Selective laser sintering with CRP Technology Windform FX Black is performed as a powder-bed fusion process in which a black polyamide-based powder is deposited, preheated, and selectively fused. The grade is supplied as a pre-pigmented black powder; the colourant is dispersed through the polymer particles rather than applied only as a post-sintering surface dye. Within the CRP Windform range, the material occupies a polyamide position below high-stiffness carbon-filled grades and above low-durometer elastomer powders for strain capacity. Manufacturer documentation identifies the material as suitable for functional prototypes and low-volume production parts that require a dark, repeatable surface and ductile mechanical response.

Industrial SLS platforms processing this powder typically use a 10.6 µm CO₂ laser and nitrogen inerting. The process depends on differential scanning calorimetry data under ISO 11357-3 to define the build-bed setpoint; the setpoint is selected below the melt onset to avoid powder-bed caking. Because the powder is black, laser absorption at 10.6 µm is not identical to natural or white polyamide 12, and parameter transfer from unpigmented powders should be qualified by exposure tests. The current manufacturer-published technical data sheet should be consulted before process qualification, because build orientation, powder refresh ratio, and machine type all shift the resulting mechanical values.

Why Does Powder Moisture Dictate the SLS Processing Window for Windform FX Black?

Before processing, polyamide powder absorbs atmospheric moisture. Moisture concentrations above 0.10 % by mass are associated with reduced powder flow, electrostatic charging, and steam porosity at the melt front. Drying in a desiccant dryer or vacuum oven at approximately 80 °C is applied until the residual moisture is confirmed by gravimetric or Karl Fischer analysis. In production-scale equipment such as an EOS P396, a 3D Systems ProX 6100, or a Farsoon HT403P, the conditioned powder is loaded into a feed bed and recoated in layers. A typical layer thickness for this material class is 100–120 µm, but the final parameter set must be tuned to the recoater speed, blade material, and build-envelope temperature. The build chamber is normally held 10–15 K below the melt onset measured by ISO 11357-3; this prevents premature sintering of the bed while allowing the laser to complete fusion at the scan line. Oxygen in the process chamber is controlled to limit thermo-oxidative yellowing and mechanical embrittlement. Lower oxygen partial pressures, commonly below 1 % by volume, are preferable; machines with nitrogen generators maintain positive pressure to reduce ingress.

Laser energy density is not a fixed number because black pigment alters the absorption of incident laser power. Qualification builds are performed using a matrix of laser power, scan speed, scan spacing, and beam offset. The objective is a melt pool that penetrates at least one layer but does not produce excessive edge overheating or curl. Large flat surfaces are particularly sensitive to in-build curl when the melt pool cools below the crystallisation onset before the layer is complete. The crystallisation exotherm measured by ISO 11357-3 therefore defines the lower practical boundary of the build envelope. Batch-to-batch variation in pigment dispersion can also influence laser absorption and melt viscosity, so differential scanning calorimetry and melt-flow-rate checks are recommended before production release.

Mechanical characterisation of Windform FX Black follows polyamide SLS practice. Test specimens are built in X-Y and Z orientations because interlayer fusion produces anisotropic properties; the Z-axis tensile elongation is often lower than the X-Y value. The table below lists representative property bands drawn from manufacturer-published polyamide SLS data for the grade. These bands are not specification limits and should be verified with the current technical data sheet for the specific build orientation and powder refresh ratio.

The bands place Windform FX Black in the ductile polyamide region rather than the high-stiffness reinforced region. Under ISO 527-2, carbon-fibre-filled SLS grades in the same product family generally report elongation at break below 10 %; Windform FX Black is therefore selected for snap-fit arms, hinges, and closures that require strain recovery. The presence of black pigment affects the visual appearance of worn or abraded surfaces, but the matrix retains the moisture sensitivity characteristic of polyamide. Conditioning at 23 °C and 50 % relative humidity can reduce modulus and increase strain relative to dry-as-printed values; this shift is normal for polyamide 12-based systems. For fatigue-critical loads, published data specific to Windform FX Black is limited, and component testing under ISO 1099 or ASTM E466 at the expected R-ratio and build orientation is required.

Differences from Carbon-Filled and Glass-Filled Windform Grades in Practise

Carbon-fibre-reinforced Windform SP and Windform XT 2.0 derive high tensile modulus and low elongation from the fibre phase. In a comparison of datasheets, the carbon-filled grades show higher tensile modulus and heat deflection temperature, but their elongation at break is lower; this makes them less suitable for living hinges or snap-fit geometries that require large recoverable strain. Windform FX Black is a black aesthetic grade that does not rely on continuous carbon fibre for colour. The absence of a high-modulus fibre phase reduces abrasive tool wear during post-machining and can preserve sharp edge definition during bead blasting. Glass-fibre-reinforced Windform LX 3.0 similarly increases stiffness and dimensional stability relative to an unreinforced polyamide, but may reduce impact toughness; instrumented impact values under ISO 179-2 are needed for a valid comparison. In unfilled or lightly filled polyamide SLS grades, the dimensional stability is lower; moisture absorption can change part dimensions by 0.5–1.5 % depending on wall thickness and conditioning time. Designers transferring a part from a glass-filled grade should compensate for higher creep and lower modulus in Windform FX Black.

Compared with Windform SP, which is carbon-filled and black, Windform FX Black is often selected when the part must be non-abrasive against adjacent surfaces. Carbon-filled SLS parts can abrade softer mating materials in sliding contact. Compared with Windform XT 2.0, the lack of fibre reinforcement in FX Black lowers tensile modulus but increases the allowable strain before break. This distinction is directly relevant for snap-fit design: the maximum permissible undercut depth for a given length and thickness is proportional to the allowable strain, and polyamide grades with higher elongation at break tolerate deeper undercuts. Calculations should use tensile stress-strain data at the actual operating temperature and moisture condition, not the dry-as-printed datasheet value.

Powder refresh ratio is a further control. Virgin Windform FX Black powder is blended with recovered powder; high refresh ratios preserve impact resistance and colour consistency, while low refresh ratios reduce cost but can narrow the sintering window. In production-scale SLS service, recovered polyamide 12-based powder increases melt viscosity and can shift the onset of crystallisation; a differential scanning calorimetry check on each powder lot is used to adjust the bed setpoint. For this specific black grade, published data on the maximum allowable number of powder re-use cycles is limited, so process validation should include melt-flow-rate measurement under ISO 1133-1 and tensile-bar builds after each refresh cycle.

When ductile components such as bellows, cable-routing clips, and protective covers are produced in short series, the build layout is designed to orient flexural axes in the X-Y plane where possible. In production-scale SLS machines, the parts are depowdered after cool-down, then bead-blasted with glass or ceramic media to remove adhered powder. The as-sintered surface roughness of polyamide SLS components is commonly in the 6–15 µm Ra range when measured by stylus profilometry according to ISO 4287; published roughness data specific to Windform FX Black is limited. The black pigmentation reduces the need for dyeing, but it also makes local overheating marks or part-orientation boundaries visible on untextured surfaces. Secondary operations include drilling, tapping, and insertion of heat-set inserts; the ductile matrix supports thread-forming screws if pilot holes are sized according to the manufacturer-published boss design rules.

Operational boundaries include hygroscopic ageing before drying, limited ultraviolet stability unless coated, and limited documented performance in chemical contact. Continuous exposure to hot water, strong acids, and certain polar solvents can promote hydrolysis and stress cracking. Compatibility testing under ISO 22088 or specific service-condition immersion is therefore required before specifying the material for fluid-contact applications. Windform FX Black is not a certified flame-retardant grade; where fire-resistance is required, Windform FR1 should be evaluated under the relevant aviation or rail standard. The current safety data sheet and REACH/RoHS declarations should be confirmed for the intended jurisdiction, because published regulatory data for this specific configuration is limited.