Polycarbonate, Nylon, and carbon/glass-filled composites take 3D printing from "prototype" to "actually replaces machined parts". They also demand the right hardware: hardened steel nozzles, all-metal hotends, an enclosure, and disciplined drying. Skip any one of those and the parts will fail. This is the working guide for serious engineering prints.
Hardened steel nozzle (mandatory for any carbon/glass-filled material), all-metal hotend rated to 290 °C+, enclosure , and active drying during the print for nylon. Print PC at 275 °C / 110 °C bed; PA12 at 260 / 80; PA-CF at 280 / 80. Expect to dial settings per spool — engineering filaments vary widely between brands.
Before you load any engineering filament, verify your printer can handle it:
PC is the strongest common FDM filament — 70+ MPa tensile, 1.2 g/cm³, HDT 140 °C. Used for tools, fixtures that see heat, automotive headlight housings, and structural brackets. The catch: warps badly without an enclosure, and unmodified PC needs 290 °C+. Most filament brands (Polymaker PolyMax PC, Prusament PC Blend, Bambu PC) ship modified blends that print at 270–280 °C.
Nylon is the toughness champion — high impact resistance, low friction, surviving repeated mechanical cycles. PA12 prints easier; PA6 has slightly better strength but absorbs more water. Used for gears, bushings, hinges, snap-fits that need to survive thousands of cycles.
A spool left out overnight in a humid room can become unprintable. Print directly from a dryer set to 80 °C or from an enclosed AMS with desiccant. Wet nylon doesn't just print poorly — it hydrolytically degrades, permanently weakening.
Chopped carbon fibres mixed into nylon. The fibres act as reinforcement, giving stunning stiffness (~7 GPa flexural) and dramatically reducing nylon's warping. The downside: highly abrasive (brass nozzles fail in <20 hours), and the fibres reduce ductility — parts are stiffer but more brittle than pure nylon.
Like PA-CF but with glass fibres. Slightly cheaper, less stiff, and roughly equivalent abrasion. Glass is electrically insulating where carbon is conductive — relevant for electronics enclosures.
Settings are nearly identical to PA-CF; pick PA-GF when you need electrical isolation or your application benefits from glass's slight transparency.
PC reinforced with carbon. Even stiffer than PA-CF, even more heat resistant (HDT >120 °C). Common in injection-molded automotive trim — you can now print it. Expensive ($70–$120/kg).