BASF 3D Ultrafuse TPU 64D is a thermoplastic polyurethane feedstock for fused filament fabrication, supplied on spools in nominal diameters of 1.75 mm and 2.85 mm. The product is part of the BASF 3D Printing Solutions Ultrafuse portfolio and is formulated to a Shore hardness of 64D when tested under ISO 868. This hardness class places the material above conventional flexible TPU of Shore 95A and below rigid polyamide or polycarbonate feedstocks. Manufacturer-published density is approximately 1.21 g/cm³ under ISO 1183-1. The filament is used for functional parts, jigs, vibration-damping mounts, housings, and protective covers in which a balance of stiffness, impact recovery, and chemical resistance is required. Because the polymer is a thermoplastic polyurethane, processing behaviour differs from amorphous PLA and brittle ABS. Moisture control, extruder drive pressure, and filament path constraint become dominant process variables.

The Ultrafuse TPU 64D grade is not a general-purpose flexible filament. Its hardness class and melt rheology place it in a narrow processing band that demands calibration of retraction, temperature, and extrusion multiplier. Manufacturer technical data sheet values should be consulted for lot-specific batch data. Published data for this specific configuration is limited for some dynamic mechanical properties, so design allowables require coupon-level testing under the relevant ISO or ASTM method.

Which Processing Variables Change the Extrusion Envelope?

Nozzle temperature, volumetric throughput, and retraction interact strongly in Shore 64D TPU. The manufacturer-specified extrusion temperature range is generally 220 °C to 240 °C. Below 220 °C, interlayer weld strength tends to decline because polymer chain diffusion across the layer interface is incomplete. Above 240 °C, the melt may begin to undergo urethane bond cleavage if residence time is prolonged. A standard brass hot end with a 0.4 mm nozzle requires an extrusion multiplier calibrated to avoid overpressurization of the melt chamber. Feed path limitations are more severe than for rigid PLA but less severe than for Shore 95A TPU because the 64D hardness reduces filament buckling under compressive load.

Direct-drive extruders with dual-drive gears and constrained filament paths are preferred. On these systems, retraction distances of 0.8 mm to 1.5 mm are typical starting values. In Bowden configurations with tube lengths greater than 300 mm, retraction distances of 2 mm to 4 mm are often required to compensate for filament compression and elastic recovery. Print speeds above 60 mm/s may reduce interlayer adhesion because the melt spends less time in the weld zone. Volumetric flow rate ceilings are hot-end-specific; published data for this exact configuration is limited. The practical approach is to calibrate linear advance and avoid rapid speed changes that create pressure oscillations in the nozzle.

Melt viscosity is highly shear-rate dependent. At typical FFF wall shear rates of 100 s⁻¹ to 1000 s⁻¹, the viscosity falls sufficiently for extrusion through a 0.4 mm nozzle, but at lower shear rates in the melt chamber, the residence time determines degradation risk. Exact rheological data are not published in the product datasheet, so pressure advance constants cannot be transferred directly from PLA or ABS profiles. The hot-end thermistor should be accurate within ±5 °C because the processing window is narrow.

Mechanical property values reported for Ultrafuse TPU 64D are generated on printed specimens, not injection-moulded plaques. Under ISO 527-2, typical tensile strength at break is approximately 34 MPa, and elongation at break is approximately 430%. The tensile modulus is approximately 80 MPa. These values vary with print orientation, layer height, nozzle temperature, and moisture content. Hardness is measured under ISO 868, while tear resistance is reported under ISO 34-1. Abrasion resistance is characterized using ISO 4649. The product exhibits higher indentation resistance than Shore 95A TPU, but its tensile modulus remains far below that of glass-filled nylon or polycarbonate. This combination supports applications in which repeated flexural cycles must be absorbed without brittle fracture. The numerical ranges should not be used for design allowables unless confirmed with in-house printed test coupons per ASTM D638-14 or ISO 527-2.

Layer orientation anisotropy remains a measurable limitation. The z-direction tensile strength is lower than the x-y plane value because layer fusion is incomplete at normal print speeds. Users who require higher z-strength may reduce layer height to 0.10 mm or increase nozzle temperature within the recommended range, but this increases build time and can alter surface appearance. Published data for the exact z-strength reduction factor is limited for this grade. Notched impact values, if required, should be measured under ISO 180 or ASTM D256-10 because layer interfaces affect crack initiation.

When Moisture Uptake and Spool Conditioning Are Not Managed

TPU absorbs atmospheric moisture. Pre-drying at 80 °C for 4 h in a desiccant dryer is recommended before processing. Spools exposed to relative humidity above 60% for more than 24 h may show surface bubbles, nozzle popping, and reduced interlayer fusion. The defect mechanism is hydrolysis of the urethane group. At melt temperatures above 220 °C, absorbed water converts to steam inside the hot end, causing filament sputter and inconsistent extrusion. The product should be stored in a sealed container with desiccant when not in use. After drying, the filament can be processed in open air for a limited window; this window shortens in humid environments.

Drying time should not exceed the manufacturer stipulation because prolonged exposure to 80 °C can soften the filament on the spool if hot spots develop. Induction or vacuum drying may be used if the temperature is controlled. In production environments where multiple spools are stored near a printer enclosure, moisture management is a practical bottleneck. A desiccant dryer with a dew point below −40 °C is more effective than a simple heated chamber at maintaining low moisture content during long builds.

These values are starting points. Actual settings must be developed on the target machine because heater cartridge wattage, thermistor calibration, and hot-end thermal mass shift the required setpoint.

Filament Diameter, Ovality, and Feed-Gear Interaction

Filament diameter variations above 0.05 mm can produce periodic over- and under-extrusion in a fixed-displacement extruder. The product is supplied with dimensional tolerances, but users should verify incoming spools with a laser micrometer. A variation of ±0.03 mm is common for industrial-grade filament. If measured ovality exceeds 0.02 mm, the effective cross-sectional area changes by more than 2%, altering volumetric flow rate. This is particularly important for Shore 64D TPU because its elastic response can magnify feed-gear marking.

Idler pressure must be set low enough to avoid shaving the filament surface. Excessive pressure creates dust that accumulates in the drive gear and can lead to under-extrusion. Hardened steel or stainless steel drive gears are preferred over brass because TPU can be abrasive after pigment addition. The spool should rotate freely to avoid filament tangling. A spool holder with a bearing-supported hub reduces feed resistance in long prints.

Chemical resistance of TPU is influenced by the ratio of hard segment to soft segment. Ultrafuse TPU 64D is used in pneumatic connectors, protective housings, and wear strips that contact oils and non-polar solvents. For prolonged immersion in strong acids, chlorinated solvents, or brake fluid, compatibility tests under ISO 175 or ASTM D543-14 are required. The grade is generally more resistant to non-polar oils than soft TPU, but swelling may still occur with high-aromatic fuels. In comparison with standard PLA, the product retains elasticity after repeated loading. Compared with ABS, TPU 64D does not require a heated chamber and has lower volatile emission during printing. Compared with nylon, it avoids the severe moisture sensitivity that requires immediate drying but still benefits from drying at 80 °C.

For impact-absorbing applications, the Shore 64D hardness class provides higher energy return than very soft TPU but lower damping than cellular elastomers. The material is not a replacement for silicone rubber in high-temperature sealing applications. Continuous-use temperature is generally below 100 °C for printed parts under load. The Vicat softening point is listed in the current manufacturer technical data sheet under ISO 306; users should verify the method and loading because printed specimens may soften earlier than injection-moulded plaques.

Regulatory data sheets for REACH and RoHS should be requested per lot. For food contact or medical use, the specific grade and colorant must be evaluated against the relevant food-contact or biocompatibility standards. BASF 3D Ultrafuse TPU 64D is not supplied with universal food-contact certification.

Fused Filament Fabrication Settings Alone Do Not Determine End-Use Performance

Post-print annealing is not typically required for TPU 64D, but stress relief at 60–80 °C for 30–60 min may reduce residual stress in thick sections. High-temperature annealing above the Vicat softening range is not advised because dimensional distortion occurs. The filament is compatible with water-soluble support in some dual-extrusion setups, but the support interface may weaken because TPU does not achieve high melt temperature with most breakaway support materials. In single-extrusion printers, overhangs above 45° require support or careful cooling. Excessive part cooling fan settings can create filament solidification before layer spreading, reducing weld strength. Fan speeds of 20–50% are typical starting points.

Comparing this grade with other Ultrafuse TPU products, the 64D hardness class is selected when a part must withstand point loads and abrasion without the floppy deformation of Shore 95A. The trade-off is lower elongation at break and reduced low-temperature flexibility. For living hinges and highly elastic straps, softer grades remain more appropriate. For rigid structural components, glass-filled PA or PC provide higher modulus but lack the energy return of TPU. The product occupies an intermediate position that is useful when both dimensional stability and impact recovery are required. Published data for the specific configuration of printed TPU 64D in dynamic fatigue is limited; rotating-beam or flexural fatigue tests must be performed on the final print orientation.

PETG and TPU 64D both offer chemical resistance but differ in deformation behaviour. PETG may yield under impact, while TPU 64D undergoes elastic deformation and recovery. This difference is measurable through tensile elongation at break and low-strain modulus. The TPU 64D grade exhibits a yield-like transition at higher strain but generally does not form whitening or stress cracking as PETG can. In flame-retardant enclosures, TPU 64D is not a substitute for UL 94 V-0 rated materials unless the specific grade is rated and certified.

Industrial FFF printers with heated build chambers are not strictly required, but a chamber temperature of 30–40 °C can improve layer adhesion in large parts. At chamber temperatures above 50 °C, the filament may soften before entering the extruder, causing feed failures. This is a practical boundary for enclosed professional machines. Changing the nozzle from 0.4 mm to 0.6 mm reduces backpressure and increases flow rate for the same feed rate, but layer adhesion may decline if the temperature is not increased accordingly. Firmware pressure advance must be recalibrated for each nozzle size because the elastic response of the melt differs.