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Flexible TPU filament

Rubbery, wear-resistant and impact-resistant: for prints that need to bend, damp or grip.

With flexible filament you print parts that bend and spring back, such as seals, grips, phone cases and shock absorbers. We stock Fiberlogy’s flexible filament: FiberFlex in two hardnesses, 30D and 40D, MattFlex 40D with a matte finish, and FiberFlex Aero, which foams during printing for extra-light prints. Which hardness suits your project and your printer? Below the products we explain. Read more…

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What is flexible filament?

Flexible filament is a thermoplastic elastomer, usually TPU (thermoplastic polyurethane). It combines the properties of rubber with those of plastic: a print bends and springs back into shape, yet is also wear-resistant, impact-resistant and resistant to oil, grease and low temperatures. That makes it suitable for parts that need to give, damp or provide grip.

30D or 40D: which hardness should you choose?

The hardness of flexible filament is expressed on the Shore scale. The lower the number, the softer the material.

TypeHardnessSuitable for
FiberFlex 30DSoft, comparable to a shoe soleVery elastic prints that need to bend a lot. Print it with a direct drive extruder and at low speed.
FiberFlex 40DFirmer, comparable to skateboard wheelsParts that need to give but keep their shape. Easier to print, also on a Bowden printer.
MattFlex 40DLike FiberFlex 40DThe same properties with a matte finish on which layer lines are barely visible.
FiberFlex AeroAdjustableLight, foaming prints: temperature, speed and flow let you set the density and hardness yourself.

Not sure? Start with FiberFlex 40D: it is the easiest to print and flexible enough for most uses.

FiberFlex Aero: foaming and light

FiberFlex Aero contains a foaming agent that is activated at a higher nozzle temperature (around 230–235 °C). By adjusting temperature, speed and flow, you print anything from compact and firm to very light and porous. Ideal for RC models, drones, soles and shock absorbers. Read more in our article on FiberFlex Aero.

Printing flexible filament: the right settings

  • Nozzle: FiberFlex and MattFlex 200–220 °C, FiberFlex Aero 200–240 °C.
  • Print bed: 50–70 °C, FiberFlex Aero 70–80 °C.
  • Speed: low. FiberFlex 40D prints at up to around 45 mm/s with a direct drive extruder, 15–30 mm/s with a Bowden setup. Go a little lower for 30D.
  • Extruder: a direct drive extruder works best, because soft filament can buckle or bunch up in a long Bowden tube.
  • Retraction: short and slow, or off altogether. Too much retraction can jam the filament in the extruder.
  • Print dry: TPU absorbs moisture. Damp filament causes bubbles, stringing and a rough surface.

The exact temperatures are listed with each product. Something going wrong? Our article on solving 3D printing problems covers the most common problems and how to fix them.

The pros and cons of flexible filament at a glance

Pros

  • Bends and springs back into shape
  • Very wear-resistant and impact-resistant
  • Resistant to oil, grease and low temperatures
  • Excellent bonding between layers
  • Damps vibration and provides grip

Cons

  • Slower to print than PLA or PETG
  • Works best with a direct drive extruder
  • Absorbs moisture, so store it dry
  • Support material is harder to remove

Uses of flexible filament

  • Seals and gaskets: rings, caps and dust covers.
  • Grip and protection: handles, phone cases, bumpers and feet.
  • Dampers: vibration dampers, bumpers and parts for drones and RC models.
  • Wearables: watch straps, soles and cosplay parts.
  • Engineering: belts, hoses and flexible couplings.

Frequently asked questions

  • What do 30D and 40D mean?

    That is the hardness on the Shore D scale. FiberFlex 30D is softer and more elastic, comparable to a shoe sole. FiberFlex 40D is firmer, comparable to skateboard wheels, and easier to print. For most uses 40D is the best choice.

  • Can I print flexible filament on a Bowden printer?

    Yes, but then choose FiberFlex 40D or MattFlex 40D and print slowly, around 15–30 mm/s. Soft filament can buckle in a long Bowden tube, so we only recommend 30D for printers with a direct drive extruder.

  • Is TPU the same as flexible filament?

    Almost. Flexible filament is an umbrella term for elastic filaments; TPU (thermoplastic polyurethane) is by far the most common type. Fiberlogy FiberFlex and MattFlex are flexible filaments from that family.

  • How do I stop flexible filament from jamming?

    Print slowly, set retraction low or off, and make sure the filament path between the extruder gears and the hotend is closed off, so the soft filament has nowhere to escape. Dry filament and a slightly higher temperature also help.

  • What is FiberFlex Aero?

    A foaming flexible filament. At a nozzle temperature of around 230–235 °C it expands, making prints much lighter. With temperature, speed and flow you decide how light and soft the result becomes. Read more in our article on FiberFlex Aero.

  • Do I need to dry flexible filament?

    Yes, TPU absorbs moisture from the air. If you hear crackling while printing or see bubbles and a lot of stringing, dry the filament for 4–6 hours at around 50–55 °C in a filament dryer. Store spools sealed with silica gel beads.