Summary of "Flexing on TPU: The Best Flexible Filament Alternatives for 3D Printing"

Summary — flexible filament alternatives, tests, and practical guidance

Overview / context

TPU (thermoplastic polyurethane) has long been the standard for flexible FDM prints: inexpensive, impact-resistant, and good at interlayer bonding. Very soft TPUs (low Shore hardness) can be tricky to print due to feeding issues, but modern direct‑drive extruders have made flexible printing far more accessible than older Bowden-style setups.

The video compares TPU to several newer flexible filament options aimed at solving common TPU problems (printability, energy return, creep, and print speed).

Main takeaway: PEBA (marketed as PEA/Symmetron/Pebber) gives the highest energy return; TPU remains the cheapest and most stable; Morflex trades some mechanical performance for much easier printing; PLA HR is a niche option.

Filaments reviewed and key properties

PEBA (referred to as “PEA” / Symmetron / Pebber)
- Chemistry: polyether block amide (a polyamide/nylon-containing elastomer).
- Standout trait: high energy return — manufacturer claims ~80%; measured in tests at ~64–68% vs TPU ~31%.
- Bounce (80 cm drop): ~51–54 cm (64–68% recovery).
- Temperature behavior: retains bounciness better at low temperature than TPU (only a slight drop in tests).
- Creep: returned to original length after a 24-hour weight test — good creep resistance.
- Printability: can run at higher volumetric flow (claimed up to 7.2 mm^3/s) → faster prints compared with typical TPU (3–6 mm^3/s).
- Downsides: more hygroscopic (requires drying/storage), contains nylon-like chemistry (consider air filtration for VOCs), anecdotal UV sensitivity.
- Cost: fewer suppliers; video used a realistic market price ~ $60/kg (varies). Lower density (~20% less) yields more filament length per kg.
Morflex / Morlex (BQ)
- Chemistry: TPU-based but engineered to feed like a stiffer filament while printing to a softer final part.
- Printability: behaves stiffer in the filament path (easy feeding on typical spool mounts and extruders) but prints to a softer Shore (claimed 75A; measured ~81–84A for printed parts).
- Bounce (80 cm drop): ~43 cm (~54% recovery).
- Downsides: noticeable performance drop when frozen; shows creep/lasting elongation in the weight test.
- Use-case: convenient for printing softer TPU-like parts on standard FDM printers — good for wearables and vibration damping, but creep can limit some applications.
- Price: ~ $50/kg (BQ).
PLA HR (BQ)
- Chemistry: PLA blend modified for flexibility (marketed for 3D‑printed basketballs).
- Printability: less temperamental than soft TPU; prints with near-TPE settings.
- Bounce (80 cm drop): poor for tennis-ball geometry (29 cm, 36%), better for larger basketball geometry (50 cm, 63%).
- Behavior: odd temperature sensitivity — improved bounce after freezing in tests.
- Use-case: niche; may work for specific designs (e.g., certain basketball models) but not a general TPU replacement.
- Price: ~ $60/kg (BQ).

Baseline TPU (generic)

Typical printed Shore range: those tested printed ~85A–96A (many consumer filaments printable down to ~90A without special setups).
Bounce (80 cm drop): ~25 cm (31% energy return).
Strengths: low cost, durable, stable across temperatures, good interlayer bonding and long-term wear resistance.
Weaknesses: slower prints for very soft grades, feeding/jamming risk on non-direct‑drive extruders, creep in some soft variants.

Testing performed (methods and results highlights)

Methods:
- Shore durometer for hardness of printed parts.
- Drop / bounce test from 80 cm onto a hard surface.
- Freeze test: overnight in a freezer for low-temperature behavior.
- 24-hour creep/elongation test with identical weights (2.5 kg).
- Weight/density measurements and comparison of claimed volumetric flow.
Measured Shore hardness (printed parts):
- Generic TPU samples: 92–96A
- 95A TPU sample: 91–95A
- 85A TPU sample: 87–90A
- Morflex (printed): ~81–84A
- PLA HR (printed): 95–97A
Bounce results (80 cm drop):
- TPU: 25 cm (31% energy recovery)
- PEA (PEBA) 9A: 54 cm (68%)
- PEA 85A: 51 cm (64%)
- Morflex: 43 cm (54%)
- PLA HR: 29 cm (36%)
Freeze test:
- TPU: stable
- PEA: slight reduction in performance
- Morflex: significant drop in performance when frozen
- PLA HR: improved after freezing
Creep/elongation:
- TPU-based samples showed lasting elongation under weight
- PEA samples returned to original length (better creep resistance)
Cost context:
- TPU is the cheapest per kg
- PEA is more expensive per kg but lower density provides more usable length per kg
- Morflex and PLA HR priced around $50–60/kg in the tested samples

Practical printing guidance and considerations

Use a direct‑drive extruder or otherwise minimize filament path length for soft elastomers. Bowden setups often struggle with flexibles.
Print slowly for flexible materials (especially very soft grades) to avoid filament compression, gear slip, and jams.
For nylon-containing elastomers (PEA/PEBA):
- Dry filament before printing and store airtight.
- Consider local air filtration if VOCs are a concern.
Tune print settings per material (flow, temperature, retraction, speeds, infill). Some filaments support higher volumetric flow, enabling faster prints.
Design matters: geometry and print parameters strongly affect bounce, feel, and durability (e.g., cavity sizes, wall thicknesses, infill patterns).

Use-case recommendations / conclusions

TPU: best for low-cost, durable flexible parts and situations that require stable behavior across conditions.
PEBA / PEA (Symmetron/Pebber): best for high energy-return applications — sports equipment, footwear midsoles, sports balls, or any application needing strong rebound.
Morflex: best when printability is a priority — easy home printing of softer parts for wearables and damping, but watch for creep and temperature sensitivity.
PLA HR: limited, design-sensitive niche — can work for specific novelty prints (like a marketed basketball design) but not a broad TPU replacement.
If you need complex flexible parts or lack a TPU-optimized printer, consider professional services (e.g., sponsored service referenced in the video) that offer SLS/SLA/FDM flexible parts and end‑to‑end manufacturing.

Sources / main speakers and manufacturers mentioned

Video creator / host (unnamed in subtitles) — conducted tests and commentary.
Sponsor: PCBWay (printing services, PCBs, CNC, injection molding, sheet metal).
Filament manufacturers/brands referenced: Symmetron (PEA/PEBA), BQ (PLA HR, Morlex/Morflex), various generic TPU brands.
Printers and hardware referenced: BambooLab H2 (H2D/H2S), a “Q2” test printer (subtitle reads “Chitty Q2”), and a discussion of direct‑drive vs Bowden extruders.
Test equipment: shore durometer, bounce/drop rig, filament scales/density measurements.