On The Benefits Of Filling 3D Prints With Spray Foam

November 29, 2025 by Maya Posch 41 Comments

Closed-cell self-expanding foam (spray foam) is an amazing material that sees common use in construction. But one application that we hadn’t heard of before was using it to fill the internal voids of 3D printed objects. As argued by [Alex] in a half-baked-research YouTube video, this foam could be very helpful with making sure that printed boats keep floating and water stays out of sensitive electronic bits.

It’s pretty common knowledge by now that 3D printed objects from FDM printers aren’t really watertight. Due to the way that these printers work, there’s plenty of opportunity for small gaps and voids between layers to permit moisture to seep through. This is where the use of this self-expanding foam comes into play, as it’s guaranteed to be watertight. In addition, [Alex] also tests how this affects the strength of the print and using its insulating properties.

The test prints are designed with the requisite port through which the spray foam is injected as well as pressure relief holes. After a 24 hour curing period the excess foam is trimmed. Early testing showed that in order for the foam to cure well inside the part, it needed to be first flushed with water to provide the moisture necessary for the chemical reaction. It’s also essential to have sufficient pressure relief holes, especially for the larger parts, as the expanding foam can cause structural failure.

As for the results, in terms of waterproofing there was some water absorption, likely in the PETG part. But after 28 hours of submerging none of the sample cubes filled up with water. The samples did not get any stronger tensile-wise, but the compression test showed a 25 – 70% increase in resistance to buckling, which is quite significant.

Finally, after tossing some ice cubes into a plain FDM printed box and one filled with foam, it took less than six hours for the ice to melt, compared to the spray foam insulated box which took just under eight hours.

This seems to suggest that adding some of this self-expanding foam to your 3D printed part makes a lot of sense if you want to keep water out, add more compressive strength, or would like to add thermal insulation beyond what FDM infill patterns can provide.

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Does It Make Sense To Upgrade A Prusa MK4S To A Core One?

August 30, 2025 by Maya Posch 7 Comments

One of the interesting things about Prusa’s FDM 3D printers is the availability of official upgrade kits, which allow you to combine bits off an older machine with those of the target machine to ideally save some money and not have an old machine gathering dust after the upgrade. While for a bedslinger-to-bedslinger upgrade this can make a lot of sense, the bedslinger to CoreXY Core One upgrade path is a bit more drastic. Recently the [Aurora Tech] channel had a look at which upgrade path makes the most sense, and in which scenario.

A big part of the comparison is the time and money spent compared to the print result, as you have effectively four options. Either you stick with the MK4S, get the DIY Core One (~8 hours of assembly time), get the pre-assembled Core One (more $$), or get the upgrade kit (also ~8 hours). There’s also the fifth option of getting the enclosure for the MK4S, but it costs about as much as the upgrade kit, so that doesn’t make a lot of logical sense.

In terms of print quality, it’s undeniable that the CoreXY motion system provides better results, with less ringing and better quality with tall prints, but unless you’re printing more than basic PLA and PETG, or care a lot about the faster print speeds of the CoreXY machine with large prints, the fully enclosed Core One is a bit overkill and sticking with the bedslinger may be the better choice.

The long and short of it is that you have look at each option and consider what works best for your needs and your wallet.

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PVDF: The Specialized Filament For Chemical And Moisture Resistance

August 28, 2025 by Maya Posch 18 Comments

There’s a dizzying number of specialist 3D printing materials out there, some of which do try to offer an alternative to PLA, PA6, ABS, etc., while others are happy to stay in their own niche. Polyvinylidene fluoride (PVDF) is one of these materials, with the [My Tech Fun] YouTube channel recently getting sent a spool of PVDF for testing, which retails for a cool $188.

Some of the build plate carnage observed after printing with PVDF. (Credit: My Tech Fun, YouTube)

Reading the specifications and datasheet for the filament over at the manufacturer’s website it’s pretty clear what the selling points are for this material are. For the chemists in the audience the addition of fluoride is probably a dead giveaway, as fluoride bonds in a material tend to be very stable. Hence PVDF ((C₂H₂F₂)_n) sees use in applications where strong resistance to aggressive chemicals as well as hydrolysis are a requirement, not to mention no hygroscopic inclinations, somewhat like PTFE and kin.

In the video’s mechanical testing it was therefore unsurprising that other than abrasion resistance it’s overall worse and more brittle than PA6 (nylon). It was also found that printing this material with two different FDM printers with the required bed temperature of 110°C was somewhat rough, with some warping and a wrecked engineering build plate in the Bambu Lab printer due to what appears to be an interaction with the usual glue stick material. Once you get the print settings dialed in it’s not too complicated, but it’s definitely not a filament for casual use.

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MorPhlex: The TPU Filament That Goes Soft After You Print It

August 16, 2025 by Maya Posch 7 Comments

In FDM 3D printing cycles TPU is a bit of a special filament. Not so much because of its properties, but because it’s rather stretchy even as a filament, which makes especially printing certain hardness grades of TPU into somewhat of an nightmare. An interesting new contender here comes from a company called BIQU, who reckon that their ‘MorPhlex’ TPU solves many of those problems. Recently the [ModBot] channel on YouTube got sent a spool of the filament for testing.

The BIQU MorPhlex TPU filament being turned into squishy slippers. (Credit: ModBot, YouTube)

The ‘magic’ here is that this TPU claims to be a 90A TPU grade while on the spool, but after printing it becomes 75A, meaning a lot softer and squishier. Perhaps unsurprisingly, a big selling point on their product page is that you can print squishy shoes with it. Beyond this is claims to be compatible with ‘most FDM printers’, and the listed printing parameters are typical for TPU in terms of extruder and bed temperature.

After drying the filament as recommended for TPU in general, test prints were printed on a Bambu Lab H2D. Here BIQU recommends not using the AMS, but rather the dedicated TPU feeding channel. For the test prints some slippers were printed over the course of two days. In hindsight glue stick should have been applied to make parts removal easier.

The slippers were indeed squishy, but the real test came in the form of a Shore A hardness meter and some test cube prints. This showed an 80 – 85A for the BIQU MorPhlex test cube depending on whether to test the side or top. As the product datasheet indicates a final hardness of 75A +/- 3A, one could argue that it’s kind-of in spec, but it mostly raises questions on how parameters like temperature and extrusion speed affect the final result.