TPU and TPE: Printing with Flexible Filaments

TPU vs TPE (SEBS) Flexible Filaments: Practical Differences for FDM/FFF Printing
Attribute	TPU Flexible Filament (Example: 82A Grade)	TPE Flexible Filament (Example: SEBS Grade)	What It Changes in Real Prints
Polymer Family	Thermoplastic polyurethane (TPU)	Thermoplastic elastomer (TPE), SEBS-based	Naming matters: the chemistry influences grip, moisture behavior, outdoor durability, and tuning style.
Hardness (Shore)	82A (Shore A scale)	90A (Shore A scale)	Lower number usually feels softer and “rubberier”, but also tends to demand tighter filament guidance.
Typical Nozzle Temperature	~240 °C (0.4 mm nozzle baseline)	~245 °C (0.4 mm nozzle baseline)	Hot enough for stable flow, not so hot that you get excess oozing and stringing.
Bed Temperature Guidance	Small parts: room temp; large parts: ~45–50 °C	~70–80 °C	Bed strategy affects first-layer grip and how “squishy” the first layers stay during printing.
Volumetric Speed Starting Point	~3.2 mm³/s (0.4 mm nozzle baseline)	~5.0 mm³/s (0.4 mm nozzle baseline)	Flexible filaments reward controlled flow. Pushing too much volume too fast often turns into under-extrusion or surface wobble.
Retraction Starting Point	~1.5–3.0 mm @ ~40 mm/s (0.4 mm nozzle baseline)	~0.8–1.2 mm @ ~30 mm/s (0.4 mm nozzle baseline)	Retraction is a balancing act: reduce strings without pulling a stretchy filament into a messy zone.
Moisture Behavior (User-Facing)	Drying commonly recommended for consistent extrusion	Often marketed as more water-repellent / hydrophobic	Moisture shows up as popping, bubbles, and rough walls. Storage habits make or break repeatability.

The numeric values above are taken from publicly posted manufacturer print-parameter pages for the example grades (TPU example and SEBS example). Filaflex 82A [f] and Filaflex SEBS [g].

Flexible filaments look simple on the spool, then they humble you the first time they hit a Bowden tube. TPU and TPE are both thermoplastic elastomers, meaning they behave like rubber in your hand but still melt and solidify like standard FDM plastics. The big win is obvious: parts that bend, grip, damp vibrations, and survive repeated flexing. The real story is in the details—hardness, flow stability, friction, and pressure—because that is what decides whether your print is clean and predictable or just a spaghetti workout.

What Makes TPU and TPE Flexible

TPU vs TPE: Naming and Chemistry

Properties That Actually Matter

Printer Hardware and Filament Path

Slicer Settings: Speed, Flow, Retraction

Moisture, Drying, and Storage

Part Design for Flex Prints

FAQ

🧬 What Makes TPU and TPE Flexible

The Core Idea

A thermoplastic elastomer is an elastomer that functions through a thermoreversible network—it behaves elastically, yet can be melted and reshaped because the “network” can be reversed with heat. That is the formal backbone behind why these materials are printable in FDM/FFF form while still feeling rubbery in use. [a]

Elastic Recovery: How well the part returns to its original shape after bending or stretching. In prints, this is what makes phone grips, straps, bumpers, and gaskets feel “alive”.
Friction Behavior: Flexible filaments can have a high surface friction, so guidance and a smooth filament path matter more than with PLA or PETG.

Melt-Flow Stability: These materials are sensitive to pressure changes. Fast accelerations, sharp retractions, and inconsistent feeding show up as surface ripples or thin walls.
Indentation Hardness: Hardness is commonly communicated as Shore A for softer elastomers. That number is a practical language for “how soft does this feel?”. It is not strength.

🧪 TPU vs TPE: Naming and Chemistry

In polymer language, TPE is the umbrella term. It’s a category defined by composition-based nomenclature used across industry and standards work. [b] In the filament market, the labeling can feel looser: some brands call very soft grades “TPE” even when the backbone is still polyurethane-based, while others reserve TPE for non-urethane elastomers like SEBS.

🧩 If you want a mental model, use this: TPE is the family name, and TPU is one popular branch inside the “flexible thermoplastic” world.

Why TPU Feels Tunable

TPUs are commonly described through their soft and hard segments. By tuning segment chemistry and ratios, manufacturers can shift feel, elasticity, transparency, impact response, and resistance profiles. That “mix-and-match” nature is a big reason TPU shows up everywhere from stiff-ish 98A parts to ultra-soft specialty grades. [c]

📏 Properties That Actually Matter

Spec sheets can be long. For printing and part performance, a few properties do most of the work. Focus here and you will understand 90% of what you see on a spool label.

Shore Hardness: A quick “feel” metric. Softer filaments usually need tighter filament guidance and calmer pressure changes.
Elongation at Break: How far a material can stretch before it breaks. Useful for straps, clips, and parts that must flex repeatedly without cracking.
Tear Resistance: Important for thin gaskets, living hinges, and any part where a small nick might grow over time.
Abrasion Resistance: Matters for wheels, bumpers, cable guides, and any part rubbing against other parts.
Compression Set: How well a gasket “springs back” after being squashed for a long time.
Layer-to-Layer Bonding: Flexible parts often fail by layer peel if settings are too cold, too fast, or too dry/wet for that grade.

🧷 Hardness numbers are typically measured using durometer methods (commonly known as Shore hardness). The standard language behind that measurement is documented in formal test methods like ASTM D2240. [d]

🛠️ Printer Hardware and Filament Path

Flexible filament printing is less about “power” and more about control. You want a setup that keeps the filament guided, reduces friction, and prevents the strand from bulging sideways when the extruder pushes.

Direct Drive vs Bowden

Direct drive shortens the path, reduces filament compression, and usually makes soft grades easier.
Bowden can still work, especially with firmer flex grades and a clean, low-friction tube path.
Tighter guidance matters more than raw extrusion force.

The “Gap Problem”

One classic issue is a gap between the drive gears and the hotend entry. Flexible filament can buckle into that empty space and jam. The practical fix is simple: eliminate the gap, guide the filament continuously, and keep the path as straight as your machine allows. [h]

Nozzle and Hotend Notes

Small nozzles can increase internal pressure. Higher pressure amplifies feeding sensitivity on very soft filaments.
Stable cooling around the heatbreak helps prevent softening too high up the filament path.
Clean extrusion is easier when the filament enters the melt zone consistently, without oscillating pressure.

⚙️ Slicer Settings: Speed, Flow, Retraction

Flexible materials don’t love chaos. Sudden speed changes, aggressive retraction, and inconsistent flow show up instantly. The smoothest results come from a steady flow limit, calm accelerations, and retraction that is just enough.

TPU Printing Behavior (Relative Priorities)

Flow Stability

Retraction Sensitivity

Speed Tolerance

TPE (SEBS) Printing Behavior (Relative Priorities)

Flow Stability

Retraction Sensitivity

Speed Tolerance

Speed Strategy: Use volumetric limits when possible. It keeps flow consistent across different line widths and layer heights.
Acceleration and Jerk: Lower values reduce pressure spikes. You get smoother walls and fewer random thin spots.

Retraction Strategy: Start conservative. With flex filaments, too much retraction can pull stretchy material into the wrong place and destabilize the next extrusion.
Travel Strategy: Fast travels reduce the time the nozzle has to ooze, which can cut stringing without extreme retraction.

🧾 Concrete starting points exist, but they are grade-specific. For example, one TPU 82A profile recommends around 240 °C for a 0.4 mm nozzle with a volumetric limit near 3.2 mm³/s, and it lists retraction and bed guidance depending on part size. [f]

💧 Moisture, Drying, and Storage

Moisture is one of those issues that pretends to be “random printer behavior”. Then you dry the spool and suddenly the surface gets cleaner, the extrusion gets quieter, and dimensions stop drifting.

How Moisture Shows Up

Surface texture that looks foamy or pitted
Inconsistent line width even when your flow is calibrated
Extra stringing that doesn’t respond to normal retraction tuning
Occasional tiny bubbles in perimeters

🧊 Not all “flex” behaves the same. A SEBS-based TPE may be described as hydrophobic, while many TPU spools still benefit from deliberate drying and sealed storage. [g]

Drying Without Guesswork

Use manufacturer guidance for your exact grade. One example TPU flexible filament profile specifies drying at 55 °C for at least 1 hour before printing. [f]

For storage, airtight containers and fresh desiccant keep results repeatable. Flexible filaments are all about consistency; storage is part of the print setup.

📐 Part Design for Flex Prints

Flexible filaments can make parts that behave more like products than prototypes. Geometry decides how that flexibility is expressed: bend, stretch, compress, or damp.

Bending and Living Flex

Fillets reduce stress concentration where flexible parts change thickness.
Thin walls bend smoothly, but too thin can magnify layer peel if bonding is weak.
Layer direction matters: bending across layers is different than bending along layers.

Compression and Sealing

Use wider contact areas for gaskets; tiny contact lines can cut in and wear faster.
Avoid razor edges in snap features; flexible polymers can tear at sharp internal corners.
Test fit with the same infill and walls you will ship—compression feel changes with internal structure.

🧷 If you are comparing “softness”, remember the measurement context: Shore A is commonly used for softer elastomeric materials, and formal methods like ISO 868 describe how indentation hardness is determined by durometer. [e]

❓ FAQ

Is TPU the same thing as TPE in 3D printing?

In standards language, TPE is a category name, and TPU is one well-known type of flexible thermoplastic used in many applications. In the filament market, labels can be looser, so it helps to check the datasheet or the polymer family named by the manufacturer.

What is the single biggest hardware factor for printing very soft filaments?

Continuous filament guidance. If there is a gap after the drive gears, flexible filament can buckle sideways and jam. A well-guided path (often easier with direct drive) reduces random failures and makes tuning feel logical.

Why does retraction feel so touchy with TPU and TPE?

Because the filament stretches and compresses. Retraction can briefly “store” elastic energy in the filament path, then release it as a surge or a delay. That is why steady flow and modest retraction often outperform aggressive settings.

Do flexible filaments always need a heated bed?

Not always. Some TPU grades report strong bed adhesion even without heat for smaller parts, while other flexible materials and larger prints may benefit from a warm bed to stabilize the first layers. Follow the guidance for your specific grade and build surface.

What should I trust more: a “generic TPU profile” or the spool’s recommended parameters?

The spool or manufacturer profile. Flexible filaments vary widely by hardness, additives, and target printer systems. A generic profile is fine as a first move, but the fastest path to stable prints is starting from the grade-specific baseline and tuning from there.