TPU Filament: Settings, Shore A Hardness and Applications

Flexible materials open up new and interesting possibilities for anyone involved in 3D printing at home or in a small workshop. Among them TPU (thermoplastic polyurethane) stands out as the most affordable and universal choice for desktop FDM/FFF printers in Bulgaria. TPU material combines elasticity, impact resistance and good abrasion resistance — qualities that rigid PLA and PETG cannot provide in the same way. Whether you want to make soft seals for household needs, protective cases for electronics, anti-vibration feet for equipment, or custom tires for RC models, TPU is the material that will allow you to realise these projects. In this detailed article, we will look at what TPU is, how to choose a suitable TPU filament for 3D printer for your needs and equipment, which settings to use for successful printing and what useful things you can craft. We will also include practical advice based on real experience from the Bulgarian 3D community and data from laboratory tests in scientific publications.

Content

• What is TPU material and why is it different from PLA/PETG?
• TPU filament for 3D printer: how to choose the right one
• Types of TPU and new formulations (high-flow, UV, conductive)
• TPU 3D Printing Settings (A Practical Guide)
• What can be printed from TPU: ideas for useful products
• Comparison of TPU filaments: TPU90 vs TPU95 vs TPU95-HF
• Recommended TPU filaments from 3DLarge
• Data from tests and surveys
• Conclusion
• Frequently Asked Questions (FAQ)

What is TPU material and why is it different from PLA/PETG?

TPU is a thermoplastic polyurethane — a flexible, elastic material with high resistance to impact, abrasion and many chemicals. Unlike rigid PLA and PETG, a TPU material can be bent, stretched and twisted repeatedly without breaking or losing its shape, making it indispensable for specific applications requiring elasticity.

Main features of TPU

Thermoplastic polyurethane belongs to the family of elastomers — a special class of polymers with unique mechanical properties. This means that its molecular structure allows it to deform under pressure and return to its original shape after the load is removed, similar to rubber. In practical terms:

In other words, a TPU part can withstand repeated bending, pressure and even a strong impact without breaking or cracking. This ability to elastically deform is the main difference from traditional rigid filaments such as PLA, PETG and ABS.

Compared to PLA, which is brittle and breaks easily when bent or hit, and PETG, which has some flexibility but is still a decidedly rigid material, TPU offers a completely different set of mechanical properties. It is not intended to replace these traditional materials, but to expand the capabilities of your 3D printer with a new class of applications that are simply not possible with rigid filaments.

The main advantages of TPU include:

• Elasticity — the material can be stretched to 300–500% of its original length depending on the specific formulation, after which it returns to its original dimensions without residual deformation
• Impact resistance — absorbs impact energy instead of breaking or cracking, making it ideal for protective items and cases
• Abrasion resistance — wears significantly more slowly than PLA or PETG in friction and contact with rough surfaces, making it ideal for rollers and wheels
• Chemical resistance — withstands oils, greases, many solvents, fuels and other chemicals without degrading or losing its properties
• Operating temperature range — most TPU filaments retain their full mechanical properties between -40°C and +80°C, which makes them suitable for outdoor applications in all seasons in Bulgaria
• Vibration and noise damping — TPU elastic structure effectively reduces vibration and noise, making it ideal for anti-vibration applications in workshops and homes

When TPU is not a good choice

Despite the many merits of this material, TPU is not a one-size-fits-all solution for every project. There are specific situations where other materials are significantly more suitable and will give better results:

Rigid mechanical parts — if you need a strong, rigid and stable construction that won't deform under load, PLA, PETG or ABS are definitely better choices. TPU will flex where you want stiffness.

Precise threads and holes — the elasticity of TPU makes it extremely difficult to achieve accurate dimensions for functional threads with tight tolerances. The threads will deform when tightened and the holes will expand or contract. For such applications use PETG or ABS.

High operating temperature — above 80–90°C TPU starts to soften significantly and loses its mechanical properties. If the part will work near heat sources or in hot environments, consider ABS, ASA or PC (polycarbonate).

Very fine details and thin walls — due to slower print speeds and natural tendency to stringing, small and delicate items can come out inaccurate or marred by stringing. PLA is significantly better suited for models with very fine detail.

Details requiring easy post-processing — TPU is difficult to sand, polish and paint. If you plan on processing after printing, choose PLA or ABS which are much more suitable for this purpose.

Comparison of TPU with other popular 3D printing filaments

For a clearer idea of how TPU fits into the arsenal of materials for desktop 3D printing, here is how it compares to the most widely used filaments in Bulgaria:

PLA is ideal for prototyping, decorative objects and novice users thanks to its easy printing, low temperature and affordable price. PETG offers a good balance between strength, some flexibility and ease of printing, with better temperature and chemical resistance than PLA. ABS is the traditional choice for functional parts with high heat resistance, but requires a closed chamber and good ventilation due to fumes. And TPU fills a unique niche in that spectrum—where true flexibility, impact resistance, and the ability to elastically deform repeatedly without breaking or material fatigue are required.

TPU filament for 3D printer: how to choose the right one

The choice of TPU depends on three main factors—Shore A hardness (lower value means softer material), your printer's extruder type (direct or Bowden), and the specific application you plan to use the part for. For most desktop direct extruder machines, the TPU 95A is the universal and recommended choice, combining good flexibility with relatively easy printing.

What does Shore A mean and why is it important?

Shore A is a standardized scale for measuring the hardness of elastomers and rubbers developed by American engineer Albert Shore in the 1920s. It measures the material's resistance to indentation by a special indenter. For TPU filaments, the most common values range between 85A and 98A, with each value having its own advantages and challenges when printing:

Shore 85A–90A — a very soft material similar to hard rubber or soft silicone. It is suitable for seals, soft handles, anti-vibration elements and applications requiring maximum elasticity and deformability. The downside is that it is significantly more difficult to print and absolutely requires a direct extruder with a well-tuned idler tension.

Shore 95A — a universal balance between flexibility and easy printing, which represents the "golden mean" for most users and projects in Bulgaria. The material is soft enough for functional flexibility in everyday applications, yet stiff enough to feed steadily through the extruder without special printer modifications.

Shore 98A and above — a harder variant of TPU that is closer to a semi-rigid material with limited elasticity. Significantly easier to print due to less tendency to crumple and can even work on some Bowden systems without special modifications, but offers limited elasticity compared to softer variants. It is suitable for applications that require some flexibility and impact resistance without extreme softness - for example, strong tool cases or wear-resistant rollers.

For a practical analogy to help understand the difference: Shore 90A is roughly like the rubber of a car tire or hard rubber, and Shore 95A is similar to the sole of a quality athletic shoe or hard silicone for seals.

Direct Extruder vs. Bowden System

Feeder type greatly affects the success of TPU printing and is one of the most important factors in filament selection. Understanding this difference is critical to achieving good results and avoiding disappointments:

Direct extruder — in this configuration, the extruder drive gear is mounted directly on the print head. The path the filament has to travel from the gear to the nozzle is very short—typically less than 5 cm. This minimizes the possibility of "squeezing," twisting, or bending the soft TPU filaments, which is a major problem when printing flexible materials. Most modern printers use a direct extruder: Prusa MK3S+/MK4, Bambu Lab series (A1, P1S, X1C), Creality Ender-3 S1/S1 Pro, Voron and many other popular models. If you have such a machine, you can print even very soft TPU 90A without many problems after proper setup.

Bowden system — here the feed mechanism is separated from the print head and mounted on the printer frame. The filament is moved through a long PTFE tube, often 30–60 cm or more in length. With soft materials like TPU 90A, this creates serious problems—the filament can buckle inside the tube, stretch on retraction, or jam when changing direction of travel. If you have a Bowden printer (such as the original Creality Ender-3, Ender-3 V2, or Prusa Mini), it is recommended to start with a stiffer TPU (95A or 98A) and reduce the print speed significantly — usually below 25 mm/s. Some users have been able to print TPU 95A on Bowden machines, but this requires patience, optimisation and often modifications to the feeder.

Filament diameter and quality

The standard for the absolute majority of desktop 3D printers in Bulgaria and around the world is 1.75 mm. Make sure the selected TPU filament matches this diameter before purchase. Some industrial and semi-professional machines use 2.85 mm (sometimes referred to as 3 mm), but this is rare for hobby use in Bulgaria.

Filament quality is critical to the success of your projects — cheap TPU filaments with unstable diameters and impurities will cause feeding problems and lead to failed prints. Investing in quality filament from a reputable manufacturer pays for itself many times over with fewer failed prints, better end results, and less time wasted on setups and troubleshooting.

Types of TPU and new formulations (high-flow, UV, conductive)

In addition to standard TPU filaments with different Shore A hardnesses, innovative high-flow versions for significantly faster printing, TPUs with improved UV-resistance for outdoor applications and even conductive variants for wearable electronics, flexible sensors and specialized applications in the field of IoT devices have reached the market in 2025–2026.

New developments in TPU (2025–2026)

The flexible filament industry is actively developing and does not stand still. Manufacturers are investing in new formulations that address TPU's traditional weaknesses — slow printing and sensitivity to moisture. Here are the most interesting trends that deserve attention:

• High-flow TPU — these innovative formulations have improved melt flow, enabling printing speeds of 80–150 mm/s instead of the standard 20–40 mm/s. This drastically shortens the time for making large parts. An example of such a filament is PolyFlex TPU95-HF, specially developed for high-speed machines. The manufacturer Prusa also introduced its Prusament TPU 95A with an optimised profile for their printers.
• Reduced hygroscopicity — new generations of TPU absorb significantly less moisture from the air compared to older formulations. This facilitates storage and reduces the frequency of drying, which is a great advantage for hobby users without specialized equipment.
• Conductive TPU (Conductive TPU) — materials with additions of carbon particles or specialized conductive polymers that allow the fabrication of flexible sensors, buttons, antennas and simple electrical connections. According to Formnext coverage, this is one of the key directions in the development of polymer materials for additive manufacturing.
• Stable feeding systems — the company Recreus, known for its Filaflex, developed Filaflex 2.20 System — an integrated solution for reliable feeding of soft filaments for different types of printers. Such innovations make TPU more accessible to a wider range of users.

Settings for 3D printing with TPU

For TPU 95A, start with nozzle temperature 220–235°C, bed temperature 50–60°C, speed 25–35 mm/s and minimal or no retraction. Use a direct extruder for best results and expect longer print times compared to solid materials like PLA or PETG.

Nozzle and bed temperature

Correct temperature is critical to successful TPU printing and requires care in setting. Too low a temperature leads to poor adhesion between the layers and a weak, brittle part. Too high — causes excessive stringing, oozing and even thermal degradation of the material.

Nozzle: 215–235°C is the recommended range for most TPU 95A filaments. Softer variants (90A) sometimes require a lower temperature (210–225°C) to avoid excessive stringing. Start in the middle of the manufacturer's recommended range and adjust based on results.

Bed: 50–60°C is the optimal range for most TPU filaments. Some users also print successfully on a cold bed (without heating) with a suitable adhesive coating, but a heated bed provides more stable results. Do not overdo the temperature — too hot a bed can cause deformation of the lower layers.

Print speed

TPU definitely does not like to rush and requires patience from the user. High speeds lead to feed problems, poor surface finish, delamination and various defects in the part. Unlike PLA, which can be printed at 60–100 mm/s without problems, TPU requires a significantly more conservative approach. Recommended starting values for standard TPU 95A:

• Perimeter (external walls): 25–35 mm/s - these walls determine the visual quality, so slow printing is important
• Infill: 30–45 mm/s — the internal structure can be printed a little faster
• First layer: 15–20 mm/s — the slow first layer provides good adhesion and a stable base
• Travel: 100–150 mm/s — non-extrusion movements can be fast

For high-flow versions like the TPU95-HF, you can experiment with 60–100 mm/s for infill and 40–60 mm/s for perimeters, but always start conservatively and increase gradually.

Retraction — a critical parameter

Retraction is a major source of problems with TPUs and requires special attention from every user. Soft filaments easily "crush" or bend in the extruder under aggressive retraction, resulting in jams and missed motor steps. The key is to balance minimising stringing against preventing feed problems.

Direct Extruder: 0.5–2 mm distance, 20–25 mm/s speed. Start at the lower limit (0.5 mm) and increase only if stringing is unacceptable. Many users achieve good results with 1 mm retraction at 20 mm/s speed.

Bowden system: If possible, turn off retraction completely or use minimum values (1–3 mm maximum). With long Bowden tubes, retraction rarely helps and often causes more problems than it solves—the filament stretches inside the tube instead of being pulled back.

An alternative approach: some experienced users turn off retraction altogether and rely on a combination of slower travel moves, active coasting (stopping extrusion before the end of the line) and wipe (a short nozzle movement at the end of the perimeter).

Cooling

TPU cools more slowly than PLA and has different fan requirements for cooling the part. Proper cooling balancing is important to achieve good surface quality without compromising adhesion between layers:

• First layer: fan off or at 20-30% — this improves adhesion to the bed and provides a stable base for the entire print
• From the second layer up: 50–80% — provides sufficient cooling without overcooling the material
• Bridges and overhangs: 80–100% — maximum cooling for rapid hardening and prevention of sagging

For very small parts or thin walls, increase cooling to avoid deformation from heat build-up. For large, massive parts, you may want to reduce the cooling for better layer adhesion.

Adhesion and first layer

Good adhesion to the bed is critical for successful TPU printing and prevents peeling during long prints. Unlike PLA, which can be difficult to separate with too good adhesion and create warping problems, TPU rarely creates such problems thanks to its low cooling shrinkage. A few proven approaches to ensure good adhesion:

PEI plate (smooth or textured): excellent choice for TPU. The parts stick firmly when heated and separate easily when the bed cools. The textured PEI surface is particularly good for TPU.

Glass bed with glue: works well with adhesive spray like 3DLAC or a regular glue stick. Clean the glass with isopropanol before applying glue.

Blue tape (blue masking tape): a classic method that still works well. The tape should be replaced periodically.

Bed leveling and proper Z-offset are extremely important for any filament, but especially for TPU. The good news is that TPU is more tolerant of slight first layer "crush" than PLA — a slightly lower Z-offset often improves adhesion.

Common problems and solutions

Even with correct settings, various problems can occur when printing with TPU. Here are the most common and their solutions based on practical experience:

Storage and drying of TPU

TPU is a hygroscopic material — it actively absorbs moisture from the surrounding air, even at normal room humidity. Wet filament leads to bubbles in the print, characteristic popping noises from the nozzle during printing, a poor and rough surface and poor layer adhesion that compromises the strength of the part. Proper storage and periodic drying are essential to achieve quality results.

Rules for storing TPU filament:

• Use vacuum bags with silica gel packets for long-term storage
• Store in a dry box (silica gel box) with humidity control — aim below 20% RH for optimal results
• Do not leave the roll on the printer for days, especially in humid conditions
• Immediately after use, return the filament to a secure storage environment

Drying procedure:

• Oven or dehydrator: 50–55°C for 4–8 hours depending on the amount of absorbed moisture. Make sure the temperature is stable and accurate — some home ovens are not accurate at low temperatures and can overheat the filament.
• Specialized filament dryer: follow the manufacturer's instructions. Most devices have preset programs for different materials, including TPU.
• Important warning: do not overdo the drying temperature. Above 60–65°C TPU may start to stick in the roll, deform or lose some of its properties.

Signs of wet filament are easy to recognize and include: visible bubbles in the extruded material during printing, characteristic popping or hissing sounds from the nozzle during extrusion, a dull or rough surface of the finished part instead of smooth, and a noticeably weakened bond between layers that compromises strength.

What can be printed from TPU: ideas for useful products

Short answer: TPU is an ideal material for gaskets, anti-vibration feet, protective electronics cases, flexible hinges, RC model tires, and dozens of other everyday items that require flexibility, impact resistance, chemical resistance, or the ability to be repeatedly deformed without breaking or losing shape.

Practical ideas for 3D printing with TPU

One of the most exciting aspects of TPU is the variety of useful objects you can make with a home 3D printer. Unlike decorative PLA models, TPU parts usually have real functional value and solve specific problems in everyday life. Here is an original list of ideas aimed at everyday and "workshop" needs of users in Bulgaria:

1. Seals and gaskets — for jars, boxes, lids, plumbing connections (for non-potable applications without certificate)
2. Anti-vibration feet — for 3D printers, washing machines, compressors, CNC machines, audio equipment
3. Tires and wheels for RC models — custom-sized wheels for RC cars, drones, robots
4. Protective cases for electronics — for phones, tablets, remotes, gamepads
5. Tool protectors — soft impact-proof caps for screwdrivers, pliers, hammers
6. Ergonomic handles and grips — bicycle handlebar pads, tools, joysticks, pens
7. Living hinges — for folding boxes, lids, cases
8. Cable organizers — elastic clips and holders that do not pinch or break cables
9. Shock absorbers and buffers for furniture — for doors, drawers, cabinets
10. Anti-slip pads — for laptops, tools, kitchen appliances, remotes
11. Belts and straps — for watches, cameras, small mechanisms, ID badge holders
12. Seals for 3D printers — silicone replacements for hotend, bowden fittings, covers
13. Soft buttons and caps — for electronic devices, control panels, keyboards
14. Corner protectors — for furniture in children's rooms, impact protection
15. Flexible couplings — between motors and screws compensating for slight misalignments
16. Masks and stencils for painting — reusable thanks to flexibility
17. Shoe soles and insoles — prototypes and custom inserts for special needs
18. Toys and fidget models — soft and durable; verify the design, material and age-appropriate safety requirements before use by children

Whaleberry - 3D Printed Sneakers

Fig.(0) Shoe design by Bambu Lab and Presq

Comparison of TPU filaments: TPU90 vs TPU95 vs TPU95-HF

To facilitate the selection of a suitable flexible filament, here is a direct comparison of three popular variants of TPU filament from the PolyFlex series available on the Bulgarian market. Each is optimised for different applications and experience levels:

Recommended TPU filaments from 3DLarge

In 3DLarge's TPU collection you'll find three main variants of the quality PolyFlex series, each optimised for different applications and experience levels — the TPU90 for maximum flexibility and specialized applications, the TPU95 for general use and beginners, and the TPU95-HF for high-speed printing on modern machines.

PolyFlex TPU90

PolyFlex TPU90 is the softest variant in the series with a hardness of 90A, which makes it extremely elastic. This filament is suitable when you need maximum elasticity and softness - for example for seals, extra soft grips or anti-vibration elements that need to absorb vibrations effectively. It requires a direct extruder and slow printing (15–30 mm/s). Not recommended for TPU beginners — better to gain experience with a stiffer variant like the TPU95 first.

PolyFlex TPU95

PolyFlex TPU95 offers an optimal balance between flexibility and ease of printing, making it ideal for most users. With a hardness of 95A, it is soft enough for most practical applications, yet significantly more tolerant of setup errors and an imprecisely calibrated printer. It's the recommended choice for first-timers with TPU and for all-round use — from protective cases to functional pieces.

PolyFlex TPU95-HF (High-Flow)

PolyFlex TPU95-HF was developed specifically for high-speed printers such as the Bambu Lab series, Prusa MK4 and other modern machines with powerful extruders and fast movement. The high-flow formulation enables printing at 50–100 mm/s without compromising surface quality or mechanical properties. An ideal choice for larger parts, small-batch production or when lead time is a critical factor for your project.

Data from tests and surveys

Laboratory studies in peer-reviewed scientific journals confirm that 3D printing parameters (layer height, infill density, orientation of the part relative to the bed) significantly affect the mechanical properties of TPU parts—from tensile strength to elasticity, elongation at break, and fatigue strength under cyclic loading.

What the research shows

Several peer-reviewed academic studies have looked at how 3D printing settings affect the strength and elasticity of TPU parts. These studies are useful for understanding the relationship between parameters and ultimate mechanical properties, although for most hobby applications it is not necessary to strictly follow laboratory protocols.

A study published in MDPI Engineering Proceedings, analyzed the influence of parameters such as layer height, printing speed and extrusion temperature on the mechanical properties of FDM printed TPU samples. The results show that a lower layer height (0.1–0.15 mm) leads to a denser structure and improved tensile strength, but at the expense of a significantly longer printing time. Also, temperature has an optimum point — too low or too high a temperature deteriorates the mechanical properties of the finished part.

Another study in PMC (PubMed Central) investigated TPU 98A and found that the orientation of the part relative to the bed had a significant effect on the strength characteristics. Samples printed in a horizontal orientation (XY plane) exhibit different properties than those printed vertically (Z axis) due to the anisotropic nature of the FDM process. Fill density is also a critical factor—higher infill density improves strength but reduces elasticity.

A practical interpretation for hobby users

For hobby users and small workshops in Bulgaria, these studies mean the following when choosing parameters for your projects:

• Lower layer height = stronger and denser part with a smoother surface, but more time to print and more nozzle wear. Use 0.12–0.16 mm for functional parts and 0.2–0.24 mm for rapid prototyping.
• Higher infill density = a more durable and hard part with a better ability to withstand a load, but with less flexibility and with more material used. For maximum flexibility use 15-25%, for strength - 50-80%.
• Orientation matters — consider how the part will be loaded in real use and orient it so that the layers are not perpendicular to the main direction of loading. This is especially important for parts that will be bent repeatedly.

You don't need to chase lab parameters for everyday projects — the important thing is to understand that the settings can be optimised according to the specific application and end product requirements. Experiment and document your results for future reference.

Key takeaways for successful TPU printing

After a detailed overview of all the important aspects of working with TPU, here are the summarized key takeaways to remember:

1. TPU is a unique material with irreplaceable properties — combines elasticity, impact resistance and abrasion resistance that PLA and PETG cannot offer. The choice of Shore A hardness (90A, 95A, 98A) determines the balance between softness and easy printing — start with 95A if you're a beginner.
2. A direct extruder is highly recommended — especially for softer variants (90A–95A). The short filament path minimizes feeding problems. If you have a Bowden system, start with a harder TPU (95A or 98A) and reduce the print speed significantly.
3. Settings should be conservative — nozzle temperature 220–235°C, bed temperature 50–60°C, print speed 25–35 mm/s, minimal or no retraction. High-flow versions such as TPU95-HF allow faster printing, but still require attention to parameters.
4. Storage is critical for quality results — TPU is a hygroscopic material that absorbs moisture from the air. Use a dry box, vacuum bags with silica gel and dry the filament as needed at 50–55°C for 4–8 hours.
5. The applications are almost limitless — from gaskets and anti-vibration feet to RC tires and custom electronics cases. The possibilities are only limited by your imagination and the needs of the particular project. Experiment with different infill percentages and patterns for different mechanical properties.

Frequently Asked Questions (FAQ)

1. Can I print TPU on a Bowden extruder printer?

Yes, but it is significantly more difficult compared to a direct extruder. Choose a harder TPU (95A or 98A), reduce the print speed to 15-25mm/s and minimize or completely eliminate retraction. Expect more stringing and possible feeding issues. Some users modify their Bowden systems to better feed flexible materials.

2. What is the difference between TPU and TPE?

TPE (Thermoplastic Elastomer) is a general term for a whole class of flexible plastics, and TPU (Thermoplastic Polyurethane) is a specific type of TPE. In practice, when you see "TPE filament" on the market, it is often polyurethane-based, but may have different formulations and properties. TPU is the most popular and widespread representative of the TPE family for 3D printing.

3. Why does my TPU print have a lot of stringing?

Stringing in TPU is usually due to one of three causes: too high a nozzle temperature, excessive or too rapid retraction, or moisture in the filament. Try reducing the temperature by 5–10°C, minimizing retraction to 0.5–1 mm, and drying the filament if it has been exposed for more than a day or two.

4. Is TPU safe for contact with food or skin?

Most TPU filaments on the market are not certified for contact with food (they are not food-safe). If this is important to your project, check the specific manufacturer's specifications and look for a food-contact certificate that is explicitly stated. For short-term skin contact, check the specific manufacturer's safety and certification information, but for medical applications or prolonged skin contact, a specialized material with appropriate certificates is required.

5. At what temperature can I use TPU parts?

Most TPU filaments retain their mechanical properties between -40°C and +80°C, which covers most everyday applications. Above 80–90°C the material begins to soften and lose elasticity and strength. If you need higher heat resistance, look for specialized high-temperature TPU formulations or consider an alternative material such as TPV or silicone.

6. How much infill should I use for TPU?

Optimal fill depends on the specific application. For maximum flexibility and softness, use 10-20% infill. For stronger, stiffer parts that need to withstand load, increase to 40–60%. Infill patterns such as Gyroid and Honeycomb work well to balance flexibility, strength and material efficiency.

7. Can I paint or glue TPU details?

Painting TPU is difficult — most standard paints don't stick well to the smooth surface and peel off when bent. For better results, use flexible primer or specialized paints for plastic and rubber. For gluing TPU to TPU or other materials, use cyanoacrylate adhesive (super glue), contact glue or specialized polyurethane glue.

8. How do I know if my filament has soaked up moisture?

Signs of wet TPU filament include: visible bubbles or bumps in the extruded material, popping or hissing sounds from the nozzle when printing, a matte or rough surface instead of smooth, and a noticeably weakened bond between layers. If you experience these symptoms, dry the filament at 50-55°C for 4-8 hours before next use.