Dip the Print - surface tension

[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

[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.

[mike_biddell]

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.

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

[erikk]

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

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.

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).

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.

[Slatye]

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.

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.

[rylangrayston]

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

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.

[rylangrayston]

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.

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.

[rylangrayston]

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.
.

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 )

[jjmouris]

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

[Kaleb]

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.

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