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Application of Consumer-grade FFF Flexible Filament
Consumer-grade FFF (Fused Filament Fabrication) 3D printers have gradually become a popular production tool as 3D printing technology continues to advance. The flexible filament is a kind of common printing material that can be used to produce various flexible parts such as seals, pipes, and robotic arms due to its elasticity and good extrudability. This article aims to review the current and future applications of flexible filament for consumer-grade FFF 3D printers, with guidance on how to use it to print more effectively.
In terms of application, the flexible filament for consumer-grade FFF 3D printers is primarily used to produce flexible parts and parts with complex shapes. For instance, TPE materials can be employed in the production of elastic seals and flexible hoses, and TPU materials can be used to produce components that demand both flexibility and toughness, such as wheels and robotic arms. Flexible filament can also be combined with other materials, such as hard ABS or PLA, to produce flexible composite components.
However, there are also some challenges in the application of flexible filament for consumer-grade FFF 3D printers. Firstly, the extrusion of flexible needs more precise control as it requires higher extrusion force and lower material viscosity. In addition, due to the high stretchability and elasticity of flexible filament, there may be a problem of weak interlayer bonding. Therefore, it is necessary to pay special attention to adjusting printing parameters and designing support structures to ensure print quality.
Generally speaking, the flexible filament for FFF 3D printers has reached a certain level of maturity in its application and can be used to produce various flexible parts and complex-shaped components. This has led to their increasing popularity in home, office, and industrial fields. As technology advances, we believe that the use of flexible filament will become more popular, bringing people more incredible inspiration and boundless potential.
2.Introduction to Flexible Printing Materials
2.1.Types of Materials
2.1.1.Classification Based on Whether the Elastomer Can Be Plasticized
It can be divided into thermoset elastomer and thermoplastic elastomer.
1)Thermoset elastomer, which is commonly known as rubber in traditional sense.
2)Thermoplastic elastomer (TPE), which can be divided into various types based on the material formulation, including thermoplastic polyurethane (TPU), thermoplastic copolyester (TPC), thermoplastic polyamide (TPA), thermoplastic rubber (TPR), thermoplastic olefin elastomer (TPO, TPV) and diene-based (TPB, TPI) types. Currently, the flexible materials applicable for Fused deposition modeling 3D printing mainly include TPE, TPU, TPC, TPA, TPR
2.1.2.Classification Based on the Filament Diameter
There are two filament diameters, i.e. 1.75 mm and 2.85 mm. Materials that are more flexible pose greater challenges in both production and printing process. Therefore, there is a certain relationship between the material’s hardness and filament diameter.
Currently, the filament diameter for materials with a hardness of 80A or higher is mainly 1.75 mm, while for materials with a hardness below 80A, the filament diameter is 2.85 mm
2.2.Material Characteristics and Application
2.2.1.Thermoplastic Rubber (TPR)
Thermoplastic rubber (TPR) is a modified thermoplastic elastomer with SBS as the base material. It has a reflective surface and high glossiness, and has the feel and resilience of rubber.
1)Physical properties
·Density 0.9 - 1.25 g/cm3
·Shore Hardness 0A - 100A
·Low moisture absorption
2)Mechanical properties
·Excellent resilience, slip resistance and shock absorption performance, high impact strength
·TPR material offers superior softness and comfort compared to rubber, but its tensile strength, fatigue resistance, and mechanical properties are inferior to vulcanized rubber. TPR filament can be pulled apart under large external forces.
3)Durability
·Moderate weather and aging resistance; temperature resistance of 70 - 75℃. Good chemical stability
4)Processing properties
·Moderate recyclability
·Weak interlayer adhesion during 3D printing
TPR is a commonly used flexible filament and has gradually become one of the main choices for the users of consumer-grade FFF 3D printers. TPR is a resilient and durable plastic that performs similarly to rubber, making it a suitable alternative material in many applications. Here are several application scenarios of TPR:
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Toys and models
TPR’s flexibility and plasticity make it an ideal material for manufacturing toys and models. It can easily form complex structures and shapes, and is tough enough to withstand rough use by children. Many consumer-grade 3D printer manufacturers recommend using TPR for the production of toys and models. -
Home, office and household uses
TPR’s durability and elasticity also make it an ideal material for making a variety of household, office, and home items. For example, TPR can be used to make 3D print items such as flowerpots, pencil cases, phone stands, keychains. Because of TPR’s good slip resistance, it can also be used to produce various grips and handles. -
Medical devices
TPR’s flexibility and slip-resistant properties also make it an ideal material for manufacturing medical devices such as handles, pads. Because TPR is a very safe material, it can be used in applications that require contact with the human body. -
Custom insoles
Many athletes require custom insoles to improve their comfort and performance. TPR can be used to create personalized insoles that are customized based on the gait and foot shape, providing better shock absorption and support. In this regard, TPR can even compete with traditional insoles.
In short, TPR is widely applied in diverse fields, and utilizing TPR in consumer-grade FFF 3D printers is an affordable and effective way to enhance design flexibility and widen the range of producible items.
2.2.2.Thermoplastic Elastomer (TPE)
TPE (thermoplastic elastomer) is a common material used as flexible filaments for consumer-grade FFF 3D printing. TPE is a thermoplastic elastic material based on SEBS (the hydrogenated product of SBS). It has matte surface that can absorb light, featuring low glossiness and smooth touch. It has the following characteristics and applications:
1)Physical properties
·Density: 0.92 - 0.98 g/cm3
·Shore Hardness: 0A - 100A
·Moisture absorption: low
2)Mechanical properties
·High flexibility and elasticity, with excellent shock absorption and high impact strength
·Good fatigue resistance, tear resistance and excellent wear resistance
3)Durability
·Chemical stability, aging resistance, UV resistance, hydrolysis resistance, and other properties are better than TPR
·Temperature resistance: service range of -30°C to +140°C
4)Processing properties
·Superior processing performance, no need for vulcanization, and recyclable
·Available for secondary injection molding or separate molding
·During 3D printing, it has low interlayer adhesion and weak adhesion with the bottom layer, and is easy to warp.
In the field of consumer goods, TPE is commonly used to manufacture non-slip pads, non-slip shower mats, and phone cases. In the industrial field, TPE can be used to make dampers, stabilizers, seals, linings, gaskets, etc., and some parts that need to withstand high temperatures can also be made with TPE. In addition, in the food and medical field, TPE is an FDA-approved food-grade material, and is commonly used to manufacture drinking water bottles, sippy cups, nozzles for baby feeding products, alternatives to latex or silicone in medical devices and prosthetics, etc.
2.2.3.Thermoplastic Polyurethane (TPU)
Thermoplastic polyurethane (TPU) has a smooth, even glossy texture.
1)Physical properties
Density 1.1 - 1.25 g/cm3; Shore Hardness 60A - 55D It has slight moisture absorption and is easy to absorb water from the air.
2)Mechanical properties
·Good elasticity and flexibility, with an elastic range of 600% to 700%
·Good resistance to impact with wonderful shock absorption effect
·High tensile strength; it is hard to break TPU filament under large external forces.
3)Durability
·Good corrosion resistance to many common industrial oils and chemicals; excellent wear resistance
4)Processing properties
·With superior processing performance, it can be processed together with some polymeric materials to obtain a polymer alloy with complementary properties.
·During 3D printing, TPU has strong interlayer adhesion ability, but it is relatively difficult to remove the supports, compared to TPR.
In the consumer goods field, TPU is commonly used to make phone cases, electronic product casings, watch straps, etc. In the automotive industry, TPU is used for dashboards, interior parts, intake hoses, side trims, and seat parts, etc. In the industrial field, TPU is used to produce seals and gaskets, sealing profiles for pipes, tubes, belts and hoses, conveyor belts, etc. In the medical field, TPU is used to produce artificial limbs and orthoses.
In the footwear and sports equipment field, TPU is used to make shoe soles, uppers, insoles, sports equipment, and sports devices.
2.2.4.Thermoplastic Copolyester (TPC)
Thermoplastic copolyester (TPC) is made by alternating sequences of short-chain and long-chain glycols. It contains both soft and hard segments, making it an engineering-grade material mainly used in the industrial field.
1)Physical properties
·Density 1.15 - 1.4g/cm3
·Shore Hardness 32D - 80D
·Low moisture absorption
2)Mechanical properties
·High strength, good flexibility
·Low fracture elongation, poor elasticity, elasticity range of 350% to 530%
3)Durability
·High temperature resistance
·Good chemical resistance
·High intensity and excellent UV resistance
4)Processing properties
·Moderate recyclability
·Strong interlayer adhesion during 3D printing
TPC materials are commonly used in hoses and ducts, flexible casings and covers, seals, gaskets, shock absorbers, spring beds, foot pads, footwear, safety equipment, wearable devices, and medical equipment.
2.2.5.Thermoplastic Copolyester (TPA)
Thermoplastic copolyester (TPA) is a copolymer of TPE and highly flexible nylon that combines the smooth texture of nylon with the flexibility of TPE.
1)Physical properties
·Density 1.0 - 1.14g/cm3
·Shore Hardness 63A - 75A
·It has excellent moisture absorption and is easy to absorb water from the air.
2)Mechanical properties
·With high strength, it is able to withstand large impact and high tensile forces without breaking.
·Poor elasticity, with an elasticity range of 370% to 497%.
3)Durability
·Good heat resistance
4)Processing properties
·Good interlayer adhesion is achieved during 3D printing, but the printed parts are prone to warping.
TPA is commonly used in manufacturing of winter sports equipment, especially ski equipment and golf balls. It is also used in the manufacturing of medical products such as catheters.
3.Research on Slicing Parameters for Flexible Filaments (Yuan Ming)
The following slicing settings are based on Ultimaker Cura 5.2.1.
3.1.Machine Setup
The success of printing relies on the setup of the machine, which mainly involves machine selection, filaments and setting of the nozzle diameter.
Due to the soft nature of flexible filament, bowden extruders have higher extrusion resistance and the risk of clogging is greater. Therefore, it is advisable to use direct extruders whenever feasible. When selecting a machine, choose the one with a direct extruder, such as Ender3 S1 equipped with a direct-drive sprite extruder.
- Add an Ender3 S1 device in the preferences settings interface.
- In the printer settings interface, select the extruder button and change the filament from 1.75 mm to 2.85 mm.
- In the material selection box in main interface, change the material to TPU and the nozzle diameter to 0.8mm.
3.2.Temperature
Temperature includes extruder temperature and printing platform temperature.
When an Fused deposition modeling printer operates, the material is fed into the nozzle through the extruder and undergoes a heat transfer process from solid to liquid in the melt chamber. The extruder temperature affects the adhesion and fluidity of the printing material, which in turn affects the printing accuracy and continuity of the printing process, ultimately affecting the quality of the 3D printed product.
Therefore, selecting the appropriate extruder temperature is crucial. The temperature of printing platform determines whether the printed object can stick to the printing platform. If the temperature is too low or too high, it won’t stick.A temperature tower model can be used to test the optimal temperature.
- Search for and download the “Calibration Shapes” plugin in the App market.
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Import the TPU temperature tower model into the Cura software, with a temperature range of 195 - 230℃.
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Click on “Extensions” in the menu bar, then click on “Post Processing” in the dropdown menu, and then click on “Modify G-Code” to open the “Post Processing Plugin” interface. Then, add a “TempFanTower” script.
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Set the parameters in the post-processing script and slice the model.
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Print the temperature tower model.
3.3.Speed
Printing speed is the speed at which the extruder moves during printing, which affects the printing time and surface quality of the printed object, and even affects the success or failure of the print. If the speed is too low, the printing time will be prolonged. If the speed is too fast, the surface quality of the printed object will be poor, and it may even cause under-extrusion and printing failure. It is important to test a suitable printing speed through a speed tower model.
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Import the TPU speed tower model into the Cura software, with a speed range of 20 - 90mm/s.
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Click on “Extensions” in the menu bar, then click on “Post Processing” in the dropdown menu, and then click on “Modify G-Code” to open the “Post Processing Plugin” interface. Then, add a “SpeedTower” script.
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Set the parameters in the post-processing script and slice the model.
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Print the speed tower model.
3.4.Lattice (Infill Pattern)
3.4.1.Introduction to Infill Pattern
The working principle of an Fused deposition modeling 3D printer is to build solid 3D parts by stacking each sliced section layer by layer, which is formed by points to lines and lines to planes. Most 3D printed parts are not completely solid. Inside a printed object, the material path and space create a pattern, which we call the infill pattern. Therefore, the cross-section of a printed Fused deposition modeling 3D part can be considered as consisting of two parts: the shell and infill, with the shell further divided into outer and inner walls.
The Cura slicing software provides 14 default infill patterns, including grid, line, triangle, hexagon, cube, cuboid, octagon, tetrahedron, concentric, zigzag, cross, cross 3D, spiral twenty-four-sided polyhedron and lightning, providing users with great flexibility. According to their uses, the infill patterns can be divided into four categories.
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Fast 2D infill: Consistent pattern on each layer, featuring fast printing speed and low strength. The infill patterns include straight lines and zigzags.
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High strength 2D infill: Consistent pattern on each layer, featuring longer printing time and high strength. The infill patterns include grids, triangles, and hexagons.
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High strength 3D infill: Pattern passes through X, Y, and Z axes, providing high strength in various directions in a 3D space. The infill patterns include cubes, octagons, tetrahedrons, and spiral twenty-four-sided polyhedrons.
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Flexible infill: Pattern passes through X, Y, and Z axes; it intentionally reduces strength to increase flexibility. Examples include concentric, cross, cross 3D, and lightning patterns.
3.4.2.The Impact of Infill Patterns on 3D Printing Models
The infill pattern in 3D printing refers to the internal filling method used to increase the stability and strength of the model. Infll pattern forms the internal structure of a 3D printed part. Different patterns can be used to achieve different goals. The infll patterns affect not only the strength but also the flexibility, printing time, and weight of 3D printed parts.
3.4.3.Selection of Infill Patterns for Printing with Flexible Filaments
If only appearance is considered, infll patterns without crossing should be chosen to maintain the flexibility of parts printed with flexible materials. In this regard, concentric, cross, and cross 3D patterns are suitable.
When considering strength, patterns with fewer cross points should be selected if possible, such as grid, cube, and spiral twenty-four-sided polyhedron.
4.Selection of Extruder
4.1.Characteristics of Fexible Extruder
A flexible extruder is a type of 3D printer specifcally designed for printing with flexible materials. It is similar to traditional Fused deposition modeling 3D printers, but employs a different extruder and hot-end design.
flexible extruders are typically classifed into 1.75 mm and 2.85 mm extruders based on the diameter of the printing material.
1.75 mm direct extruder
The 1.75 mm direct extruders are currently the most widely used direct extruders, which are applicable for the flament with a diameter of 1.75mm. Like Creality’s sprite extruder, which is compatible with various 1.75 mm flaments, including flexible flaments such as TPU and TPR. The diffculty of extrusion increases with the softness of flexible flaments, resulting in higher failure rates. The sprite extruder installed on the Ender-3 S1 equipment can stably extrude TPU95A and TPU85A. Smooth printing of the softer TPU80A flament requires the use of a nozzle with internal PTfE lining in the extruder to lower the friction of the inner wall.
2.85 mm direct extruder
The minimum hardness attainable with φ1.75 mm flexible flament is currently 80A, with no possibility of producing at a lower level of hardness. filaments with a diameter of 2.85 mm can produce flaments with a hardness of 65A, so a 2.85 mm direct extruder is needed to accommodate the flaments with a diameter of 2.85 mm. Complete shoe manufacturers nowadays opt for 2.85 mm direct extruders in conjunction with 0.6 mm or 0.8 mm nozzles for faster flament output and more supple printing materials.
4.2.Introduction to the 2.85mm Fexible Sprite Extruder
4.2.1.1.Characteristics of the Extruder:
1.Based on the sprite extruder, it uses most of the parts for sprite extruder and has the same installation size, allowing for quick switching to machines equipped with sprite extruders.
2.It has excellent performance in printing flexible flaments and can print TPR65A, which is the flament with the lowest hardness.
3.It offers stable printing quality and high success rate. Since printing a shoe usually takes a longer time, stability in printing is crucial.
4.The clearance between the flament pipelines is extremely small, allowing for joining the end of the old flament with the beginning of the new flament and feeding the new flament into the extruder gear by hand, enabling material replacement at any time.
4.2.1.2.Technology Used:
1.An arc-shaped extruder gear tailored for 2.85 mm flexible flament maintains optimal extrusion force while the flament is being deformed during the extrusion process. Excessive extrusion force can cause the flament to bend and accumulate in the axial direction, leading to poor or no material output from the nozzle. Insuffcient extrusion force can result in incomplete material output and the formation of empty layers during printing.
2.Using a high-temperature heat break with a smooth inner wall ensures long-term printing stability. In addition, the inner diameter of the heat break is slightly larger than the diameter of the flament to avoid positive pressure formation on the inner wall due to thermal expansion, which can cause excessive friction between feeding and discharging.
3.The distance from the nozzle to the extruder gear needs to be as short as possible. Currently, the sprite extruder has the shortest distance from the nozzle to the extrusion gear among all extruders, minimizing the weak point of axial forces on flexible flament with maximum effciency.
4.2.1.3.Compatible Printers:
1.All Ender-3 series machines, including Ender-3, Ender-3 V2, Ender-3 S1, Ender-3 S1 Pro.
2.All CR-10 series machines, including CR-10 Smart, CR-10 Smart Pro, CR-10S Pro.