Heated tank to mitigate surface tension?

[Anuvin]

Very pricey compared to an aquarium heater, but I wonder if this magnetic stirrer with heat would be effective in reducing resin viscosity and wash resin over printed surfaces further reducing visible layers.

SH-2.jpg
http://labsuppliesusa.com/product/ma...-klm-sh2-each/

[Deadbot1]

Very pricey compared to an aquarium heater, but I wonder if this magnetic stirrer with heat would be effective in reducing resin viscosity and wash resin over printed surfaces further reducing visible layers.

SH-2.jpg
http://labsuppliesusa.com/product/ma...-klm-sh2-each/

The only problem with "washing" the resin over the print is it may lead to inaccurate layer height. I think we'll want to avoid excessive ripples or waves at the surface ( where the printing actually happens). The idea behind getting the viscosity down is to allow the resin to flow in at a faster rate with (hopefully) a reduction in any voids that could lead to the holes in some prints.

[Anuvin]

The only problem with "washing" the resin over the print is it may lead to inaccurate layer height. I think we'll want to avoid excessive ripples or waves at the surface ( where the printing actually happens). The idea behind getting the viscosity down is to allow the resin to flow in at a faster rate with (hopefully) a reduction in any voids that could lead to the holes in some prints.

If I end up trying anything to reduce viscosity, I do think the aquarium heater is the way to go. Dead simple, and dirt cheap. If surface tension was still an issue though, I do think a stirrer would help out. I agree that magnetic mixers are quite vigorous and it does appear that it could create problems at the print layer. However, one could get the mixing bar to spin only a few times, maybe every few layers, to gently disturb any resin bound by surface tension.

This might also help distribute the hot saline flowing into the lower reservoir. A diy magnetic mixer coupled with an aquarium heater could get the resin heated thoroughly and have the resin occasionally disturbed on the cheap! Much cheaper than a Form1 style motorized plate that dips the print into the resin anyway.

Cheap mixer I mentioned (not my video) : https://www.youtube.com/watch?v=LviLZToPx1c

[rylangrayston]

I think that controlled surface ripples could be a solution to break over, and it really just needs testing, because at some amplitudes and frequency it will also cause problems.
One Word of caution, a changing magnetic field near the printer head can make the make the mirrors move.
So I suggest a little hack. Say using an arduino connected to the laser enable pin, so that you can try disabling the "wave maker" while the layer is being exposed.

On time I used a solenoid to poke the shutter button of a camera that I couldn't get a trigger cable for, I was time lapsing a print.
To my surprise I couldn't print any thing because when the solenoid was on, the layer been printed were shifted by a hole 5 mm !

[iplayfast]

I think that controlled surface ripples could be a solution to break over, and it really just needs testing, because at some amplitudes and frequency it will also cause problems.
One Word of caution, a changing magnetic field near the printer head can make the make the mirrors move.
So I suggest a little hack. Say using an arduino connected to the laser enable pin, so that you can try disabling the "wave maker" while the layer is being exposed.

On time I used a solenoid to poke the shutter button of a camera that I couldn't get a trigger cable for, I was time lapsing a print.
To my surprise I couldn't print any thing because when the solenoid was on, the layer been printed were shifted by a hole 5 mm !

I'm not sure how big the waves would need to be, but I suspect small. If that is true, perhaps a piezo speaker dipped into the solution at a resonant frequency. No magnetics to worry about.

[Anuvin]

I am terrible at electronics, so that tends to be the last thing I think of, but a little piezoelectric speaker just might do it. On the other hand, these ideas do ruin the silent operation of the peachy printer, which is lame. Is there something else that is electric but makes no sound that would create the occasional ripple?

[Slatye]

I am terrible at electronics, so that tends to be the last thing I think of, but a little piezoelectric speaker just might do it. On the other hand, these ideas do ruin the silent operation of the peachy printer, which is lame. Is there something else that is electric but makes no sound that would create the occasional ripple?

Ultrasonic? Has the advantage of keeping dogs away from the printer while it's active!

Alternatively, we already have a wave-generator ready to go: the dripper. By default it 'drips' under the surface to prevent ripples, but if you move it so that it drips from above the surface you'll get ripples. What I'm not sure about is whether that can be calibrated. One approach would be to have it drip from just above the surface (so there's only a tiny fall, and a small ripple) - but then you have to keep it just above the surface as the level rises.

I know people are looking into pumps to get more consistent drip speed, and those might be able to provide suitable ripple too. Pretty much all the 'cheap' pumps that can accurately provide a small amount of liquid (which rules out impeller pumps) have a pulsing motion. If they're run very slowly then that'll be almost irrelevant. If they're run fast (even if it's just a fast pulse for a single cycle, to avoid raising the level too much) they'll give a much bigger pulse. Not totally silent, but very close.

[cephdon]

I was thinking of using a peristaltic pump to control liquid height, rather than the drip. That also means that I can raise and lower the water level at will. So my thought was to run cycles where I raise the level, let the resin relax and then lower the level for exposure.

So heights might be like:
1 - expose,
5 - relax,
2 - expose,
6 - relax,
3 - expose
...

It will take longer to print, but because I fully control exposure time I should be able to get solid prints with very thin layers. Also, assuming the resin will coat the object sufficiently on the exposure step, I might be able to subtract some additional fraction of resin height in the fluid to get even better control.

Has anyone at peachy tried that yet?

I am in for two printers, so I was also thinking of using them together to speed up exposure and get double coverage.

Since the code is open, theses things should be possible to test when I get my printer, though the first one eliminates the worry about surface tension, I think.

[Slatye]

A peristaltic pump seems like a good option for this. A small, constant volume delivered on each revolution is exactly what we need, and it should be largely immune to corrosion from salt water. And, of course, they're only a couple of dollars on eBay.

It'd also open up some really interesting possibilities - you could build a perfectly horizontal surface just by turning off the pump for a while and continually drawing slightly larger shapes with the laser. Obviously with the dripper you can't do this properly; it may take thousands of laser passes to build a large flat surface and in the time it takes to do those the dripper will have raised the surface substantially.


Edit: ooh, you can get stepper-motor peristaltic pumps on eBay! They're not cheap ($50 AU or thereabouts), but for extremely small and accurate movements they'd be perfect. With a DC one, I'm not sure how you'd tell where it's up to - maybe measuring current or with a magnetic sensor.

[cephdon]

Yeah. That kind of control is what I am going for.

I would definitely go with a stepper, or buy the DC motor version and convert it to using a stepper.