3D Printer Project Question

[fireant911]

I purchased a 3D printer last year and absolutely love it! The initial purpose was to pursue an idea I had for modifying/improving equipment for collection methods for maple sap for eventual processing into that tasty maple syrup. Unfortunately, this idea came late in the season so I did not have the opportunity to actually test any of my models. Over this winter, I did some more design work and prototyping of a few different versions I would like to test ‘in the field’ for the upcoming 2023 sugar maple syruping season. One change I made involved incorporating a John Guest push fitting at one end of my models – there is nothing especially profound about this modification… it is just one of the many attributes of the new design that I want to test and examine.

After a little Internet research, I found out that it is possible to purchase John Guest half-cartridges which permits manufacturers to incorporate push fittings onto their existing equipment as long as they follow the dimensional sizing as required… so I could, in theory, make my own push fitting. I did the design work, sliced the print, and sent it to my Creality 3D CR-6 SE printer and had a very good-looking part in my hand (after my second attempt of tweaking the print parameters!). Next, I assembled the half-cartridge components into my freshly printed part and was in awe of the seemingly perfect fit! Finally, inserting a polyethylene tube into the assembly demonstrated that, at least dimensionally, everything was spot on.

And now, for my question… research indicates that 3D printed parts are NOT good in environments where the pressure varies from normal atmospheric pressure. So, attempting to use this 3D printed housing in either a vacuum or under a positive pressure, leakage/seepage will occur from the minute spaces between the printed layers. Pressures for my intended usage will be only at normal atmospheric but, in order to minimize/eliminate areas for potential bacteria to hide and grow, I would like to improve the ‘seal’ between the layers, if possible… essentially make it water-proof at low positive pressures above atmospheric. Epoxy resins are available for this specific purpose; however, I am afraid that this addition of this material will affect the dimensional accuracy required by the John Guest half-cartridge rendering it unusable. I have NOT tested the part under pressure to see if it leaks between layers though, due to the plethora in info on the Internet about the lack of water-proof integrity of 3D printed parts, it seems extremely likely that this novice’s design will leak/seep as well. Do you 3D modeling experts have any help/guidance/suggestions on how to improve the water tightness of a 3D printed part? Maybe 3D printing this part is not the best option???

Current machine settings: profile – super quality 0.12mm, 100% infill, 0.01mm layer height, and 50.0 mm/s print speed. Nozzle size is 0.4mm. Material is 0.175mm diameter PLA filament. The part is cylindrical in shape and the minimum wall thickness is 0.08”.

[island911]

Yeah, you just need to test the pressures.

Typically external pressures won't be a problem as that compresses the layers.

For internal pressures it all comes down to how well the layers adhere. Obviously more dense infill will give more strength, but you will need to test.

Also, perhaps start printing with PET clear. Settings can be a bit tricky but it's the most common food-grade plastic, and you can see inside ... see what's happening.

Long ago I printed a little thin-walled calibration box (30x30mm 1.25mm wall) out of clear ABS - to check the scale factor. Anyway, because your post, I grabbed that box and just tested it for water tightness. Yep, no layer leaks. No leaks at all.

I wouldn't try to coat anything. Maybe 3D print a pattern for a urethane casting (if small volume) or go to injection molding if you need hundreds. Side note, injection molding may be weaker around the cartridge than the print. (hoop stress and injection flow knit-lines...)

Those half-cartridges are neat. I've design food-grade equipment components with those. I'm trying to think if I've ever prototyped with a 3D print on those. ...don't think so. pressures too high on that stuff.

[island911]

Just had one more piece of info.. the box I just water tested did get finished with an acetone vapor. That may have helped, but I'm thinking it would have also been water tight without.

[908/930]

Many years ago when we were printing a part that needed to be sealed we would quickly dip it into a solvent, (basically plastic solvent for bonding acrylic, fairly toxic) can brush it using the solvent, also you can dissolve some material into the solvent to thicken it up. Not sure what material you are using.

[fireant911]

Thanks island911 & 908/930! In regards to actual usage, this probably isn't the best method to test my designs BUT it is the easiest since I can tweak and existing design and reinstall it in the tree in a relatively short amount of time. I had read about the 'acetone smoothing' which would most likely help seal the part but, I think, that is for ABS material and I am using the standard PLA material.

Yes, I concur, those half cartridges are neat and have many applications! I will continue testing and see if my current design leaks - I can rig up something to do some 'air under water' testing and see how much pressure is required to see bubbles.

I certainly appreciate your input here - thanks again!

[908/930]

We used a product called Weld on, contains methylene chloride mostly on Polycarb, worked quite well. Would likely work with PLA, use in well ventilated area or outside. You could also try pulling a small amount of vac in your part while dissolving some material on the outside of the part to fill any voids.

[cstreit]

Id choose the print material you use carefully. PLA for example does absorb humidity. I don't know if this causes dimensional issues.....

[Pazuzu]

PLA is not food safe, I would not eat anything that was stored in it.

As well, it has a relatively short half-life when exposed to the outside world, it will become brittle and shatter after months of UV exposure.

[dad911]

Outdoor you want to print with ASA, but IDK if it's food safe.

Looks like those fittings are available with NPT threads. I've been pretty successful printing threads on a well-set up printer.

[fireant911]

dad911, I have never heard of the ASA filament. I just Googled it and the temperature requirements are above my entry-level printer. My Creality printer is only suitable for PLA, TPU, PETG, ABS, and Wood filaments.

Pazuzu, Originally when I looked to see if PLA is food-safe, most sources indicated the material PLA (polylactic acid) itself fulfills that requirement as some food packaging is actually made from PLA... however, as I see now, PLA filament may not always make the grade and numerous studies show NOT to use PLA filament in food-type applications for many reasons. Plus, even if a food-safe PLA material was used on a properly prepared 3D printer, there will still be all those hiding places between each layer for nasty organisms to hide.

Since I am looking just for proof of concept, PLA filament may suffice for this initial round of testing - I will just not process any of the maple sap that has been in contact with this material. Thanks for all the help!