Lehvoss LUVOCOM 3F PAHT CF 9742 BK Nylon, Mineral Filled, for Additive Manufacturing is a black filament-grade compound formulated specifically for melt-extrusion additive manufacturing. The product belongs to the LUVOCOM 3F family, which is supplied as filament rather than as powder for laser sintering or as a resin for vat photopolymerization. The matrix is a high-temperature polyamide (PAHT). The reinforcement package combines chopped carbon fibre with a mineral filler, and the BK designation identifies the black colour. The mineral phase is not a passive extender; it modifies nucleation density, solidification rate, shrinkage anisotropy, and printed surface appearance. Because the material is printed rather than injection-moulded, its mechanical response is orthotropic and strongly affected by layer height, extrusion temperature, chamber temperature, and moisture content. Published values in the manufacturer’s datasheet are specific to the stated specimen preparation route and cannot be transferred directly to parts with different infill geometry or print orientation.

The polymer matrix is a semicrystalline high-temperature polyamide. Compared with PA6 and PA66, PAHT grades exhibit a higher deflection temperature under load and reduced softening during short-term thermal excursions. The carbon fibre raises elastic modulus and lowers creep under sustained load. The mineral filler reduces warpage by increasing nucleation site density and lowering the coefficient of volumetric shrinkage during crystallization. The trade-off is a reduction in ductility and interlayer toughness relative to unfilled or impact-modified polyamide filaments. In printed form, the material is not isotropic. The interlayer boundary is the limiting plane, and tensile values obtained in the XY orientation must not be extrapolated to the ZX orientation without separate testing.

The carbon fibre is a short chopped fibre rather than continuous fibre. The fibre population is oriented primarily along the print path because of the shear field in the nozzle. The mineral particles have a low aspect ratio and do not orient to the same degree, which reduces in-plane/out-of-plane anisotropy and contributes to flatness retention in large parts. During nozzle flow, the fibre phase can migrate toward the core of the bead, while the mineral particles remain more uniformly dispersed. This core–shell distribution can create a resin-rich skin that influences surface appearance but does not eliminate abrasive wear on the nozzle. The final printed part also contains a shorter fibre length distribution than the as-compounded granulate, because high-shear flow through the nozzle fractures some fibre. This is one reason injection-moulded values for the same nominal filler content are not directly transferable to fused filament fabrication specimens.

What Limits the Processing Window for PAHT CF 9742 BK?

Moisture is the first processing boundary. The filament is hygroscopic. If a spool is left unsealed at 60 % RH, the surface and near-surface resin can absorb sufficient water to hydrolyze during extrusion. Drying at 80 °C for 4 h to 8 h in a desiccant dryer with a dew point at or below −40 °C is required before processing. Filament exposed for more than 48 h at 60 % RH should be re-dried, and a Karl Fischer moisture check should show residual water below 0.1 % by mass for critical parts. Printing wet filament produces voids, irregular bead width, audible outgassing, and reduced interlayer peel strength. Spools should be stored in sealed bags with fresh desiccant or in a dry cabinet below 20 % RH. Indicating silica gel is not sufficient for critical applications because its colour transition occurs above the target moisture level.

The melt viscosity of the carbon-fibre/mineral-filled PAHT is higher than that of unfilled PAHT. PTFE-lined hotends are not acceptable because the required melt temperature exceeds the degradation limit of the lining. The hotend should be an all-metal design with a hardened steel or ruby nozzle; the carbon fibre is abrasive and will enlarge a brass orifice during a single spool. Extruder backpressure increases with filler content, and volumetric flow should be limited to a range that the extruder can maintain without step loss. The processing parameters in the following table are starting values, not universal settings; they require adjustment for nozzle diameter, layer height, and machine enclosure efficiency.

Chamber temperature is a critical variable because PAHT crystallizes quickly when the deposited bead cools. A chamber below 80 °C can produce differential contraction between the heated bed and the upper layers, causing corner lifting or mid-layer delamination in parts longer than 200 mm. Conversely, chamber temperatures above 120 °C can soften the part and cause sagging in overhanging regions. The build plate temperature should be maintained within ±5 °C across the tool surface. Edge-to-centre gradients on aluminium plates can initiate edge lifting even when the setpoint is within the recommended band. On production-scale machines, the first observable failure mode from insufficient chamber heat is corner lifting on large flat parts, followed by mid-layer delamination along the long axis of the part. Raising bed temperature alone may not resolve these failures because the upper layers cool below the crystallization temperature; the heated chamber must bring the entire part volume into a narrower temperature window. If the chamber is not well insulated, the power required to maintain 100 °C can exceed the machine heater capacity in cool environments.

Bed adhesion with PAHT CF is sensitive to surface preparation. PEI or PEX surfaces are preferred; glass and polypropylene are not reliable. A polyamide-compatible adhesion promoter can be used, but silicone-based release agents should be avoided because they migrate and contaminate the part surface. For parts with large continuous perimeters, a brim or raft may be required when the chamber is below 100 °C. Sharp internal corners should be radiused to reduce stress concentration and the tendency to lift.

Mechanical testing for this compound follows ISO 527-2 for tensile properties and ISO 178 for flexural properties on printed specimens. Specimens are usually printed flat in the XY orientation with 100 % infill and conditioned under ISO 291 before testing. Density is determined according to ISO 1183-1, and heat deflection temperature is reported according to ISO 75-2 method A or B. These test methods do not characterize interlayer strength; for that, a bond tensile or peel specimen is required. Manufacturer datasheets may report XY values, but ZX values are normally lower because the interface between layers remains the fracture path. Published data for this specific configuration is limited; users should validate ZX values on the target machine rather than relying on XY data or injection-moulded reference values.

The following table lists the standard methods that are relevant to specification review for this material. The table is not a certificate of analysis, and lot-specific values must be obtained from the supplier.

When Mineral Filler Is Combined with Carbon Fibre, the Warpage–Toughness Trade-off Shifts

Compared with an unfilled PAHT filament from the LUVOCOM 3F family, 9742 BK has a higher elastic modulus and lower elongation at break. The unfilled grade generally shows better interlayer fusion and higher impact toughness, but it also exhibits greater warpage and lower dimensional stability on large flat parts. Compared with a carbon-fibre-only PAHT compound, the mineral component in 9742 BK reduces anisotropic shrinkage and can improve flatness at the expense of some impact resistance. The mineral filler may also increase melt viscosity and nozzle backpressure. Within the LUVOCOM 3F range, a grade without carbon fibre has lower modulus but higher impact resistance, while a grade with carbon fibre but without mineral may show slightly higher modulus and lower viscosity, with less effective warpage control. The 9742 BK designation therefore identifies a balance between stiffness and dimensional stability rather than the maximum possible strength or toughness.

Compared with carbon-fibre-filled PEEK or PEI filaments, 9742 BK processes at lower nozzle and chamber temperatures, which expands the machine population on which it can be printed, but the continuous service temperature and chemical resistance are lower. Compared with PA12 CF, the PAHT matrix provides higher short-term heat resistance and stiffness, but moisture absorption is higher, and the filament must be kept dry more actively. Compared with PA6 CF, the high-temperature polyamide matrix generally offers a higher heat deflection temperature and better retention of stiffness in warm environments, while PA6 CF may be easier to print on low-temperature enclosures.

Applications are therefore in dimensionally stable tooling, inspection fixtures, soldering pallets, wave-soldering fixtures, and end-of-arm tooling that are exposed to elevated temperatures for short periods. The material can also be used for functional prototypes that must survive under-hood air temperatures before final metal tooling is produced. In these applications, the design should use fewer unsupported spans and thicker wall sections than would be acceptable in unfilled nylon, because the filled grade has lower strain at failure. In soldering pallets, the material is expected to maintain flatness after repeated exposure to solder wave temperatures. In inspection fixtures, the mineral filler reduces warpage enough that close-tolerance holes can be machined after printing without excessive internal stress. For end-of-arm tooling, the lower density compared with metal reduces inertial load, but the stiffness and thermal stability must be verified for the specific robot acceleration.

Post-annealing is sometimes used to increase crystallinity and raise the heat deflection temperature. A typical annealing cycle in a convection oven at 120 °C–150 °C for 2 h is used in some production environments, but dimensional change must be measured and compensated in the CAD model. Annealing in an unsupported condition can cause distortion; parts should be fixtured or annealed on a flat ceramic plate. A printed PAHT CF part annealed at 120 °C may shrink differently in the X, Y, and Z directions, and the dimensional change is also affected by infill density and raster orientation. Close-tolerance holes may close or ovalize during annealing. Pre-compensation factors must be established on the target machine and with the same slicing parameters. A fixture that holds the part flat during annealing reduces out-of-plane distortion but can introduce residual stress if the fixture expansion coefficient differs from the part.

Spool-to-spool consistency in filled polymer filaments is controlled by online diameter monitoring, melt filtration, and filler dispersion analysis. For end users, moisture exposure history is the largest source of property variation. Two spools from the same lot can produce different mechanical results if one has been stored on an open shop floor at 60 % RH for several days and the other was kept sealed. This batch-to-batch processing variance is reduced by following a standard drying procedure and recording drying time, dew point, and spool exposure time. Filament diameter should also be checked periodically with a laser micrometer. A diametral variation of ±0.05 mm can alter the extruded bead width and create under- or over-extrusion at higher linear speeds.

The operational boundary for moisture requires sealed storage whenever the relative humidity exceeds 60 %. The compound is not recommended for continuous immersion in hot water or steam, because polyamides are hydrolytically unstable under those conditions. Strong aqueous acids, oxidizing media, and some metal chloride solutions can attack the polymer or the mineral filler. Ethylene glycol and some brake fluids can plasticize or dissolve nylon at elevated temperature. Compatibility testing should be performed for any chemical environment that includes cutting fluids, mould release agents, or continuous oil contact. The material is not intended for food-contact or medical-device use unless the finished component is separately validated under the applicable food-contact or medical regulation. For structural parts, creep and fatigue data must be generated on the target machine because short-term tensile and flexural values do not capture the effect of interlayer interfaces over long service times.