Why Engineers Specify Polyamide
Polyamides (commonly called Nylon) are the standard for high-wear sliding surfaces, mechanical gears, living hinges, and load-bearing fixtures. With low coefficient of friction against metals, exceptional abrasion resistance, and high chemical tolerance against oils and hydrocarbons, Nylon handles tough workshop duty.
The two main commercial variants are PA6 and PA12:
- PA6: Higher tensile strength and heat resistance (up to 160 °C), but absorbs up to 8-9% atmospheric moisture by weight, causing noticeable dimensional expansion.
- PA12: Lower moisture uptake (~1.5% at saturation), vastly superior dimensional stability, and lower melting point (prints smoothly at 250-270 °C).
The Moisture Dilemma: Drying vs Conditioning
Before printing, Nylon must be bone dry (moisture content below 0.05%). Even 0.2% moisture in the filament turns to steam in the hotend, creating foamy beads, terrible stringing, and weak layer bonding. We bake nylon spools in dedicated convection ovens at 75-80 °C for 12 hours prior to production.
Paradoxically, after printing, nylon parts benefit from moisture. Dry-as-molded nylon is rigid and brittle. As it absorbs 1-2% ambient humidity, water molecules act as plasticizers between polymer chains, increasing toughness and impact resistance fivefold.
Annealing for Dimensional Stability
For parts operating in elevated temperatures, post-print thermal annealing (heating the part to 110 °C for 4 hours and slow cooling) releases internal crystallization stresses, preventing warping and maximizing mechanical lifetime.
