If you’ve ever printed with flexible filaments, you know the struggle: stringing, filament entanglement, poor bridging and overhangs, ugly surface finish, jams and extrusion problems,… the list goes on. Many of these headaches stem from a notoriously difficult challenge: achieving a truly consistent diameter with flexible filament.

We spent a considerable amount of time on the development of Prusament TPU 95A – maybe even more than we would have expected. But we wanted to do it right and bring something new to the market. And we eventually made a breakthrough: we’re now introducing filament like no other on the market. So let’s give it a proper introduction! In the first half of this article, we’ll talk about the Prusament TPU 95A specifications and in the other half, we’ll sum up the properties of TPU in general. And in the last chapter, we’ll have a closer look at technical specifications, because some of those may sound a little bit strange if taken out of context.

Precise and consistent diameter

Let’s start with our greatest achievement. TPU (in general) is hard to manufacture while maintaining a precise and consistent diameter. Most manufacturers don’t consider this issue and simply sell their filaments with significantly varying diameters. And, as usual, we didn’t like it and decided to work on it. So, after long and tedious testing, we found a way to make the filament with the precision you know from other Prusament. Here’s how it works:

After manufacturing the filament, TPU undergoes a relaxation process, where the polymer reshapes to a more energy-efficient state. During this process, which takes approximately one day, the filament slightly changes its diameter, and it’s really difficult to find the sweet spot, where the filament ends up evenly thick with a 1.75mm diameter.

Again, most manufacturers don’t consider this issue. The diameter is within tolerance at the time of manufacturing, but it’s not obvious that by the time you package it and ship it to the customer, the diameter has significantly changed. This results in a higher risk of filament clogging and uneven distribution during printing.

So, how did we deal with this issue? Without revealing too much of our R&D, we are artificially creating the filament with an offset diameter, which dynamically changes as the spool gets fuller. Once the spool is manufactured, the filament then changes to our desired target dimensions. We can proudly say that our TPU is truly 1.75 mm in diameter; however, for maximum transparency, we’re stating 0.06 mm as the highest tolerance. As always, you can check each individual spool for manufacturing data and see for yourself.

Prusa Air Blower

Easy printability: No idler tweaking and flawless printing with the Nextruder!

We worked on several factors that make printing of Prusament TPU 95A as easy as it could be: first, there’s the precise diameter. Second, there’s a chemical modification of the polymer, which, in its final state, is harder to deform. This prevents filament from being entangled in the extruder gears. Third, the Nextruder (MK4/S, Core One, XL) is built in a way that makes printing soft filaments easier than ever: the flexible filaments in general tend to fail less, and in this combination, the Prusament TPU 95A becomes one of the most reliable flex filaments you can get. And finally, the filament guide (part of the Original Prusa 3D printer kit) creates a slight tension, which helps with more reliable feeding to the Nextruder.

Improved mechanical resistance

The Prusament TPU 95A polymer structure (ether diol type) slightly differs from most TPU filaments (ester diol type). This difference gives this material some advantages in both mechanical and chemical resistance. Prusament TPU 95A offers very low moisture absorption and high hydrolysis resistance*. Its high elasticity and impact resistance remain even at low temperatures (as low as -50 °C). Finally, this material is resistant to microbial degradation, comes with good temperature resistance (HDT 78.6 °C at 1.80 MPa), and great chemical resistance (mostly to oil and grease).

*Ether type of TPU (Prusament 95A) is more stable and doesn’t degrade as much as the ester type when exposed to steam or hot water.

Prusament TPU 95A specifications

Pros
	Soft and bendable at thin layers, strong and durable at thick layers
	High print reliability with little to no stringing
	Precise diameter
	Good at printing bridges and overhangs (compared with other TPUs)
	Great wear resistance
	Flexible and durable at sub-zero temperatures
	High resistance to hydrolysis and microbial degradation
	Very low moisture absorption

Cons
	Some extra tweaking before printing may be required (depending on your printer)
	Printing with a smooth sheet requires a separation layer
	Drying may be necessary when stored in high-moisture conditions
	Large prints tend to warp

Material color, weight and price

So far, you can get the Prusament TPU 95A in one color: natural. This is a warm white/creamy color that resembles Prusament PLA Vanilla White. Plus, we are preparing more colors, so stay tuned. For now, one 500g spool of Prusament TPU 95A Natural costs 34.99 USD / 38.99 EUR (VAT incl.).

Prusa Pneu (LEGO compatible)

Recommended printer settings

The most amazing thing is that you don’t have to make any special preparations when printing using the Nextruder. No idler tweaking, no drying, or whatsoever. Still, even with this improved filament, you might occasionally encounter minor struggles, just like with PLA. For these scenarios, we made an article on Prusa online help, which covers the whole printing guide and troubleshooting of Prusament TPU 95A. Don’t forget to read it before printing. Also, you can check the Material Table, where you’ll find the most crucial parameters, such as suitable print sheets. In any case, here’s the basic overview:

Supported PrusaSlicer profiles: Core One, XL, MK4S, MK4, Prusa Pro HT90

Nozzle temperature: 220-240 °C

Heatbed temperature: 55-75 °C

Recommended print sheets: Satin and PA Nylon

Drying before printing: not necessary (only when issues like stringing or nozzle clogging occur)

Best use

Finally, here are a few tips for the best use. Obviously, the main advantage is the material’s rubber-like properties. In general, people tend to print soft and bendable objects with such filaments. And why not? When printed with little infill, the models can get very soft (especially with gyroid infill). However, we’d like to remind you of the high wear resistance of TPU materials. With 100% infill and in thick layers, the material gets virtually indestructible. The high mechanical resistance can be quite usable for really demanding industrial applications, for example, printing some spacers for heavy machinery, etc. One particularly cool thing is the interlocking infill option in PrusaSlicer. When printing on the multitool version of XL, this infill will make a very strong connection between the flexible and rigid parts.

Various straps and bendable parts	Durable grips (Prusa Bow Grip)
Sharp edge covers: TPU 95A’s high wear resistance is great for covering skis, skates, etc.	Cable protector by Michal Fanta: another good use case for showing high mechanical resistance
Custom RC car tires by Prusa3D and Anton	Protective phone cases by Antony and SHOT
Door stopper by Steve	Cleaning air blower (Prusa Air Blower)
Various haptic models and massage tools: Soft touch knobs by Rorys3D, massage tools by Anze and a69291954, fidget toy by Prusa Polymers	Durable replacement parts: Puntas de sifon de acuario by Fidelio

What is TPU?

Want to dig deeper into the material’s specifics? We have the details! TPU, as the base polymer used for making our new Prusament, is one of the most common types of flexible materials used in 3D printing. Plus, this whole family is a part of a much larger group of flexible materials called TPE (thermoplastic elastomers). TPU itself is a block copolymer containing both hard (polyurethane) and soft (polyol) segments. Apart from elasticity, the material is also known for its resistance to impact, abrasion, oil, and grease. For its desirable properties, it is used for making parts in the automotive industry, power tools, medical devices, electronic device outer cases, and generally everywhere, where high wear and impact resistance are a must.

Schematic illustration of the a) TPU polymer chain components and b) their phase structure. Source: Thermoplastic polyurethanes: synthesis, fabrication techniques, blends, composites, and applications – Scientific Figure on ResearchGate.

TPU has quite easy printability, lower moisture absorption, and doesn’t warp as much as some other TPE materials. Plus, it adheres to the PEI print surface very well (too well, to be honest): see our material guide to learn more.

Although most hobby users use TPU for its flexible properties, some forget that it has exceptional wear resistance. When printed in thick layers, the material becomes less flexible and virtually indestructible. It can be used for many things that would otherwise irreversibly deform or even break.

Shore hardness

The shore hardness is a value that every filament manufacturer provides to describe its hardness, or softness, to be specific (in our case, it’s 95A). This is a parameter measured by a device called a shore durometer. It tells how soft (or hard) the material is by measuring the depth of indentation created by a metallic pin pushed against the material with a given force.

The shore hardness can be measured on several scales, but in this case, we use the Shore Hardness A. In the A scale, the values range from 0 to 100, where some of the softest materials are rubber bands (20A) and the hardest are materials like skateboard wheels (90-100A).

The 3D printing filaments are usually on the harder side of the shore A spectrum (mostly somewhere between 85 and 100), as the harder materials are easier to print. Generally, the softer the filament is, the easier it is to entangle in the extruder gears.

Shore Hardness scale. Source: Smooth-On

On the whole scale, our TPU is quite a hard material, but among flexible filaments, it’s somewhere in the middle. Prusament TPU 95A is very soft and bendable in thin layers and very hard and durable in thick layers (with solid infill).

Mechanical properties

One last thing: we feel that it might be worth explaining some basic technical parameters you may find in the technical datasheet. After all, some parameters are impossible to measure (Charpy impact resistance at room temperature, for example), some test methods differ from tough filaments and there are few values specific for flexible materials.

Charpy impact resistance: Not applicable as TPU doesn’t break at room temperature.

Tensile strength: Maximum tensile strength and maximum elongation are used, according to ISO 37, specific for rubber materials.

Heat Deflection Temperature: 0.45 MPa values were not used, instead, Vicat Softening Point A was added (ISO 306).

Shore hardness: The measured hardness is around 93A, due to chemical modification used during the manufacturing process and due to the air cavities in the 3D printed test objects. We measured the Shore D hardness for the comparison as well.

Compression Set under Constant Deflection [%]: This is a tricky value to comprehend. It may seem like the object gets deformed by dozens of %. But how does it work really? The test object is squeezed by 10 % under certain conditions (time and temperature). Then, we let the model relax and then measure the difference in dimensions. So, when there’s 33.5 % deformation in the datasheet, it simply can’t be 33.5 % of the whole test object. Instead, the 33.5 % is calculated from 10 % of it. Here’s an example: (hypothetical) test object has 10 mm and gets squeezed by 10 % to 9 mm. After relaxation, the object dimension is 9.665 mm. The 33.5 % represents the 0.335 mm when related to the 10 % (1 mm). It’s as easy as that. 😊

Fidget toy by Prusa Polymers

That was a lot of technical details – hope you found it useful! It might be easy to say, „What’s the big deal? It’s just another TPU, “ but as you can see, even with something as basic as TPU, you can do a lot of things to make it truly amazing. So, how do you like our new Prusament? Don’t forget to let us know in the comments.

Happy printing!