z.

Unfortunately, you cannot remove the wheel...it has to still spin freely or the projector will not work. I haven't found it necessary to remove the filter. I did a few tests without the filter (two 15 minute prints)...layer times were slighty faster. The increased heat in the light tunnel without the filter was not worth the risk of possible damage for the small increase in UV.

Which projector was this? I was under the impressive the color wheel would provide a modest decrease in cure time but your results seem to say otherwise.

The 7820bd and the littlerp build size, I wouldn't remove the uv filter personally. The projector is already on the higher end of uv production given the available options. Removal of the uv filter is more important for larger build area where the uv production gets spread thin quickly.