What Controlled Viscosity Means for Melt Extrusion Repeatability

Envalior Novamid ID 1070 is an unfilled polyamide 6 (PA6) supplied specifically for material extrusion additive manufacturing. The grade is characterized under ISO 527-2 for tensile response and ISO 1133-1 for melt volume-flow rate. Its melt-viscosity stability is relevant where filament-fed hoppers and single-screw extruders operate with short residence times and inconsistent backpressure. Published data for this specific configuration describes a melt temperature window of 240 °C to 270 °C, although the optimum setpoint depends on nozzle alloy, layer height, and extrusion speed.

Because unfilled PA6 is semicrystalline, solidification shrinkage is anisotropic. The resin supplier addresses this through a nucleation package that reduces warpage during open-chamber builds. That additive package distinguishes Novamid ID 1070 from general-purpose PA6 extrusion grades, which often exhibit greater in-plane distortion at bed temperatures below 80 °C. The material is shipped as filament with controlled diameter tolerance, typically 1.75 mm or 2.85 mm, and must be stored in sealed containers with desiccant.

Moisture content at the feed zone is a processing boundary. At relative humidity above 60%, PA6 filament can exceed 0.20 wt% water within 24 h. Hydrolytic degradation during extrusion then causes bubbles, surface roughness, and reduced interlayer tensile strength. Conditioning after printing is a separate phenomenon: PA6 absorbs atmospheric moisture and transitions from a stiff dry state to a tougher conditioned state. This moisture uptake is measured per ISO 62 and can reach approximately 9–10 wt% at saturation for unfilled PA6, with dimensional change of 0.5–1.0% in thin sections.

What Limits Bed Adhesion on Glass and PEI Build Surfaces?

With an unfilled PA6 grade, the first-layer bond is governed by bed temperature, surface preparation, and residual oligomer contamination. For Novamid ID 1070, the bed setpoint is commonly maintained between 90 °C and 110 °C. On borosilicate glass, a polyvinyl acetate adhesive or an acidified nylon-specific bed coating improves wetting. On PEI, over-adhesion can result in surface delamination when the part is removed; a release film or sacrificial first layer is therefore used. The manufacturer’s processing guidance indicates that chamber air temperatures above 45 °C reduce early-stage warping on parts longer than 150 mm, but published data for this specific configuration is limited to machine-dependent trials.

Nozzle pressure below 0.4 MPa is generally sufficient for unfilled PA6 at 250 °C through a 0.4 mm brass nozzle, provided the filament is dried to 0.10 wt% moisture or lower. Above 0.6 mm layer height, melt flow becomes shear-thinning, and the extrusion multiplier may require reduction by 2–4% to prevent overfill. These parameters should be verified against lot-specific melt volume-flow rate data because PA6 is sensitive to hydrolytic chain scission during storage.

The dry-state values represent specimens printed with 0.2 mm layer height, 100% rectilinear infill, and tensile loading parallel to the X–Y plane. Conditioning per ISO 1110 to equilibrium at 23 °C and 50% RH lowers stiffness but raises ductility. The change is reversible and must be considered when load-bearing fixtures are designed from printed PA6 parts. Z-direction tensile strength remains lower than X–Y values, typically 40–70% of in-plane strength depending on thermal history.

Moisture Uptake and Drying Requirements Before Extrusion

Storage conditions for Novamid ID 1070 require a dry cabinet or sealed desiccant container. At 23 °C and 50% RH, unfilled PA6 filament reaches approximately 2.5 wt% moisture within 7 days when exposed without barrier packaging. Printing at wet conditions above 0.15 wt% moisture produces hydrolysis: tensile strength falls because the molecular weight distribution broadens and lower-molecular-weight fractions act as defects. A forced-air dryer at 80 °C for 4–12 h restores processability, but repeated drying cycles can embrittle the filament if the temperature exceeds 90 °C.

In production-scale material extrusion cells, batch-to-batch variance in moisture content is controlled by weighing spools before and after drying. A spool with an initial mass of 750 g losing 2 g of water indicates a moisture reduction of approximately 0.27 wt%. The drying endpoint is reached when weight loss per hour falls below 0.01% of spool mass. Because PA6 is hygroscopic, the dried spool must be fed through a heated dry box with a setpoint of 40–50 °C and a purge gas dew point below −30 °C during long builds.

When PA6 Filament Replaces ABS or PA12 in Functional Prototyping

Unfilled PA6 such as Novamid ID 1070 is specified where ABS lacks chemical resistance to hydrocarbons and where PA12 has insufficient stiffness at elevated temperature. Under ISO 175 immersion testing, PA6 resists aliphatic oils and fuels better than ABS, although it swells in water and alcohols. PA6 also exhibits higher tensile modulus than PA12, with dry modulus commonly 2.6–2.9 GPa versus PA12 at 1.3–1.6 GPa. The trade-off is dimensional stability: PA6 absorbs more water and shows larger mold shrinkage, which translates into greater printed-part distortion if chamber temperatures are not controlled.

Compared with PA6/66 blends, Novamid ID 1070 has a lower crystalline melting point and a broader processing window. The melting temperature of PA6 is approximately 220 °C, measured by ISO 11357-3 differential scanning calorimetry. This is lower than PA66 at 260 °C, which reduces bed adhesion requirements and allows lower chamber temperatures. However, the same property reduces heat deflection temperature at 1.80 MPa, confining continuous service in load-bearing applications to below 65 °C unless post-annealing is applied.

Differences from other Novamid grades are visible primarily in melt flow and batch consistency. A general-purpose PA6 may have a melt volume-flow rate that varies by ±15% between production lots, while a printing grade is supplied under a tightened specification because filament extrusion and subsequent additive processing require reproducible backpressure. The exact MVR limits for Novamid ID 1070 should be confirmed against the supplier lot certificate; published data in the public domain for this specific identification code remains limited.

Post-annealing in nitrogen or vacuum at 100–120 °C for 4–8 h increases crystallinity and raises HDT by 5–15 °C in unfilled PA6. It also reduces residual stress from layer deposition. The process must be performed with the part restrained or on a flat ceramic plate, otherwise out-of-plane warpage may exceed 1.0 mm per 100 mm part length.

Chemical exposure limits should be evaluated per ISO 22088 for environmental stress cracking and per ISO 175 for mass and dimension changes. Strong acids, phenolic compounds, and glycol-based brake fluids are incompatible with PA6. Amine-rich adhesives should be avoided because residual amine can plasticize the surface and reduce interlayer bond strength. When chemical welding is required, formic acid or a low-molecular-weight polyamide adhesive is used with a post-weld bake at 60 °C to remove solvent.

For compliance documentation, unfilled PA6 grades from Envalior are generally supplied with statements covering RoHS 2011/65/EU and REACH. Food-contact suitability is not inherent and must be validated for the specific additive package, print surface, and post-processing solvent history. No medical or implant claim is established for standard filament without USP Class VI or ISO 10993 testing on the finished printed device.

The defining operational boundary for Novamid ID 1070 is its hygroscopicity. When a batch is poorly dried, interlayer tensile strength falls below half of in-plane virgin strength, and the failure mode shifts from ductile tearing to brittle delamination. This failure is identifiable in fracture surfaces by foam-like voids along layer interfaces. On production lines with twin-screw-compounded filament and direct-drive extruders, the most common root cause of intermittent extrusion is spool moisture rather than melt temperature instability.

Material selection should therefore treat drying, bed adhesion, and moisture reuptake as primary process variables. If the build chamber cannot sustain a low dew point below 5 °C for more than 12 h, PA6 becomes difficult to use in continuous production even when the resin itself is well characterized. In such conditions, PA12 or a low-moisture polyamide blend may be substituted, but at the cost of reduced dry-state modulus.