PDMS clouding

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Metalcaster
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PDMS clouding

Post#21 » Tue Sep 16, 2014 10:55 am

Perhaps, from this info, the clouding is partially caused by heat transfer through the pdms.
I have a cooling fan on both my B9's pointing at a slight angle so that it cools the projector a bit and mostly cools the Vat from underneath .
I think Robert did that as well. Both of us are getting longer life on our pdms .
Dow corning is a defintely good source for info, Glad you looked that up..

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TAJS
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PDMS clouding

Post#22 » Tue Sep 16, 2014 11:36 am

What sort of fans are you guys using? Mind sharing a pic of your setup?

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bvwjewelers
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PDMS clouding

Post#23 » Tue Sep 16, 2014 11:45 am

Think it's the combo of over curing the PDMS in ovens, then for some the alcohol on it. My prints today did not even come close to 100 Celsius inside after 5 hours. I'm going to super glue a CPU sensor on the glass and see what are the temps. She made it clear it has nothing to do with light, just heat.
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akgold
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PDMS clouding

Post#24 » Tue Sep 16, 2014 12:55 pm

I would think that the heat would be from the concentrated light emitted by the projector building up in a specific print area as opposed to the resin heating up ( which seems to be a good thing )
The glass would dissipate the heat between slices but eventually it would have an affect on that area exposed
makes sense even if you think about it in hours of intense heat in one area like turning the spot light on every 3 or 4 seconds eventually that area it is on will heat up over a 3 to 8 hour period of time.

The one factor that seems to be unnoticed here about Robert's longevity of PDMS is he has a computer fan placed on the side blowing across the lens of the projector to reduce heat. That alone may be the answer to longevity of pdms.
Robert shut off your fan see how long the PDMS lasts ( just kiddn)
anyway that is what I see as a difference here
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Metalcaster
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PDMS clouding

Post#25 » Tue Sep 16, 2014 2:03 pm

Yes, thats what I meant. Heat created by the projector light. Gets pretty warm. I am using a 12 volt large computer fan. It's about 6 " square.

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Robert Howle
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PDMS clouding

Post#26 » Tue Sep 16, 2014 2:14 pm

I am using a 4" usb powered as suggested by Justin. I have it set up to pull air away from the projector (its on the right side). Fan bracket was designed by Justn. Printed on deposition type printer.


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PDMS clouding

Post#27 » Thu Sep 18, 2014 3:08 pm

The comment about humidity got me curious.
I have read that silicone can absorb water vapor and the gas can condense trapping it inside.
Is anyone storing the resin in the vat with the resin covering the window? Could the resin be a humidity shield? Does the PDMS need to be exposed to air?

kirkrhino
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PDMS clouding

Post#28 » Fri Sep 19, 2014 3:23 am

HI Robert,

Amazing stuff!

Did you cook this particular PDMS that has not clouded? If so do you remember what time and temps?

Also, was it ever exposed to alcohol?

Thanks for sharing. Best, Kirk

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lobby
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PDMS clouding

Post#29 » Fri Oct 10, 2014 6:39 am

But doesn't cleaning with a squeegee leave some resin in the vat? Would this not be a problem?

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Robert Howle
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PDMS clouding

Post#30 » Fri Oct 10, 2014 7:16 am

yes cooked for 10 min at 250 and 30 min at 275. I use full cover PDMS. No alcohol or water ever touched this one. Watch this video for saver method just substitute dam for tape also check to get correct volume for the new vat.

http://www.b9c.com/support/?mingleforumaction=viewtopic&t=958.8
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