3D printing filament
3D printing filament is a thermoplastic material, typically supplied as a continuous strand with a diameter of 1.75 mm or 2.85 mm, that serves as the primary feedstock for fused deposition modeling (FDM) or fused filament fabrication (FFF) additive manufacturing processes.[1] In these methods, the filament is fed into a heated extruder nozzle, where it is melted and precisely deposited in layers to construct three-dimensional objects, enabling the creation of prototypes, functional parts, and custom designs across industries such as engineering, medicine, and consumer products.[1] This technology, popularized since the early 2000s, relies on the filament's ability to solidify rapidly upon cooling, ensuring structural integrity and dimensional accuracy in printed parts.[2] The most common filaments are derived from polymers like polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate glycol (PETG), and thermoplastic polyurethane (TPU), each offering distinct mechanical and thermal properties suited to specific applications.[1] PLA, a biodegradable bioplastic sourced from renewable resources such as corn starch, is favored for its ease of printing at low temperatures (180–230°C), minimal warping, and high detail resolution, though it has limited heat resistance (up to 60°C) and is not ideal for load-bearing or outdoor use.[1] ABS provides superior durability, impact resistance, and heat tolerance (up to 105°C), making it suitable for functional prototypes and automotive parts, but it requires an enclosed printer to mitigate warping and fumes during printing at 220–250°C.[1] PETG combines strength, flexibility, and chemical resistance with food-safe variants, printing at 220–250°C, though it can be prone to stringing and demands good bed adhesion.[1] Flexible filaments like TPU exhibit rubber-like elasticity and abrasion resistance, ideal for gaskets or wearables, but require slower print speeds (20–50 mm/s) and direct-drive extruders.[1] Advanced filaments, including nylon (PA) for high-tensile mechanical components and polycarbonate (PC) for heat-resistant engineering applications (up to 110°C), expand versatility but often necessitate drying to prevent moisture absorption, which can cause defects like bubbling or poor layer adhesion.[1] Specialized composites, such as carbon fiber-filled variants, enhance stiffness and lightweight properties for aerospace or robotics, though they are abrasive and require hardened nozzles.[1] Key considerations for filament selection include printer compatibility, environmental factors (e.g., hygroscopicity in nylon and PETG), post-processing needs like annealing for improved strength, and sustainability— with PLA offering compostability while others like ABS are recyclable.[3] Overall, the diversity of filaments enables FDM 3D printing to produce cost-effective, customizable objects with properties rivaling traditional manufacturing, driving innovations in rapid prototyping and small-scale production.[1]Overview
Definition and principles
3D printing filament refers to a continuous thermoplastic wire or thread that serves as the primary feedstock material in fused deposition modeling (FDM) and fused filament fabrication (FFF) processes, which are types of material extrusion additive manufacturing.[4][5] In these methods, the filament is fed into a heated extruder where it is softened or melted, then precisely deposited through a nozzle onto a build platform in successive layers to construct three-dimensional objects based on a digital model.[4][5] This layer-by-layer buildup allows for the creation of complex geometries with minimal material waste compared to subtractive manufacturing techniques.[5] The standard diameters for 3D printing filament are 1.75 mm and 2.85 mm, with the former being more prevalent in consumer and prosumer printers due to its finer precision and broader compatibility, while the latter is common in some industrial models for higher flow rates.[6][7] These dimensions ensure consistent feeding and extrusion, but mismatches can lead to issues like jamming or inaccurate deposition, necessitating printer-specific selection.[6] Unlike other 3D printing feedstocks, such as metal or polymer powders used in powder bed fusion processes or liquid resins in vat photopolymerization, filament's solid, spool-wound form enables straightforward handling and low-cost implementation in desktop setups, democratizing access to additive manufacturing for hobbyists and small-scale production.[8][9] Filament-based printing was popularized by the invention of FDM, patented in 1989 by S. Scott Crump, who described a system for extruding thermoplastic material from a filament supply to form layered prototypes.[10][11] This foundational technology, commercialized through Stratasys, established filament as a versatile medium for rapid prototyping and functional part creation, often using accessible thermoplastics such as ABS.[11]Historical development
The origins of 3D printing filament trace back to the late 1980s, when additive manufacturing technologies began to emerge as viable methods for layer-by-layer fabrication. While Charles "Chuck" Hull patented stereolithography in 1984, which used liquid resins cured by UV light, it was S. Scott Crump's invention of fused deposition modeling (FDM) in 1989 that introduced thermoplastic filament as a practical extrusion medium.[12][13] Crump's U.S. Patent No. 5,121,329 described a process where a continuous filament of thermoplastic material is heated and extruded through a nozzle to build objects, establishing filament as the core feedstock for this extrusion-based technique.[14] In the 1990s, Stratasys, founded by Crump in 1989, commercialized FDM technology, marking the first widespread use of filament in industrial applications. The company's debut of the 3D Modeler in 1992 represented the initial commercial FDM machine, accompanied by sales of proprietary ABS filament spools starting in the early 1990s.[15][16] This period solidified filament's role in rapid prototyping, though high costs limited access to professional sectors. By the 2000s, the RepRap project, launched in 2005 by Adrian Bowyer at the University of Bath, open-sourced FDM designs, enabling DIY communities to produce and experiment with affordable filament-based printers and fostering broader adoption among hobbyists.[17][18] The 2010s saw explosive growth following the expiration of Stratasys's key FDM patents in 2009, which democratized the technology and led to the widespread availability of low-cost filaments. Entrepreneurs, including former RepRap contributors, founded MakerBot in 2009, releasing consumer-grade printers like the Thing-O-Matic in 2010 that popularized 1.75 mm diameter PLA and ABS filaments as industry norms, shifting from the earlier 3 mm standard used in open-source printers, while Stratasys had employed approximately 1.78 mm filament.[19][20] Standardization efforts accelerated with the formation of ASTM International's F42 Committee on Additive Manufacturing Technologies around 2009-2010, which developed guidelines for filament-based processes to ensure interoperability and quality.[21] In the 2020s, the filament landscape has shifted toward sustainability, driven by environmental concerns and innovations in recycled and bio-based materials. Companies have introduced filaments from post-consumer plastics and natural fibers, reducing reliance on virgin petroleum-based thermoplastics and aligning with circular economy principles.[22][23] This evolution reflects ongoing efforts to make filament production more eco-friendly while maintaining performance for diverse applications.[24]Materials
Common filament types
3D printing filaments are predominantly thermoplastics, which soften when heated and solidify upon cooling, enabling layer-by-layer extrusion in fused deposition modeling (FDM) processes.[25] Among these, polylactic acid (PLA) stands out as a biodegradable, entry-level material derived from renewable sources like corn starch, with commercial availability emerging in the early 2000s.[26] PLA offers ease of use for beginners due to its low printing temperatures and minimal warping, making it ideal for prototypes and decorative items.[25] Acrylonitrile butadiene styrene (ABS) provides greater durability and impact resistance compared to PLA, often used for functional parts resembling the toughness of LEGO bricks, which are primarily made from ABS.[27] However, ABS is prone to warping during cooling due to significant shrinkage, necessitating enclosed printers and heated beds for successful prints.[28] Engineering filaments build on these basics with enhanced performance for demanding applications. Polyethylene terephthalate glycol (PETG) combines the clarity and chemical resistance of PET with glycol modification for improved impact resistance and layer adhesion, serving as a versatile alternative to ABS without the warping issues.[29] Nylon, or polyamide, excels in flexibility and tensile strength, offering abrasion resistance suitable for gears, hinges, and wear-prone components.[30] Specialty filaments address niche needs beyond standard thermoplastics. Thermoplastic polyurethane (TPU) functions as an elastomer, providing rubber-like flexibility and elasticity for parts such as phone cases, seals, and gaskets that require stretch and rebound properties.[31] Composite filaments, such as those filled with carbon fiber, incorporate short fibers into a base like PLA or Nylon to enhance rigidity and stiffness while reducing weight, ideal for structural prototypes in aerospace and automotive fields.[32] Metal and ceramic filaments differ from pure thermoplastics by embedding fine powders in a polymer binder, allowing FDM printing followed by debinding and high-temperature sintering to achieve dense, functional metal or ceramic parts.[33] These powder-in-binder types enable complex geometries in materials like stainless steel or alumina, with post-processing removing the binder to yield high-strength components for tooling and medical implants.[34]Material properties and selection
Material properties in 3D printing filaments encompass thermal, mechanical, and environmental characteristics that determine their suitability for extrusion-based fabrication. Thermal properties, such as melting temperature, are critical for ensuring proper flow during printing; for instance, polylactic acid (PLA) typically melts around 140-160°C, while acrylonitrile butadiene styrene (ABS), an amorphous thermoplastic, softens above approximately 100–105°C and requires extrusion temperatures exceeding 220°C.[35][36] Mechanical properties include tensile strength, which measures resistance to pulling forces, with PLA exhibiting higher values around 65 MPa compared to ABS at approximately 40 MPa, and flexibility, where ABS demonstrates greater ductility to absorb impacts without fracturing.[37] Layer adhesion, influenced by material composition and printing parameters, affects overall part integrity; poor adhesion can lead to delamination, significantly reducing effective strength in multi-layer prints.[29] Environmental factors further influence filament performance, particularly shrinkage rates upon cooling, which can cause warping and dimensional inaccuracies. PLA exhibits low shrinkage of 0.3-0.5%, minimizing distortion, whereas ABS shows higher rates, often 0.7-1.5% or more, necessitating enclosure and heated beds to mitigate stress.[38] UV resistance varies, with ABS offering moderate protection against degradation from sunlight exposure, while PLA is more susceptible, leading to brittleness over time outdoors. Biodegradability is another key trait; PLA can decompose in industrial composting conditions within 50 days, unlike petroleum-based ABS, which persists in the environment.[39] Selection of filaments hinges on aligning these properties with application demands and printer capabilities. For heat-sensitive parts, materials with lower melting points like PLA suit printers without high-temperature nozzles (up to 220°C), but ABS requires nozzles capable of 250°C and heated beds at 80-110°C to prevent cracking. Cost-performance trade-offs are evident: PLA's affordability and ease make it ideal for prototypes, while ABS's durability justifies higher expense for functional components, though its warping risk increases processing time.[40] Quality assurance relies on standardized testing, such as ISO/ASTM specifications for filament dimensions and mechanical performance. Diameter tolerance is typically ±0.05 mm to ensure consistent extrusion, as deviations can cause under- or over-extrusion, affecting print accuracy by 10-20%. Mechanical tests follow ASTM D638 for tensile properties, providing benchmarks for strength and elongation.[41][42] Certain filaments exhibit unique behaviors requiring specific handling; for example, nylon is highly hygroscopic, absorbing over 10% of its weight in moisture from ambient air, which hydrolyzes the polymer during printing and reduces layer adhesion. Dry storage in desiccants or vacuum bags is essential to maintain integrity. Additionally, color additives in pigments can alter thermal conductivity and viscosity, affecting printing parameters and potentially print quality through inconsistent flow.[43]Production
Commercial manufacturing
The commercial manufacturing of 3D printing filament relies on industrial extrusion processes designed for high-volume, precise production of thermoplastic strands suitable for fused deposition modeling (FDM) printers. Polymer pellets serve as the primary raw material; for petroleum-based filaments like ABS, they are derived from refined petroleum products like naphtha and polymerized into resins, while biopolymers like PLA are sourced from renewable resources such as corn starch.[1] These pellets are first dried at temperatures of 60–80°C to eliminate moisture, which could cause defects, and then blended with additives including colorants, impact modifiers, or fillers to achieve desired properties like strength or aesthetics. This preparation occurs in large industrial mixers before the material is fed into the extrusion system.[44][45] In the core extrusion step, the blended pellets enter a single-screw extruder, where a rotating screw transports them through a series of heated zones—often 4–6 sections with temperatures escalating from 180–250°C depending on the polymer—to melt and homogenize the material under controlled pressure. The molten polymer is then forced through a circular die to form continuous strands of standard diameters, such as 1.75 mm or 2.85 mm. To ensure uniformity, the extrusion speed is precisely regulated, integrating additives directly into the melt for even distribution without post-processing.[44][45][46] Following extrusion, the hot strands pass through cooling systems consisting of sequential water baths: an initial warm bath (around 40–60°C) to gradually set the shape and prevent warping or shrinkage, followed by a cold bath (below 20°C) for rapid solidification. The filament is pulled through these baths by tractor units at speeds up to several meters per minute, maintaining dimensional accuracy. Quality control is integrated throughout, with dual-axis laser micrometers—accurate to 0.8 µm—continuously scanning the diameter in real-time, rejecting any sections outside tolerances like ±0.02–0.05 mm and logging data for traceability.[44][45] The cooled filament is automatically wound onto spools or reels, typically holding 0.5–1 kg, using tension-controlled winders to avoid tangling or stretching. Completed spools are then labeled, inspected for defects, and packaged in moisture-barrier materials such as vacuum-sealed foil bags or desiccated boxes to prevent humidity-induced degradation, which is critical for hygroscopic materials like nylon. Production lines in commercial facilities often operate at capacities of 20–50 kg per hour per extruder, with larger plants scaling to hundreds of kilograms per hour across multiple units for efficiency.[44][45][47] Key players in this sector include established firms like Stratasys (US), a pioneer in FDM technology since 1989 with filament production starting in the early 1990s, and more recent entrants such as Hatchbox (founded 2017) and Prusa Research, alongside global suppliers like Polymaker and Shenzhen Esun Industrial Co., Ltd.[48][49] The industry has seen rapid expansion, with the global 3D printing filament market growing from approximately USD 0.33 billion in 2020 to over USD 1 billion by 2025 and estimated at USD 1.05–1.77 billion as of 2025, projected to reach USD 2.58–4.20 billion by 2030 at a CAGR of 18–19%.[50][51][52] To meet regulatory requirements, particularly in the European Union, manufacturers ensure compliance with REACH (Regulation (EC) No 1907/2006), which mandates registration of chemical substances, assessment of risks, and restriction of hazardous materials like certain phthalates or heavy metals in filaments. This involves supplier declarations and testing to confirm that all ingredients exceed tonnage thresholds for registration while limiting substances of very high concern (SVHCs) below 0.1% by weight, promoting safe use in consumer and industrial applications.[53][54]DIY and recycling methods
DIY filament production emerged prominently within the RepRap community following the project's launch in 2005, emphasizing self-replication and cost reduction through open-source designs for extruders that process plastic pellets into filament.[55] These efforts promoted accessibility by enabling hobbyists to manufacture filament at home using modified 3D printers or dedicated kits, often focusing on pellet-based feeding to bypass commercial spools.[55] One popular approach involves hobbyist extruders like the Filastruder kit, which extrudes filament from plastic pellets fed into a hopper, heated to temperatures up to 260°C, and forced through a nozzle for manual spooling.[56] The system allows diameter control via interchangeable nozzles (e.g., 1.75mm or 3.0mm) and a melt filter to remove impurities greater than 200μm, achieving tolerances of ±0.02mm for ABS and ±0.03mm for PLA when paired with a winder.[56] Pellet feeding supports customization, such as mixing colors or recycling shredded waste, though users must ensure pellets are under 5mm for consistent flow.[56] Recycling methods further enhance sustainability by converting failed prints and waste into reusable filament through a multi-step process: shredding scraps into small fragments (typically ≤5mm using devices like the Precious Plastic Shredder), drying to remove moisture, re-extruding into uniform pellets, and then forming new filament strands.[57] Closed-loop systems like the ProtoCycler, developed in the 2010s, automate this by integrating a grinder, extruder, and digital diameter sensors (±0.05mm tolerance) to process materials such as PLA and ABS directly from 3D printing waste.[58] These desktop recyclers support multiple polymers, including PETG and Nylon 12, enabling on-demand production from rafts, supports, or prototypes.[58] Challenges in DIY extrusion include inconsistent filament diameter, often caused by fluctuating room temperatures, improper heater profiles, or material contamination leading to bubbles and blockages.[59] To mitigate this, users should stabilize the environment, pre-dry hygroscopic materials below their glass transition temperature, and adjust winder tension to prevent stretching.[59] Safety concerns arise from fumes generated during heating; adequate ventilation and respirators are essential, while avoiding ovens for drying to prevent toxic residue buildup—opt instead for dedicated dryers or silica gel storage.[60] By the 2020s, innovations like Sulzer and TripleW's process transformed food waste—such as bakery rejects—into lactic acid and subsequently PLA bioplastic, providing a sustainable feedstock for recycled filament and reducing reliance on virgin materials.[61] Environmentally, distributed recycling of post-consumer plastics like HDPE for filament yields 24% less embodied energy than virgin production and cuts greenhouse gas emissions, particularly in low-density areas where transportation savings exceed 80%.[62] For PLA specifically, recycling lowers the carbon footprint by minimizing waste and energy-intensive virgin synthesis, though multiple cycles may slightly reduce mechanical strength by over 15%.[63] Overall, these methods divert plastic waste from landfills, fostering a circular economy in 3D printing.[64]Usage
Extrusion process in FDM printing
In fused deposition modeling (FDM) 3D printing, the extrusion process begins with filament loading into the extruder, where a motorized drive gear grips and advances the filament from its spool toward the hotend.[65] The filament, typically 1.75 mm or 2.85 mm in diameter, is pushed through a tube or directly into the heating zone, depending on the extruder configuration.[66] Once loaded, the hotend heats the filament to a semi-liquid state, usually above its glass transition temperature but below full decomposition, allowing it to flow under pressure.[67] This molten material is then extruded through a precision nozzle, commonly 0.4 mm in diameter, and deposited onto the build plate in a controlled path dictated by the printer's motion system.[65] The build plate lowers incrementally after each layer, enabling the layer-by-layer construction of the object.[68] The mechanics of extrusion vary between Bowden and direct drive systems, which influence filament control and print quality. In a Bowden system, the drive gear is mounted remotely on the printer frame, pushing the filament through a flexible PTFE tube to the hotend on the print head, reducing moving mass for faster speeds but potentially increasing filament compression and backlash.[69] Conversely, a direct drive system positions the drive gear directly above the hotend on the print head, providing more precise filament control and better performance with flexible materials, though it adds weight that can limit acceleration.[70] The hotend itself consists of a heat block and barrel, often lined with PTFE tubing to minimize friction and prevent premature melting in the transition zone, particularly for high-temperature filaments like ABS or nylon.[66] Key printing parameters govern the extrusion flow and deposition accuracy. The extrusion multiplier adjusts the filament feed rate relative to the slicer's calculated volume, compensating for variations in filament diameter or under-extrusion to ensure consistent line width and avoid gaps or overfills.[71] Layer height, typically ranging from 0.1 to 0.3 mm, determines vertical resolution and affects surface finish, with thinner layers improving detail but increasing print time.[72] Print speed, often set between 40 and 60 mm/s, influences cooling and interlayer bonding, where higher speeds can reduce quality if not balanced with adequate extrusion rates.[73] To optimize print quality, retraction pulls the filament back slightly (0.5-2 mm) during non-extrusion moves, minimizing oozing and stringing between features.[74] Bed adhesion techniques, such as adding a brim—a single-layer outline extending from the print base—or a raft—a thicker foundational layer—enhance initial grip on the build plate, reducing warping especially for large or complex geometries.[75] These methods increase contact area and promote even cooling.[76] The layer-by-layer nature of FDM extrusion inherently produces anisotropic parts, with mechanical strength varying by direction: interlayer bonds are weaker than intra-layer fusion, leading to up to 50% lower tensile strength perpendicular to the build plane compared to in-plane directions.[77] This directional variation arises from incomplete diffusion across layer interfaces during deposition.[78]Handling, storage, and troubleshooting
Proper storage of 3D printing filament is essential to prevent degradation, particularly for hygroscopic materials that absorb moisture from the air. Hygroscopic filaments such as nylon, PETG, and TPU can absorb significant amounts of water—nylon up to 10% of its weight within 24 hours of exposure—leading to printing defects like bubbling or poor layer adhesion.[43] To mitigate this, store filaments in sealed, airtight containers equipped with desiccants like silica gel packets, which effectively absorb ambient humidity.[79] PLA filament, being less hygroscopic, has a longer shelf life of 1-2 years when kept in its original packaging or a dry environment at temperatures between 20-25°C (68-77°F).[80] Avoid exposure to direct sunlight or high humidity areas, as these accelerate breakdown.[81] Handling filament requires care to maintain its integrity and ensure smooth feeding into the printer. Always uncoil filament gently to avoid creating bends or kinks, which can jam the extruder; provide a straight, unobstructed path from the spool to the printer, especially for brittle or flexible materials.[82] Before use, verify compatibility by checking filament diameter (typically 1.75 mm or 2.85 mm) against the printer's specifications and slicer software settings, such as standard filament guides in programs like PrusaSlicer or Cura.[83] For moisture-affected filament, drying conditions vary by material to effectively remove absorbed water without degrading the polymer; over-drying should be avoided, as excessive heat can alter the filament's molecular structure. Recommended parameters include:| Filament | Temperature (°C) | Time (hours) |
|---|---|---|
| PLA | 40-50 | 4-6 |
| PETG | 60-70 | 4-6 |
| TPU | 50-60 | 4-6 |
| Nylon | 70-90 | 6-12 (or longer if saturated) |