EOS CarbonMide PA12-CF is supplied as a carbon-fibre-reinforced polyamide 12 powder for selective laser sintering. The grade combines a PA12 matrix with chopped carbon fibre, yielding a black feedstock intended for functional prototypes and series-production components where stiffness per unit mass and heat deflection are design controls. On industrial SLS platforms with nitrogen inertisation, the material is typically processed at layer thicknesses between 0.10 mm and 0.12 mm. Supplier technical literature reports tensile modulus in the XY orientation between 6.0 GPa and 6.8 GPa when tested according to ISO 527-2, with elongation at break below 4%. The low elongation places the grade outside the ductile response envelope of unfilled PA12 such as EOS PA 2200. Carbon reinforcement raises heat deflection temperature and creep resistance, but it also increases thermal conductivity, which alters melt-pool solidification and makes the process sensitive to bed-temperature drift. The material is not a drop-in replacement for neat PA12; laser power, scan strategy, and powder management must be re-qualified on the target SLS machine.

Particle size distribution is controlled to maintain powder-bed density and flow. SLS polyamide powders typically occupy a range of 20 µm to 100 µm, with a D50 near 50 µm. Carbon-filled grades may exhibit a slightly broader distribution because fibre bundles require sizing and dispersion. The powder is supplied in sealed containers to limit moisture uptake before use. Bulk density and tapped density are lower than neat PA12 on a mass basis but are not directly comparable because the carbon fibre modifies packing behaviour. The product is designated for use on EOS SLS platforms in the P series, typically the EOS P 396 or comparable systems with 100 W CO2 lasers. Compatibility with other machine generations should be confirmed through the supplier’s parameter release. Published data for this specific configuration on non-EOS systems is limited.

Thermal calorimetry of PA12 feedstock typically shows a melting peak in the region of 184 °C to 186 °C and a crystallisation peak near 145 °C to 150 °C on cooling at 10 K/min according to ISO 11357-3. The gap between melting and crystallisation defines the intrinsic process window for laser sintering. Carbon fibres do not alter the PA12 phase transition temperatures substantially, but they increase the apparent thermal diffusivity of the powder bed. This narrows the practical processing window because heat is removed from the melt pool more rapidly. On industrial systems, the operator-visible symptom of a window violation is either curling at the edges of large flat parts or secondary sintering in thin-walled lattice regions. Curling typically appears when post-fusion cooling is too fast, whereas secondary sintering appears when local bulk temperature exceeds the crystallisation onset due to accumulated laser energy. Carbon-filled powder can exhibit both failure modes in a single build if scan speed and beam offset are not optimised.

What Limits the Processing Window of Carbon-Filled PA12 in Laser Sintering?

Neat PA12 SLS powders are commonly processed with a part bed temperature in the range of 168 °C to 176 °C, just below the crystalline melting region. Carbon-filled PA12, however, conducts heat away from the melt pool more readily than neat polymer. If the bed temperature drifts by more than ±3 K from the validated setpoint, the scan region can cool below the crystallisation temperature before the next layer is fused, resulting in curl and interlayer delamination. On production machines with 100 W CO2 lasers and 0.10 mm to 0.12 mm layer thickness, stable operation requires closed-loop nitrogen flow with oxygen content below 0.2% during the build. Excess oxygen produces oxidative yellowing and molecular weight reduction in the PA12 phase, lowering notched impact strength and shifting the melting peak.

Powder moisture should be controlled to below 0.1 wt%; moisture not only causes steam porosity but also changes the apparent laser absorption of the feedstock. PA12 absorbs moisture by Fickian diffusion, and at 50% RH and 23 °C neat PA12 can approach an equilibrium moisture content near 1.5 wt%. The carbon-filled grade is less hygroscopic than neat PA12 because fibre replaces a fraction of the polymer mass, but sealed storage is still required. Drying is frequently carried out in a vacuum dryer or dry-air hopper at temperatures not exceeding 80 °C; prolonged drying above this temperature can cause particle sintering in the hopper and degrade recyclability.

Process development on EOS P 396 class systems should start from the supplier-validated parameter set because carbon fibre absorbs a broader portion of the laser wavelength than neat PA12 and can create hotter local regions at equivalent laser power. Carbon-filled powders exhibit higher bulk thermal conductivity than neat PA12, which can reduce part-bed thermal gradients but also broadens the heat-affected zone around each scan vector. Thin walls and unsupported overhangs are at greater risk of secondary sintering because heat is conducted laterally into adjacent powder. Operators commonly reduce laser power or increase scan spacing by 5% to 15% relative to unfilled PA12 when moving from flat geometries to lattice-dominated builds. Failure to adjust scan parameters produces local overfusing, loss of feature resolution, and higher post-sintering extraction effort. Batch-to-batch variance in fibre dispersion also requires monitoring of powder melt flow or tapped density; variations outside the supplier control limits can produce inconsistent mechanical properties in Z-axis tensile specimens.

Property Profile and Test Data for EOS CarbonMide PA12-CF

The property ranges below consolidate supplier technical literature for X/Y-oriented specimens. They are not specification limits; Z-axis values are normally lower because SLS interlayer fusion is governed by coalescence time and melt viscosity. The carbon fibre raises tensile modulus into the range of 6.0 GPa to 6.8 GPa, while density remains near 1.03 g/cm³ to 1.07 g/cm³. Elongation at break is deliberately sacrificed, with direct implications for joining and snap-fit design.

The sharp drop in elongation relative to unfilled PA 2200 means that tensile data alone are insufficient for design. Components that undergo snap-fit assembly or impact-dominated loading should be evaluated using Charpy or instrumented puncture tests under the same build orientation and post-processing history. Bending stiffness, by contrast, scales approximately with flexural modulus; a rectangular beam of equal section can be made thinner when substituting CarbonMide PA12-CF for PA 2200, provided local buckling or fracture does not govern. Fatigue life in cyclic loading is dominated by residual porosity and fusion defects, not by fibre content alone; computed tomography or density measurement according to ISO 1183-1 is used to establish process capability.

SLS parts are anisotropic because interlayer fusion is less complete than intralayer fusion. X/Y tensile strength is therefore higher than Z tensile strength. For carbon-filled PA12, the gap can be larger than for neat PA12 because carbon fibres align preferentially in the powder-bed plane during recoating. Z-axis tensile strength may be 30% to 50% lower than X/Y values, and Z-axis elongation at break is often below 2%. Designers should orient the primary load path in the X/Y plane and avoid through-thickness tensile loads at hole edges or threaded inserts. When Z-axis loading cannot be avoided, the component should be qualified with witness coupons built in the same orientation and exposed to the same post-processing steps.

As-built surface roughness of laser-sintered PA12-CF is governed by layer thickness and powder particle size distribution. Typical Ra values are in the range of 8 µm to 15 µm for a 0.12 mm layer thickness. Carbon-filled grades may show higher roughness than neat PA12 because fibre ends protrude from the melt surface. Porosity is controlled by energy density; insufficient energy produces elongated interlayer pores that concentrate near the part surface. Density measured by hydrostatic weighing according to ISO 1183-1 can be used as a process capability metric, with production parts typically exceeding 96% relative density when parameters are centred.

When CarbonMide PA12-CF Replaces Glass-Filled or Unfilled PA12 in Load-Bearing Components

Substitution is technically justified when the primary design criterion is specific stiffness or heat deflection rather than impact toughness. Relative to unfilled PA 2200, the carbon-filled grade raises tensile modulus from approximately 1.7 GPa to 6.0–6.8 GPa, a factor of 3.5–4.0. Relative to a glass-filled PA12 such as EOS PA 3200 GF, tensile modulus increases from approximately 3.2 GPa to 6.0–6.8 GPa, while density remains lower. PA 3200 GF typically has a density near 1.22 g/cm³, whereas CarbonMide PA12-CF sits at 1.03–1.07 g/cm³. The specific modulus gain is therefore larger than the absolute modulus gain, which is relevant for drone brackets, intake plenums, and rotating or unsprung components where mass reduction is a load-path requirement.

The penalty is ductility. PA 2200 exhibits elongation at break above 15%, and PA 3200 GF is commonly near 9%; CarbonMide PA12-CF is below 4%. Snap-fit arms, living hinges, and impact-loaded enclosures are therefore poor substitution candidates unless the geometry is redesigned to reduce local strain or the loading is predominantly compressive. The carbon-filled grade also processes differently from glass-filled and unfilled PA12. Shrinkage compensation factors require recalibration because the carbon fibre constrains dimensional change in the X/Y plane; dimensional tolerance qualification should follow the same GD&T protocol used for production SLS parts. The thermal conductivity difference means that process parameters transferred from PA 2200 can create overfused surfaces and loss of sharp corners, while parameters transferred from PA 3200 GF can leave insufficient energy density for complete melting of the carbon-filled powder.

In metal-replacement applications, CarbonMide PA12-CF is often specified for thin-wall structures where metal stiffness is not required and corrosion resistance is beneficial. The material can be machined, tapped, and bonded after sintering, but low elongation influences hole-bearing strength and thread durability. For threaded inserts, insert bosses should be designed with larger wall sections than would be used with unfilled PA12 because the carbon-filled grade is more notch-sensitive. When paint or adhesive bonding is required, surface preparation must account for the carbon-filled surface; the blast-cleaned surface contains exposed carbon fibre and may differ in wetting behaviour from neat PA12.

Design rules for SLS still apply: minimum wall thickness should not be less than 0.6 mm for stable unsupported sections, and gap clearances should be at least 0.3 mm for moving parts after depowdering. For carbon-filled PA12, the minimum detail size may be slightly larger than for unfilled PA12 because the fibre reinforcement reduces melt flow and increases surface roughness. Deep channels and blind holes should be vented or opened for powder removal; trapped powder is difficult to extract from high-aspect-ratio cavities and can create mass imbalance in rotating parts. Escape holes with a diameter of at least 2 mm are used in production practice for enclosed volumes, though geometry-specific validation is required.

Chemical resistance is largely inherited from the PA12 matrix. The material generally resists hydrocarbon oils, greases, and aliphatic solvents, but is not suitable for strong acids, oxidising acids, or phenols. The carbon fibre is inert in most service environments; however, galvanic corrosion can occur if the conductive carbon-filled part is in contact with a more noble metal and an electrolyte is present. In such joints, insulating washers or coatings are used. Continuous-use temperature under load is limited by the PA12 matrix rather than by the carbon fibre. Applications with sustained stress above 80 °C should be reviewed for creep and stress relaxation, while short-term temperature spikes up to the heat deflection temperature range are tolerated only in low-stress conditions.

Machining of sintered CarbonMide PA12-CF requires carbide or diamond-coated tools because carbon fibre is abrasive. Cutting speeds are typically reduced by 20% to 40% relative to neat PA12 to limit tool edge wear and local melting. Tapping is performed with air blast or lubricant to remove conductive chips; chips should not enter electrical enclosures. Bead blasting with glass or ceramic media removes surface powder and produces a uniform matte finish, but aggressive blasting can erode the PA12 matrix around surface fibres and reduce surface hardness. If dimensional accuracy after blasting is critical, masked reference surfaces should be used to prevent rounding of sharp edges.

Closed-loop production with SLS generates surplus powder that is refreshed with virgin powder. For CarbonMide PA12-CF, the recommended refresh ratio is often lower than for PA 2200 because fibre length degrades during recoating and laser exposure. Sieving is performed through 150 µm or 180 µm mesh to remove agglomerates and coarse fused particles. The powder tapped density and angle of repose are monitored as indirect indicators of flowability. A tap density outside the supplier-listed control band may indicate fibre segregation or fines accumulation and should trigger a full mechanical-property coupon build. Published data for this exact grade across all recycled-powder ratios is limited; users should sample the powder according to ISO 527-2 and ISO 179-1 before releasing production batches.

Regulatory documentation supplied with EOS CarbonMide PA12-CF should be consulted for REACH and RoHS status. The powder is not intended for food-contact or medical implant use unless validated under the relevant EU or FDA framework. Carbon-fibre dust generated during blasting or machining can be conductive; dust extraction and collection should be rated for combustible particulate and conform to NFPA 484 or an equivalent facility standard. Dry powder can be recycled in closed-loop systems, but the recycled fraction is normally limited by the machine manufacturer’s powder management protocol. Fibre attrition during recycling reduces fibre length and lowers tensile modulus and strength; batches exceeding the recommended refresh ratio should be sampled according to ISO 527-2 and ISO 179-1 before release. Storage of opened powder should maintain dry conditions because PA12 absorbs moisture from ambient air; the supplier’s drying instructions are part of the process qualification record.