The spec, the moisture story, the design rules, and where PA6-GF actually wins · cross-checked against the manufacturer's TDS V1.1, written by the team that prints it.
PA6-GF glass filled nylon 3D printing service · UK · quoted in 6 hours.
Holds its shape close to 190°C · near-equal strength in every direction.
Four quick visuals. Start with which material to pick and where PA6-GF works; the engineering detail is at the end if you want it.
Injection-moulding replacement · gear housings · brackets · no heated chamber · highest HDT in commodity FDM
Stiffness-critical = PA12-CF · sustained humidity = PA12-CF · clear = PC · outdoor = ASA
Tensile strength is near-isotropic (90.1 XY / 90.7 Z · ~1.0×) · unusual for a fibre-filled grade. Stiffness is still direction-dependent (modulus 5357 XY / 3376 Z ≈ 1.6×). Glass keeps toughness where CF goes brittle at the edges.
Dry tensile is near-isotropic (~1.0× XY/Z) but stiffness is not (modulus ~1.6× XY/Z) · plan orientation for stiffness-critical parts. Annealing 100°C/16h locks in crystallinity. Wet-state tensile anisotropy rises to ~1.53× as Z weakens faster than XY.
"James handled the 3D printing for a functional heat resistant component we needed in batch production. He helped dial in the prototype first with their design service, then produced the final batch with really consistent results. Super fast 3D print turnaround and great quality across all the 3D printed parts. Will 100% be coming back."
"We needed a sit-in F1-car for an exhibition to showcase our new racing game. 3D Printing Express took our CAD, optimised it for strength and weight as we had no idea how it all worked! Turned out beautifully. They colour matched the finish and was looking like the real deal. On show day the cockpit ran non-stop, adults and kids jumped in. Multiple visitors asked who built it."
"We ordered a batch of 100 PA-12 parts from 3D Printing Express and could not be happier. Every part arrived consistent, dimensionally accurate, and ready for use straight from the box. The PA-12 gave us the strength and stability we needed for functional testing, with minimal post-processing required. Delivery was on time, communication was excellent, and their QC clearly made a difference."
Near-isotropic strength (90.1 XY / 90.7 Z) for brackets, gear housings, injection-moulding replacement. Drops ~55% to 40 MPa fully wet · print and store bone-dry.
Highest HDT in commodity FDM · 60°C above PA12-CF. Holds 157°C even under 1.8 MPa structural load.
The PA6 inversion. Notched impact strength rises 180% when wet · absorbed water plasticises the matrix. Unique among reinforced nylons.
Prints without a heated chamber · unlike most engineering nylons. Build plate 40-50°C is the only heat. Easier process window than PC, PA12-CF, or PEEK.
The use cases where PA6-GF earns its place · injection-moulding-replacement engineering parts, 191°C HDT, room-temperature chamber, and a printable lead time when CNC or moulding can't justify the cost.
Engineering materials are bought on what they can do · sold on what they can't. Pick a different filament if any of these apply to your part.
PA6-GF is the most-replicated injection-moulded engineering polymer in cars · same chemistry as automotive cable trays, fan shrouds, and gearbox housings. 191°C HDT covers sub-bonnet ambient.
Direct injection-moulded-part replacement when MOQ doesn't justify tooling. 90 MPa near-isotropic tensile + 4314 MPa flexural modulus = same load-bearing geometry as a moulded part in days, not months.
UL 94 HB flame rating at 1.5mm + 191°C HDT + surface resistivity >10¹² Ω/sq · the standard polymer for in-cabinet electrical hardware where heat tolerance matters more than self-extinguishing.
Holds tolerance against repeated metal-on-plastic clamping in production environments. The room-temperature chamber requirement makes it printable on standard industrial FDM hardware vs PEEK-class chambers.
A side-by-side of the three engineering nylons most engineers compare when they're looking at PA6-GF. Pick PA6-GF unless one of the other columns wins your specific row · stiffness goes to PA12-CF, ductility goes to plain PA12.
PA6-GF values from the manufacturer's PA6-GF25 TDS V1.1 (ISO 527, ISO 178, ISO 75, ISO 62). PA12-CF and PA12 values from sibling-grade printing guides. Cost reflects typical UK 2026 filament pricing.
| Property | PA6-GF (here) | PA12-CF | PA12 (plain) |
|---|---|---|---|
| Tensile strength XY (dry) | 90 MPa | 77 MPa | 50 MPa |
| Stiffness (Young's modulus) | 5357 MPa | 3311 MPa | 1500 MPa |
| Heat deflection (HDT 0.45) | 191°C | 131°C | 108°C |
| Heat deflection (HDT 1.8) | 157°C | 105°C | ~70°C |
| Charpy notched (dry → wet) | 10 → 28 kJ/m² | 4-5 kJ/m² | ~3 kJ/m² |
| Equilibrium water absorption | 3.33% | ~1.5% | ~1.5% |
| Heated chamber required? | No · room temp | Yes · 40-50°C | Yes · 40-50°C |
| Tensile anisotropy XY / Z (dry) | ~1.0× (near-isotropic) | 1.48× | 1.10× |
| UV resistance (sustained) | Limited | Limited | Limited |
| Cost per kg (filament) | £60-110 | £90-130 | £40-80 |
| Best for | Injection-moulding replacement, gear housings, high-HDT brackets | Stiffest light brackets, dry-storage parts | Tough one-piece parts, hinges, low-moisture-stable |
The other common engineering-nylon process decision. SLS is a different machine entirely · different base polymer, near-isotropic strength, different cost structure. Pick the row that matches your job.
| Property | FDM PA6-GF (here) | SLS PA12 (powder-bed) |
|---|---|---|
| Process | Filament extrusion, layer-by-layer | Powder-bed, laser-sintered |
| Tensile strength XY | 90 MPa | 48 MPa |
| Stiffness (Young's modulus) | 5357 MPa | 1700 MPa |
| Tensile anisotropy XY/Z | ~1.0× (near-isotropic) | ~1.1× |
| Elongation at break | 2.4% | ~20% (ductile) |
| HDT @ 0.45 MPa | 191°C | 163°C |
| Water absorption | 3.33% (PA6) | ~1.5% (PA12) |
| Surface finish · as printed | Layer lines visible · sand or paint for smooth | Matte powder-grain finish, uniform |
| Min wall thickness | 1.5 mm structural | 0.7 mm achievable |
| Internal channels / lattices | Limited (support material) | Excellent (powder is the support) |
| Per-part cost · 1-off | Lower | Higher (machine + powder cost) |
| Per-part cost · batch of 100 | Comparable | Lower (efficient bed packing) |
| Best for | Stiff, high-HDT engineering parts, injection-moulding replacement, gear housings | Complex geometry, lattices, near-isotropic strength, batch-of-50+, lower-moisture parts |
This is 3DPE's standard process for PA6-GF · the equipment and the dried-filament discipline are included, no surcharge. Slicer profile and orientation are tuned per part at quote stage.
File or sketch in. We confirm material, orientation, finish, service-humidity.
Engineer reviewed. Lead time + per-unit cost back inside 24 hours.
Wall thickness, anisotropy, dry-vs-wet design loads flagged before print.
Filament dried 100°C / 10h pre-print. Hardened steel nozzle. ISO-spec adherence.
100°C / 16h anneal recommended. Sand or paint to spec.
Tracked UK courier, tracking number sent the moment it leaves.
Drying adds 10 hours and annealing adds 24 hours (16h dwell + cooldown) to any of the above. Lead times start when CAD is signed off · CAD round-trips on rev requests can extend the clock.
Discontinued moulded-PA6-GF gear housings printed in PA6-GF25 as direct injection-moulding replacements · 191°C HDT covered the gearbox heat-soak envelope, 80 MPa XY tensile carried the mounting loads, and the room-temperature chamber requirement kept the run on standard FDM hardware.
PA6-GF is 25% glass-fibre-reinforced polyamide 6 · a short-chain semi-crystalline engineering nylon filament with chopped glass fibre as reinforcement. Used in FDM 3D printing as a direct injection-moulding-replacement engineering thermoplastic. The base polymer (PA6, nylon 6) is the most-produced engineering nylon globally · same chemistry as automotive under-bonnet brackets, gear housings, and moulded engineering hardware. Glass-fibre at 25 wt% delivers a near-isotropic 90 MPa tensile (90.1 XY / 90.7 Z) dry, 191°C HDT at 0.45 MPa (highest in commodity FDM), and the unusual property that notched Charpy impact INCREASES when wet (10 kJ/m² dry → 28 kJ/m² wet) because absorbed water plasticises the matrix. PA6 is the most hygroscopic engineering nylon · 3.33% equilibrium water absorption · dry-state design margin is mandatory for stiff service. Density 1.20 g/cm³. Tensile strength is near-isotropic (~1.0× XY/Z) but stiffness is direction-dependent (modulus ~1.6× XY/Z).
"PA6-GF is what I reach for when a customer wants an injection-moulded engineering part without the MOQ. It's the same chemistry as half the brackets in a car engine bay, prints without a heated chamber, and holds 191°C HDT · numbers I couldn't get out of any other commodity filament. The trade is the moisture story · dry-state strength halves when the part saturates, and notched impact triples. You design for the wet state on parts that see humidity, the dry state on parts that don't. Get that decision right and PA6-GF earns its place in the workshop."
Three questions every engineer Googles when picking PA6-GF · the base polymer chemistry, how the glass fibre changes it, and what the wet/dry property inversion means in service.
PA6 has 6 carbons between each amide linkage vs 12 in PA12 · denser hydrogen-bonding gives higher melting point (214.5°C vs 171°C), higher HDT (191°C vs 131°C with the same fibre loading), and more strength. The trade is moisture: more amide groups means more water-attackable sites · 3.33% absorption vs 1.5%.
25% chopped glass fibre aligns along extrusion during deposition. Tensile strength comes out near-isotropic (90.1 XY / 90.7 Z · ~1.0×) · unusually direction-independent for a fibre-filled grade · while stiffness stays anisotropic (modulus 5357 XY / 3376 Z ≈ 1.6×).
Charpy notched 10 kJ/m² dry → 28 kJ/m² wet (per ISO 179). Absorbed water plasticises the matrix · tensile halves but impact toughness triples. Unique to PA6 chemistry.
Polyamide 6 (PA6, also called nylon 6) is a short-chain semi-crystalline engineering thermoplastic. It's the most-produced engineering nylon globally · the polymer behind injection-moulded automotive brackets, gearbox housings, cable ducts, fan shrouds, and a large share of moulded electrical hardware. Compared to longer-chain nylons like PA12, the denser amide-group spacing gives PA6 higher melting point (214.5°C vs 171°C), higher crystallinity, higher strength, and significantly higher HDT.
The compromise is moisture. Every amide linkage is a potential hydrogen-bonding site for water · more amides per chain length means more water uptake. PA6 sits at 3.33% equilibrium water absorption, the highest of the engineering nylons. That moisture plasticises the polymer · dry-state stiffness falls, but impact toughness rises sharply. This wet/dry inversion is the defining design consideration when specifying PA6-GF.
Our stocked grade is 25% glass fibre by weight, chopped to short segments (typically 100-300 microns, not continuous strands). The fibres orient along the print-head direction as the molten filament extrudes. That orientation drives anisotropy · XY (in the print plane) inherits most of the fibre-alignment strength, while Z (layer-to-layer) relies on polymer-to-polymer bonding with minimal fibre-bridging across layers.
Glass fibre reinforces differently from carbon fibre. GF gives near-isotropic tensile strength (90.1 XY / 90.7 Z · ~1.0× vs ~1.48× for typical PA-CF) and less brittle behaviour at peak load · the matrix retains more elongation-at-break. The trade is stiffness · 25% glass fibre delivers 5357 MPa Young's modulus, roughly 60% more than 10% carbon fibre in PA12, but less than a 20%+ CF loading, and modulus stays direction-dependent (~1.6× XY/Z). GF is also less abrasive on print hardware than CF, though hardened steel or ruby nozzles are still mandatory · brass lasts roughly 9 hours in this grade.
This is the property unique to PA6 that catches most engineers by surprise. Dry-state tensile strength is 80 MPa XY · wet-state is 40 MPa (halved). Dry flexural modulus is 4314 MPa · wet is 1448 MPa (33% of dry). But notched Charpy impact strength climbs from 10 kJ/m² dry to 28 kJ/m² wet · a 180% increase. The absorbed water plasticises the polymer matrix, making it less stiff but more able to dissipate impact energy.
In practice this means specifying the right property for the right service. Dry-storage indoor parts (climate-controlled cabinets, indoor brackets, factory tooling) use the dry properties. Parts that see sustained humidity, occasional splash, or outdoor service (sealed, not UV-exposed) should be designed against the wet properties. Cycling between states is fine · PA6-GF is dimensionally reversible across the wet/dry transition once the saturation cycle settles, with the manufacturer noting equilibrium settles after ~48h immersion at 60°C.
Values measured to the ISO standards cited in the right-hand column, on the manufacturer's own injection-moulded test specimens · directly comparable to other engineering thermoplastics.
| Property | XY · print plane | Z · build axis | Wet · XY / Z · post-immersion | Unit | Standard |
|---|---|---|---|---|---|
| Mechanical · dry status | |||||
| Tensile strength | 90.1 | 90.7 | 40.2 / 26.3 (wet) | MPa | ISO 527 · Fiberon PA6-GF25 TDS V1.1 |
| Young's modulus | 5357 | 3376 | 1794 / 1165 | MPa | ISO 527 |
| Elongation at break | 2.4 | 4.0 | 4.2 / 7.1 | % | ISO 527 |
| Flexural strength | 133.8 | 99.9 | 47.8 / 33.8 | MPa | ISO 178 |
| Flexural modulus | 4314 | 2850 | 1448 / 836 | MPa | ISO 178 |
| Charpy impact (notched, XY) | 10.0 | · | 28.0 ↑ | kJ/m² | ISO 179 |
| Charpy impact (unnotched, XY) | 27.4 | 16.2 | 82.1 / 17.5 | kJ/m² | ISO 179 |
| Thermal | |||||
| Heat deflection (HDT @ 0.45 MPa) | 191 | °C | ISO 75 | ||
| Heat deflection (HDT @ 1.8 MPa) | 157 | °C | ISO 75 | ||
| Glass transition temperature (Tg) | 70.4 | °C | DSC, 10°C/min | ||
| Melting temperature (Tm) | 214.5 | °C | DSC lab figure · not the print temperature or the in-service softening limit (see HDT/Tg) | ||
| Crystallisation temperature (Tc) | 174.5 | °C | DSC, 10°C/min | ||
| Vicat softening temperature | 211.7 | °C | ISO 306 | ||
| Decomposition temperature | 437.1 | °C | TGA, 20°C/min | ||
| Physical | |||||
| Density | 1.20 | g/cm³ @ 23°C | ISO 1183 | ||
| Glass-fibre content | 25 | % by weight | manufacturer spec | ||
| Equilibrium water absorption | 3.33 | % | manufacturer test | ||
| Melt flow index | 15.9 | g/10min (300°C, 2.16kg) | ISO 1133 | ||
| UL94 flame rating | HB at 1.5mm | · | UL 94 | ||
| Surface resistivity | >10¹² | Ω/sq (insulator) | ANSI ESD S11.11 | ||
| Processing | |||||
| Recommended print temperature | 280-300 | °C | manufacturer spec | ||
| Recommended bed temperature | 40-50 | °C | manufacturer spec | ||
| Chamber requirement | Room temperature (no heated chamber) | · | manufacturer spec | ||
| Drying conditions | 100°C / 10h before printing | · | manufacturer spec | ||
| Annealing | 100°C / 16h post-print (recommended) | · | manufacturer spec | ||
| Nozzle material | Hardened steel or ruby (brass ~9h life) | · | manufacturer spec | ||
Tensile strength is near-isotropic (90.1 XY / 90.7 Z) so orientation matters less for raw strength · but stiffness is not (modulus 5357 XY / 3376 Z ≈ 1.6×), so orient stiffness-critical features in XY.
Sub-1 mm walls can snap cold under load · 0.8 mm is cosmetic only · 1.5 mm or thicker for engineering use (GF reinforcement amplifies brittle failure at thin sections more than carbon-fibre).
Above 45° from vertical needs support material · plan part orientation to keep critical surfaces support-free.
Tight-tolerance ±0.1 mm achievable on small parts with calibration · ask before finalising CAD.
Removes 0.1-0.3 mm per surface · pre-paint prep or stand-alone hand-feel polish.
Anneal IF service temp > 60°C OR sustained load OR thermal cycling. Skip IF prototype, indoor, no temperature swings. Costs ~1% Z shrinkage, XY ≤0.1%.
Adds 0.05-0.15 mm per surface · sand 800 grit first, primer + topcoat · for colour-matched exterior parts.
Vapour fuses the matrix without flattening exposed glass · glossy but textured · sand + paint instead.
Every value on this page traces to an ISO test method. We don't quote derived numbers without naming the standard.
No offshore subcontracting. Files, prints, and couriers all stay in the UK.
Send three things: peak load (N or MPa), peak service temperature (°C), and service humidity. our team come back inside 24 hours with material, orientation, and post-process recommendation · if PA12-CF, PC-ABS, or PEEK fits better, we say so.
our team review every brief before quote. No ticket queue, no account managers.
According to the Fiberon PA6-GF25 TDS, PA6-GF25 reaches Young's modulus 5357 ± 211 MPa (XY) dry per ISO 527 with HDT 191 °C @ 0.45 MPa and Tm 214.5 °C · drops 66.5% to 1794 MPa when moisture-saturated.
This is the defining property of PA6 chemistry. Absorbed water plasticises the matrix · the polymer becomes less stiff but more able to dissipate impact energy. Notched Charpy impact climbs from 10 kJ/m² dry to 28 kJ/m² wet (a 180% increase). The trade is that tensile strength halves (80 → 40 MPa) and flexural modulus drops to 33% of dry. Design for the dominant service state: dry parts in climate-controlled cabinets use dry properties; wet/humid-service parts use wet properties.
Correct, and it's unusual. Most engineering nylons (PA12-CF, PA6-CF, PC, PEEK) need a heated build chamber to prevent thermal stress and warping. PA6-GF prints at room temperature on standard open-frame industrial FDM. Build plate 40-50°C is the only heating required. This is the practical wedge that lets engineering-grade PA6-GF run on commodity printer hardware.
Tg is 70.4°C per the manufacturer TDS (DSC, 10°C/min). This is higher than bulk PA6 textbook values (~47°C) because the 25% glass-fibre reinforcement constrains polymer-chain mobility. Above Tg, the polymer becomes more compliant but doesn't fail · the structural ceiling is the HDT (157°C at 1.8 MPa).
PA6-GF wins on strength (90 vs 77 MPa XY tensile, and near-isotropic), stiffness (5357 vs 3311 MPa Young's modulus), HDT (191 vs 131°C at 0.45 MPa), wet-state impact toughness, and printability without a heated chamber. PA12-CF wins decisively on moisture stability (moisture-immune vs PA6-GF losing ~55% tensile / ~67% stiffness wet) and dry-storage dimensional accuracy. Pick PA6-GF for stiff, hot-service, injection-moulding-replacement parts kept dry; pick PA12-CF for dimensionally-critical parts in humid service.
Hardened-steel or ruby-tip. Glass-fibre filament destroys a brass nozzle in roughly 9 hours of print time per the manufacturer · about the same lifetime as carbon-fibre. We run hardened-steel on every GF print as standard, included in the quote · no surcharge, no surprise.
Near-isotropic in tensile · ~1.0× XY/Z dry (90.1 MPa XY / 90.7 MPa Z), unusual for a fibre-filled grade. Stiffness is still direction-dependent (modulus 5357 XY / 3376 Z ≈ 1.6×). Wet-state tensile anisotropy rises to ~1.53× (40.2 / 26.3 MPa) as Z weakens faster than XY.
Our stocked grade is rated UL94 HB at 1.5mm wall (the lowest horizontal-burn rating, but rated). For self-certification applications needing UL94 V-0 or V-2 (vertical burn), we stock UL-rated alternative grades on request, including dedicated flame-retardant nylons.
Annealing is controlled heat treatment after printing (100°C for 16 hours per the manufacturer TDS) that relaxes residual stresses and increases crystallinity. Recommended for all engineering parts in PA6-GF · stabilises dimensions before the part enters its first wet/dry humidity cycle. Causes ~0.7% Z-axis shrinkage and ~0.15% XY shrinkage (per the manufacturer shrinkage block).
Short-term outdoor exposure is fine. Sustained outdoor UV degrades nylons · standard PA6-GF yellows and embrittles over months of direct sunlight. For sustained outdoor use, choose ASA (UV-stabilised by chemistry), UV-stabilised PC, or PA6-GF with a 2K polyurethane UV-resistant overcoat over a 2K epoxy primer (e.g. Hempel Hempathane HS 55610).
PA6-GF inherits PA6's chemistry. Excellent for engine-bay oils, fuels, and indoor industrial environments. Vulnerable to strong acids, sustained hot water (hydrolysis), and chlorinated solvents. Glass fibre is chemically inert; the matrix dominates.
| Chemical / family | Resistance | Notes |
|---|---|---|
| Petrol / gasoline | Excellent | Native nylon-family fuel-line application |
| Diesel | Excellent | Including biodiesel blends |
| Engine oil, gear oil, hydraulic oil | Excellent | All standard service grades |
| Brake fluid (DOT 3 / 4 / 5.1 glycol) | Excellent | DOT 5 silicone also fine |
| Coolant / antifreeze (ethylene glycol) | Excellent | Including diluted service coolant |
| Methanol, ethanol, IPA | Excellent | Cleaning + assembly OK |
| Detergents, soap, weak alkalis | Good | Workshop wash-down OK · sustained hot soap softer than PA12 |
| Sea water / saline solution | Limited | PA6 swells more than PA12 in salt water · short-term only |
| Hydrogen peroxide ≤ 6% | Limited | Slow oxidative attack on PA6 |
| Acetone | Limited | Surface attack + softening over hours |
| MEK, toluene, xylene | Limited | Brief contact only · no soak |
| Strong alkalis (NaOH > 10%) | Limited | Polymer-chain hydrolysis risk |
| Weak organic acids (acetic, citric) | Limited | Slow attack over weeks |
| Hot water (sustained > 80°C) | Fails | Hydrolysis attacks PA6 backbone · weeks-to-months |
| Strong acids (sulphuric, HCl, nitric) | Fails | Polymer chain breakdown |
| Chlorinated solvents long-term (TCE, DCM) | Fails | Solvent crazing + dissolution |
| Phenols | Fails | Strong PA6 solvent |
| Formic acid | Fails | Industry-standard PA6 dissolution solvent |
Ratings reflect long-term immersion / sustained exposure. Brief contact (cleaning wipes, splashes) is more forgiving than the table suggests. For mission-critical chemical service, request a 7-day immersion sample before committing the design.
PA6-GF is dimensionally reversible across the wet/dry cycle once equilibrium is reached. The first absorption cycle (factory-dry filament → printed part → ambient moisture) causes ~0.5-1% linear expansion and the property shifts above. Engineering parts in stable indoor service stay close to dry properties (factory air-conditioning, sealed cabinets). Outdoor or humid parts equilibrate to wet properties within weeks. Design tolerance for the dominant service state · sealed assemblies with internal climate control are dry, exposed assemblies are wet.
SLS PA6-GF is a different process · laser-sintered powder rather than filament extrusion. SLS gives near-isotropic strength, better complex geometry (lattices, internal channels), and slightly better dimensional accuracy. FDM PA6-GF (this page) gives higher strength on the XY plane, lower per-part cost on 1-off and small-batch jobs, and the room-temperature chamber advantage. We default to FDM PA6-GF for < 50-unit batches and structural parts where XY-orientation loading is achievable.
You'll hear back from our team within 24 hours · with material-fit check, ISO-referenced spec, and lead time on every quote.