Why Can’t I 3D Print With Rubber?

December 31, 2025 by Jenny List 13 Comments

A friend of mine and I both have a similar project in mind, the manufacture of custom footwear with our hackerspace’s shiny new multi-material 3D printer. It seems like a match made in heaven, a machine that can seamlessly integrate components made with widely differing materials into a complex three-dimensional structure. As is so often the case though, there are limits to what can be done with the tool in hand, and here I’ve met one of them.

I can’t get a good range of footwear for my significantly oversized feet, and I want a set of extra grippy soles for a particular sporting application. For that the best material is a rubber, yet the types of rubber that are best for the job can unfortunately not be 3D printed. In understanding why that is the case I’ve followed a fascinating path which has taught me stuff about 3D printing that I certainly didn’t know.

The extruder unit from a Prusa Mini 3D printer — Newton strikes back, and I can’t force rubber through this thing.

A friend of mine from way back is a petrochemist, so I asked him about the melting points of various rubbers to see if I could find an appropriate filament His answer, predictably, was that it’s not that simple, because rubbers don’t behave in the same way as the polymers I am used to. With a conventional 3D printer filament, as the polymer is fed into the extruder and heated up, it turns to liquid and flows out of the nozzle to the print. It ‘s then hot enough to fuse with the layer below as it solidifies, which is how our 3D prints retain their shape. This property is where we get the term “plastic” from, which loosely means “Able to be moulded”.

My problem is that rubber doesn’t behave that way. As any casual glance at a motor vehicle will tell you, rubber can be moulded, but it doesn’t neatly liquefy and flow in the way my PLA or PET does. It’s a non-Newtonian fluid, a term which I was familiar with from such things as non-drip paint, tomato ketchup, or oobleck, but had never as an electronic engineer directly encountered in something I am working on. Continue reading “Why Can’t I 3D Print With Rubber?” →

Blocky tread, yellow hub-- yep, it looks like LEGO

10″ LEGO Tyre Is Practical Nostalgia

September 29, 2025 by Tyler August 6 Comments

If there’s one thing that has come to define the generations after the baby boom, it’s probably nostalgia. It’s heavily marketed and weaponized by the market: yearning for better, simpler times seems to be a core thread of the consumer economy these days. [Makerneer] combined his xilennial love of LEGO bricks with the flat tires on his log splitter to produce a 10″ TPU tyre will never go flat, and provide a dopamine release every time he sees it.

The tyre is a custom model to fit his particular rims, but he does provide STEP and F3D files if you’d like to try modifing it for your own purpose — they’re at Step 6 of the Instructable. Props to [Makerneer] for truly open-sourcing the design instead of just tossing STL files online. His build log also takes the time to point out the ways he had to modify the LEGO tyre profile to make it amenable to 3D printing: notably chamfering some of the tread pattern to eliminate bridging, which is a bit of a no-no with TPU.

As you can see in the (unfortunately vertical) demo video below, it’s a bit quite a bit squishier than a regular run-flat tyre, but that was part of [Makerneer]’s design goal. He didn’t like how rigid the non-pneumatic tyres he’d tried were, so endevoured to design something himself; the whole LEGO thing was just for fun. If you wanted to replicate this tyre with a bit less skoosh, you need only tune the infill on your print.

While only time will tell how long this LEGO-inspired add-on will continue adding whimsy to [Makerneer]’s log-splitting, we have tests to show it will outperform any other plastic he might have printed. This project is probably more practical than a 3D printed bicycle tyre, which doesn’t even have the side benefit of whimsy. Continue reading “10″ LEGO Tyre Is Practical Nostalgia” →

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.

Nylon-Like TPU Filament: Testing CC3D’s 72D TPU

July 22, 2025 by Maya Posch 8 Comments

Another entry in the world of interesting FDM filaments comes courtesy of CC3D with their 72D TPU filament, with [Dr. Igor Gaspar] putting it to the test in his recent video. The use of the Shore hardness D scale rather than the typical A scale is a strong indication that something is different about this TPU. The manufacturer claims ‘nylon-like’ performance, which should give this TPU filament much more hardness and resistance to abrasion. The questions are whether this filament lives up to these promises, and whether it is at all fun to print with.

The CC3D 72D TPU filament used to print a bicycle's handlebar. (Credit: My Tech Fun, YouTube) — The CC3D 72D TPU filament used to print a bicycle’s handlebar grips. (Credit: My Tech Fun, YouTube)

TPU is of course highly hydrophilic, so keeping the filament away from moisture is essential. Printing temperature is listed on the spool as 225 – 245°C, and the filament is very bendable but not stretchable. For the testing a Bambu Lab X-1 Carbon was used, with the filament directly loaded from the filament dryer. After an overnight print session resulted in spaghetti due to warping, it was found that generic TPU settings at 240ºC with some more nylon-specific tweaks seemed to give the best results, with other FDM printers also working well that way.

The comparison was against Bambu Lab’s 68D TPU for AMS. Most noticeable is that the 72D TPU easily suffers permanent deformation, while being much more wear resistant than e.g. PLA. That said, it does indeed seem to perform more like polyamide filaments, making it perhaps an interesting alternative there. Although there’s some confusion about whether this TPU filament has polyamide added to it, it seems to be pure TPU, just like the Bambu Lab 68D filament.

Continue reading “Nylon-Like TPU Filament: Testing CC3D’s 72D TPU” →

3D Filament lizards show decomposable joints

Sustainable 3D Prints With Decomposable Filaments

May 30, 2025 by Heidi Ulrich 24 Comments

What if you could design your 3D print to fall apart on purpose? That’s the curious promise of a new paper from CHI 2025, which brings a serious hacker vibe to the sustainability problem of multi-material 3D printing. Titled Enabling Recycling of Multi-Material 3D Printed Objects through Computational Design and Disassembly by Dissolution, it proposes a technique that lets complex prints disassemble themselves via water-soluble seams. Just a bit of H₂O is needed, no drills or pliers.

At its core, this method builds dissolvable interfaces between materials like PLA and TPU using water-soluble PVA. Their algorithm auto-generates jointed seams (think shrink-wrap meets mushroom pegs) that don’t interfere with the part’s function. Once printed, the object behaves like any ordinary 3D creation. But at end-of-life, a water bath breaks it down into clean, separable materials, ready for recycling. That gives 90% material recovery, and over 50% reduction in carbon emissions.

This is the research – call it a very, very well documented hack – we need more of. It’s climate-conscious and machine-savvy. If you’re into computational fabrication or environmental tinkering, it’s worth your time. Hats off to [Wen, Bae, and Rivera] for turning what might otherwise be considered a failure into a feature.

Continue reading “Sustainable 3D Prints With Decomposable Filaments” →

3D Printed TPU Bellows With PLA Interface Layers

May 8, 2025 by Maya Posch 24 Comments

Of all FDM filament types, flexible ones such as TPU invite a whole new way of thinking, as well as applications. Case in point the TPU-based bellows that the [Functional Part Friday] channel on YouTube recently demonstrated.

The idea is quite straightforward: you print TPU and PLA in alternating layers, making sure that the TPU is connected to its previous layer in an alternating fashion. After printing, you peel the PLA and TPU apart, remove the PLA layers and presto, you got yourself bellows.

There were some issues along the way, of course. Case in point the differences between TPU from different brands (Sainsmart, Sunlu) that caused some headaches, and most of all the incompatibility between the Bambu Lab AMS and TPU that led to incredibly brittle TPU prints. This required bypassing the feed mechanism in the AMS, which subsequently went down a rabbit hole of preventing the PTFE tube from getting sucked into the AMS. Being able to print TPU & PLA at the same time also requires a printer with two independent extruders like the Bambu Lab H2D used here, as both materials do not mix in any way. Great news for H2D and IDEX printer owners, of course.

As for practical applications for bellows, beyond printing your own 1900s-era camera, accordion or hand air bellows, you can also create lathe way covers and so on.

Continue reading “3D Printed TPU Bellows With PLA Interface Layers” →

Bar of conductive filament with leds and a battery

Putting Conductive TPU To The Test

March 15, 2025 by Heidi Ulrich 3 Comments

Ever pried apart an LCD? If so, you’ve likely stumbled at the unassuming zebra strip — the pliable connector that makes bridging PCB pads to glass traces look effortless. [Chuck] recently set out to test if he could hack together his own zebra strip using conductive TPU and a 3D printer.

[Chuck] started by printing alternating bands of conductive and non-conductive TPU, aiming to mimic the compressible, striped conductor. Despite careful tuning and slow prints, the results were mixed to say the least. The conductive TPU measured a whopping 16 megaohms, barely touching the definition of conductivity! LEDs stayed dark, multimeters sulked, and frustration mounted. Not one to give up, [Chuck] took to his trusty Proto-pasta conductive PLA, and got bright, blinky success. It left no room for flexibility, though.

It would appear that conductive TPU still isn’t quite ready for prime time in fine-pitch interconnects. But if you find a better filament – or fancy prototyping your own zebra strip – jump in! We’d love to hear about your attempts in the comments.

Continue reading “Putting Conductive TPU To The Test” →