Dear Network,
I am trying to print a reactor frame using PLA on 3D printer. However, I am facing a problem with it being waterproof even at tap water pressure.
I am seeking recommendations on printing parameters to better link the frame layers or for some specific post-printing treatment to refine any potential gaps in the layers that lead to water leaking.
I would appreciate if you share with me your experience.
What is the diameter of the channels inside of your reactor? If they're not too small you could post-process your reactor with a coating.
I've had good success sealing PLA by coating it with SLA photopolymer resin... admittedly not for waterproofing specifically, but the process should work fine for it as long as you dial in the rheology right. You can increase the viscosity and even achieve shear-thinning behavior by mixing it with fumed silica ( SiO2 ). I've found ~~ 24mg SiO2 ( FAS-SIL 200 ) per 1 mL of resin ( Anycubic Eco Clear ) works well for the structures I deal with in the 100μm - 1mm range to help them hold their shape pre-UV curing. Be careful about entrapped air too.
I've only used it on exterior PLA surfaces and standalone extrusion printing, so I don't know if it would work... but you'd probably have to experiment with filling it with the resin mix then clearing it with compressed air. Depending on your viscosity and level of shear-thinning it would leave a coating on the reactor channels that's thick enough to coat the PLA and fill the interlayer gaps.
The channel has a diameter of 8 mm, yet the turbulent promoters inside present a major barrier for the coating option.
As you mentioned, I believe coating the exterior PLA surfaces with SLA would result in waterproof frame as this later is more accurate comparing to FFF 3D printing. However, since I have access to only a Fused Filament Fabrication printer, I'm first looking after specific printing settings for a PLA watertight frame. Currently, I'm going for 0.06 mm layer height, 1.6 mm shell thickness and 100 % fill density as I'm dealing with small overall volume object. Yet, I'm not sure of the outcome quality. Furthermore, I'm thinking of an epoxy coating.
Lexa Baldwin Thanks for sharing your experience regarding the subject. I would appreciate any further comments or recommendations regarding my approach.
Taha Zier, My pleasure, I'm always happy to help!
In terms of specific print settings on your FFF printer, I'd recommend printing at a higher temperature, ~215°C depending on your PLA's specifications; making sure your extrusion width is calibrated right to ensure you have good interline fusion; and ensuring you have proper interlayer adhesion. As you're going for quite short layer heights, also make sure your height is an appropriate multiple of your leadscrew linear travel distance per step... e.g. if you're using 1.8° steppers and a screw with a 4mm pitch, 4 / ( 360 / 1.8 ) = 0.02mm, in which case your 0.06mm would be perfect. Printing with 100% infill will do a good job to minimize the air entrapped in the part, but there will always be some due to the ovaloid shape of the printed lines. Interline and interlayer adhesion is never perfectly homogenous either. Heated chambers on a relatively high heat setting greatly help with the latter problem if you happen to have access to one, also reducing your part cooling fan's speed will help with this.
Now with untreated PLA, you're still going to have issues with its hygroscopicity. All printer filaments that I'm familiar with are hygroscopic to some extent, but based on my anecdotal experience ( I haven't conducted any proper tests on the matter, and I don't know off the top of my head where to refer you for those kinds of data ), PLA is worse than average. I know of a researcher in my institution who has been designing an experiment involving long-term submersion of printed parts in adverse environments ( hot springs ) using PETG, it may be a good alternative for you to look into as its printability is close to that of PLA and it sounds like your circumstances require you to use specific printing hardware.
As for the resin... I wasn't actually referring to the use of the SLA resin with an SLA printer, in applications such as this I paint it on or submerge the part for a coating just like you would with epoxy. I use it in similar projects because I can quickly polymerize it with near-UV ( 405nm for the resin I mentioned ), thus reducing gradual dripping and loss of dimensional accuracy. You would obviously need to use clear PLA if you decide to go that route.
If you are eager to use FDM technology than try printing it with PVB filament (Polymaker Polysmooth of Prusament PVB) and then spray it with IPA or put it in fuming chamber for smoothing and water tightness.
Also rhere is XTC 3D coating from Smooth-On.
I have got very good result, a well refined PLA watertight frame without coating treatment, with the following printing settings: 0.06 mm layer height, 1.6 mm shell thickness, 100 % fill density, printing temperature 210 C a and bed temperature 70 C.
I just wanted to share the info. Thank you for your comments and contribution !
Fantastic! I'm glad you were able to get good results without needing any post-processing! :)
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