Dip the Print - surface tension

It occurs to me, that since we are switching the laser on and off successfully, that signal could also operate a small solenoid to dip the print. So that laser OFF dips the print 2 - 3 mm and then laser ON returns the print to its former position. The solenoid would move a print platform down and then back up, in synchronisation with the laser (there's probably enough power with the existing 10 amp FET, to use the same output FET, so no extra components required). This would allow each layer to be well exposed before doing the next and reduce a lot of the calibration problems. So the laser would make maybe 10 transits of the current z, laser OFF (solenoid OFF) then dips the print, laser ON (solenoid ON) then returns the print to its former position. The laser will obviously have to wait for any ripples to die down, before carrying on. The solenoid would obviously be positioned on the outside of the tank and could just tilt the platform via a plastic lever, to allow wetting of the print surface. This is quite easy to design mechanically and would be analogous to the form1 tilting tray (used to tear the current layer off).

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Originally Posted by mike_biddell

It occurs to me, that since we are switching the laser on and off successfully, that signal could also operate a small solenoid to dip the print. So that laser OFF dips the print 2 - 3 mm and then laser ON returns the print to its former position. The solenoid would move a print platform down and then back up, in synchronisation with the laser (there's probably enough power with the existing 10 amp FET, to use the same output FET, so no extra components required). This would allow each layer to be well exposed before doing the next and reduce a lot of the calibration problems. So the laser would make maybe 10 transits of the current z, laser OFF (solenoid OFF) then dips the print, laser ON (solenoid ON) then returns the print to its former position. The laser will obviously have to wait for any ripples to die down, before carrying on. The solenoid would obviously be positioned on the outside of the tank and could just tilt the platform via a plastic lever, to allow wetting of the print surface. This is quite easy to design mechanically and would be analogous to the form1 tilting tray (used to tear the current layer off).

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Forgot to say, that tilting platform could be sold as an optional extra, with jack plug into a socket connection on the Peachy. It would just clip on to the existing tank.

The part dosent move, It's "glued" (not really glued but hold there) to the ground and then, the resine float on the top salt water and that's what make the "Z". The only way to do this would be to remove/add salt water and this wont work very well.

The print would be glued to the moveable platform ........... I need to sketch it............ but it would certainly work. I don't think I am explaining this very well, the print is started on the tilting platform i.e. glued to it or a wire insert on the platform. Thus tilting the platform, dips the print beneath the surface of the resin by 2-3 mm. The tilt rod runs up the side of the tank and is operated by a spring loaded solenoid. Laser OFF, turns power off to the solenoid, allowing the spring to release and push the rod to tilt the platform. Laser ON, repowers the solenoid and re-compresses the spring, pulling the rod back.

Might be easier to just have the servo/solenoid push a piston down into the tank and then lift it back out. Pushing it down obviously displaces water/resin and causes the surface to rise, which has much the same effect as tilting the printing surface but without having to add hinges.

However, I think that the ripples would make either idea impractical. If you wait five minutes before starting each layer so that the surface is perfectly smooth, printing is going to take days.

Slayte............ good idea............ dunno, if the resin is quite viscous, ripples will die very quick, but I suppose the saline could ripple for a bit. However, if it means very good quality prints, I'm not sure I care about the time factor..... just leave it overnight !!!! The solenoid could simply be wired in parallel with the laser, with a spike killing diode obviously. Actually, your idea with a wedge shape, wouldnt cause much of a ripple and it only has to raise the level a millimeter or so, the volume displaced would relatively small. And the whole thing could just clip on the side of the tank. I like your idea better than mine............we'll run with that. I genuinely believe it has legs LOL !!!!!

Form1 tilts the entire tray, so they must have a delay whilst the resin stops slopping around. It's probably pretty viscous, so probably doesn't oscillate for long.

IMO, could be as a second step. You finish the print then attach it to the piston and UV lamp to do it.

All-in-one sound great, but not in a short term.

Ah! I really like the wedge idea to for 2 reasons
1 its not submerged
2 it would make no substantial ripples


Have you guys heard of the raft idea (alows the peachy to do at least 4 materials in one print at very low cost)
its talked about here
http://forums.reprap.org/read.php?18...062#msg-249062
and the idea started here
http://blenderartists.org/forum/show...ly-100-dollars!

The raft idea requres a slight up and down motion of the resin between material changes and so the there is alot of valuable ideas there too.
but i havent seen this wedge one there yet so hope you post it on reprap !


What we have being doing so far is simply printing so slow that there is alwase a layer of wet resin on top the print. All the actual hardening actually happens below a very very thin layer of liquid resin over the wall of the print. I think the dipping combined with a very thick resin would actually get you Faster prints.

Rylan.... very interesting thread........... didn't realise there was any dialogue going on in the reprap forum, so will now start mooching there too!!!!

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Originally Posted by mike_biddell

Rylan.... very interesting thread........... didn't realise there was any dialogue going on in the reprap forum, so will now start mooching there too!!!!

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Just realised a solenoid probably wouldnt work, because of the length of travel required. Probably have to be a screw drive.

Morning all, my first post here. Been in contact with Rylan a week or so ago. My intended application is very demanding in that I am after very accurate prints. Looking at making carbon fibre laminate parts strait off a print.

Was just wondering how much of the laser power is lost if it shines through water as supposed to air. Would it not be an idea to have a layer of normal water on top of the resin to help remove the surface tension? The water would put pressure on the resin and smooth it out? If the water does soak up some of the important rays, can we overcome this with slightly higher laser power?

For the Peachy Pro, would it be possible to adjust the laser power on the go? Then you could vary the focus and the laser power to print a thicker patch across the printing surface to save time and go down to a tiny spot round the edges to improve the finish?

J

If a tube were attached to the container so that it extended to the bottom, then the waterlevel could be raised and lowered by adding or reducing a plunger into the tube. That is, not air tight, just adding more volume to the water to it raises. By doing it in an external tube, you eliminate the ripples (they would have to travel through the water, not on top, so they would be dispersed better).

A second totally different thought is by having a system that creates ripples on the surface on purpose, the effects of surface tension would go away, and the laser could be calibrated to be timed with the ripples.

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Originally Posted by iplayfast

If a tube were attached to the container so that it extended to the bottom, then the waterlevel could be raised and lowered by adding or reducing a plunger into the tube. That is, not air tight, just adding more volume to the water to it raises. By doing it in an external tube, you eliminate the ripples (they would have to travel through the water, not on top, so they would be dispersed better).

A second totally different thought is by having a system that creates ripples on the surface on purpose, the effects of surface tension would go away, and the laser could be calibrated to be timed with the ripples.

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Like the tube idea...... that wud allow a simple solenoid to be used !!!!

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Originally Posted by jjmouris

Would it not be an idea to have a layer of normal water on top of the resin to help remove the surface tension? The water would put pressure on the resin and smooth it out? If the water does soak up some of the important rays, can we overcome this with slightly higher laser power?
J

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Thats a great idea, I think it was brought up somewhere else. I talked to Rylan about it a while ago, it seemed plausible but we didn't spend much time on it. It might be something a beta tester tries out.

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Originally Posted by iplayfast

If a tube were attached to the container so that it extended to the bottom, then the waterlevel could be raised and lowered by adding or reducing a plunger into the tube. That is, not air tight, just adding more volume to the water to it raises. By doing it in an external tube, you eliminate the ripples (they would have to travel through the water, not on top, so they would be dispersed better).

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I like the idea of adding water to submerge the print, maybe thats the best way to do the raft idea (multi-resin prints) too.
I'm not sure of the best way to automate that cheaply though. It's important that you get the exact amount of water back and forth each time.
I think I got one: motor with a cam pushing a syringe. Just needs to start and end at the same spot each time.

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Originally Posted by erikk

I'm not sure of the best way to automate that cheaply though. It's important that you get the exact amount of water back and forth each time.
I think I got one: motor with a cam pushing a syringe. Just needs to start and end at the same spot each time.

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Hah, I've actually built this exact device for a completely different project. It's literally a $3 HobbyKing servo hot-glued to the plunger of a syringe, with a pushrod from the servo arm clamped onto the syringe body. Works okay, although this one is right on the torque limit for the servo.


I suppose that there's a completely different alternative to look at too, which is different resins. If Makerjuice have been able to come up with the flexible resins, is there any chance that they can produce less viscous resins? That'd be the easiest option of all.


Another thing to consider: if you raise the resin above the top of the print, and then lower it back below the top of the print, how much resin remains stuck to the top of the print? If it's enough to print a layer with then ripples don't matter. Preivously we've assumed that the part has to be lowered to below resin level and then raised back to exactly level with the resin. Obviously for this to work you have to wait until the resin has a consistent level (ie no ripples). However, if the resin will stick to the top surface of the part then you can lower the part to below resin level and then raise it to 1cm above resin level. There's still enough resin on top of it to print the layer, and ripples aren't an issue at all because they're happening 1cm below the actual printing surface.

Edit: actually, forget that last point. Works fine if you've building vertical walls, fails completely if you're building any sort of overhang.

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Originally Posted by jjmouris

Morning all, my first post here. Been in contact with Rylan a week or so ago. My intended application is very demanding in that I am after very accurate prints. Looking at making carbon fibre laminate parts strait off a print.

Was just wondering how much of the laser power is lost if it shines through water as supposed to air. Would it not be an idea to have a layer of normal water on top of the resin to help remove the surface tension? The water would put pressure on the resin and smooth it out? If the water does soak up some of the important rays, can we overcome this with slightly higher laser power?

For the Peachy Pro, would it be possible to adjust the laser power on the go? Then you could vary the focus and the laser power to print a thicker patch across the printing surface to save time and go down to a tiny spot round the edges to improve the finish?

J

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Wellcome jjmouris!

Just did a test to make sure, 405 nm light from our laser shines thru water very well, just as i thought there is no noticeable drop in cure rate going thru 2 cm of water.
I think water carry's Blue light very well, and lots of deep sea creatures emit blue light, taking advantage of this.... googling.....
looks like we(405nm) just snuck in ! http://library.thinkquest.org/26153/...ages/elec1.jpg

Looking forward to testing this idea out. There is a liquid that would help by being above the resin I think it would do so with its adhesion properties not its mass which.
In fact i think the mass of the water on top the resin would make things worse not better, as there will be less pressure difference in a void filled by water than a void filed by air.

As for the pro we have high hopes of accomplishing everything you mention, but are still in the early stages of R and D.

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Originally Posted by iplayfast

A second totally different thought is by having a system that creates ripples on the surface on purpose, the effects of surface tension would go away, and the laser could be calibrated to be timed with the ripples.

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:) in the early days i used to Tap the bottom container repeatedly to help it out. A little wave in the resin can actually help! I tried to get the surface of the resin to have a constant micro sized ripple using cell phone vibrators
.. i didnt really get that working... so far the best solution is just to go slow enough that you dont ever cure the surface of the resin hard.

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Originally Posted by Slatye

Hah, I've actually built this exact device for a completely different project. It's literally a $3 HobbyKing servo hot-glued to the plunger of a syringe, with a pushrod from the servo arm clamped onto the syringe body. Works okay, although this one is right on the torque limit for the servo.


I suppose that there's a completely different alternative to look at too, which is different resins. If Makerjuice have been able to come up with the flexible resins, is there any chance that they can produce less viscous resins? That'd be the easiest option of all.
.

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Great! Hope you try hooking your plunger up to the peachy and post about this much talked about hack!!

And yes supper thin resin is the first thing on our list ... its one of the 4 or so things that seem to limit the speed at which you can print.

1 galvo speed
2 laser power
3 drip speed
4 time it takes for resin to flow over top last layer printed ( resin viscosity )

Thank you Rylan, I had another idea following on from the water on top idea. It would be to have the peachy laser shine through a submerged lens and have the water flow out of the container through a dedicated hose, just above this level. So that when the printer level rises, the water on top does not overflow the container. It would mean there are no ripples on the water surface effecting the accuracy of the laser, no scattered light beams.

Do we know if ripples on the resin surface is currently scattering any of the all important laser light?

J

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Originally Posted by rylangrayston

Wellcome jjmouris!

Just did a test to make sure, 405 nm light from our laser shines thru water very well, just as i thought there is no noticeable drop in cure rate going thru 2 cm of water.
I think water carry's Blue light very well, and lots of deep sea creatures emit blue light, taking advantage of this.... googling.....
looks like we(405nm) just snuck in ! http://library.thinkquest.org/26153/...ages/elec1.jpg

Looking forward to testing this idea out. There is a liquid that would help by being above the resin I think it would do so with its adhesion properties not its mass which.
In fact i think the mass of the water on top the resin would make things worse not better, as there will be less pressure difference in a void filled by water than a void filed by air.

As for the pro we have high hopes of accomplishing everything you mention, but are still in the early stages of R and D.

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If their is a layer of water on top, I can see their being an issue with diffraction, that may distort the print. I dont really know much about predicting how light is diffracted by a layer of water but that may be possible and maybe the software can make up for it.

This is a little off topic but here are some ideas I had to reduce surface tension without changing the resin. I have not tried yet and am not sure if they will work, and if anybody experiments with them they should keep safety in mind.

Increase the temperature of the resin. One way this maybe could be done would be by putting a small aquarium heater in the reservoirs to keep the fluids at a higher temperature.
Increasing humidity of the air (this works with water, I dont know about resin)
Run electricity though the liquid.

Another idea I had was a small vibrator, maybe sound waves? I dont know if this is technically reducing the surface tension but it may have a similar effect.

As for moving the print down and then up again, what if you had a T inside the reservoir on a spring, with a piece of metal on the end. Then an electromagnet on the underside of the reservoir (not even in it if possible). When you turned the electromagnet on it pulled the T down, then when it let go the spring put it back. Not sure maybe this exact idea what mentioned already.

-Kaleb

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Originally Posted by rylangrayston

Have you guys heard of the raft idea (alows the peachy to do at least 4 materials in one print at very low cost)

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CMYK - and we are almost there

I've been doing some tests with a pump I've got and written about it in the drip governor thread. The pump in and out test I just did could well be a solution to this as well. http://3dprintboard.com/showthread.p...rst-hack/page5

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Originally Posted by mike_biddell

It occurs to me, that since we are switching the laser on and off successfully, that signal could also operate a small solenoid to dip the print. So that laser OFF dips the print 2 - 3 mm and then laser ON returns the print to its former position. The solenoid would move a print platform down and then back up, in synchronisation with the laser (there's probably enough power with the existing 10 amp FET, to use the same output FET, so no extra components required). This would allow each layer to be well exposed before doing the next and reduce a lot of the calibration problems. So the laser would make maybe 10 transits of the current z, laser OFF (solenoid OFF) then dips the print, laser ON (solenoid ON) then returns the print to its former position. The laser will obviously have to wait for any ripples to die down, before carrying on. The solenoid would obviously be positioned on the outside of the tank and could just tilt the platform via a plastic lever, to allow wetting of the print surface. This is quite easy to design mechanically and would be analogous to the form1 tilting tray (used to tear the current layer off).

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I've been thinking about this problem for a VERY long time now and I think I may have come up with a simpler solution, it seems to me that the easiest way to deal with the surface tension problem is to simply displace the water in between layers, so on the side of your build tank you have a vertical pipe with an opening at the bottom, in the pipe you have a piston hooked up to your solenoid, the piston is set so that the area inside the pipe while the solenoid to the solenoid at full travel has the same volume as 1mm thick layer of your build tank, then as each layer finishes being printed the piston extends displacing exactly 1mm of water and then resets bringing the water back to its normal height to be raised by the drips to the next layer print by having the opening at the bottom of the pipe it should eliminate the rippling in the build tank and just cause the water to move up and down once every layer, if you want to take extra precaution, make the pipe double walled to prevent any vibrations from the solenoid from disturbing the water.