Hey all …I am using a PS1 and tried the density trick…unfortunately the part failed miserably as the video actually didn’t go any further then changing from 15% to 100% …I am hoping someone can share their settings so that I can make this item actually solid all the way through…I am using Black PLA if that helps
Thanks in advance
Your post is way too vague for anyone to help.
What exactly is the “density trick”?
How did the part fail? Picture?
What video are you talking about?
What did you change from 15% to 100%?
Even if you print something with 100% infill (which is all that should be required to print something “solid”, and which is what I’m assuming you’re referencing with “15-100%”), it won’t be waterproof. 3D prints are porous. Not very porous, but they will leak over time. You need to seal them if you want them to be truly watertight.
But also, if it’s solid, it can’t really be airtight because airtight would need to have an interior volume that wasn’t solid for the air to not be able to get in to our out of. So it might also help if you explained what you were trying to accomplish. 
5 Likes
Thanks for your reply Rocket.
This is the item I wish to make and it does fit on the table on the diagonal
Unfortunately my first attempt had the items leaking air at the necks of this spigots you see in the first picture…The density trick is a setting that was briefly put up as a video that I found on Youtube…my own fault for not coming here to the forum to ask real printers what I should do.
I attempting to make this either water tight at 40 to 65 psi and changing to something that is stronger if necessary.
You had mentioned a sealer …is this something that Bambu supplies or would I need to source another supplier for this?
This is going to be quite an adventure!
Try to design such that an o-ring or gasket will provide your sealing surface, 3d printed threads [especially printed vertically] are likely going to let you down. There may not be enough teflon tape in the world to make that work.
If you print with 6 walls, 6 tops, 6 bottoms, it will give the interior part a good chance of being waterproof. pressureproof? hmm
That looks like a rather tricky task.
Due to the process, FDM leads to parts with quite a significant porosity. Last years summer, I determined a 20% difference between CAD weight and actual weight => porosity. In those prints, I used a wall count of 999 to force a solid infill. A deliberate pressure increase by choosing line widths much higher than the nozzle diameter helped a little, but not as much as I had hoped.
So obtaining a lasting seal will be quite challenging even with post-print coatings (especially since you’ll want to coat the inside).
Another issue for medium to longer term use with internal pressure is the low z-performance of FDM parts. This is even worse when local sagging occurs as a result of, for example, overhangs being printed on supports with a non-zero z-distance.
If aesthetics are not important, I’d avoid a round shape at the bottom. I.e. I’d flip the part around and continue an angled extrusion to the build plate with no more than a 30° overhang.
& 
Maybe resin printer is better in this case?
Bullocks - I can add an O-Ring surface to the threads on the bottomof them with a few clicks of a mouse to extrude internally and I had actually one internally on the bottom thread underneath(not shown)…I had sealed the entire thing with plugs and o-rings outside initially but was surprised when I immersed it in water to find bubbles coming out at the junctions of the joints like a hot tub jet. Teflon Tape is not an option and sadly gasket sealer will not take ahold either…I will try with more than 6 walls -tops and bottoms as the material in it’s thinnest form is 7mm thick.
Eno The Thracian - Does the 999 wall count actually force a solid infill as weight is not an issue with this part…and what post print coatings are available or would it be more feasible to change to PetG for this application?
Eried - Are you familiar with using resin printers and if so what brands would you recommend?
Do not use PLA as it can become brittle under heavy loads and may fail under excessive pressure without warning.
The 999 wall count approach essentially eliminates all infill and replaces it with walls. It is quite a common work around to get more consistent 100% infill parts. However, even with increased line widths, it is not able to eliminate porosity.
As for coatings, I occasionally paint prints using Emaille color or use acryllic spray to apply a UV protective coating. These approaches would probably not be suitable for your application though.
Maybe a dip coating using epoxy could give a better performance, but that is quite actually quite difficult as coating thickness will vary even with multiple layers.
Using PETG may improve some aspects like longetivity when used outsides, but PETG has its own pitfalls. A TPU will probably improve some aspects (like interlayer bonding), but will probably allow too much movement under internal pressure. It is actually quite difficult to beat PLA in z-impact. Besides TPU, only PA6 is stated with a higher z-impact. By a mere 12%.
So there just are some basic limitations to FDM which can become quite extensive to overcome.
For workable prototypes, short term applications, etc, it may be realizable using PLA/PETG with TPU thrown into the mix with many thick lines. But I’d not consider FDM for long term use under internal pressure. And it is quite important not to expose such parts to freezing conditions. Their porosity means that they’ll have water insides its solid surfaces after a few weeks. You do not want that to freeze…
Alternatives are of course prototype development using FDM followed by classical milling/turning or, if “the way” is the goal, consider printing moulds for fibre reinforced epoxy.
&
Plenty of good advice I won’t repeat.
My comment: the levels of pressure you want this part to hold is pretty high. If it’s sized based on how big a metal part, or an injection molded plastic part would be, it’s not going to be strong enough. I would substantially increase wall thicknesses.
Also, threaded holes should be deeper for more thread engagement. Printed threads are going to be weaker, too.
And orientation on the bed might need consideration. Those threaded holes aren’t going to be perfectly round, and that will also contribute to leakage.
2 Likes
Hi
Great project you’ve got in your hands.
Water-tight
Sealing a 3d print for liquids is possible by using a sealing agent in the post-processing stage. Nowadays, you can use specific products for 3d prints, e.g., https://diamant-polymer.de/en/industry/3d-printing-additive-manufacturing/impregnating-and-sealing/make-3d-print-waterproof/ or rely on the well-known sealing materials, such as epoxy.
Notes:
- while sealing is mainly attained by impregnation of the sealant, 3d printing can also be optimised;
- In any case, you must consider that you are adding extra material to the print, and if dimensions (e.g. internal diameters) are relevant, you may need to account for them.
- 5 bar is doable, with correct materials; yet, you should evaluate it using an adequate method, e.g., using some simple CAD software simulation tools or relying on old-school calculations. Standard rules set a common safety factor of 3 times the rated working pressure; I tend to set higher limits to account for anisotropic behaviour and infill non-uniformity.
Even so, the inlets, outlets, and threaded connections are the most prone to leaking in your design. You may try the traditional Teflon or the old school vedox putties with linen in a water-tight. An anaerobic sealant if all others fail.
Air-tight
Gas molecules are significantly smaller than liquid ones, so sealing is challenging even with equal connections. We usually measure the loss over time and extrapolate it to the annual amount, which, depending on the gas, has acceptance limits.
You may achieve good sealing with an extra sealing material. But the gas-tight connections are significantly harder to achieve.
- The threads adequate for this case are extra fine, which may pose issues when printing them.
- You can open it afterwards, but without proper instrumentation, achieving the correct size, pitch, and perfect alignment between the tap and hole is a trial-and-error process.
- I advise using anaerobic thread sealants to seal the thread, e.g., Loctite has many. They not only seal and resist the pressure, but also are easy to remove. I would check compatibility, but you must try to be sure.
Water-tight + Air Tight
This is what I didn’t understand. Why have both? If you run with a fluid with a gas within, the sealing coat will be eroded quickly.
PS: All coatings, even if not disclaimed as, should be considered toxic. Buy good protective equipment and work in a well-ventilated area.
3 Likes
Thank you all for your wisdom and experience here.
The metal part I am replacing is 1.6mm thick and it is tested with air at 85psi to make sure it will not leak, then the air is substituted with Glycol that is around 60 psi and brought down -2 C so that we can cool internal lines that are going to be put through it. Surprisingly enough the threads are 3/4 bsp-14 TPI and the large bore underneath is 11 TPI-these threaded holes are cleaned out with a tap that takes out any material that might be hindering the thread.
As an R&D project we are hoping to achieve an item that can either go straight to print or into an injection mould that can sustain constant use on a regular basis.
To all of you, thanks for your assistance in this matter as I will continue to investigate this further so that all avenues have been well vetted and trialled.
I will keep an eye on this thread for further input that may be indeed vital to this quest
Best Regards
It does sound like you have corrosion and/or leakage problems with the part to be replaced?
Injection molded PPS may at first seem like a good option if the thickness is tailored to fit the long term stresses (including reserve factors!). However, screwing in metallic connectors would incur stress.concentrations in the threads which could lead to an even quicker formation of leakage paths, especially if pressures are dynamic.
If you have a workshop in house, you may want to present the problem (not a solution!) to them to get some safe (!) and pragmatic proposals.
Alternatively, speak with the original supplier about the problems with the current part.
&
Eno:
The end game is actually to surround this item with a cylindrical body also made with PLA but honeycombed for insulation purposes. We have discovered that the steel items when surrounded by such transfer very little heat and cold to the outer container that is will be introduced to.
Sealing with O-rings + adhesives and other tricks we can use in our arsenal.
We thought by replacing the internal items with plastic and incorporating the honeycombed outer layer to the item we could provide a (slip in solution) instead of fabricating the internals that incur error during fabrication
Ethylene Glycol? What concentration? I don’t know of any extensive chemical compatibility database of conventional FDM materials. Still, if you are dealing with high concentration (> 50%), I would do some chemical compatibility test, e.g. immersing the material (including coating if relevant) in the same fluid used and assessing it over 30 days. PA66 is widely used in the automobile industry and will likely (with coating) fulfil your application’s mechanical and chemical requirements, but others may also work.
1 Like
Thanks JayZay.
Our content % is 19-20%, We do intend on making multiple iterations of this concept and even with success there is still a 3 to 6 month testing cycle which includes NDT and DT testing to assess it’s true feasibility. Our company prides itself on full warranty of items for an finite time period but would expect analysis after the testing phase, this product may not be economically viable for our requirements.
But we have to give it a go with all the promising aspects that 3D printing can provide for us.
Regards