Unlocking the Potential of Gas-Tight FDM 3D Printing: A Comprehensive Guide

The widespread availability of inexpensive 3D printers has brought about a revolution in what can be easily made at home. However these creations aren’t perfect, particularly when it comes to the adhesion between their layers. Aside from structural failures along the layer lines there is also the question of those joins being permeable, limiting the possibility for waterproof or gas proof prints. It’s something a German Engineer has tackled in a new video, in which he’s looking at the design and preparation of small propane tanks.

The attraction of propane as a fuel is that it liquefies easily on compression, so a propane cylinder or tank will be an equilibrium of liquid propane with pressurized gas above it, whose pressure depends on the ambient temperature. This means that any tank must be expected to have a working pressure somewhere between 150 and 200 PSI, with of course a design pressure far exceeding that for safety reasons.

Filling a 3D printed tank immediately results in the propane escaping, as he demonstrates by putting one of his prints under water. He solves this with a sealant, Diamant Dichtol, which is intended to polymerize in the gaps between layers and create a gas-tight tank. A range of three tanks of different thicknesses are treated this way, and while the 1 mm thick variety bursts, the thicker ones survive.

It’s clear that this technique successfully creates gas-tight prints, and we can see the attraction of a small and lightweight fuel tank. But we can’t help worrying slightly about the safety, for even when the material is a lightweight 3D print, high pressure equipment is not to be trifled with. Tanks do burst, and when that happens anyone unfortunate enough to be close by sustains nasty, even life-threatening injuries. Use the technique, but maybe don’t hit it with high pressures.

“but maybe don’t hit it with high pressures”…

It’s crucial to clarify what we mean by “high pressures”. For example, even at 30 psi / 2 bar, which is normal for car tires, a bursting container might cause devastating injuries.

While I support experimentation for educational purposes, the safety risks cannot be ignored, particularly for those who might try to replicate these experiments without proper knowledge of the potential hazards.

In the United States, 20# propane tanks are only allowed to be used for up to 12 years. Given this limitation, it’s advisable not to store highly volatile liquids or explosive gases in them.

They are subject to stringent regulations regarding the type of materials used, tests conducted on these materials to avoid scenarios like the El Nassir incident, as well as specific hardware and valve standards, pressure testing, safety margins, and failure modes engineered to maximize safety.

The regulations are comprehensive.

The regulations are ESSENTIAL.

This represents a grave lack of responsibility.

Concerns about embrittlement are valid as propane in its liquid form can be extremely cold. For example, I have a BBQ grill that tends to malfunction because the regulator often freezes, and the tanks themselves become very cold as they empty. Normally, PLA material is quite brittle, which only worsens in cold conditions.

Combining pressure vessels and DIY efforts can be highly risky, particularly with 3D printed items that lack stringent quality testing. Questions remain about how these homemade vessels might deteriorate over time.

Many severe injuries and even deaths have resulted from incidents like exploding car tires and misused airbags, among other things. Viewing some videos on YouTube could provide insights into the potential hazards involved.

While I am curious about methods that can enhance layer adhesion and strengthen components, I believe it’s safer to leave such experiments to experts like those at CNC Kitchen rather than engaging with videos of reckless experiments involving propane and DIY 3D printed pressure vessels. Such actions could end disastrously, earning the perpetrator nothing but a Darwin Award, unfortunately at the emotional expense of their friends and family.

I don’t object to DIY pressure vessels, but the makeshift ones constructed from 3D prints combined with random sealing materials are a different story. You’d think people would avoid inadvertently crafting explosive devices by learning from the mistakes of others who’ve pursued risky DIY projects.

Crafting a safe pressure vessel isn’t overly complicated for those who grasp the relevant physics or adhere to meticulously calculated designs with appropriate safety margins tailored for the intended use.

Statements like yours, which exhibit an overestimation of one’s abilities, are precisely what render these endeavors hazardous.

Consider this response:

How can you ensure the material properties of a self-made 3D printed device?

Without verified and consistent material properties, any calculations you perform can be ineffective, or even perilous.

When dealing with 3D printed plastic objects, one might initially think it’s as simple as estimating material properties, applying a safety margin, performing some calculations, and conducting a pressure test. However, these steps don’t fully ensure the object’s safety over time, as it may still be susceptible to issues such as UV exposure, material creep, or chemical degradation. This problem can be exacerbated when the items are distributed, whether they are gifted, sold, or rediscovered years later in storage.

Reflecting on history, it was over 150 years ago, after multiple failures and accidents, that rigorous standards were established for steam vessels. These regulations mandated the use of certified steel for their construction to ensure a baseline safety level, recognizing that regular construction steel was inadequate. Even in historical contexts, there was a clear recognition of the importance of safety, prompting the implementation of strict guidelines.

In the realm of DIY model steam engines, there are structured measures to uphold a minimal safety standard. However, the certification process for such engines varies based on geographic or regional standards. Enthusiasts and builders might find valuable guidance and insights on safety standards by engaging with DIY hobby clubs and groups that focus on steam vessels.

The acceptance of risk is a necessary part of the process.

Even with a well-calculated and thoroughly tested design, different print batches might possess tiny faults that could lead to catastrophic failures.

Discussing how A: reckless, B: thoughtless this scenario is without proper gas containment and spontaneous unsecured parts would be insightful. Nonetheless, it did drive clicks and downloads. It must be educational, so let’s try it at home.

I don’t typically align with the safety critics in the comments, but in this case, I agree.

The information provided is valuable, but I would not recommend attempting it without full comprehension of the potential dangers.

My primary worry is that although the pressure testing demonstrated in the clip provides valuable insight, a significant number of additional tests would be necessary to ensure reliability of these findings, and still, this does not assess the longevity of the product. Plastic and composite commercial pressure vessels typically have an established maximum lifespan, while metal containers require periodic testing and recertification.

Even under moderate pressure levels, the manner in which these containers fail can result in small plastic fragments being propelled with enough force to penetrate the human body. A particular issue with plastic is its low visibility on x-rays, posing a challenge for medical professionals to locate and remove the fragments. This concern also applies to non-3D printed plastic tanks, although materials like PVC piping come with a formal, thoroughly tested pressure rating that, when assembled correctly, can be relied upon.

However, there’s a silver lining. The inherent fragility of FDM technology might make it safer compared to other methods, such as using a soda bottle. The weakest links in FDM are the bonds between the layers, and it’s likely that failure will occur at these points, as shown in the video, where the container splits into several pieces along a layer line rather than turning into dangerous shrapel.

It’s important to remember that local regulations might prohibit the use of uncertified pressure vessels for holding or transporting flammable substances.

Hackaday mentioned with the specific phrase “Use the technique.”


For further reading, Chapter 6 of Shigley’s work on Fatigue Failure comes highly recommended.

Might be fun for target practice, but I strain to think of any other application. I do appreciate the tenacity some people have for using FDM in ways that are simply not suited to FDM.

It’s totally worthwhile to investigate how far you can push printed pressure vessels. There are lots of ways pneumatics or hydraulics could be useful in printed designs, and if you need 30psi then it’s helpful to know how to make a tank that fails at 150psi.

But framing it as a way to make propane tanks is way over the line. Everyone uses propane tanks, most don’t really get how dangerous they would be without regulation, and anyone can watch this video. The only question is how many maimings it will lead to.

total waste of time(for propane/fuel)
the certification procedure involves propelling a full propane
tank through a concrete block wall at 100kph
they dent, or partially crush, but must not suffer a catastrophic failure
and then there are the DOT tanks
in any case the tank must not turn into a bomb during
a car crash

Cool idea, but just not for the current plastic and resin printers, better safe than sorry!

This is one of the dumbest 3D printing projects HaD has ever highlighted.

And that speaks volumes, given HaD’s tendency to showcase projects that shouldn’t be 3D printed.

Art and prototyping.

That is the exhaustive list of things that should be printed using a plastic or resin printer.

Not a box.

Not a flat sheet.

Not a full-size boat.

Not a door lock.

Not an automotive transmission.

Not a pressure vessel *new*

3D printers excel only in a very narrow range of applications.

Many of the 3D printing stories shared here at HaD essentially praise the use of makeshift solutions for repairs. Often, it’s not the best way to handle a problem.

Are you aware that 3D printers are used to create hundreds of components for commercial aviation turbines? Search for the GE9X for more information if you’re skeptical.

Maybe you meant to discuss the utility of desktop FFF printers being limited to arts and prototyping, but the way it’s currently stated seems quite preposterous.

This is absolutely the most idiotic and dangerous thing I’ve ever seen on this site, and that’s a high bar.

Failure to point out the lethality of this project is irresponsible and represents vile incompetence by the author and editors here.

The regulations for pressure vessel design are extensive, each guideline crafted through experiences of fire, shrapnel, suffering, blood, and death.

Where are the 3D files for that hat that points all the shotgun shells towards your head?

Where can one find the instructions for creating a DIY suicide bag?

These methods are considered safer than others, as they solely affect the person who utilizes them.

“This ranks as the most reckless and hazardous thing I’ve encountered on this website, and that says a lot.”

Methods include printing a handgun or constructing a spot welder using a microwave oven transformer.

Have to chime in on this with a couple of things not mentioned yet:

1) Propane and butane are excellent solvents for solid hydrocarbons. While they may or may not dissolve the plastic used for this project they will almost certainly leach out at least some of the all pervasive plasticisers. Many plastics are extremely susceptible to solvent embrittlement for this reason.

2) many plastics suffer from cold embrittlement. What happens when propane is drawn off a tank whether on purpose or from a leak? It gets frosty cold.

3) shape is almost everything in a pressure vessel and at 200psi in the sun that thing will try to be a sphere any way it can.

4) someone trying this probably doesn’t know that you are only allowed to fill propane tanks to 80% capacity to begin with so you don’t get really big pressure changes from heat with a failed relief valve (hydraulic vs vapor pressure) most of the kids that fill my tanks don’t know…

and lastly … why? by the time you get the right plastic and make a valve and a relief (over pressure) valve that can hold up it will be heavier than the 1Lb, 7.5 Lb, 20 Lb tanks available (see SpaceX carbon fiber tanks).

I’m all for personal freedom, but please just don’t on this one

THANK you. I’m guessing even this bozo would know better than to soak a print in xylene or hexane and expect it to maintain its strength for long. Propane, compressed to a liquid, will attack nearly anything that hexane will.

This is the Titan submersible, but in reverse.

As others have said, a completely dumb idea.

Haven’t seen the clip (and won’t) but from the ~50€/l price tag on “Diamant Dichtol” I’m guessing the video was sponsored?

But aren’t the gases like methane, ethane, and propane often utilized as solvents for organic materials?

This is extremely useful. Are you familiar with ‘blow moulding’?

Create a shape, immerse it in warm water, and use air pressure to enlarge specific sections of the structure. This method is quite fascinating for manufacturing, allowing quick production of small items that can expand into larger forms, which saves on materials and perfectly fits certain spaces. See more at dl.acm.org/doi/10.1145/3544548.3580923

One should never take risks with pressure vessels. Personally, I would steer clear of experimenting with propane.

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