Polycarbonate vs Nylon for Gears and Tough Mechanical Parts

Why Gears and Mechanical Parts Are a Special Case

Most strength comparisons focus on static tensile load — how hard you have to pull a material apart. For gears, bushings, cams, and impact-prone parts, the relevant properties are different:

• Toughness — energy absorbed before fracture (related to elongation at break, not just tensile strength)
• Fatigue resistance — surviving thousands of load cycles without crack initiation
• Surface hardness and wear resistance — tooth-to-tooth contact in gears creates sustained abrasion
• Dimensional stability under load — a gear that creeps over time causes backlash and eventual failure
• Lubricity — PA has inherent self-lubrication that reduces gear wear without grease

On every metric except stiffness and heat resistance, Nylon has the advantage for dynamic mechanical parts. PC's brittleness — it typically fractures at 4–14% elongation — makes it a poor choice for parts that experience impact or cyclic stress.

Tensile Strength: Nylon Wins on Average

Across all unfilled grades in our database with tensile data, Nylon averages higher than pure PC:

• PA (Nylon): 36–130 MPa, average 64 MPa across 34 materials
• PC: 25–75 MPa, average 52 MPa across 36 materials

The higher Nylon average is partly driven by high-performance PA6 grades. Yousu PA6 reaches 96 MPa tensile strength with a flexural modulus of 2,270 MPa. Taulman3D PA Cast Plate hits 92 MPa. FormFutura LUVOCOM PAHT 9825 reaches 85 MPa. These are the Nylon grades that challenge engineering-grade PC.

On the PC side, the strongest unfilled grades are Polymaker PolyCore PC-7413 at 74.6 MPa (HDT 139°C), Prusament PC Space Grade at 72 MPa (HDT 137°C, print temp 290°C), and Overture PC Professional at 70.2 MPa (flexural modulus 2,588 MPa). These all outperform common Nylon grades, but they require demanding print conditions.

Mainstream consumer PC grades cluster lower: Bambu Lab PC (55 MPa, HDT 117°C), Elegoo PC (54 MPa, HDT 109°C), Polymaker PolyLite PC (69 MPa, HDT 111°C). At this level, a well-dried Nylon like Sunlu Easy PA (75 MPa, HDT 121°C) or Overture Easy Nylon (71 MPa) is stronger or comparable while being far easier to print.

Toughness: Where Nylon Has a Clear Edge

For gears and mechanical parts, toughness matters more than peak tensile strength. A gear tooth that bends before snapping survives shock loads; a brittle one fractures. Elongation at break tells this story clearly:

• PA (Nylon): average elongation 39% across grades with data, range 1.2–180%
• PC: average elongation 24% across grades with data, range 2.4–75% (most pure PC grades: 3–14%)

The typical PC elongation range of 3–14% means most PC grades will fracture under sudden impact rather than deform. Bambu Lab PC has just 3.8% elongation at break — it is a stiff, rigid material that will crack under shock loading. Prusament PC Blend (63 MPa, HDT 113°C) has 5.8% elongation.

In contrast, 3DXTech WearX Nylon (62 MPa, HDT 143°C) achieves 18% elongation. colorFabb PA Neat (63 MPa, HDT 90°C) and Polymaker PolyMide CoPA (66 MPa, HDT 110°C) offer 8.5–10% elongation while matching mid-range PC on tensile strength. 3DXTech AmideX Nylon 6-66 (55 MPa, HDT 140°C) reaches 100% elongation — it stretches to twice its length before fracturing.

This difference is decisive for gear applications. Nylon gear teeth flex and recover under load; PC gear teeth either hold or snap.

Flexural Modulus: PC Is Stiffer

For applications requiring dimensional rigidity — mounting brackets, structural connectors, parts that must not flex — the stiffness comparison runs the other way:

• PC: average flexural modulus 2,117 MPa (25 materials with data), range 380–6,540 MPa
• PA (Nylon): average flexural modulus 2,098 MPa (16 materials with data), range 1,370–4,700 MPa

The averages are nearly identical, but this obscures a critical practical difference: PA flexural modulus varies substantially with moisture content. Dry Nylon (just out of the dryer) can be quite stiff; fully moisture-conditioned Nylon in service is notably more flexible. PC maintains its flexural modulus regardless of humidity.

Anycubic PC achieves 2,900 MPa flexural modulus with 65 MPa tensile strength — offering both stiffness and reasonable strength. Elegoo PC combines 2,615 MPa flexural modulus with a 109°C HDT for under-temperature-sensitive applications.

Heat Deflection Temperature: PC Wins Clearly

If your gears or mechanical parts operate in a warm environment — near motors, inside enclosures, in automotive applications — HDT becomes the critical selection criterion:

• PC: 57–207°C across 31 materials, average 112°C
• PA (Nylon): 55–155°C across 26 materials, average 99°C

PC's 13°C average advantage is significant when operating near 100°C. 3DXTech 3DXMAX PC (62 MPa, HDT 135°C) and Prusament PC Space Grade (72 MPa, HDT 137°C) are especially well-suited to high-temperature mechanical use. The Polymaker PolyCore PC-7413 (74.6 MPa, HDT 139°C) combines the best tensile strength and heat resistance in our PC dataset.

Some PA grades approach PC's heat resistance. 3DXTech WearX Nylon has an HDT of 143°C — above most consumer PC grades. 3DXTech AmideX Nylon 6-66 (HDT 140°C) and Sunlu Easy PA (HDT 121°C) match or exceed mid-range consumer PC grades. However, Nylon HDT values are measured on dry specimens; in a humid environment, absorbed moisture plasticizes the polymer and can reduce effective heat resistance below the rated value.

Side-by-Side: Key Properties for Gears and Mechanical Parts

Based on median values across materials in our database with available data:

Wear Resistance: Nylon's Practical Advantage for Gears

Beyond the datasheet numbers, Nylon has a structural advantage for gear and bushing applications that doesn't appear in standard TDS data: inherent lubricity. The amide groups in the polymer backbone act as internal lubricants, allowing PA gear teeth to slide against each other or against metal with minimal friction and wear. PC lacks this property — PC gears sliding against metal or other hard surfaces will wear faster and generate more heat from friction.

For dry-running gear trains where you cannot apply external lubricant, this is a decisive advantage. In applications where grease is acceptable, PC can close some of this gap, but Nylon remains the more forgiving choice.

3DXTech WearX Nylon is specifically formulated for wear resistance — it combines 62 MPa tensile strength, HDT 143°C, and 18% elongation, making it one of the strongest all-round choices for printed mechanical parts in our database. For higher-temperature gear applications, FormFutura LUVOCOM PAHT 9936 (78 MPa, HDT 90°C) and FormFutura LUVOCOM PAHT 9825 (85 MPa, HDT 90°C) are high-performance PAHT grades targeting mechanical applications.

Printability for Mechanical Parts

Nylon: Moisture Is the Main Challenge

PA grades in our database print at 220–300°C nozzle, with most grades at 250–280°C. 3DXTech WearX Nylon runs 260–275°C with an 80–95°C bed. colorFabb PA Neat and colorFabb PA BMD (65 MPa tensile, 4.5% EAB) are available in that range as well. The critical requirement is moisture control — Nylon absorbs ambient moisture rapidly and will print with stringing, foaming, and weak layer adhesion if wet. Dry at 80–90°C for 12+ hours before printing and use a dry box or sealed container. An enclosure is strongly recommended for larger mechanical parts to prevent warping.

Polycarbonate: Demanding Printer Requirements

PC requires 260–295°C nozzle temperatures and 90–140°C bed temperatures. Bambu Lab PC is among the more accessible grades at 260–280°C nozzle and 90–110°C bed, yet still requires a printer capable of sustained high bed temperatures. Prusament PC Space Grade demands 290°C nozzle and 120°C bed. An enclosed printer is essential for PC; large mechanical parts printed without an enclosure will warp severely. PC also requires a PEI surface or specific adhesive for reliable bed adhesion.

The practical consequence for gear printing: PC parts with multiple overhangs, internal features, or aggressive geometries are harder to get right. The higher print temperature and enclosure requirement also mean longer heat-soak times and slower first layers.

When to Choose Each Material

Choose Nylon (PA) for Gears and Mechanical Parts When:

• The gear runs dry or with minimal lubrication — PA's inherent lubricity reduces wear and friction without additives
• The part must survive impact or shock loading — PA's high elongation (up to 18–100% depending on grade) prevents catastrophic fracture
• You need reliable mechanical performance after assembly — PA's fatigue resistance under cyclic load is substantially better than PC
• Temperature stays below 90–110°C in service — most PA grades maintain properties well within this range
• Weight matters — PA grades density runs 1.06–1.24 g/cm³, generally lighter than PC at 1.14–1.24 g/cm³
• You can manage moisture — dry storage and a dry box are non-negotiable, but the printing process itself is more forgiving than PC

Choose Polycarbonate for Gears and Mechanical Parts When:

• The application runs hot — motors, near heat sources, automotive under-hood; PC's average HDT of 112°C (up to 137–139°C for top grades) provides margin Nylon cannot always match
• Dimensional stability in high humidity is critical — PC does not absorb moisture, so its properties remain constant; PA in a humid environment will become softer and may swell slightly
• Rigidity under sustained load matters more than toughness — PC does not creep or stress-relax at the rate PA does when moisture-conditioned
• You have an enclosed printer capable of 270–295°C nozzle and 110–130°C bed temperatures
• The loading is predominantly static or compressive rather than impact-dominated

Carbon Fiber Reinforced Variants Change the Equation

Both PA and PC are available in carbon fiber-reinforced grades that significantly alter the comparison. CF grades are excluded from the stats above, but they are worth noting for mechanical applications. PA-CF grades can reach tensile strengths of 63–87 MPa with flexural moduli of 3,800–7,900 MPa — transforming a tough but somewhat flexible material into a stiff engineering compound. Similarly, PC-CF grades like 3DXTech CarbonX PC+CF (70 MPa tensile, HDT 135°C, flexural modulus 5,890 MPa) offer a high-stiffness option with PC's heat resistance. CF-reinforced grades require hardened steel nozzles (brass will wear rapidly), and their brittleness increases further, making them suitable for stiff structural parts but not impact-absorbing gear applications.

Summary: Which Material Wins for Gears and Tough Parts?

For printed gears that need to actually work under real load, Nylon is the standard recommendation — and the data supports it. Higher average tensile strength (64 vs 52 MPa), far better toughness (39% vs 24% elongation, with most pure PC grades fracturing under 14%), inherent lubricity, and adequate heat resistance for most applications. The key tradeoff is moisture management: you must dry Nylon thoroughly and use a dry box.

Polycarbonate is the better choice when operating temperature exceeds what Nylon can reliably handle (above 110°C), when humidity stability is required, or when you need the specific combination of rigidity and heat resistance that PC delivers. If you need both stiffness and heat resistance, look at the high-performance grades: Polymaker PolyCore PC-7413 (74.6 MPa, HDT 139°C) or Prusament PC Space Grade (72 MPa, HDT 137°C) are the strongest pure PC grades in our database.