Flexible 3D Printing Materials
shore hardness, TPU grades
& multimaterial compatibility.
Bend, stretch, and compress without fracturing. Flexible materials unlock prosthetics, wearables, gaskets, seals, soft robotics, and impact-resistant components that rigid plastics cannot produce. Understanding shore hardness, material types, and printer compatibility is the difference between a successful flexible print and a clogged extruder.
Not all flexible materials are the same. The number on the spool — Shore hardness — determines how soft the printed part feels, how fast you can print it, whether your printer can feed it at all, and whether it can run through a multimaterial system. This guide covers the full spectrum from rigid-flex 98A to ultra-soft 60A, with print settings, printer compatibility matrices, and multimaterial constraints for every grade.
Understanding shore hardness: the number that defines your flexible print.
Shore hardness is a standardized measurement of a material's resistance to indentation. A calibrated probe presses into the material under a fixed load, and the depth of the indent determines the hardness number. Two scales matter for flexible filaments.
Shore hardness reference by everyday objects.
| Shore Hardness | Feels Like | Printability | Best For |
|---|---|---|---|
| 60A | Gel insole, rubber band | Extremely difficult — direct drive only | Ultra-soft wearables, medical seals |
| 75A | Shoe heel cushion, earplug | Very difficult — direct drive, 15–20 mm/s | Wearables, skin-contact parts, vibration dampening |
| 85A | Pencil eraser, soft shoe sole | Difficult — direct drive, 15–25 mm/s | Gaskets, seals, phone cases, wearables |
| 90A | Car tire, firm shoe sole | Moderate — direct drive preferred, 25–40 mm/s | Functional rubber parts, wheels, grips |
| 95A | Skateboard wheel, rubber mallet | Easy — direct drive or Bowden, 40–60 mm/s | Phone cases, drone bumpers, general engineering |
| 98A | Hard rubber, hockey puck | Easy — any printer, 30–50 mm/s | Impact-resistant parts, semi-flexible enclosures |
| 60D–68D | Stiff plastic with slight give | Easy — AMS-compatible at 68D | Protective cases, automotive parts, multi-material prints |
TPU grades by shore hardness: detailed profiles.
TPU dominates flexible 3D printing because it balances elasticity, durability, and printability better than any alternative. Here is exactly what each grade does — and what hardware it demands.
85A TPU — Ultra-soft flexibility
85A is soft enough to compress easily under finger pressure and recover — like a pencil eraser, with high grip and excellent vibration dampening. Ideal for wearables, gaskets, and medical applications. It is also the most demanding grade to feed: direct drive only, with retraction disabled.
| Property | Value |
|---|---|
| Shore Hardness | 85A |
| Nozzle Temperature | 220–250°C |
| Bed Temperature | 50–60°C |
| Print Speed | 15–25 mm/s |
| Retraction | Disabled (0 mm) — retraction grinds soft filament |
| Extruder Type Required | Direct drive only — Bowden will buckle |
| Elongation at Break | 500–700% |
| Multimaterial Compatible | No — external spool only |
Printing tips for 85A: use a direct drive extruder with zero retraction, print the first layer at 10–15 mm/s, minimize cooling fan (over-cooling causes poor layer adhesion), and store filament in a dry box — 85A is highly hygroscopic.
90A TPU — Medium-soft functional flexibility
90A delivers genuinely rubbery feel with somewhat easier printability than 85A. Use it when a part needs real compressibility — a gasket that seals under light clamping force, a wearable that conforms to skin, or a grip that deforms under finger pressure.
| Property | Value |
|---|---|
| Shore Hardness | 90A |
| Nozzle Temperature | 220–240°C |
| Bed Temperature | 40–60°C |
| Print Speed | 25–40 mm/s |
| Retraction | Minimal (1–2 mm) or disabled |
| Extruder Type Required | Direct drive preferred; Bowden possible with care |
| Elongation at Break | 400–600% |
| Multimaterial Compatible | No — too soft for AMS/MMU feed paths |
When to choose 90A over 95A: when the part needs genuine compressibility. For most other applications, 95A with 20–40% infill produces comparable results with much easier printing.
95A TPU — The industry standard
95A is the default TPU grade — the one most manufacturers produce, most printers handle, and most users reach for first. Flexible enough for phone cases, drone bumpers, wheels, straps, and feet; firm enough to feed through any direct-drive extruder and most Bowden setups. New high-flow 95A formulations print at 150–200 mm/s.
| Property | Value |
|---|---|
| Shore Hardness | 95A |
| Nozzle Temperature | 220–240°C |
| Bed Temperature | 40–60°C |
| Print Speed | 40–60 mm/s (up to 200 mm/s on high-flow variants) |
| Retraction | 1–3 mm at 25 mm/s |
| Extruder Type Required | Direct drive or Bowden (with care) |
| Elongation at Break | 400–650% |
| Multimaterial Compatible | No for standard 95A — external spool only |
High-speed TPU 95A: formulations like Polymaker PolyFlex TPU95-HF and Bambu TPU 95A HF reduce the viscosity bottleneck that normally limits TPU speed — printing 150–200 mm/s on compatible machines without sacrificing elasticity or layer adhesion.
98A TPU — Semi-rigid flexibility
98A is the firmest end of the Shore A scale for FDM. Thin walls feel almost rigid — the flex is there under deliberate force but not under light handling. Hard rubber, in effect: impact-resistant, durable, and abrasion-resistant with just enough give to absorb shock. Prints like PETG with slightly more patience.
| Property | Value |
|---|---|
| Shore Hardness | 98A |
| Nozzle Temperature | 225–245°C |
| Bed Temperature | 50–60°C |
| Print Speed | 30–50 mm/s |
| Retraction | 1–3 mm |
| Extruder Type Required | Any — direct drive or Bowden |
| Elongation at Break | 80–100% |
| Multimaterial Compatible | Yes — runs on AMS and MMU with care |
When to choose 98A: housings, enclosures, bumpers, wheels, and structural components that must absorb drops without cracking — nearly as stiff as rigid plastics yet far more impact-tolerant.
60D–68D — Semi-rigid AMS-compatible TPU
Shore D TPU grades feel like hard plastic with a slight give. They exist primarily to fill one gap: multimaterial system compatibility. Bambu Lab's TPU for AMS at 68D is the only TPU that reliably feeds through the Bambu AMS and AMS Lite automatic material systems.
| Property | Bambu TPU for AMS (68D) |
|---|---|
| Shore Hardness | 68D |
| Nozzle Temperature | 220–240°C |
| Bed Temperature | 30–35°C (with glue) |
| Print Speed | Up to 250 mm/s |
| Max Volumetric Speed | 18 mm³/s |
| Elongation at Break | > 650% |
| AMS / AMS Lite Compatible | Yes — all AMS series |
| Nozzle Compatibility | 0.4mm / 0.6mm / 0.8mm hardened steel — 0.2mm not compatible |
The AMS trade-off: 68D is a deliberate compromise — the filament must be stiff enough to survive the AMS's long PTFE path without buckling. If your application needs rubbery flex (85A–95A), print from the external spool; if it needs impact resistance and multi-material printing, 68D AMS TPU is the answer.
Multimaterial printer compatibility: what actually works.
The biggest misconception in flexible printing is that "TPU" is one material you can load into any printer. Each shore hardness has different hardware requirements — and multimaterial systems make the constraints dramatically tighter.
Why soft TPU cannot run through AMS / MMU systems.
Automatic Material Systems — Bambu AMS, Prusa MMU, Creality CFS — push filament through long PTFE tubes with multiple drive gear engagements and sharp path changes. Soft TPU (95A and below) compresses inside the tube, buckles at the drive gears, and jams the system. The softer the filament, the worse the problem.
Printer compatibility matrix by shore hardness.
| Printer Category | 60A | 75A | 85A | 90A | 95A | 98A | 68D (AMS) |
|---|---|---|---|---|---|---|---|
| Bambu Lab (direct drive, external spool) | Possible | Yes | Yes | Yes | Yes | Yes | Yes |
| Bambu Lab (via AMS) | No | No | No | No | No | No | Yes |
| Prusa MK4/S + MMU3 | No | No | No | No | Marginal | Possible | Possible |
| Direct drive (Ender 3 DD, Voron, etc.) | Possible | Yes | Yes | Yes | Yes | Yes | Yes |
| Bowden (Ender 3 stock, etc.) | No | No | No | Marginal | Yes (25–30 mm/s) | Yes | Yes |
| Dual nozzle (IDEX, H2D) | Possible | Yes | Yes | Yes | Yes | Yes | Yes |
Flexible material types beyond TPU.
TPU is the most common flexible filament, but it is not the only option. Each material type below offers distinct properties that may better suit a specific application.
TPU (Thermoplastic Polyurethane)
The workhorse of flexible printing — excellent abrasion resistance, chemical resistance, and durability. Available in the widest shore hardness range (85A–98A) with the most manufacturer options. The default recommendation for most flexible applications.
TPE (Thermoplastic Elastomer)
A broader category with rubber-like feel and higher elasticity — typically softer at equivalent hardness ratings with better grip. More challenging to print: slower speeds and precise extruder control. Best for soft-touch grips, seals, and wearable contact surfaces.
TPC (Thermoplastic Copolyester)
An engineering-grade flexible material with excellent chemical resistance and thermal stability — less flexible than TPU but superior in harsh environments. Resists oils, fuels, and solvents. Best for automotive components, outdoor seals, and chemical-resistant gaskets.
Soft PLA
A modified PLA offering rubber-like flexibility while retaining PLA's ease of printing. Around 92A shore, prints at PLA temperatures and speeds — accessible to printers that cannot handle true TPU. The trade-off: lower elongation and abrasion resistance.
TPA (Thermoplastic Polyamide)
Blends TPE flexibility with nylon smoothness — high flexibility, excellent surface finish, and durability against repeated bending. Suitable for functional prototypes that flex without degrading over thousands of cycles.
PEBA (Polyether Block Amide)
A premium elastomer used in high-performance footwear and athletic equipment. Extremely high rebound energy, low density, and flexibility across a wide temperature range. More expensive and harder to print — but delivers energy return TPU cannot match.
Flexible material comparison.
A quick reference across every flexible filament family ALT evaluates when selecting a material for your part.
| Property | TPU | TPE | TPC | Soft PLA | TPA | PEBA |
|---|---|---|---|---|---|---|
| Shore Hardness Range | 85A–98A, 60D–68D | 60A–90A | 85A–95A | ~92A | 85A–95A | ~95A |
| Print Difficulty | Easy (95A) to Hard (85A) | Moderate to Hard | Moderate | Easy — PLA-like | Moderate | Hard |
| Abrasion Resistance | Excellent | Good | Excellent | Fair | Very good | Good |
| Chemical Resistance | Good | Fair | Excellent | Fair | Good | Good |
| Temperature Resistance | Good (80–120°C) | Fair | Excellent (120°C+) | Low (~60°C) | Good | Excellent |
| Elongation at Break | 400–700% | 500–800% | 300–500% | 200–300% | 400–600% | 500%+ |
| Biodegradable | No | No | No | Yes | No | No |
| Best For | General engineering, wearables, gaskets | Soft grips, seals, skin-contact | Automotive, chemical environments | Biodegradable flex, easy prototypes | Repeated flex cycles, smooth flex | Footwear, sports, energy return |
Designing parts for flexible materials.
Flexible materials behave differently from rigid plastics during and after printing. These design principles improve print success and final part performance.
Control flexibility with wall loops and infill
Wall loop count is the most powerful variable. More walls = stiffer part; fewer walls = more flexible. A phone case at 2 wall loops with 15% infill flexes easily; the same model at 5 wall loops with 60% infill feels nearly rigid.
Orient for layer adhesion strength
Flexible parts are weakest between layers. Design so the primary flex direction is perpendicular to the layer lines — a strap that bends around a wrist should print flat, not upright.
Avoid thin walls and sharp corners
Thin walls (1–2 perimeters) in soft TPU tear during use — use at least 3 perimeters for structural parts. Sharp internal corners create stress concentrations that crack under repeated flexing; add generous fillets.
Design for print orientation
Overhangs and bridges in soft TPU are extremely difficult to print cleanly, and support removal on soft TPU risks tearing the part surface. Design to minimize or eliminate supports.
Tune compression with infill pattern
Gyroid and cubic infill compress uniformly in all directions and recover quickly — preferred for wearables and gaskets. Rectilinear infill compresses more in one direction — useful for directional seals.
Consider moisture absorption in design
Most flexible filaments are hygroscopic — moisture causes stringing, bubbling, and weak layer adhesion while printing. Dry all flexible filament before printing (70–80°C for 8–12 hours), and account for dimensional change in precision applications.
Flexible materials in practice.
The applications that put flexible materials to work — across the prosthetics, robotics, automotive, and consumer product programs ALT serves.
Prosthetic liners and wearable interfaces
Medical-grade prosthetic liners require ultra-soft materials (75A–85A) that conform to skin, distribute pressure evenly, and withstand repeated donning and doffing. TPU and TPE in the 75A–85A range produce comfortable, durable liners.
Automotive gaskets and seals
Engine bay gaskets, weatherstripping, and fluid seals need chemical resistance, temperature stability, and low compression set. TPC and high-grade TPU (95A–98A) resist oil, fuel, and coolant — ideal for prototyping and low-volume production before mold tooling.
Soft robotics and grippers
Soft grippers conform around objects without damaging them. NinjaFlex 85A and similar soft TPUs grip fragile items with consistent pressure, and pneumatic soft actuators printed in 85A TPU inflate and deflate to create gripping motion.
Consumer product prototyping
Phone cases, watch bands, shoe soles, and ergonomic grips benefit from flexible materials that feel like the final injection-molded product. 95A TPU produces prototypes that closely match mass-produced flexible goods for realistic user testing.
Vibration dampening and mounts
Electronic enclosures, sensor housings, and motor mounts printed in 90A–95A TPU absorb vibration that would damage sensitive components or generate noise — ideal for drone flight controllers and industrial sensor housings.
Flexible materials available at ALT.
ALT stocks flexible filaments from leading manufacturers across multiple shore hardness grades. Our engineering team recommends the optimal material and settings for your specific application.
| Material | Hardness | Print Speed | Best For | Supplier |
|---|---|---|---|---|
| NinjaFlex Chinchilla | 75A | 15–20 mm/s | Ultra-soft wearables, skin-contact | NinjaTek |
| NinjaFlex | 85A | 15–35 mm/s | Gaskets, seals, vibration dampening | NinjaTek |
| NinjaFlex Edge | 83A | 20–40 mm/s | Flexible with faster print speed | NinjaTek |
| NinjaTek Cheetah | 95A | 40–60 mm/s | General flexible parts, high-speed printing | NinjaTek |
| NinjaTek Armadillo | 75D | 30–50 mm/s | Impact-resistant, wear-resistant parts | NinjaTek |
| Polymaker PolyFlex TPU95 | 95A | 40–60 mm/s | Dimensionally consistent general flex | Polymaker |
| Polymaker PolyFlex TPU95-HF | 95A | Up to 200 mm/s | Rapid production, high-speed printers | Polymaker |
| Overture TPU | 95A | 40–60 mm/s | Budget-friendly entry TPU | Overture |
| Bambu TPU 95A HF | 95A | Up to 147 mm/s | Bambu ecosystem, fast flexible | Bambu Lab |
| Bambu TPU for AMS | 68D | Up to 250 mm/s | Multi-color/multi-material flexible | Bambu Lab |
| SainSmart TPU | 95A | 30–50 mm/s | Forgiving entry-level flexible | SainSmart |
| eSun eTPU-95A | 95A | 40–60 mm/s | Reliable mid-range TPU | eSun |
| Fillamentum Flexfill | 92A, 98A | 30–50 mm/s | Food-contact applications, multiple hardnesses | Fillamentum |
Flexible printing questions, answered.
Straight answers about flexible 3D printing materials — shore hardness, TPU grades, printer compatibility, and what ALT prints in-house.
Need help selecting the right flexible material?
Every flexible application has unique requirements — shore hardness, chemical resistance, multimaterial compatibility, and print speed all influence material selection. ALT's additive manufacturing engineers recommend the optimal material and settings so your parts meet performance requirements on the first print.