UV filter removal?

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ryanbahr
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UV filter removal?

Postby ryanbahr » Mon Apr 11, 2016 10:24 am

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.

Head-Zonk Studios
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Re: UV filter removal?

Postby Head-Zonk Studios » Wed May 25, 2016 10:22 pm

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

chill74
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Re: UV filter removal?

Postby chill74 » Thu May 26, 2016 12:49 am

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.

goopyplastic
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Re: UV filter removal?

Postby goopyplastic » Sat May 28, 2016 8:35 pm

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.

chill74
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Re: UV filter removal?

Postby chill74 » Mon May 30, 2016 1:14 am

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.

goopyplastic
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Re: UV filter removal?

Postby goopyplastic » Tue May 31, 2016 7:38 pm

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.

Nitros
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Re: UV filter removal?

Postby Nitros » Tue Sep 27, 2016 12:37 pm


goopyplastic
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Re: UV filter removal?

Postby goopyplastic » Fri Oct 07, 2016 4:17 pm

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.


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