Idea for fail safe to protect the projector in case of vat failure

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Burnsjt
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Idea for fail safe to protect the projector in case of vat failure

Post#1 » Mon Nov 24, 2014 7:45 pm

Hi everyone,

I have been following the testing of the NuVat by Evert, a very exciting development in the search for a PDMS alternative, and I came accost the catastrophic vat failure that Mike experienced. ( you can read about it here http://www.b9c.com/support/?mingleforumaction=viewtopic&t=2257.0#postid-23637 )

This got me thinking about a way to help protect the projector in case of absolute failure of vat integrity. My rough idea right now involves installing a peace of glass or acrylic over the window with a rubber gasket to form a seal around the window. This most likely would not stop all resin from dripping down in the event of vat failure due to the large number of other holes that the resin could flow through, however, it would prevent the resin from pouring into the projector through the window and should give you enough time to react to the problem.
This mod is not necessary for most users, however, for those who are actively looking for a PDMS alternative this might be a useful fail safe.

Here is a quick image of my idea.
Image

My only concern is that adding a new peace of glass /acrylic to the system would affect print quality.
What do you think?

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mikej
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Idea for fail safe to protect the projector in case of vat failure

Post#2 » Tue Nov 25, 2014 12:59 am

I decided against this initially, due to the fact this is potential dust collector, could distort the image, and will absorb some of the energy (no such thing as 100% UV/blue transparent).
But even if you just used the frame without the glass, the raised lip would stop spills not directly over the openly from flowing into it.
Measure Twice, Cut Once.

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Yianni-VJ
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Idea for fail safe to protect the projector in case of vat failure

Post#3 » Tue Nov 25, 2014 3:32 am

I can use Envisiontec's radiometer to check exactly how much blue light you are going to loose.
I can order some thin glass and acrylic to take some measurements and report back.
@Burnsjt do you have any particular requirements for glass type? If you find a source online I can order some.

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Robert Howle
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Idea for fail safe to protect the projector in case of vat failure

Post#4 » Tue Nov 25, 2014 5:39 am

Do you happen to know how much blue is lost using regular "Float plate" glass. This is what Evert is coating for the test runs. Just curious.

Robert Howle
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Metalcaster
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Idea for fail safe to protect the projector in case of vat failure

Post#5 » Tue Nov 25, 2014 6:00 am

There is a type of glass that is very UV transparent called "soda Glass" I bumped into this when I was thinking of building a glass bottom on my acrylic vats which were useless after lots of prints.( Still not a bad Idea for those who are in need of a vat).
1 of the other printers that I researched uses this kind of glass to build their entire tray from.

I think having a safety spill system is a very good Idea. When I got my first machine I had lot of spillage all over when the pdms ripped up and was throwing solution all over the machine. It got all over and I was very lucky that the drips of Resin were only hitting the outside of the Projector case and did not go inside. Another 5 minutes and the projector would probably have been toast.

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Yianni-VJ
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Idea for fail safe to protect the projector in case of vat failure

Post#6 » Tue Nov 25, 2014 6:39 am

@RobertHowle, I have to test float plate glass, it does not have to be 1/8" I think they make half as thin as that. I ll try to get a sample around the neighborhood.
@Metalcaster: "Soda lime Glass" and "float glass" often refer to the same thing?

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Metalcaster
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Idea for fail safe to protect the projector in case of vat failure

Post#7 » Tue Nov 25, 2014 6:50 am

Looks like we all think alike ! :-)

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Robert Howle
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Idea for fail safe to protect the projector in case of vat failure

Post#8 » Tue Nov 25, 2014 7:05 am

I was just wondering if the glass Evert is using would be causing much loss of the UV spectrum. Thanks.

Robert
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Burnsjt
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Idea for fail safe to protect the projector in case of vat failure

Post#9 » Tue Nov 25, 2014 7:15 am

@ Yianni - That would be great if you could test that and get back to us. As to your question, I don't have any specific type of glass in mind so whatever would let the most UV through. The plans that I posted are just a rough idea so you don't haft to hold to the dimensions that I had in the image. Just know that if its much thicker it would haft to be mounted on the under side of the frame.

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Burnsjt
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Idea for fail safe to protect the projector in case of vat failure

Post#10 » Tue Nov 25, 2014 7:30 am

@ Mike - would using just the frame without any glass have saved your projector in the type of failure you experienced? Its hard to tell from the photo exactly where the resin traveled from. If it leaked out on to the frame and then through the window then installing just the frame and gasket would be perfect, with the exception of the glass actually breaking down the middle, but that seems very unlikely.

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mikej
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Idea for fail safe to protect the projector in case of vat failure

Post#11 » Tue Nov 25, 2014 7:33 am

In my example, it would have helped a lot, but maybe not enough, but mine was a worst case scenario.
Measure Twice, Cut Once.

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Yianni-VJ
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Idea for fail safe to protect the projector in case of vat failure

Post#12 » Tue Nov 25, 2014 8:30 am

I removed the silicone and PDMS/Teflon from an old ETs VAT and got left with a 6mm thick glass. (an overkill for our purpose)
It looks like Soda-lime Glass because of the heavy green tint on the sides.

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Yianni-VJ
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Idea for fail safe to protect the projector in case of vat failure

Post#13 » Tue Nov 25, 2014 8:31 am

.... I will test how much light is absorbs once I start the printer tonight.

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Yianni-VJ
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Idea for fail safe to protect the projector in case of vat failure

Post#14 » Tue Nov 25, 2014 8:34 am

Sorry, I m trying to include the photo....
Image

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Robert Howle
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Idea for fail safe to protect the projector in case of vat failure

Post#15 » Tue Nov 25, 2014 9:10 am

Looks like there is enough room between the bottom slide plate and the floor of the machine to have a snap in square thingy with a lip (above floor) to catch run off. Wouldn't help with stuff falling straight from vat to lens.. Would def help with splash out that usually happens on right end of an overfilled vat.

Spill guard. Snaps in underneath floor of machine.

Def can't print this at 30 xy.
Image
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Yianni-VJ
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Idea for fail safe to protect the projector in case of vat failure

Post#16 » Tue Nov 25, 2014 9:58 am

The glass depicted above absorbed about 100mW per square decimeter.
With the glass I read 720mW per square decimeter, without it the value was about 830mW per square decimeter.
A thinner glass will absorb allot less.
One other thin that may interest people to know, is that ET's lens assembly has a removable UV lens filter. (you are not supposed to remove it)
My guessing is that they are more interested in PDMS lifespan than light intensity.
Other misc information:
When I point the sensor to the diffused fluorescence light in the ceiling, it reads 7mW per square decimeter.
When I used it on an LED dentist's curing light, the value was 2000mW per square decimeter.

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tim.yoshi
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Idea for fail safe to protect the projector in case of vat failure

Post#17 » Wed Nov 26, 2014 4:04 am

Have you tried how much actual VAT with glass and PDMS (typical print setup for v1.2) absorbs?
Or even how much PDMS alone absorbs?
Image

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Yianni-VJ
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Idea for fail safe to protect the projector in case of vat failure

Post#18 » Wed Nov 26, 2014 5:33 am

Haven't tested it Tim, will do so.

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Yianni-VJ
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Idea for fail safe to protect the projector in case of vat failure

Post#19 » Wed Nov 26, 2014 5:44 am

Its also important to find out the power our V1.2 projector outputs at 30microns XY setup.
Keep in mind, the measurements I reported yesterday refer to ET's output at 50microns XY setup.
Moving up/down changes results greatly.

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tim.yoshi
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Idea for fail safe to protect the projector in case of vat failure

Post#20 » Wed Nov 26, 2014 9:00 pm

Decreasing/increasing distance to projector should quadruple/divide by 4 light output, as we all know here, right? :)

Will be interesting to know how much PDMS absorbs. Bu the way how do you measure it? What spectra are used?
Image

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