The Complete Guide to Printing TPU and Flexible Filaments

Thermoplastic Polyurethane (TPU) bridges the gap between rigid plastics and soft rubber. When standard PLA or PETG cracks under stress, TPU bends, stretches, and returns to its original shape. However, this elasticity makes TPU notoriously difficult to print on standard hardware without careful tuning.

This guide covers the mechanics of TPU, the critical difference between shore hardness ratings, hardware requirements, optimal slicer settings to combat stringing, real-world applications, and the current market landscape for top flexible filament brands.

Understanding Shore Hardness: 95A vs. 85A

The defining characteristic of any flexible filament is its shore hardness, which dictates both its physical properties and its printability. The 3D printing industry relies primarily on the Shore A scale, which measures the resistance of a material to indentation [1].

While the scale ranges from 0 to 100, the vast majority of consumer TPU filaments fall between 85A and 95A.

95A TPU: The Industry Standard

If a spool is simply labeled "TPU" without a specific hardness rating, it is almost certainly 95A [1]. This grade represents the sweet spot for consumer 3D printing.

• Physical Feel: 95A TPU feels similar to a skateboard wheel or a shoe sole [1] [2]. It is firm and requires deliberate force to compress. When printed with dense infill, it can feel nearly rigid; when printed with thin walls, it flexes readily.
• Printability: This is the easiest flexible filament to print. 95A TPU possesses sufficient "columnar strength," meaning that when the extruder gear pushes the filament, it moves forward into the hotend rather than buckling sideways [1].

85A TPU: True Soft Rubber

Moving down the scale to 85A introduces significant printing challenges but unlocks entirely different material properties.

• Physical Feel: 85A TPU is genuinely soft, resembling a pencil eraser, a rubber band, or a shoe insole [1] [2]. It squishes easily under light pressure and offers true elasticity and rebound.
• Printability: Printing 85A is exceptionally difficult. It lacks columnar strength and acts like a wet noodle in the extruder [1]. Any gap in the filament path between the drive gears and the melt zone will cause the filament to buckle, coil, and jam the printer instantly.

Feature	95A TPU (Harder)	85A TPU (Softer)
Physical Comparison	Skateboard wheel, shoe sole	Pencil eraser, rubber band
Print Speed	Moderate (25-40 mm/s)	Very Slow (15-25 mm/s)
Hardware Requirement	Direct-drive preferred; Bowden possible	Direct-drive strictly required
Retraction	Low (0.5-2.0 mm)	Zero to minimal (0-0.5 mm)

Hardware: Direct-Drive vs. Bowden Extruders

The elasticity of TPU fundamentally alters how it travels through a 3D printer. The type of extruder dictates whether a printer can handle flexible materials reliably.

Direct-Drive Extruders

In a direct-drive setup, the extruder motor and gears are mounted directly above the hotend. The filament path between the driving gears and the melt zone is extremely short—often just a few millimeters.

Direct-drive is strongly recommended for 95A TPU and is strictly required for 85A TPU [1] [3]. The short, constrained path prevents the flexible filament from buckling under the pressure required to extrude it.

Bowden Extruders

Bowden setups place the extruder motor on the frame of the printer, pushing the filament through a long PTFE tube to reach the hotend.

Pushing flexible filament through a long tube is akin to pushing a rope. The filament compresses and buckles inside the tube, causing severe lag (hysteresis) [1]. When the extruder pushes, the filament compresses rather than extruding immediately; when the extruder retracts, the filament decompresses rather than pulling back from the nozzle.

While careful tuning can allow a Bowden printer to handle firm 95A TPU at very slow speeds, softer grades like 85A are generally unprintable on Bowden systems [1] [2].

Tuning TPU Print Settings

Standard profiles for PLA or PETG will fail when applied to TPU. The following setting ranges provide a baseline for tuning flexible filaments.

Temperature and Flow

• Nozzle Temperature: 210°C to 240°C [3]. Unlike rigid filaments where lowering the temperature drastically reduces stringing, TPU requires a specific thermal window to flow correctly. If the temperature is too low, the extruder will grind the filament; if too high, the material will boil and ooze uncontrollably.
• Bed Temperature: 25°C to 60°C [3]. TPU adheres exceptionally well to most surfaces, including PEI and glass. A heated bed is not strictly necessary but helps with initial layer adhesion. In fact, TPU can adhere so strongly that a release agent, such as a glue stick, is sometimes required to prevent damage to the build plate upon removal [3].

Print Speed

Speed is the single most critical variable for TPU.

• Standard TPU: Print speeds must be kept slow, typically between 20 mm/s and 30 mm/s [3]. Attempting to print faster causes the extruder gears to push material faster than the hotend can melt and extrude it, resulting in back-pressure that forces the filament to buckle and jam.
• High-Speed TPU: Recent advancements in polymer chemistry have introduced "High-Speed" or "High-Flow" TPU formulations. These materials have a higher melt index, allowing them to be printed at speeds exceeding 60 mm/s, sometimes up to 120 mm/s on modern CoreXY machines, while maintaining 95A flexibility [2] [4].

Controlling Stringing and Retraction

Stringing—the fine webs of plastic left between printed parts—is the most common cosmetic issue with TPU.

• Retraction Distance: Retraction must be kept minimal. For direct-drive extruders, use 0.5 mm to 1.5 mm [3]. For Bowden extruders, use 2.0 mm to 4.0 mm. Pulling flexible filament back too far causes it to stretch and snap back, leading to inconsistent extrusion and jams upon restart [3].
• Retraction Speed: Keep retraction speeds low, around 20 mm/s to 30 mm/s [3].
• Travel Speed: Increase non-printing travel speeds to 150 mm/s or higher [5]. Faster travel moves reduce the time the nozzle spends crossing open air, giving the molten TPU less time to ooze.
• Combing Mode: Enable "Combing" or "Avoid Crossing Walls" in the slicer. This forces the nozzle to travel within the perimeter of the printed part, wiping any oozed filament on the infill rather than stringing it across open spaces [5].

The Moisture Problem

TPU is highly hygroscopic; it absorbs moisture from the ambient air rapidly. Wet TPU will boil in the hotend, resulting in popping sounds, severe stringing, rough surface textures, and poor layer adhesion [1] [3].

Drying TPU is not optional. Before printing, TPU should be dried in a filament dehydrator at 65°C to 70°C for 6 to 8 hours [3] [6].

Real-World Applications

TPU is utilized for functional parts where rigid plastics fail.

• Gaskets and Seals: 90A and 85A TPU are ideal for custom O-rings, fluid seals, and dust gaskets [1] [7]. The material compresses to fill irregular gaps and resists degradation from many oils and chemicals.
• RC Car Tires: The RC community heavily relies on TPU for custom tires. Softer 85A grades are used for rock crawlers to maximize grip and deformation over obstacles, while firmer 95A grades are used for street racing to maintain stability at high speeds [1] [8]. Specialized foaming TPUs, like colorFabb varioShore, can even mimic the wear patterns and thermal degradation of real racing tires [8].
• Protective Cases: Phone cases, tablet bumpers, and GoPro mounts benefit from TPU's impact absorption [1] [7]. A 95A case will deform to absorb the kinetic energy of a drop, protecting the device inside without shattering.
• Wearables and Grips: Watch bands, custom tool handles, and vibration dampeners utilize TPU for its tactile grip and resistance to abrasion [1] [7].

Top TPU Filament Brands and Pricing

The market offers a range of flexible filaments, varying in consistency, hardness, and price.

Polymaker PolyFlex

Polymaker is recognized for strict dimensional accuracy, which is crucial for preventing jams in flexible filaments.

• PolyFlex TPU95: The benchmark 95A filament, offering consistent extrusion and reliable layer adhesion. Price tier: Mid-range [9].
• PolyFlex TPU95-HF: A high-flow variant engineered for modern, fast printers, allowing speeds triple that of standard TPU [2].

NinjaTek NinjaFlex

NinjaTek effectively pioneered the consumer flexible filament market.

• NinjaFlex 85A: The industry standard for true soft-rubber prints. It boasts a 660% elongation before breaking and excellent abrasion resistance [10]. Due to its extreme softness, it strictly requires a direct-drive extruder and very slow print speeds. Price tier: Premium [10].

Overture

Overture dominates the budget-friendly segment while maintaining reliable quality.

• Overture TPU 95A: A dependable, affordable 95A filament that is widely used for general-purpose flexible printing. Price tier: Budget [11].
• Overture High Speed TPU: Designed to print 3 to 5 times faster than standard TPU, making it highly efficient for rapid prototyping [4].

SainSmart

SainSmart has long been a staple in the drone and RC communities.

• SainSmart TPU 95A: Known for being highly forgiving with imperfect slicer settings, making it an excellent choice for beginners learning to print flexibles [2]. Price tier: Budget [12].

colorFabb varioShore

• varioShore TPU: A unique, active-foaming TPU. By adjusting the print temperature, users can control the density and softness of the final part. Printing hotter activates the foaming agent, resulting in a lighter, softer part; printing cooler results in a denser, firmer part [8] [13]. Price tier: Mid-range [13].

Conclusion

Successfully printing TPU requires abandoning the speed and retraction habits developed with PLA. By understanding the physical limitations of the shore hardness scale, ensuring a constrained filament path, prioritizing dry material, and printing slowly, TPU transitions from a frustrating challenge to a reliable engineering material. Whether printing custom gaskets, impact-resistant drone parts, or soft wearables, TPU expands the functional capabilities of desktop 3D printing far beyond rigid plastics.

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References

[1] Siraya Tech. "TPU Shore Hardness Explained: Choosing 85A vs 95A." https://siraya.tech/blogs/news/tpu-shore-hardness [2] 3DPrinting.com. "Best TPU Filament 2026: Flexible Picks by Shore Hardness." https://3dprinting.com/filament/best-tpu-filament/ [3] Overture 3D. "How to Print TPU Filament — Complete Settings Guide." https://overture3d.com/blogs/overture-blogs/tpu-filament-print-settings-guide [4] Overture 3D. "Overture High Speed TPU 3D Printer Filament 1.75mm." https://overture3d.com/products/overture-high-speed-tpu-3d-printer-filament-1-75mm [5] Overture 3D. "How to Fix Stringing in 3D Printing — Every Setting That Actually Works." https://overture3d.com/blogs/overture-blogs/how-to-fix-stringing-3d-printing [6] Bambu Lab. "TPU Printing Guide." https://wiki.bambulab.com/en/knowledge-sharing/tpu-printing-guide [7] Mandarin3D. "TPU Flexible Filament: Perfect for Gaskets, Grips, and More." https://mandarin3d.com/blog/tpu-flexible-filament-perfect-for-gaskets-grips-and-more [8] colorFabb. "3D Printed RC Tires with VarioShore TPU with Velocity Projects." https://colorfabb.com/blog/post/rc-tires-made-with-varioshore-tpu-with-velocity-projects [9] Polymaker. "PolyFlex™ TPU95." https://shop.polymaker.com/products/polyflex-tpu95 [10] NinjaTek. "NinjaFlex 3D Printer Filament (85A)." https://ninjatek.com/shop/ninjaflex/ [11] 3D Filament Profiles. "Overture TPU 95A Black - Filaments." https://3dfilamentprofiles.com/filament/details/2063 [12] SainSmart. "Orange, Flexible TPU Filament 1.75 mm 0.8 kg/1.76 lb." https://www.sainsmart.com/products/orange-flexible-tpu-filament-1-75mm-0-8kg-1-76lb [13] colorFabb. "Varioshore TPU Filaments – Adjustable Flexibility for 3D Printing." https://colorfabb.us/filaments/materials/tpu-filaments/varioshore-tpu