Lehvoss LUVOCOM 3F PAHT CF 9743 BK is a black carbon-fibre-reinforced high-temperature polyamide compound supplied in filament form for material extrusion additive manufacturing. Although category listings may describe the broader product family as “Nylon, Mineral Filled,” the “CF” designation identifies discontinuous carbon fibre as the primary reinforcing phase in this specific grade, while “BK” is the black colour identifier. The product is intended for fused filament fabrication of functional prototypes, assembly fixtures, forming tools, machining aids, and short-run production components that require higher stiffness, lower thermal expansion, and better creep resistance than unfilled or mineral-filled PAHT grades.

Specifications for this material are controlled by the current Lehvoss technical data sheet, the safety data sheet, and the published processing guide. All values cited here are indicative and should be verified against the revision issued for the production lot. Mechanical test data for printed specimens are generated according to ISO/ASTM 52921:2013 for specimen naming and build orientation and are commonly reported in XY and Z orientation under ISO 527-1:2019, ISO 527-2:2012, ISO 178:2019, and ISO 75-1:2020.

How Does the FFF Processing Window Change When Carbon Fibre Is Dispersed in the PAHT Matrix?

Before extrusion, the material is dried in a desiccant or vacuum dryer at 80 °C to 100 °C for 4 h to 12 h. For open-feed systems, the dew point of the drying air should be below -20 °C. The target residual moisture is below 0.05 wt% because hydrolytic chain scission of the high-temperature polyamide matrix becomes measurable above 0.10 wt% at melt temperatures. Batch-to-batch variation in moisture content is a documented failure mode when filament is left exposed to ambient relative humidity above 50 % for more than 4 h in unsealed conditions.

The extrusion temperature at the nozzle is normally set between 300 °C and 330 °C. A hardened steel, nickel-chromium, or ruby-tipped nozzle with a diameter of 0.4 mm or 0.6 mm is required; a brass orifice wears rapidly because of the discontinuous carbon fibre content, and measurable diameter drift can occur after 1 kg to 3 kg of throughput. The build platform temperature is maintained at 100 °C to 130 °C. A passively or actively heated build chamber in the range of 65 °C to 90 °C is used to limit warpage and delamination at the layer interface. Chamber temperature below 60 °C raises the risk of corner lifting and interlayer cracking in components with long continuous toolpaths or wall thicknesses above 4 mm.

Printing speed is typically set between 35 mm/s and 60 mm/s for a 0.4 mm nozzle and is adjusted to keep volumetric flow rate below approximately 8 mm³/s to 12 mm³/s. Retraction distance is kept between 0.5 mm and 1.2 mm at 20 mm/s to 30 mm/s for direct-drive extruders. The part-cooling fan is disabled or limited to 0 % to 20 % because rapid superficial cooling increases crystallisation gradients and amplifies warpage. A 0.15 mm to 0.25 mm layer height is used for the balance between interlayer bonding and deposition time.

At idling temperatures above 300 °C, the melt residence time in the hot zone should be kept below 10 min to 15 min. Prolonged idle at extrusion temperature can generate molecular weight reduction and carbon-fibre agglomeration near the nozzle constriction. After idle periods longer than 15 min, a purge length of 50 mm to 100 mm is typically discarded until a smooth, continuous extrudate with no surface voids is observed. These measures are based on production floor failure reports in which thermal degradation caused nozzle clogging and intermittent extrusion in reinforced PAHT filament.

Adhesion to unheated polyetherimide or borosilicate glass build surfaces is improved with a thin, dried polyamide-compatible adhesive film. Carbon-fibre-filled PAHT can bond so strongly to unprepared PEI that part removal damages the build sheet; a release-compatible adhesive layer or a flexible spring-steel build plate is therefore preferred for production batches. The material is not recommended for open-print environments without local exhaust ventilation because the heated ejection of reinforced filament generates particulate emissions that must be controlled under the printer operator’s workplace exposure assessment.

In direct-drive systems, filament handling is preferred over long bowden tubes because the stiff, brittle filament can buckle or fracture when fed through constrained paths with bend radii below 150 mm. In printer configurations where a bowden feed is unavoidable, a low-friction reverse-bowden guide with an inner diameter of 2.2 mm to 2.8 mm reduces drag and prevents filament scoring. These constraints are drawn from production-scale behaviour on enclosed FFF machines with build volumes up to 300 mm cube; published data for printer-specific configurations beyond that size is limited.

Thermomechanical Property Anisotropy Across ISO 527-1/-2 and ISO 75-1/-2 Geometries

Material property data for FFF grades must be interpreted in terms of print orientation. The following table summarises representative property ranges for the LUVOCOM 3F PAHT family when specimens are built in the XY orientation and tested according to the indicated standards. The values are not a substitute for lot-specific certificate data but provide a comparative envelope for unfilled, glass-fibre-reinforced, and the CF 9743 BK grade.

For the CF 9743 BK grade, the carbon fibre lowers the coefficient of linear thermal expansion in the XY plane relative to unfilled high-temperature polyamide. Published data for the exact grade-specific CLTE in the Z direction is limited; however, FFF deposition of discontinuous-fibre-filled semi-crystalline polyamide typically produces Z-direction thermal expansion closer to the matrix value because of the uninterrupted polymer-rich interlayer domain. This anisotropy must be accounted for in tolerance calculations for parts with critical hole-to-hole dimensions across multiple build layers.

Mechanical anisotropy follows the same logic. Tensile strength in the Z orientation commonly falls to 40 % to 60 % of the XY value for carbon-fibre-reinforced PAHT processed by FFF, depending on chamber temperature, layer height, and extrusion temperature. Interlayer fusion is improved by maintaining the melt temperature at the upper end of the processing window and by minimising the time between the deposition of adjacent layers. For geometrically stable tooling, a dwell time that allows the previous layer to reach a temperature near the crystallisation onset is more effective than increasing print speed.

Raster angle modifies the measured tensile modulus in the XY plane. When tensile specimens are built with all raster lines parallel to the load axis, the modulus approaches the upper end of the reported range; when the same specimens are built at ±45° or with alternating orthogonal layers, the effective tensile modulus can decrease by 20 % to 40 %. This dependency is more pronounced for the carbon-fibre-filled grade than for unfilled PAHT because the discontinuous reinforcement is aligned by the extrusion flow and does not fully randomise across layer interfaces. Mechanical testing of a representative build orientation is therefore part of first-article approval for load-bearing components under ISO 527-2.

Moisture uptake after printing reduces the glass transition temperature and tensile modulus of the polyamide matrix. Conditioning under ISO 1110 may be used to stabilise parts before dimensional inspection; dimensional changes of 0.5 % to 1.5 % can occur in uncontrolled humid environments for unfilled or lightly filled polyamides, while carbon fibre constrains volumetric expansion but does not eliminate it. For close-tolerance fixtures, parts should be annealed or conditioned in a controlled environment before final machining or metrology.

In forming tools for thermoforming or composite layup, the material is exposed to contact temperatures that may reach 130 °C to 160 °C for short cycle times. The suitability of the CF 9743 BK grade for a specific mould surface must be confirmed by thermal ageing tests under the actual contact pressure and exposure duration; published data for this specific configuration is limited, but continuous exposure above the heat deflection temperature can produce localised surface marking and reduction of flexural modulus under ISO 178. For low-contact-pressure vacuum fixtures operated below 90 °C, the material is an alternative to machined aluminium tooling when electrically conductive or non-marring surfaces are acceptable.

The carbon-fibre-filled grade is used in high-stiffness robotic end-effectors, CNC workholding jaws, inspection gauges, and pick-and-place nests. In such parts, the build orientation is set so that bending loads act along the XY plane; loading across the layer interface is avoided or reduced by increasing wall loops and using a solid infill in the load-bearing region. On production machines with a build chamber maintained above 70 °C, the interlayer tensile strength measured on printed tensile bars is less variable than on open-frame machines; the absolute value remains orientation-dependent and must be tested as part of process capability studies.

When a Mineral-Filled Nylon Data Sheet Is Used as an Inappropriate Proxy

The grade should not be substituted with a generic mineral-filled nylon data sheet or with an unfilled PAHT grade. Mineral-filled polyamide products are commonly formulated to improve low-warp dimensional stability and surface finish, but their tensile modulus and heat deflection temperature are lower than those of a carbon-fibre-filled PAHT in the XY build orientation. The CF 9743 BK grade is distinguished from the mineral-filled LUVOCOM 3F PAHT variants by its higher specific stiffness, lower creep under mechanical load, and a more pronounced difference between XY and Z mechanical properties.

Compared with the glass-fibre-reinforced LUVOCOM 3F PAHT grade, the carbon-fibre-reinforced version provides higher tensile modulus and a darker, more wear-resistant surface, but it also introduces a higher risk of nozzle abrasion and may exhibit measurable surface electrical conductivity. If electrical insulation is a requirement, the glass-filled or mineral-filled grade should be evaluated under the specific voltage and frequency conditions; surface resistivity and dielectric strength should be confirmed according to IEC 62631 and IEC 60243 rather than inferred from material class.

Compared with high-temperature amorphous filaments such as polyetherimide or semicrystalline materials such as PEEK, the PAHT CF 9743 BK grade is processed at a lower extrusion temperature and can be used on a wider range of closed-chamber FFF machines. Its continuous-use temperature is lower than PEEK and its moisture absorption is higher than polyetherimide; therefore, dried storage and pre-printing moisture control are mandatory boundary conditions. The use of a mineral-filled nylon specification as a proxy for this product creates three risks: underestimation of interlayer thermal expansion, overestimation of Z-direction interlayer strength, and incorrect nozzle material selection.

Field experience on twin-screw compounding lines for carbon-fibre-filled polyamide highlights that fibre-length retention during masterbatch production and filament extrusion controls final stiffness. Fibre attrition in a co-rotating twin-screw extruder with a screw L/D ratio of 24:1 to 40:1 can reduce the final fibre length below the critical length for effective load transfer. Filament produced with excessive shear heating can show higher melt flow rate under ISO 1133-1 but lower mechanical performance; this trade-off is monitored through melt viscosity and filament diameter consistency. For the end user, filament diameter tolerance should be verified with a laser or dual-axis micrometer across the spool; outlier regions above ±0.05 mm can cause extrusion flow variation and localised porosity.

Support structures for the material are typically removed mechanically; water-soluble PVA supports are unsuitable because the high build chamber temperature and prolonged heat exposure degrade PVA at the interface. Breakaway supports printed in the same material or a dedicated PA support grade are used where overhangs exceed 45°. The use of support roofs and dense interfaces should be validated because the high melt temperature of the CF 9743 BK grade can fuse to adjacent support surfaces more strongly than unfilled PAHT.

Regulatory compliance with EU REACH and RoHS Directive 2011/65/EU should be confirmed against the current declaration issued for the specific production lot. The carbon-fibre-filled PAHT product is not intended for food-contact or medical applications unless explicitly cleared by the manufacturer.

The product is stored in sealed containers with desiccant at ambient temperatures below 30 °C and relative humidity below 20 %. Before resumed printing after storage, the filament is re-dried at 80 °C for 4 h to 6 h. Failure to re-dry after exposure to ambient humidity above 60 % is a recurring cause of steam discharge from the nozzle, which appears as surface hazing and reduced interlayer tensile strength under ISO 527-2.