The BASF 3D Ultrafuse PA Fused Filament, Conditioned is an unfilled polyamide-based feedstock for fused filament fabrication, supplied in 1.75 mm and 2.85 mm diameter formats. The base polymer is a polyamide 6/66 copolymer produced without chopped carbon fibre or mineral reinforcement; the conditioned designation identifies a bulk moisture state in the filament, not a surface coating. Supplier documentation places the product within the Ultrafuse PA family and specifies a packaging moisture target intended to maintain interlayer fusion behaviour during open-chamber printing. The conditioned state is achieved by controlled humidification of the wound spool to a defined residual water content before the spool is sealed in a desiccant-lined barrier film. The result is a filament that enters the hot end with more moisture than a dried PA grade and less than a moisture-saturated polyamide stored at ambient conditions.

How does the conditioning state alter the FFF weld-line response?

Water in polyamide 6/66 acts as a temporary plasticizer. During deposition, the conditioned melt retains a lower viscosity at the road interface, which promotes polymer-chain diffusion across adjacent extrusion roads before crystallisation locks the weld line. The same moisture also depresses the glass transition of the amorphous phase and delays solidification, so the weld line remains above the critical chain-entanglement threshold for a longer portion of the cooling cycle. The mechanical consequence is measurable under ISO 527-2: conditioned XY specimens typically exhibit lower tensile modulus and higher elongation at break than freshly dried specimens of the same filament. Published technical literature for unfilled polyamide 6/66 FFF feedstock places conditioned tensile modulus in the range of 2,200–2,600 MPa, while dried samples may approach the upper portion of that band or slightly exceed it. Elongation at break commonly falls between 25% and 40% in conditioned specimens, depending on print orientation, nozzle temperature, and test speed. The shift is reversible: if the filament is dried to below 0.1 wt% water, the modulus increases and the weld-line ductility decreases.

Moisture uptake in this polyamide follows Fickian absorption behaviour. Under ISO 62 conditions of 23 °C and 50% relative humidity, an unfilled PA6/66 copolymer approaches an equilibrium water content of approximately 2.5–3.0 wt%. The conditioned product is packaged below that saturation point, generally within a 0.4–0.9 wt% window, so that the spool does not exhibit the gross steam pitting and road foaming associated with saturated nylon. Once the barrier packaging is opened, the moisture content drifts toward the ambient equilibrium value; at 50% relative humidity the drift is slow enough for a one-day print campaign, but at 70% relative humidity the spool can exceed the useful conditioning window within 24–48 h. Operators printing in high-humidity enclosures should transfer the spool to a desiccant chamber below 25% relative humidity between builds.

Mechanical and thermal data reported for conditioned unfilled polyamide 6/66 FFF specimens are summarised below as typical ranges, not guaranteed minima, because print orientation, nozzle temperature, infill geometry, and ambient humidity shift the values. Exact acceptance values should be taken from the supplier’s technical datasheet for the specific diameter and spool lot.

The wide heat deflection range reflects the shift in polyamide behaviour across different moisture states; a saturated part has a lower effective service temperature than a freshly conditioned part because plasticization reduces stiffness and accelerates creep under load. Creep rupture and long-term fatigue data for this specific filament are not fully published; any load-bearing specification should be validated on test coupons printed in the same orientation as the final component.

Extruder, build-surface, and feed-path parameter window

The melt processing window for conditioned PA is bounded by incomplete fusion below 235 °C and oxidative yellowing above 265 °C. A direct-drive all-metal hot end with a 0.4 mm brass or hardened steel nozzle is the baseline configuration; the first layer is typically deposited 5–10 °C above the remaining layers to promote adhesion. Build-platform temperature is maintained at 80–100 °C. Glass surfaces coated with a thin polyvinyl acetate glue layer are commonly used, although polycarbonate or PEI sheets can also be used if cleaned and roughened. Enclosed builds are not mandatory for small sections, but open-frame systems should maintain an ambient air temperature above 20 °C because cold draughts accelerate edge lift.

Bowden-feed systems with tube lengths above 700 mm produce higher drag force with this filament than with PLA or PETG because conditioned polyamide is flexible and can buckle in unsupported tube bends. Production lines that convert from PLA to conditioned PA frequently retain the same extruder spring tension and then observe under-extrusion at print speeds above 60 mm/s. Reducing the idler compression and shortening the filament path to 400 mm or less restores feed consistency on direct-drive mounts. The heat break should be of an all-metal design with a cold-side fan delivering at least 5 CFM; if the build volume approaches 40 °C, the cooling fan must be ducted to prevent heat creep and plugging. Brass nozzles are acceptable for unfilled PA, but diameter erosion should be checked after 200 h of run time at the upper end of the temperature range.

Build planning for large-format parts should account for the crystallisation shrinkage of polyamide. On unheated open-frame machines, the first 10–20 mm of a long part can curl upward because the bed temperature at the outer edges is often 10–15 °C below the centre setpoint. Adding a full-height brim and maintaining a bed surface flatness better than 0.2 mm reduces this defect more effectively than increasing extrusion temperature alone. Adhesive films should be inspected for wear after each build because polyamide can tear the film surface when removed warm. Warm part removal is preferred; removing a part from a cold bed below 40 °C can peel the adhesive film or fracture thin base flanges.

If the service environment includes aliphatic hydrocarbons or cyclic humidity

Where cutting fluids, mineral oil, or aliphatic hydrocarbon exposure governs the specification, polyamide is generally screened after chemical compatibility testing under ISO 175 or ASTM D543. The PA6/66 backbone shows lower swelling in mineral oil than many PLA and PETG grades, but the same polymer absorbs polar solvents and water more aggressively than amorphous PETG. A part moved from a 30% relative-humidity inspection room to a 70% relative-humidity installation can exhibit linear expansion above 0.5% depending on section thickness and local moisture equilibration time. Toleranced features should therefore be evaluated after a humidity stabilisation period, not immediately after print removal. Compared with PLA, the conditioned PA has lower tensile modulus and higher elongation at break under ISO 527-2; PLA datasheets frequently report tensile modulus between 3,000 MPa and 3,500 MPa, whereas this conditioned polyamide is typically below 2,600 MPa. The trade-off is inverted in fatigue and impact: the PA grade’s ductility and notch-insensitive response to ISO 179-1/1eA loading often exceed PLA and ABS in thin-wall fixtures.

Test data for this filament are commonly generated on FFF specimens printed in the XY axis and conditioned to a standard atmosphere before testing. XY values should not be compared directly with injection-moulded ISO specimens because the road structure introduces porosity and anisotropic strength. Z-axis tensile strength is typically lower than the XY value and depends on layer height, nozzle temperature, and chamber temperature. Designers using this material should request or generate Z-strength data where the load path crosses layer boundaries; published data for this specific configuration is limited beyond the supplier’s XY datasheet.

Conditioned unfilled polyamide is not a drop-in replacement for dry or fibre-reinforced PA

Profiles written for dried PA require adjustment when the conditioned product is loaded. Lower melt viscosity alters die swell and stringing behaviour; retraction distance on direct-drive systems may need to be increased from 1.0 mm to 1.5–2.5 mm, and Bowden systems may require 4–6 mm, depending on nozzle diameter and barrel temperature. Drying the conditioned product before use removes the very moisture that improves interlayer toughness. The operational boundary is therefore narrow: the spool should remain sealed until loaded, and partial spools should be returned to a desiccant chamber below 25% relative humidity within 4 h of exposure. If the material has exceeded 0.9 wt% moisture due to ambient storage, recovery consists of drying at 80 °C for 4–6 h, followed by reconditioning at 23 °C and 50% relative humidity until extrusion no longer produces visible steam pitting. For carbon-fibre-reinforced Ultrafuse PAHT grades, the stiffness and heat deflection temperature are higher, but the conditioned unfilled grade generates less nozzle abrasion and retains higher elongation at break.

Failure modes documented on open-enclosure FFF systems include edge lift at the build surface, interlayer delamination in thin-walled zones, and microbubble formation when moisture exceeds approximately 1.2 wt%. Microbubbles are not merely cosmetic defects; they reduce the effective load-bearing cross-section and lower tensile strength under ISO 527-2. Sections with wall thickness above 4 mm are particularly prone to midplane residual stress from crystallisation shrinkage, so a heated chamber or enclosed build volume is recommended. Without a chamber, reducing layer height to 0.15 mm and increasing perimeters to at least 4 suppresses visible stress-relief cracking at the part base. Dimensional inspection should occur no earlier than 24 h after printing and at a controlled relative humidity, because conditioned polyamide continues to exchange moisture with the environment for several days. Any downstream bonding operation should be validated after that stabilisation period, because residual moisture affects paint adhesion and solvent-borne coating performance.