Has there been any thought of using a heated tank/heated water to help lower viscosity and thus surface tension of the resin?
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Has there been any thought of using a heated tank/heated water to help lower viscosity and thus surface tension of the resin?
It may be interesting idea, but I think it will be of no use to most people who ordered Peachy Printer Kit. It's way too complicated. However, if it turns out to really improve results, it may be an idea/option for Peachy Pro.
However, when I have Peachy Printer, I will definitely try this, among other things, in order to try improve printing quality and widen range of resins I can use. If it turns out to be useful, I'm sure many other people who do not mind adding temperature sensor, heater and microcontroller will try it too.
P.S. In future, please do not cross-post basically the same thing in multiple topics; it would be enough to just create new topic.
I did some quick research/googling, and I do not think that heating resin will help much. It may reduce viscosity greatly, but surface tension will remain mostly unchanged. At least this is what I think at the moment; I did not find general study of many types of resins, but all studies I have found so far do not mention big change of surface tension. For example, some resin has slightly more than 41 dyn/cm surface tension at 25°C, after heating to 60°C it is reduced, but very slightly, by 6-7% (to 38.5 dyn/cm). I guess this is why some manufactures who provided surface tension in datasheet do not even bother to specify temperature. I could be wrong about all of this, if so, feel free to provide example of a resin which can reduce its surface tension greatly (relatively to its state at room temperature). But at the moment I have an impression that heating resin is mostly useful to reduce its viscosity. This does not mean that you idea is not useful - it's still possible that heated resin could produce higher quality prints, it is hard to tell without experimenting. Heating also may help with some thick or old resins.
Sorry about the cross posting. It may not help reduce surface tension, but I think that a thinner resin that can flow easier should be able to fill in faster and more uniformly. this should make for a better finish, more uniform layers, and any reduction in surface tension is a good thing.
As far as complicated, a simple aquarium heater should suffice. A more complicated system using PID controllers is not a requirement. It's just a better system to have steady temps.
I think you aren't giving those who ordered the kits enough credit. When ordering the kit we already need to supply our own reservoir and build tank. How hard is it to add a heater to the mix? This is childs play for most anyone who will be using the kit. I think that if it gives a better result, then many will be willing to go that little extra bit to achieve it.
I'd love to do the experiment myself, but I have 2 problems...
1. I don't have a peachy yet. I plan on putting my preorder in after this next pay period(yay overtime).
2. I don't have a peachy yet.....
edit: After further research on the subject, it seems that there is little to no correlation between viscosity and surface tension. The only way I have determined to lower surface tension will be with an additive, which may adversely affect the bonding during curing of the resin.
That said, it is still my firm belief that raising the temp to lower the viscosity would be beneficial and at the least would result in an ability to print at faster speeds with better results.
and I found yet a third reason why I can't complete the experiment on my own...
3. I still don't have a peachy yet....
I think you will find that surface tension decreases significantly with temperatureQuote:
Originally Posted by Deadbot1
No, /dev/null is correct from what I have been reading. Surface tension doesn't seem to be affected by anything other than additive(surfactants). Heat will lower the viscosity(how easily a fluid flows). However the lower the viscosity the less that surface tension should be a factor, I believe. If the resin can flow easier, it shouldn't be held back as much by its surface tension. It's the difference between trying to push an object into a bubble of tar and a bubble of water. the water actually has higher surface tension, but lower viscosity so is easier to push into. the difference is that the tar will coat and adhere more quickly, where the water may actually form a film above the part until the surface tension breaks.
edit: Think of it this way, we use soap to make the surface tension of water lower, this helps the water to reach the dirt on our hands. We use heat to make the water dissolve more of the dirt. In our application we will be using heat to make the resin better flow into the void left by the raising of the z axis.
According to rylangrayston, "all of the resins that maker juice sells will work well with the peachy printer, and also some of them work better", and MakerJuice resins can have viscosity as low as 25cP with 8% shrinkage and up to 90cP with 3.3% shrinkage. Is lower shrinkage more important than lower viscosity? We do not know that yet. It may be that viscosity is not that much important by itself, unless it's too high. But I think your idea is worth checking out regardless, just print first object normally and then the same object with heated resin and then it would be possible to compare them. With thicker resins difference maybe more apparent (if there will be noticeable difference).Quote:
Originally Posted by Deadbot1
I'm not sure if using simple aquarium heater for this purpose is a good idea. Surface temperature of the resin is what the most important in this case, and it will be lower than temperature of the water below, so the water needs to be hot enough. But I looked at some aquarium heaters at eBay and they are usually limited to 34C max. Perhaps there are better aquarium heaters or you know some easy hack for specific model. Also, there must appear no unwanted bubbles when heater works. I never used aquarium heaters, so I have no idea if this problem usually exists in practice or not.Quote:
Originally Posted by Deadbot1
That's exactly what I meant by "it's still possible that heated resin could produce higher quality prints".Quote:
Originally Posted by Deadbot1
That's one thing you can experiment with without Peachy (I would do it myself, but I do not have aquarium heater, and it seems like not every aquarium heater would be useful for this purpose). Put your aquarium heater in the tank you plan to use with Peachy and fill it with water just enough for aquarium heater to work. Increase power very slowly, small step at a time, until you start getting bubbles around it, then go back few steps to eliminate bubbles. Then after a while measure the temperature around water surface in different points. Then fill the tank as much as necessary to "cover" the tallest object you plan to print in it, wait for while, and take few measurements again. For all time monitor water to make sure there is no air bubbles because of heating. The higher the temperature the better, as long as there is no air bubbles (so if there are two heaters of same power but different surface area, heater with the most surface area is more likely to work better for this purpose). Keep in my mind that resin will be colder than water, so warm water is unlikely to noticeably improve result (assuming room temperature 25C).Quote:
Originally Posted by Deadbot1
I think you are underestimating difficulty. Adding heater is not easy, and requires effort, spending time and money.Quote:
Originally Posted by Deadbot1
You are right, modifying resin with additives may ruin it. And considering that manufacturer already worked a lot before releasing the resin to the market, finding a way to improve it would be difficult. This is why usually people experiment only with pigmentation.Quote:
Originally Posted by Deadbot1
It may give better results, but I do not see how it can increase printing speed.Quote:
Originally Posted by Deadbot1
This might make the whole build more complicated than it's worth but to avoid the bubbles around the heater to an effect on the resin you could construct a double walled containter where the outerwall has water with the heater and the inner tank is the build area.
You could even add some stirring or or similar effect in the heated water to improve heat transfer.
Another option to improve the heating and keeping the temperature steady to have the water reservoir heated aswell
Bubbles??? How hot do you think we need to get? I would expect that we could stay reasonably below boiling temps. I am a Yank so I'm thinking in Fahrenheit, but I'll try to do metric conversions as well.
Boiling point of water at sea level...212 F /100 C
typical room temp.... 72 F / 22.2 C
expected heat of water for heating resin to comfortable 100 F.... 120 F / 48.9 C
There should be no bubbles. I don't think we need to get crazy hot. The resin I was thinking of when this thought struck me was Wahoo Int. ZeroVOC. They recommend heating to 100 F to thin the resin down. Most resins, even UV cure resins will go off if they are heated too far.
The way the Peachy is set up, I would heat the standby reservoir and have a well insulated build tank.
As far as how it could help to speed up prints, a thinner(lower viscosity fluid) can move into the next layer faster. Less time waiting for the resin to get into place before the next layer prints means faster overall print times.
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.
Attachment 8317
http://labsuppliesusa.com/product/ma...-klm-sh2-each/
Quote:
Originally Posted by 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.
Quote:
Originally Posted by Deadbot1
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
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.Quote:
Originally Posted by rylangrayston
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!Quote:
Originally Posted by Anuvin
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.
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.
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.
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.
Mostly because we havent figured out a way that we can do this for with in the 100 dollar price point we have not tested this enough to really have an opinion on how well it can work. I have built more expensive printers that can do this but Ive barely used them with a feature like you suggest above.Quote:
Originally Posted by cephdon
I highly encourage pump hacks! like Slatye says some layers take longer than others, but the dripper wont slow down for those layers, so you have to drip at a rate that gives your longest layer time to print.
Yeah. Stepper pumps are a bit more. However, I was thinking that it could be possible to use a stepper like this for $5:
https://www.adafruit.com/products/858
There are chips to control it, as you know, but for simplicity one could use this for an additional $5:
https://www.adafruit.com/products/2448
The pump head is the most expensive, but there are ways to do it cheaply to keep costs down. Like:
http://m.instructables.com/id/Inexpe...istaltic-pump/
And:
http://blogs.rsc.org/chipsandtips/20...istaltic-pump/
It seems like it wouldn't take more than $10 to $15 more in single quantities and less if you build your own drivers.
Not that I am advocating it for initial release. ;-) Maybe after we get our printers some of us can figure out the cheapest way to make that happen so that others can make use of it.
On a side note, one other thing I considered was the idea of viewing water level as a linear servo.
In this view, a small dc peristaltic pump is the motor. A variable resistor water level sensor is used to detect position like: https://www.adafruit.com/products/464
Then a cheap servo can be sacrificed and used to control water level by having the electronics drive the pump based on the water level feedback.
To bring this back on topic, controlling water level is going to be my way to avoid issues with surface tension, and these are the ways I was thinking of doing it.