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Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Fri Dec 13, 2013 12:05 am
by tim.yoshi
So here is a concept - I thought why to use something liquid instead of solid as a separation layer.
Well you know what inspired such an idea! Yes, the Peachy printer. So I used liquid, but not water. I found properties of glycerin while experimented with pigments. Ordered some set of local pigments designed for home soap making. And they was mixed on the glycerin base. And that pigment with glycerin in no means wanted to mix with the resin no matter how well i stirred it. So then I thought - why not to try it instead of PDMS? It is very cheap, say few dollars for 100-200 grams.

But then I thought - if B9C will act as usual it will be a mess. I need to overcome sliding in some way - it need to be still. First I thought of disassembling entire sliding mech and coupling sensor with motor arm separately so that while it will move, it will "close" the contacts of the sensor. But I found simpler solution :)
On photos you can see it. I just lifted VAT up on the pencils so that VAT sliding mechanism will freely open/close beneath the "lifted" VAT :) All sensors will be engaged as usual. But the main trick here is to fool the home sensor, coz it is it who responsible for build table descending accurately on the VAT window. After few simple workarounds and test I found the simple solution :) You can see it on the photos too. Just glued with tape some alu foil (it should not be translucent, but hard paper will do it too) on the red part of build table arm in the place where it "contacts" with sensor. It should stretch down on the same amount as you lifted your VAT + added height because of thickness of glycerin. It's hard to measure it all precisely from the start, but solution is simple - you should use "spoofer" of the higher length then needed. And after few "calibrations" you can just cut it with scissors to the desired length.
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Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Fri Dec 13, 2013 12:18 am
by cerberus333
Hi,
I had wondered the same after seeing the peachy.
the question i have is was the test sucessful? I don't see a printed article.
If so, i think a software solution would make sense as just moving the z would be necessary.
If that in fact is a workable solution it would considerably speed cycle times, pretty excited about this
idea please do post results as you go forward.
I was actually wondering about what liquid would be a good choice after seeing the peachy, thanks for
discovering glycerine.
-perry

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Fri Dec 13, 2013 12:19 am
by tim.yoshi
I poured glycerin in the old VAT which is no longer usable due to scratches and cured resin to the window. Well it is not usable to commercial printing, but it is awesome testbed for such a try! :) But you can always just do the trick with your ordinary VAT with PDMS. That will definitely will keep you on the safe side.

So how about results will you ask! Well, it's not that PDMS killer so far :( Moreover I did a lot of tries but the best I achieved is what you can see on the photos. Almost complete mess.

From what I see the main thing here is to reliably make a base layers. Following layers will be more or less right. I think that perforated build table in such a case will be way more nice alternative.


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Conclusions are - it will most likely not replace the PDMS in the jeweller quality prints, but possibly can do it with some thick layer settings, like 100z, or even 200-300z. Pigments and resin are not mixing with glycerine under no circumstances. At least MJR resin which I tried here. If it finally will be forced to work someway it will significantly reduce the price of DLP 3d printing reducing any consumables like PDMS of Teflon films. Also printer itself will be way more simpler by design - only projector, arduino and lifting mechanics. No x-motor, no sliding rails, no VAT sensor. Electronics will be simpler as do a controlling program. VAT will be simple square. But such a method makes one other problem of which I can't imagine solution - pigments will settle and will not be able to shake it. While glycerin is not mixing with resin it can take a lot of time for them to separate from each other and that's no good.

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Fri Dec 13, 2013 12:26 am
by tim.yoshi
Quote from cerberus333 on December 13, 2013, 07:18
Hi,
I had wondered the same after seeing the peachy.
the question i have is was the test successful? I don't see a printed article.
If so, i think a software solution would make sense as just moving the z would be necessary.
If that in fact is a workable solution it would considerably speed cycle times, pretty excited about this
idea please do post results as you go forward.
I was actually wondering about what liquid would be a good choice after seeing the peachy, thanks for
discovering glycerine.
-perry


Yes, glycerine is a nice find. It is cheap, it is completely transparent. It has more specific gravity than resin and hence lays down under resin. And you will not be able to mix it no matter how well you'll stir.
One will need around 100-200 grams of glycerin to fill the VAT.

Yes, of course it will be easier just to tick a checkbox somewhere and it will not move left/right - only up/down. But I don't wanted to bother Mike while I haven't got any results. I don't want to ask about it still - it is very easy to overcome the sliding mech as proposed in the first post :)

Ah one more benefit - if implemented it will be very quiet 3D printer! :)

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Fri Dec 13, 2013 3:52 pm
by cerberus333
While most probably see this as a dismal failure, I see it as a very positive first attempt!
Yes there are issues to work out for sure, but it seems like it might mean glycerine might not be the
perfect bath but the basic premise of a "inert" transparent medium with a higher density
to float the liquid resin on (as opposed to a PDMS/teflon etc sheet) has merit.
I look forward to refinements.
the prospect of finding a working "solution" (pun intended) has a number of benefits

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Fri Dec 13, 2013 10:39 pm
by mikej
The trick is to get new material (for the next layer) under the previous layer, at the right thickness. Simply lifting up and then lowering back down tends to "mix" the two materials a bit too much. Maybe add an ultrasonic vibrator to energize the fluid flow rates, slowly over raise just a bit, and then slowly lower back down?

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Fri Dec 13, 2013 11:17 pm
by tim.yoshi
mikej, that's why I mentioned that in this way one will not be able to achieve very thin layers. Only hundreds of micron.
Ultrasonic? But it will probably introduce microbubbles? Don't it?

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Fri Dec 13, 2013 11:41 pm
by mikej
Bubbles? Probably, need to try it I guess.
Also leveling the machine becomes pretty critical.
Lot's of challenges!

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Sat Dec 14, 2013 7:13 am
by tim.yoshi
Levelling? Liquid will level itself finely :) The trick here is to stick to build table. Once that done pretty thick base will become more levelled with every cycle and will result in precisely levelled print, even if printer is at some angle. That is how I see that situation.

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Sat Dec 14, 2013 7:38 am
by mikej
Just thought it would be nice if the XY plane was perpendicular to the z axis. :)

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Sat Dec 14, 2013 6:46 pm
by Robert Howle
If you can somehow level the build table to earth, then the liquid level will match.

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Mon Dec 16, 2013 2:27 am
by benoy
Hello Tim. Congratulations.
Hello Mike, Robert Howie,
Leveling the Build table is fine and appears easy - all you need to do is a floating build table -- It levels itself.

Just thought of few options
1) Fixed build table leveled to earth
2)The XY positioning controlled, stationary build table
3)Vat containing glycerin moving up or down
4) Acrylic resin in a separate amber colored chamber allowing a thin layer of resin to float on the glycerin surface
5) Light from the projector passing through a fiber optic face-plate to limit the Z axis bleed

A second reading told me it is crazy. But I thought post it anyway.
Benoy

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Mon Dec 16, 2013 11:39 am
by akgold
the peachy printer uses salt water or saline.
if I understand this thread correctly your trying to float the resin above the pdms base on another liquid?
it would have to be clear liquid heavier than the resin I am assuming. the difference between the peachy printer and the B9 is it works off sound waves and the lazer drops down from above onto the resin that uses the liquid as a table as it rises.
if that worked then on B9 light from the bottom you wouldn't need a PDMS layer. nor would you need to move the tray to clear the resign to re oxygenate it.
the left side could act as a reservoir for the resin as it was used up it would flow to the other side where the printing takes place above the liquid that could be only the thickness or depth of the water fall . will the liquid or there a that could allow a projected light through it without distorting it due to the refraction and still be heavy enough to float resin.
the liquid would only have to be a small amount considering the depth of the waterfall to reduce the refraction.
I don't know what I am talking about it just seems like this could work without pdms if the clear liquid was level and the projected light through it to the resin was not bent due to a slight angle of the light source being not lined up perfectly perpendicular to the object being produced. http://en.wikipedia.org/wiki/Snell%27s_window

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Mon Dec 16, 2013 3:24 pm
by behold3d
sorry akgold. They are looking to replace the pdms with a liquid.

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Mon Dec 16, 2013 4:55 pm
by cerberus333
I think with the right liquid as a base the lift would not need to have a lift followed by a drop back down.
a simple lift would be sufficient and the advantage being less turbulence, no bubbles created and a faster settle time.
(not to mention as the direction being only up, the backlash is no longer an issue.) Overall I think the basic idea has great merit.
the bigger engineering challenges are due to refractory index differences between the glass, floatation medium and the resin
could cause issues. resin pigment suspension would possibly be an issue due to lessened agitation (which might need adjusting(a oil/wax based emollient?)) but the real question is one of engineering tradeoffs and intelectual property. is the best method using a peel or a floating resin?
does someone own the patent on floating resin?

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Tue Dec 17, 2013 2:53 am
by tobyramp@hotmail.com
To get the first layer to stick, an adhesive backed sand paper on the build table? Just make sure its made to get wet.

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Tue Dec 17, 2013 3:58 am
by mikej
I think the elephant in the room is how do you get a resin to "refill" the 100 micron or less space for the next layer after you lift current layer.
Simply raising 100 microns probably won't be enough to break the force between the cured resin and the liquid it is sitting on.
If you over raise to break the force, then you have to wait for the resin to refill and form an even surface, expecting that to happen at 100 microns thick is not practical. You could have a thicker layer (~1mm) that might refill efficiently, but then you must push the object down into it in an attempt to squeeze it out and get 100 microns which again, it's probably not practical for such thin layers (you "churn the mix").

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Thu Dec 19, 2013 1:27 am
by tim.yoshi
Yeah - Mike is right here. That is what I found also on the experiments. Most possibly it will be limited to 0.5-1 mm thick layers. Lower than that - I guess not.
Regarding patents - I haven't did any investigation, but I hardly doubt it is the case. I never heard of nothing like that.

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Mon Dec 30, 2013 3:31 pm
by danmr
@yoshi, Dunno if this will help you but here it goes, as I'm also into remote control airplanes and helicopters and often you can crash them into water, I remember someone recommending me to "Dip/spray" the electronics with a solution that will repel water, I had never tried but I been told that once applied is very persistent and nothing will stick to it. here I attached some links that might be useful.
http://solutions.3m.com/wps/portal/3M/en_US/3MNovec/Home/Applications/CoatingSurfactants/PrintedCircuitBoards/
http://www.echeloninc.com/conformalcoating.htm

Tried to replace PDMS with liquid glycerin... well, take a look :)

Posted: Sat Jan 18, 2014 10:03 pm
by etienne
have a look at the "solidator" (it's a kickstarter project right now).
They are apparently using a Teflon layer, thus do not have the problem of a sliding/tilting VAT. They claim to have patented this mechanism. The printer seems to operate well, however no details are visible, and certainly no macro pictures. For now, they only have the prototype out.

after a layer has been cured, the z-axis moves up, then down again, then cures the next layer.