TPU (thermoplastic polyurethane) is the most widely used flexible 3D printing filament. It prints reliably on most desktop printers, resists abrasion and tearing, and comes in a range of softness levels from semi-rigid to rubber-like. Other flexible options exist, including TPC and flexible PLA, but TPU is the standard choice for most projects that need to bend, stretch, or compress.
Types of Flexible Filament
All flexible filaments fall under a broad category called TPE, or thermoplastic elastomer. TPE is not a single material but a family of plastics that blend rigid and elastic properties. The three you’ll encounter most often are TPU, TPC, and flexible PLA, and they differ in meaningful ways.
TPU is the go-to for most flexible prints. It has excellent abrasion resistance, high tensile strength, and true rubber-like elasticity. It bounces back after being stretched or compressed, holds up under repetitive stress, and tolerates environmental exposure well. Phone cases, shoe insoles, drone bumpers, and custom gaskets are all common TPU prints.
TPC (thermoplastic copolyester) is a polyester-based flexible filament with good chemical resistance and toughness. It shows up in automotive and medical applications but is far less common on consumer 3D printers. If you have a specific engineering need for chemical resistance, TPC is worth investigating, but for general-purpose flexibility, TPU is more accessible and better supported.
Flexible PLA is standard PLA modified to bend instead of snap. It springs back to its original shape under pressure and absorbs vibrations and impacts, but it can’t stretch nearly as far as TPU before breaking. It has a Shore hardness around 90A, placing it on the stiffer end of the flexible spectrum. It’s also vulnerable to heat and UV light, with a lower glass transition temperature than even standard PLA. A flexible PLA part left in the sun on a hot day can deform or fail entirely. The upside: it sands easily, supports come off cleanly, and post-processing is straightforward. TPU supports are notoriously difficult to remove and the material can’t be sanded.
Understanding Shore Hardness
Flexible filaments are rated on the Shore hardness scale, which tells you how soft or rigid the material is. Two scales matter here: Shore A (for softer materials) and Shore D (for harder ones). Both run from 0 to 100, with lower numbers meaning softer. A material rated 100A is roughly equivalent to 60D, so the scales overlap in the middle.
For practical purposes, here’s what the numbers mean for filament selection:
- Shore A 60–90: Very flexible. These filaments feel genuinely rubbery and work for applications where bending and compression are the whole point, like seals, wearable straps, or soft grips.
- Shore D 30–50: Semi-flexible. These offer some give while maintaining enough structure for parts that need to hold a shape, like hinges or protective bumpers.
- Shore D 50–70: Rigid. These barely flex at all and overlap with standard hard plastics.
The softer the filament, the harder it is to print. A 60D or 40D filament prints on most direct drive extruders without fuss. A 30D or 60A filament needs a more constrained filament path to prevent the material from buckling and jamming. If you’re new to flexible printing, start with something in the 95A to 85A range before attempting the really soft stuff.
What Flexible Filament Is Used For
The practical applications break into a few categories. Protective parts like bumpers, padding, and shock absorbers take advantage of flexible filament’s ability to absorb impact. Functional seals and gaskets rely on its ability to compress and conform to surfaces. Wearables like watch straps, orthotics, and prosthetic liners need materials that flex with the body without cracking.
On the hobbyist side, TPU is popular for drone landing gear, RC car tires, custom phone cases, grip covers for tools, and vibration dampeners for electronics. Any part that would traditionally be injection-molded in rubber is a candidate for flexible filament printing.
Printer Hardware: Direct Drive vs. Bowden
Your extruder type matters more for flexible filament than for any other material. A direct drive extruder mounts the motor right above the hot end, giving it tight control over filament feeding. A Bowden extruder sits farther away and pushes filament through a long tube to reach the hot end.
Direct drive is strongly preferred for flexible filaments. The short distance between the drive gear and the nozzle gives the filament less room to stretch, compress, or buckle. Retraction control is also significantly better, which means cleaner prints with less stringing and oozing.
Bowden setups can technically print flexible filament, but the experience is frustrating. The filament tends to bunch up inside the tube, especially softer varieties. When the extruder tries to retract, the slack in the long tube means the filament just wiggles around rather than pulling back cleanly. The softer the filament, the worse the problem gets. If your printer has a Bowden setup and you only plan to print semi-flexible materials (95A or stiffer), you may get acceptable results. For anything softer, a direct drive upgrade or a different printer is worth considering.
Print Settings for Flexible Filament
TPU prints at nozzle temperatures between 225°C and 250°C, with bed temperatures of 40–60°C. Always check the specific recommendations on your filament spool, as different brands and hardness levels vary.
Speed is where flexible filament diverges most from rigid materials. Print slowly: 15–40 mm/s, with 25 mm/s being a reliable starting point. Softer filaments (85A and below) do best at the low end of that range, around 15–25 mm/s. Pushing the speed too high causes the filament to buckle in the extruder, leading to jams.
Retraction needs to be minimal. Keep retraction distance between 0 and 2 mm at a speed of about 20–30 mm/s. Too much retraction compresses and clogs the filament. Too little causes stringing. Finding the sweet spot takes some test prints, but starting at 1 mm of retraction and adjusting from there is a reasonable approach. Dry your filament before printing, as moisture makes clogging significantly worse.
Bed Adhesion and Part Removal
Flexible filaments stick well to build plates, sometimes too well. Certain bed surfaces can bond permanently to the material, making removal impossible without damaging the print or the bed. Blue painter’s tape is one of the safest options. A heated glass bed with a thin layer of PVA glue stick also works reliably.
If you’re using painter’s tape, keep bed temperature between 55°C and 65°C. Going higher can make the tape fuse to the print. If your first layer isn’t sticking, check that your nozzle is close enough to the bed to produce a visibly squished line of filament. A light application of glue stick on glass adds just enough grip without making the part impossible to pop off once it cools.
The general rule: you want enough adhesion to keep the print in place during the job, but not so much that removal becomes destructive. PVA glue stick on glass gives you that balance for most flexible materials.