TPU and Flexible Filament Guide - Printing Rubber-Like Parts

TPU (thermoplastic polyurethane) prints rubber-like parts. It’s incredibly useful—and incredibly frustrating to print. This guide explains why and how to succeed.

Why Flexible Filament is Different

Material property: TPU doesn’t become rigid like PLA. It stays flexible (like rubber).

This changes everything:

• Standard extrusion principles partially fail
• Cooling behavior is different
• Support removal is easier (flexible bends away)
• Print speed must be dramatically lower
• Settings are different from all other materials

Real comparison:

• PLA at 100mm/s: Reliable, predictable
• TPU at 100mm/s: Constant jams, horrible prints
• TPU at 40mm/s: Works, even good

Flexible materials demand 50-60% speed reduction vs. rigid plastics.

TPU Properties

Durometer (hardness measurement):

Rating	Flexibility	Use Case	Difficulty
95A	Very flexible	Phone cases, gaskets	Hardest to print
85A	Flexible	Cushioning, bumpers	Hard to print
75A	Somewhat flexible	Flexible parts, enclosures	Moderate
60A	Stiff	Tough parts, barely flexible	Easier to print

Key insight: Higher A (softer) = harder to print. Start with 75A or 85A, not 95A.

Other properties:

• Elongation: 300-600% (stretches significantly before breaking)
• Tensile strength: 45-65 MPa (moderate, but flexibility compensates)
• Temperature range: -40°C to 80°C (wide range)
• Chemical resistance: Good (resists oils, solvents)

Print Settings for TPU

Critical settings:

Setting	TPU Value	PLA for Comparison
Nozzle temp	210-230°C	200-210°C
Bed temp	60-70°C	60°C
Print speed	30-50mm/s	100mm/s
Retraction	Minimal (2-3mm)	Normal (4-6mm)
Line width	0.45-0.5mm	0.4mm
Layer height	0.2mm	0.2mm
Extruder pressure	Normal	Normal

Detailed breakdown:

Nozzle Temperature (210-230°C):

• TPU flows slowly, needs heat
• Too cold (200°C): Doesn’t flow, jams
• Optimal (220°C): Smooth flow
• Too hot (240°C): Oozing, stringing

Bed Temperature (60-70°C):

• Higher bed = better adhesion (flexible parts slide more)
• 70°C is aggressive but helps with adhesion
• 60°C minimum, otherwise first layer fails

Print Speed (30-50mm/s):

• Cannot emphasize this enough: SLOW IS REQUIRED
• 30mm/s: Safest, most reliable
• 40mm/s: Good balance of speed/reliability
• 50mm/s: Pushing it, occasional jams

• 60mm/s: Almost guaranteed failure

Why so slow: Flexible filament requires:

1. More time for extrusion (flexibility resists pushing)
2. More time for cooling (flexible cools differently)
3. Time for nozzle temperature to stabilize

Retraction (2-3mm):

• Standard retraction (5-6mm) can cause pressure buildup
• Reduced retraction (2-3mm) works better
• Some users disable retraction entirely (works, but more stringing)
• Speed: 30-40mm/s (slow retractions are better)

Important: Less retraction = more stringing, but less jamming. Trade-off is acceptable.

Line Width (0.45-0.5mm):

• Slightly wider than standard (0.4mm)
• Flexible material needs room to stretch
• Tighter nozzles (0.4mm) can jam with flexible
• Wider nozzle (0.5mm) can accommodate flexibility

Layer Height:

• 0.2mm standard works
• Can go to 0.3mm for speed (still need slow overall speed)
• Can go to 0.1mm for detail (very slow)
• Flexibility doesn’t care much about layer height

Common TPU Failures and Fixes

Failure 1: Nozzle jam (most common)

Symptoms:

• Filament stops flowing
• Nozzle feels hard when you push filament
• Extruder makes clicking sound (gear skipping)

Causes:

• Speed too fast
• Temperature too low
• Retraction too aggressive

Fixes:

1. Reduce print speed by 10mm/s
2. Increase nozzle temp +5°C
3. Reduce retraction to 2mm
4. Do cold pull to clear jam

Prevention:

• Start at 40mm/s (not 60mm/s)
• Heat to 220°C (not 210°C)
• Use minimal retraction

Failure 2: First layer adhesion

Symptoms:

• Filament extrudes but doesn’t stick
• Plastic bunches around nozzle
• Flexible filament slides on bed

Causes:

• Bed too cold
• Bed not clean
• First layer speed too fast

Fixes:

1. Increase bed temp to 70°C
2. Clean bed with alcohol
3. Slow first layer to 20-30mm/s (in slicer settings)
4. Use brim (extra adhesion margin)

Failure 3: Stringing (excessive)

Symptoms:

• Thin plastic threads between parts
• More than normal, even with retraction

Causes:

• Temperature too high
• Retraction still not enough (2mm not pulling back enough)
• Speed too high for material

Fixes:

1. Reduce nozzle temp to 210°C
2. Disable retraction, accept stringing (counterintuitive but works)
3. Reduce speed to 30mm/s
4. Clean up stringing with craft knife after printing (acceptable for TPU)

Successful TPU Print Settings (Starting Point)

Use these exact settings and modify from there:

Nozzle: 220°C Bed: 70°C Speed: 40mm/s Retraction: 2mm at 30mm/s Layer height: 0.2mm Infill: 20% (sufficient, faster than 100%) Supports: No (flexible can bend around obstacles) Brim: Yes, 5mm (helps adhesion)

First print:

1. Load TPU filament
2. Set printer to above settings
3. Print small test cube (20×20×20mm)
4. Watch first 10 minutes (ensure sticking)
5. Let complete
6. Evaluate

What you should see:

• First layer sticks and stays stuck
• Visible layer lines (normal for 0.2mm)
• Some stringing (acceptable)
• Flexible part that bends (confirming material worked)

Why TPU Design Matters

Good TPU designs:

• Thick walls (2mm minimum, 3mm better)
• Curves (flex at curves, not sharp corners)
• No thin features (<1mm impossible)
• Negative space (hollows that compress)

Bad TPU designs:

• Thin walls (1mm or less snaps)
• Sharp corners (stress concentrators)
• Complex geometry (hard to remove supports)
• Heavy structures (weight stresses walls)

Design advice: Print functional designs, not cosmetic. TPU’s value is in use cases where flexibility matters: bumpers, gaskets, flexible hinges.

TPU vs. Other Flexible Materials

TPU:

• Most common flexible filament
• Moderate difficulty
• Good balance of flexibility/strength
• Widely available

Ninjaflex (brand of flexible):

• Variant of TPU
• Slightly easier to print than standard TPU
• More expensive
• Reputation for reliability

Shore A (various brands):

• Similar to TPU
• Settings usually identical

PETG-Flex:

• PETG with flexibility
• Easier to print than TPU
• Less flexible than TPU
• Good compromise

Silicone:

• True rubber alternative
• Extremely difficult to print
• Not recommended for consumer printers
• Professional-only

Recommendation: Start with TPU (85A or 75A hardness), master it, then explore others.

Post-Processing TPU

Cleaning:

• Remove supports easily (flexible bends away)
• Minimal sanding needed (flexible smooths naturally)
• Chemical cleaning optional (alcohol, acetone don’t affect TPU)

Coloring:

• Hard to paint (flexible resists adhesion)
• Use flexible paint (craft acrylics often work)
• Dye in water solution can color TPU

Assembly:

• Gluing: TPU doesn’t bond well with CA glue
• Use: Flexible adhesive, 3D printing another TPU part attached
• Fasteners: M3 screws work, avoid pulling TPU threads

Real-World TPU Projects

Phone case:

• Design: Simple rectangular enclosure, 2-3mm walls
• Settings: 40mm/s, 220°C
• Time: 6-8 hours
• Cost: $2-3 in material
• Result: Professional case (costs $15-30 retail)

Flexible hinge:

• Design: Thin wall with snap points
• Settings: 40mm/s, 220°C
• Time: 2-4 hours
• Cost: $0.50-1.00
• Result: Working hinge that flexes 1000+ times

Gasket or seal:

• Design: O-ring or compression shape
• Settings: 35-40mm/s, 220°C
• Time: 1-2 hours
• Cost: $0.10-0.30
• Result: Custom seal (impossible to buy)

The Learning Curve

Your first TPU print: Probability of success: 60% (high failure rate due to jam)

After 5 TPU prints: Probability of success: 85% (settings understood, common mistakes avoided)

After 20 TPU prints: Probability of success: 95% (automatic adjustments for material variation)

Timeline: 2-3 weeks of regular printing to master TPU.

Honest Take on TPU

TPU is worth learning. Flexible parts unlock project categories impossible with rigid plastics.

But it’s frustrating. Be prepared for jams, adhesion failures, and stringing. It’s the most difficult consumer filament to print (easier than nylon, harder than ABS).

When to use TPU:

• Phone cases (genuinely useful, saves money vs. buying)
• Protective bumpers (absorbs impact, prevents breaks)
• Gaskets and seals (custom, impossible to buy)
• Flexible mechanical components (gears that flex, hinges)

When to skip TPU:

• Decorative items (don’t need flexibility)
• Load-bearing functional (use rigid PETG instead)
• First 3D prints (master rigid materials first)

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TPU is the advanced step. Master PLA and PETG first. Then tackle TPU with realistic expectations: slower speeds, more failures, but incredible utility for specific applications.

Start with a simple phone case. After success, you’ll appreciate why flexible printing matters.