3D printers - messin' with resin

[Steve_Cornford]

Thanks for that Martin, two tips in one!

I have just ordered the heater.
I have found that be pre-warming the resin before adding to the tank that the resin flows better, proved by the improved draining & dripping after the print has finished.
Now to find my reel of parcel tape to keep the pesky rubber seal onto the cover!
Steve

 

[Phil G]

Hi Martin,
well your ahead of me again, I am still waiting for my temp controller coming from AliExpress just a quick comment. Are you in a position to do a controlled test using resin temps of the recommend 20-25 which is a very wide band primarily intended to show it has a good working temp range. Then try if possible to increase the temp to the previously recommended 26 to 27 degrees. which is a much tighter working range.
What should happen is the viscosity will be bit lower and the UV reaction a bit faster, this results in a much lower hysteresis effect in the vat as the Z axis moves up after each exposure, you should also find the exposure time can be reduced, although I think you said your already using 2.2 seconds which is likely optimum.
this should represent very close to the best possible printing conditions, and is quite likely to create the most consistent shrinkage, from there it can be measured and offset by shrinkage allowance.
phil

 

[Martin Wynne]

Are you in a position to do a controlled test using resin temps of the recommend 20-25 which is a very wide band primarily intended to show it has a good working temp range. Then try if possible to increase the temp to the previously recommended 26 to 27 degrees. which is a much tighter working range.

@Phil G

Hi Phil,

I'm not sure I can do much in the way of a controlled test in July which would have much relevance in January. For accurate results it would need a sensor dipping in the actual resin, which is impossible to arrange clear of the Mars build plate while printing. It needs a special tank with a built-in temperature sensor.

I did think of conducting the hi-tech experiment of putting a cardboard box over the whole thing while it warms up.

The resin instructions recommend 20-25 degC so I'm a bit puzzled why you want to go to 26-27 degC? My understanding is that higher temperatures significantly affect the shelf-life of the resin, so they must do something to it. There's likely to be a reason why Elegoo suggest 25 degC as the maximum recommended. It's also the maximum I'm happy to go in externally warming the printer internals at this time of year. It got to 27.5 decC yesterday, but that was without the machine switched on or the resin tank in place.

I did get the Inkbird temperature controller while it was on special offer last week. I had it in mind for a different project. But I might get a spare sensor probe and fix it into the Mars lid to monitor the internal temperature.

The heating belt is a mains 230v device, so I'm minded to fit an earth (ground) connection to the Mars metal case, just to be sure. In the meantime I have it plugged into an RCD adaptor.

cheers,

Martin.

 

[Martin Wynne]

.
The Inkbird temperature controller is excellent. I'm glad I got it last week on special offer from Amazon. There is still a 20% voucher currently showing.

https://www.amazon.co.uk/dp/B01AWA2PTG

Very nicely made with big bright red LED displays (no UV from those). Big buttons with a proper click (no fiddly touch screen). A detailed user manual with full technical details, written in proper English. The sensor probe can be unplugged, so I can get another one to use elsewhere when I'm not 3D printing.

I drilled a 5mm hole in the back corner of the Mars lid, about an inch from the bottom, and the sensor probe is a nice push fit in it, to measure the inside air temperature. If it does work loose I shall probably epoxy it permanently in place. That means remembering to put the lid on the right way round, otherwise the probe would hit the tank. Place your bets.

I set the temperature to 24.5 degC with a 1.5 degC differential. Which means it switches the heater off when the sensor reaches 24.5 degC, waits for the temperature to drop to 23.0 degC, and then switches the heater back on. It is switching at about 10-minute intervals, so I could probably set a much smaller differential without it going mad.

I set the alarm level at a low 35.0 degC because I don't want to cook the printer internals if something goes wrong.

In practice, after switching off, the temperature continues to rise to about 25.2 degC before starting to fall back. The tank+resin has a much higher thermal capacity than the air in the lid, so it would vary a lot less and probably settle down around a constant 24 degC.

I have no way of checking the accuracy of the sensor, but the results match as far as I can tell on my old photographic thermometers. I don't know the accuracy of those either.

The controller also has a cooling output, which could switch on a fan or a cold-water pump or whatever if the temperature goes too far above the set value, but I can't see that being needed with the 3D printer -- global warming permitting.

It's been running now for 4 hours and seems entirely happy. Of course it's hardly serving any purpose in July, the test will come in the winter. It would be possible to run a second heater belt below the first one -- just about, without obscuring the printer display too much. That would take the heater to 50W which would make a significant difference in very cold conditions. The controller won't mind -- it is rated 2kW.

cheers,

Martin.

 

[Steve_Cornford]

I must stop reading your tips!
But at leat I have saved £6.60

Your parcel tape tip is an absolute winner, especiall if the tape is aligned with the tank thumbscrews.
It is so much easier to remove the lid without catching the ruber seal, thanks again for that one.
Steve

 

[Martin Wynne]

.
A possible use for your well-used first-wash "dirty dunk" IPA. Working away from daylight/UV brush it over paper, card, cork, ply, etc. Take it out into the sun for an hour. The IPA evaporates, the resin cures, and you have a nice rigid sheet of sealed board for modelling, etc.

Not sure if there is any advantage over traditional shellac, sanding sealer, etc. -- except that you have lots of it, and it's effectively free.

Like any other sealant, it needs to be on both sides to prevent curling.

And the further thought is -- would it work like a solvent to fix resin chairs to plywood? I know you can get the UV adhesives, but this would be brushable and penetrating like other solvents. Perhaps we would need to make a stronger resin/IPA mix, but still thin enough to be brushable.

The alternative is to try to recycle used IPA by curing it in the sun to precipitate the resin, and then filtering. As I've been finding out, that's a messy business because the resin precipitate stays very sticky and slimy while in contact with the IPA.

cheers,

Martin.

 

[AndyB]

Oh dear! It's well over two years since I got my resin printer and it's hardly been used at all. I did get as far as fitting a small fan in the workshop's wall where I was going to put the printer in a sort of fume cabinet but that's about it. Maybe I'll get it going in earnest over the Winter

The current project is rail welding, just not that sort of rail. The rails are 1.5 inch square steel tubes and I'm arc welding 5/8" square steel tube palings to them. I'm making railings to replace the wooden railings around our deck. They've been there for almost forty years and are falling to bits. The steel I'm using is quite thin which makes it a bit challenging. By the time it's all finished I should be an excellent welder

 

[Steve_Cornford]

That's good if your deck has lasted forty years!

 

[Martin Wynne]

.
This looks interesting:

Martin.

 

[James Walters]

Hi Martin & co,
This company (Geetech) have just contacted me, they're sending me one of these printers to try out and review. I'll make a video about it in the fullness of time, and obviously give it a thorough test with plug track components and report back on here as to its usefulness.
At $99 one wonders whether the technology could become any cheaper.
It only has a 2k screen, but that is more than capable of producing detail which none of us can actually see.

 

[Martin Wynne]

@James Walters

Hi James,

I'm very interested to see what you make of this, compared with results for the same STL from the Mars.

One thing I'm very keen to see you confirm is that this printer has a CLEAR FEP film, and not the ludicrous FROSTED ACF film which some printers are now being supplied with. A frosted film obviously kills the sharpness of fine detail, the excuse being that it allows the machine to run much faster by releasing each layer from the film much more easily.

Also be sure to switch off the anti-aliasing in Chitubox if it is on by default with the supplied version. That again softens detail and changes dimensions, the excuse this time being that it gives a smoother surface finish.

I wish these printers would have a single button labelled "Engineering" for those of us who want accurate dimensions and sharp corners, and not a nice smooth Toby Jug printed at breakneck speed.

cheers,

Martin.