Nylon Injection Moulding: Engineering-Grade Thermoplastic
Nylon injection moulding: PA6, PA66, and PA12 for strong, wear-resistant parts. Glass fiber reinforced grades available. Ideal for gears, brackets, and housings.
Nylon Injection Moulding: Engineering-Grade Thermoplastic
Nylon (polyamide, PA) is a family of engineering thermoplastics known for exceptional strength, wear resistance, and oil resistance. From PA6 and PA66 to flexible PA12 and glass-fiber-reinforced PA66-GF30, nylon injection moulding produces durable mechanical and automotive components that outlast commodity plastics.
At FIRMFG, we mould all major nylon grades, including glass fiber and carbon fiber reinforced compounds. Our process controls the challenges unique to nylon — moisture absorption, high shrinkage, and high melt temperature — to deliver dimensionally stable, production-grade parts for gears, brackets, housings, and structural components.
This guide covers nylon grades, complete material properties, moisture management, design guidelines, and a comparison with POM and PEEK. Or, skip ahead and request a quote for an immediate price and lead time.
Nylon Quick Specifications
Key specifications for nylon injection moulding across PA6, PA66, and reinforced grades.
| Specification | Value |
|---|---|
| Tensile Strength | 70 – 180 MPa (GF reinforced up to 180) |
| Density | 1.13 – 1.40 g/cm³ |
| Heat Deflection Temperature | 70 – 220 °C |
| Shrinkage Rate | 1 – 2.5% (0.3 – 0.7% with GF) |
| Melting Temperature | 220 – 290 °C |
| Moisture Absorption | 2.5 – 3.5% |
Nylon Grades & Compounds
Each polyamide grade balances strength, flexibility, heat resistance, and cost for different engineering applications.
PA6
General-purpose polyamide with balanced strength, toughness, and processability. Lower melting point than PA66, easier to mould, and more economical.
Best for: Consumer goods, fasteners, general mechanical parts
PA66
Higher strength, stiffness, and heat resistance than PA6. The most widely used nylon for engineering and automotive applications.
Best for: Gears, brackets, automotive under-hood parts
PA12
Lower moisture absorption and density than PA6/PA66. Excellent flexibility, impact resistance, and chemical stability.
Best for: Fuel lines, pneumatic tubing, flexible couplings
PA66-GF30
30% glass fiber reinforced PA66. Doubles tensile strength and stiffness, reduces shrinkage to 0.3–0.7%, and raises HDT above 200°C.
Best for: Structural housings, load-bearing brackets, power tool cases
PA66-CF
Carbon fiber reinforced PA66. Highest strength-to-weight ratio, EMI shielding, low thermal expansion for premium engineering applications.
Best for: Aerospace components, drone frames, high-performance gears
Complete Material Properties
Mechanical, thermal, wear, chemical, and moisture properties for nylon injection moulding.
| Category | Property | Value |
|---|---|---|
| Mechanical | Tensile Strength | 70 – 180 MPa (unfilled 70–83, GF30 170–180) |
| Mechanical | Flexural Strength | 100 – 260 MPa |
| Mechanical | Impact Strength (Notched Izod) | 4 – 12 kJ/m² |
| Mechanical | Hardness (Rockwell) | R110 – R120 |
| Thermal | Heat Deflection Temp (0.45 MPa) | 70 – 220 °C |
| Thermal | Melting Point | 220 – 290 °C |
| Thermal | CLTE | 5 – 14 × 10⁻⁵ /°C (GF reduces to 2–5) |
| Wear | Friction Coefficient | 0.2 – 0.4 |
| Wear | PV Limit | 0.5 – 1.0 MPa·m/s |
| Chemical | Oil Resistance | Excellent |
| Chemical | Solvent Resistance | Good |
| Chemical | Acid Resistance | Poor (attacked by strong acids) |
| Moisture | Moisture Absorption | 2.5 – 3.5% (PA6 higher, PA12 ~0.3%) |
Moisture Management
Nylon is hygroscopic. Controlling moisture before and after moulding is critical for dimensional stability and mechanical performance.
Drying Requirement
Nylon is hygroscopic and must be dried before moulding. Dry at 80°C for 4–6 hours to reduce moisture below 0.2%. Moulding wet nylon causes splay marks and hydrolysis-degraded strength.
Guide: Dehumidifying dryer, 80°C, 4–6h, target < 0.2% moisture
Moisture Absorption Effects
Absorbed moisture plasticizes nylon, lowering tensile strength and stiffness while increasing toughness and impact resistance. Properties drift with ambient humidity over days to weeks.
Guide: Strength drops 30–40% at equilibrium vs dry
Conditioning Treatment
Post-mould moisture conditioning accelerates equilibrium. Parts are placed in hot water or humidity chambers to reach service-condition moisture levels, stabilizing dimensions and toughness.
Guide: Hot water conditioning at 80–100°C for 8–24h
Pre-Dry vs Post-Mould Conditioning
Pre-drying ensures defect-free moulding. Post-mould conditioning tunes final dimensions and toughness for the end-use environment. Precision nylon parts often require both steps.
Guide: Pre-dry for processing, condition for service
Impact on Dimensions and Strength
Moisture absorption causes dimensional swelling of 0.5–1.5% and reduces tensile strength. Tolerances on critical features must account for moisture-driven growth across the product service life.
Guide: Add 0.5–1.5% to critical dimensions for moisture growth
Design Guidelines for Nylon
DFM rules that account for nylon shrinkage, moisture growth, and reinforced-grade behavior.
| Parameter | Guideline | Notes |
|---|---|---|
| Min Wall Thickness | 1.2 mm | Thicker for GF grades to prevent brittleness |
| Draft Angle | 1.5° | Increase to 2° for textured surfaces |
| Shrinkage Rate | 1 – 2.5% | GF reinforcement reduces to 0.3–0.7% |
| Rib Design | Rib thickness ≤ 0.6 × wall | Prevents sink; add 1–2° draft |
| Boss Design | Boss wall ≤ 0.6 × nominal wall | Avoid thick sections that sink |
| Thread Design | Moulded or insert threads | Insert threads preferred for repeated assembly |
| Tolerance | ±0.1 mm | Tighter (±0.05) needs steel mold + moisture control |
| Moisture Compensation | +0.5 – 1.5% on critical dims | Account for in-service moisture growth |
Post-Processing & Finishing
Secondary operations that enhance nylon parts for assembly, appearance, and traceability.
Annealing Treatment
Post-mould annealing at 150–180°C relieves molded-in stress, improves dimensional stability, and raises crystallinity for better mechanical and chemical performance.
Painting
Nylon accepts paint with proper surface preparation (flame or plasma treatment). Primers improve adhesion; UV-stable topcoats protect outdoor applications.
Ultrasonic Welding
Ultrasonic welding joins nylon parts via energy directors. Dry parts weld best; moisture degrades weld strength. Suitable for housings and sealed assemblies.
Mechanical Fastening
Screws, snap-fits, and insert fastening suit nylon toughness. Self-tapping screws form threads reliably; metal inserts handle repeated assembly cycles.
Laser Marking
Laser marking etches permanent part numbers, QR codes, and traceability marks. Dark marks on light nylon; GF-filled grades mark with higher contrast.
Nylon vs POM vs PEEK Comparison
Compare nylon against acetal (POM) and PEEK to choose the right engineering plastic.
| Property | Nylon (PA66) | POM (Acetal) | PEEK |
|---|---|---|---|
| Tensile Strength | 70 – 180 MPa | 60 – 70 MPa | 90 – 100 MPa |
| Wear Resistance | Excellent | Excellent | Outstanding |
| Heat Resistance (HDT) | 70 – 220 °C | 110 °C | 160 – 315 °C |
| Moisture Absorption | 2.5 – 3.5% | 0.2% | 0.1% |
| Chemical Resistance | Good (poor to acids) | Excellent | Outstanding |
| Cost | Low – Medium | Low | Very High |
| Best Applications | Gears, brackets, housings | Precision gears, snaps | Aerospace, medical implants |
Nylon offers the best strength-to-cost ratio for mechanical parts. POM wins on dimensional stability and friction; PEEK leads in heat and chemical resistance at a premium price.
Nylon Moulding FAQ
Answers to the most common questions about nylon injection moulding at FIRMFG.
QHow does moisture affect nylon injection moulded parts?
Nylon is hygroscopic, absorbing 2.5–3.5% moisture at equilibrium. Absorbed moisture plasticizes the polymer: tensile strength and stiffness drop 30–40% while impact toughness increases. Moisture also causes dimensional swelling of 0.5–1.5%. Parts must be dried before moulding (80°C, 4–6 hours) to below 0.2% moisture to avoid splay marks and hydrolysis. For precision parts, post-mould conditioning brings dimensions to service-equilibrium levels so they remain stable in use.
QWhat are the benefits of glass fiber reinforced nylon (PA66-GF30)?
Adding 30% glass fiber to PA66 doubles tensile strength (to 170–180 MPa), increases stiffness by 3–4×, raises heat deflection temperature above 200°C, and cuts shrinkage from 1.5–2.5% down to 0.3–0.7%. This makes PA66-GF30 ideal for structural housings, load-bearing brackets, and power tool cases. The trade-offs are higher mold wear (glass is abrasive), reduced impact toughness, and anisotropic shrinkage that requires careful gate placement. Mold life is shorter with GF grades.
QHow wear-resistant is nylon compared to other plastics?
Nylon has excellent wear resistance and a low friction coefficient (0.2–0.4), making it a top choice for gears, bearings, and sliding components. It outperforms most unfilled engineering plastics in tribological applications. POM (acetal) is its main competitor—slightly lower friction but lower strength. For extreme wear loads, adding PTFE, MoS2, or silicone oil to nylon further lowers friction and raises the PV limit. PEEK surpasses both but at 10–20× the cost.
QWhat is the shrinkage rate of nylon and how is it controlled?
Unfilled nylon shrinks 1–2.5% (PA6 around 1–1.5%, PA66 around 1.5–2.5%). Glass fiber reinforcement reduces shrinkage to 0.3–0.7% but introduces anisotropic shrinkage—lower along the fiber orientation and higher across it, which can warp flat parts. We control shrinkage through gate placement, uniform wall thickness, mold temperature, and holding pressure. For tight tolerances (±0.05mm), we run trials and adjust cavity dimensions after measuring the first shots.
QWhat drying is required before moulding nylon?
Nylon must be dried to below 0.2% moisture before moulding. Use a dehumidifying dryer at 80°C for 4–6 hours (PA66 may need 6–8 hours). Moulding wet nylon causes splay/silver streaks, reduced molecular weight from hydrolysis, and weaker parts. Drying is mandatory even for "dry" as-received pellets because nylon absorbs moisture rapidly from the air. Use a hopper dryer during production to maintain dryness. Over-drying above 90°C or beyond 12 hours can cause oxidation and yellowing.
QHow much does nylon injection moulding cost?
Nylon resin costs $3–8/kg for unfilled PA6/PA66 and $6–15/kg for GF-reinforced grades. Carbon-fiber PA66 is $25–40/kg. Per-part cost depends on weight, cycle time, and volume: a 50g PA66 bracket at 1,000 parts might cost $2–5/part plus mold amortization. Mold cost: $3,000–8,000 (aluminum, low volume) to $15,000–50,000+ (steel, production). Nylon fast cycle (20–40s) and good flow keep processing costs competitive. Request a quote for an exact price.
Applications of Nylon Moulding
Nylon strength, wear resistance, and toughness serve demanding mechanical and automotive applications.
Gears
Spur, helical, and worm gears with self-lubricating wear
Bearings
Sleeve and thrust bearings running dry or grease-lubricated
Brackets
Structural brackets and mounts with high strength-to-weight
Intake Manifolds
PA66-GF30 manifolds replacing metal for weight reduction
Power Tool Housings
Impact-resistant, glass-filled housings for drills and saws
Cable Ties
High-strength, flexible PA6/PA66 ties for bundling
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Learn MoreStart Your Nylon Moulding Project
Upload your CAD files and get a free nylon injection moulding quote within 24 hours. PA6, PA66, PA12, and glass/carbon fiber reinforced grades available. Production-grade materials, ISO 9001 quality.