Printing Nozzle Research Articles

All-aqueous printing of viscoelastic droplets in yield-stress fluids

All-aqueous printing of viscoelastic droplets (aaPVD) in yield-stress fluids is the core of an emerging voxelated bioprinting technology that enables the digital assembly of spherical bio-ink particles (DASP) to create functional tissue mimics. However, the mechanism of aaPVD is largely unknown. Here, by quantifying the dynamics of the whole printing process in real-time, we identify two parameters critical to aaPVD: (1) acceleration of print nozzle, and (2) droplet/nozzle diameter ratio. Moreover, we distinguish three stages associated with aaPVD: droplet generation, detachment, and relaxation. To generate a droplet of good roundness, the ink should be a highly viscous shear-thinning fluid. Using particle image velocimetry and scaling theory, we establish a universal description for the droplet displacements at various printing conditions. Along the direction of nozzle movement, the droplet displacement is determined by the detachment number, a dimensionless parameter defined as the ratio between the dragging force from the nozzle and the confinement force from the supporting matrix. Perpendicular to the direction of nozzle movement, the droplet displacement is determined by the Oldroyd number, a dimensionless parameter that describes the yielded area of the supporting matrix near the print nozzle. For a relaxed droplet, the droplet tail length is independent of droplet/nozzle diameter ratio but determined by the nozzle acceleration. We conclude that printing droplets of good fidelity requires a relatively large droplet/nozzle diameter ratio and intermediate nozzle accelerations. These ensure that the droplet is more solid-like to not flow with the nozzle to form a tadpole-like morphology and that the confinement force from the yield-stress fluid is large enough to prevent large droplet displacement. Our results provide the knowledge and tools for in situ generating and depositing highly viscoelastic droplets of good roundness at prescribed locations in 3D space, which help establish the foundational science for voxelated bioprinting. Analogues of pixels to two-dimensional (2D) pictures, voxels – in the form of small cubes or spheres – are the basic units of three-dimensional (3D) objects. All-aqueous printing of viscoelastic droplets (aaPVD) is the core of voxelated bioprinting, an emerging technology that uses spherical bio-ink voxels as building blocks to create 3D tissue mimics. Unlike existing technologies relying on the classic Rayleigh-Plateau instability to generate droplets, aaPVD exploits previously unexplored nonlinear fluid dynamics of complex fluids to precisely manipulate viscoelastic droplets in 3D space. The developed knowledge and tools not only help advance biomanufacturing but also stimulate new research directions in soft matter and complex fluids.

Bigels as potential inks for extrusion-based 3d food printing: Effect of oleogel fraction on physical characterization and printability

This study aimed to develop, characterize, and evaluate the three-dimensional (3D) printing performance of new food-grade bigels using different printer parameters (nozzle diameter and printing speed) and material properties (hydrogel (HG)/oleogel (OG) ratio). Two types of bigels were prepared by constant homogenization of beeswax OG with agar and xanthan gum (XG) HG (ABs), and the same OG with gelatin and XG HG (GBs) with different OG concentrations (5, 10, and 20% w/w). Bright-field micrographs confirmed the presence of an OG-in-HG system in all bigel formulations. Scanning electron microscopy images showed that particles in the bigels with a higher OG concentration were better distributed and denser networks were formed. The FTIR results suggested that all bigels were formed from a physical mixture of the OG and HG phases. The rheological analyses of both bigels showed that regardless of the OG concentration, they were more solid than liquid (G′ > G″) and exhibited noticeable shear thinning, which allowed the printing of all bigels. However, the ABs with 10 and 20% OG exhibited better printing performances, with less dimensional variability, excellent surface quality, and good reproducibility. The same results were achieved for GBs with an OG concentration of 20%. The texture profile of the components printed using the ABs and GBs was dependent on the printing parameters, and the GBs presented greater values than the ABs. 3D printing of bigels has not been comprehensively studied. This study expands the development of these systems with potential in 3D food printing and generates insights for possible applications and future studies.

Nanocellulose Reinforced Hyaluronan-Based Bioinks.

Bioprinting of hydrogel-based bioinks can allow for the fabrication of elaborate, cell-laden 3D structures. In addition to providing an adequate extracellular matrix mimetic environment and high cell viability, the hydrogels must offer facile extrusion through the printing nozzle and retain the shape of the printed structure. We demonstrate a strategy to incorporate cellulose oxalate nanofibrils in hyaluronan-based hydrogels to generate shear thinning bioinks that allowed for printing of free-standing multilayer structures, covalently cross-linked after bioprinting, yielding long-term stability. The storage modulus of the hydrogels was tunable between 0.5 and 1.5 kPa. The nanocellulose containing hydrogels showed good biocompatibility, with viability of primary human dermal fibroblasts above 80% at day 7 after seeding. The cells were also shown to tolerate the printing process well, with viability above 80% 24 h after printing. We anticipate that this hydrogel system can find broad use as a bioink to produce complex geometries that can support cell growth.

Understanding the process-microstructure-property relationships in material extrusion additive manufacturing of polylactic acid microcellular foams

Process-microstructure-property relationships are reported for microcellular foams printed via material extrusion (MEX) additive manufacturing (AM) process. Polylactic acid and thermally expandable microspheres were mixed and extruded to prepare the filament. In situ foaming during MEX AM process was then conducted to investigate the impact of nozzle temperature, flow rate, and print speed on the cellular morphology, mesostructure, part density, and the mechanical behavior of the foams. The temperature and the residence time were identified as the two key factors governing the foaming behavior and thus the resultant microstructure and properties. Too excessive temperature and residence time resulted in the deformed, wrinkled, or collapsed microspheres due to gas loss and contraction. On the other hand, too low temperature and residence time caused limited number of microspheres to expand, due to insufficient energy and time. Both overly activated and partially unexpanded microspheres provided nonuniform cellular morphologies and higher densities and thus adversely affected the tensile properties. The foam expansion/shrinkage behavior during the MEX AM process was demonstrated as a function of a combined process variable that unifies temperature, flow rate, and print speed. Upon the utilization of the optimum process variables, foam samples with uniform morphology, low density, and high toughness were achieved. The results shed light on the understanding and advancing of MEX AM process as a novel manufacturing approach to produce quality foams.

Synchronized 3D Printing and Corona Charging for One-Step Prototyping of Polarized Polylactic Acid Electrets.

Three-dimensional (3D) printing technology is advantageous in the fast prototyping of complex structures, but its utilization in functional material fabrication is still limited due to a lack of activation capability. To fabricate and activate the functional material of electrets, a synchronized 3D printing and corona charging method is presented to prototype and polarize polylactic acid electrets in one step. By upgrading the 3D printer nozzle and incorporating a needle electrode to apply high voltage, parameters such as needle tip distance and applied voltage level were compared and optimized. Under different experimental conditions, the average surface distribution in the center of the samples was -1498.87 V, -1115.73 V, and -814.51 V. Scanning electron microscopy results showed that the electric field contributes to keeping the printed fiber structure straight. The polylactic acid electrets exhibited relatively uniform surface potential distribution on a sufficiently large sample surface. In addition, the average surface potential retention rate was improved by 12.021-fold compared to ordinary corona-charged samples. The above advantages are unique to the 3D-printed and polarized polylactic acid electrets, proving that the proposed method is suitable for quickly prototyping and effectively polarizing the polylactic acid electrets simultaneously.

Design and fabrication of high-performance 3D printed continuous flax fibre/PLA composites

The mechanical properties of 3D-printed continuous plant fibre-reinforced poly(lactic) acid (PLA) composites are insufficient due to the low fibre volume fraction (∼30 %). Further increase of fibre volume fraction of composites by reducing the line width may result in a composite with low fibre impregnation degree or the clogging of printer nozzle because of the twisted nature and uneven diameter of plant yarns, which also degrades the mechanical properties. This study proposed a method to obtain 3D printed continuous flax fibre reinforced composites (CFFRCs) with a high fibre volume fraction and excellent mechanical performance by statistical analysis of the dimensions of flax fibre yarns as well as surface modification. The CFFRCs were printed by a fibre prepreg-based 3D printing method, and an in-situ impregnation method was also used to prepare CFFRCs for comparison. The results showed that the CFFRCs by the fibre prepreg method had a fibre volume fraction of 44.1 % and a void content of ∼1.9 % due to the high impregnation degree. Correspondingly, the tensile modulus and strength of the CFFRCs were the highest among the existing reported values of the composites made by 3D printing and even greater than those of the CFFRCs with a fibre volume fraction of ∼51.4 % prepared by the in-situ impregnation method.

An exploratory study of topographical signatures within 3D fused deposition modelling using Polylactic Acid (PLA) filament

This preliminary limited study considers the possibility of the same source identification of consecutively 3D printed components using polymer filament by the examination of deposition artifacts as distinctive macroscopic and microscopic surface characteristics upon the surface of 3D printed objects. Hot-end printer nozzle deposition using polymer filaments can create distinctive surface characteristics upon 3D FDM-printed manufactured objects that can be identified, examined, and compared. Such artifacts can occur as repeatable patterns known as 'deposition striae', 'detachment points', and 'start points' upon the surfaces of an object and on consecutively manufactured components that have used the same 3D Fused Deposition Modelling (FDM) printer hardware. Some of these observable artifacts can fulfil the sufficient agreement requirements of the Association of Firearm and Tool Mark Examiners (AFTE) Theory of Identification as it relates to tool marks when applied to consecutively produced 3D Additive Manufacture (AM) components. For this criteria to apply, the influence of subclass characteristics on any identification must be ruled out.

Texture in silicon carbide via aqueous suspension material extrusion and seeded grain growth

Textured SiC with anisotropic crystallographic texture is proposed as a material with improved mechanical properties. Textured SiC was created via alignment of platelet seed particles during aqueous suspension material extrusion, also known as direct ink writing, and subsequent pressureless liquid phase sintering and annealing. The microstructure and texture of the SiC fabricated with and without 5 vol% platelet seeds, and with and without annealing at 2050 °C and 2150 °C was explored via SEM, XRD, and EBSD. All samples fabricated had over 95% theoretical density. Annealing leads to the development of large, high aspect ratio plate-shaped grains among a matrix of many finer, low aspect ratio grains. Higher annealing temperatures and addition of platelet seeds both increased the size of the large grains. Samples were found to be textured regardless of having platelet seeds. Via XRD and EBSD, unseeded SiC was found to have texture where the crystallographic direction [0001] had a preferred orientation perpendicular to the normal direction. This occurred for both direct ink written and cast SiC, so the texture development must have occurred during sintering, though the mechanism is unknown. For seeded SiC, platelet seeds aligned in direct ink writing seeded the grain growth to develop crystallographic texture. The texture was mainly influenced by the alignment of platelet seed particles via shear stresses in the print nozzle, causing a one-dimensional texture where [0001] is perpendicular to the printing direction. However, it was found that the texture was not the expected concentric alignment of platelet particles in direct ink writing, so the shear stresses in the nozzle are not solely responsible for the texture developed.

Three-Dimensional Printing of Large Ceramic Products and Process Simulation.

Ceramic 3D printing is a promising technology that overcomes the limitations of traditional ceramic molding. It offers advantages such as refined models, reduced mold manufacturing costs, simplified processes, and automatic operation, which have attracted a growing number of researchers. However, current research tends to focus more on the molding process and print molding quality rather than exploring printing parameters in detail. In this study, we successfully prepared a large-size ceramic blank using screw extrusion stacking printing technology. Subsequent glazing and sintering processes were used to create complex ceramic handicrafts. Additionally, we used modeling and simulation technology to explore the fluid model printed by the printing nozzle at different flow rates. We adjusted two core parameters that affect the printing speed separately: three feed rates were set to be 0.001 m/s, 0.005 m/s, and 0.010 m/s, and three screw speeds were set to be 0.5 r/s, 1.5 r/s, and 2.5 r/s. Through a comparative analysis, we were able to simulate the printing exit speed, which ranged from 0.0751 m/s to 0.6828 m/s. It is evident that these two parameters have a significant impact on the printing exit speed. Our findings show that the extrusion velocity of clay is approximately 700 times faster than the inlet velocity at an inlet velocity of 0.001-0.010 m/s. Furthermore, the screw speed is influenced by the inlet velocity. Overall, our study sheds light on the importance of exploring printing parameters in ceramic 3D printing. By gaining a deeper understanding of the printing process, we can optimize printing parameters and further improve the quality of ceramic 3D printing.

Influence of 3D Microstructure Pattern and Infill Density on the Mechanical and Thermal Properties of PET-G Filaments.

This study aims to evaluate the thermal and mechanical performances of PET-G thermoplastics with different 3D microstructure patterns and infill densities. The production costs were also estimated to identify the most cost-effective solution. A total of 12 infill patterns were analysed, including Gyroid, Grid, Hilbert curve, Line, Rectilinear, Stars, Triangles, 3D Honeycomb, Honeycomb, Concentric, Cubic, and Octagram spiral with a fixed infill density of 25%. Different infill densities ranging from 5% to 20% were also tested to determine the best geometries. Thermal tests were conducted in a hotbox test chamber and mechanical properties were evaluated using a series of three-point bending tests. The study used printing parameters to meet the construction sector's specific needs, including a larger nozzle diameter and printing speed. The internal microstructures led to variations of up to 70% in thermal performance and up to 300% in mechanical performance. For each geometry, the mechanical and thermal performance was highly correlated with the infill pattern, where higher infill improved thermal and mechanical performances. The economic performance showed that, in most cases, except for the Honeycomb and 3D Honeycomb, there were no significant cost differences between infill geometries. These findings can provide valuable insights for selecting the optimal 3D printing parameters in the construction industry.

3D graphene-based active electrodes with large areal capacitance by modified direct ink writing method

The application of 3D printing technology in the field of energy storage is of great practical significance but still remains challenging. Recently, 3D-printed graphene-based architecture has been found to be a promising material for electrochemical energy storage devices. In this study, graphene-based conductive filaments were printed through direct ink writing method (DIW), and then dense poly-pyrrole film (PPy) was formed on the surface of the 3D frame by simple electrodeposition. And followed by post treatment three-dimensional heterogeneous graphene-based electrodes wrapped by nanocarbon cloth (3DCGs) were readily prepared. 3D-printed open porous structure provides effective aligned channels for ion transport as well as large ion accessible area for electrochemical reaction. PPy layer helps to maintain the structural integrity and obtain high capacitance retention rate. A series of 3DCGs with controllable channels were prepared by adjusting the number printing layers, infilled spacing and nozzle size. Thus, we gained an insight into the influence of structural engineering of electrode materials on electrochemical performance. The 5-layer 3DCG with filament spacing of 300 µm and filament diameter of 400 µm achieved an areal capacitance of 2265.19 mF/cm2 at a scan rate of 5 mV/s, which was significantly higher than that of non-3DCG (400.15 mF/cm2). Briefly, this study reports the integration of DIW 3D-printing and electrodeposition techniques allowing a facile way of fabricating customized 3D-electrodes with large areal capacitance.

On the selection of rheological tests for the prediction of 3D printability

Direct ink writing is used to print multiple polydimethylsiloxane (PDMS) mixtures with fumed silica or as a two-part commercial liquid silicone rubber (LSR) mixed with polyethylene glycol (PEG) or as a two-part commercial vulcanizing (RTV) silicone. We correlate their printability into a hollow slump cone with rheological measurements, including (1) a shear rate up-ramp followed by (2) a down-ramp in the shear rate, (3) creep tests, and (4) large-amplitude oscillatory shear (LAOS) with increasing amplitude. The PDMS-fumed silica mixtures fail to print even at the highest fumed silica loading used (9 wt. %), while LSR-PEG with 4 or 6 wt. % PEG prints well, and one of the two RTV silicone components is printable, as is the mixture due in part to its rapid chemical curing. The large differences in printability of these materials do not correlate well with any single rheological test. They do correlate with a combination of a measure of material strength, given by either the yield stress σycr from creep tests or the “flow stress” σf at which G′ and G″ cross-over in LAOS, and of material recoverability given by the dynamic yield stress σy− in test 2. The latter is measured during a down-ramp in the shear rate after reaching a maximum shear rate of 1000 s−1, the highest shear rate in the print nozzle.

Effects of Rheological Properties on 3D Printing of Poly(lactic acid) (PLA) and Poly(hydroxy alkenoate) (PHA) Hybrid Materials

Fused filament fabrication (FFF) has been extensively studied for conventional polymers, but there are few studies that address the processing challenges for biobased, biodegradable polymers such as poly(lactic acid) (PLA) and poly(hydroxy alkenoates) (PHA) in FFF processes. This study has investigated the elongational and shear rheological properties and thermophysical characteristics of PLA/PHA hybrid materials to determine the effects of processing conditions, including nozzle temperatures, bed temperatures, and speeds, on the quality of the PLA/PHA printed products, e.g., adhesion strength and tensile properties. Our findings showed that adding PHA to the composition of the PLA/PHA hybrid material leads to a reduction in shear and extensional viscosities, causing a rise in elongation at break and adhesion strength while showing comparable tensile strength with the PLA samples. In addition to the presence of PHA in the combination of the hybrid materials, processing conditions, including nozzle temperature, bed temperature, and print speed, were found to be effective on the adhesion strength and tensile characteristics of the printed products. Our results suggested that among processing parameters, nozzle temperature has the most significant effect on adhesion strength and tensile characteristics. Samples printed at the nozzle temperature of 215 °C showed an order of magnitude higher adhesion strength and up to 34% enhancement in elongation at break compared to the printed samples at 185 °C. This study sheds light on the significance of the material and processing parameters in obtaining quality products from biobased, biodegradable polymers.

3D Printing‐Assisted Self‐Assembly to Bio‐Inspired Bouligand Nanostructures (Small 19/2023)

Bio-Inspired Bouligand Nanostructures In article number 2206847, Monirosadat Sadati and co-workers present a 3D printing method for replicating intricate self-assemblies in biomaterials. Using the flow in the 3D printer's nozzle, helical assemblies of cellulose nanorods are arranged in a uniform and long-range concentric pattern that resembles Bouligand nanostructures found in mammalian cortical bones. By incorporating embedded printing and in-situ photo-polymerization techniques, Bouligand-type nanostructures are immobilized in self-supporting 3D constructs.

Three-dimensional printing of a high-impact resistant polylactic acid-based ternary polymer blend

Three-dimensional printing of polylactic acid (PLA)-based polymer blends has several benefits, including low cost, dimensional accuracy and tunability of mechanical properties. Although the addition of Polybutylene adipate terephthalate (PBAT) into PLA improves the ductility of the blend, the two polymers are immiscible. This work introduced polymethyl methacrylate (PMMA) into PLA/PBAT blends as a compatibiliser to improve the interfacial interaction between PLA and PBAT phases. PLA/PBAT/PMMA blends were prepared with varying concentrations of PLA, PBAT (10–20 wt%) and PMMA (0–6 wt%) for 3D printing applications. The mechanical and thermal behaviours of the PLA/PBAT/PMMA ternary blends and their suitability for 3D printing were investigated. The thermal properties of the blends were used to determine the 3D printing nozzle temperature and bed temperature. Three-dimensional printing of the polymer blends was carried out using a Bowden extruder 3D printer. Additionally, the compatibilisation effects of PMMA and interfacial interaction of the polymer phases were investigated using SEM analysis.

Accurate measurements of particle emissions from a three-dimensional printer using a chamber test with a mixer-installed sampling system

Recently, three-dimensional (3D) printing has attracted attention as a new manufacturing technology. However, there is lack of data and regulations regarding the emissions of ultrafine particles from 3D printers. Therefore, we investigated particle emissions from a 3D printer using a chamber system. The test system was improved by installing a developed mixer for accurate measurement. Without a mixer, the particle concentration was unstable depending on the sampling point; however, reliable data with good uniformity were obtained by installing a mixer. Using the test system with a mixer, we investigated particle emissions from a 3D printer during operation. Filaments made each of acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) were used as the printing material. The effects of nozzle temperature and printing time were investigated. Compared to the effect of the printing time, the nozzle temperature had greater impact on the particle emissions. The dominant particle size for the emissions from a 3D printer is less than 10 nm, and the particle concentration decreased with increasing particle size.

Hierarchical fibrous collagen/poly(ε-caprolactone) structure fabricated with a 3D-printing process for tissue engineering applications

Hierarchical scaffolds have been extensively used in various tissue engineering applications as they can provide unique biofunctional properties, including biophysical cues, to successfully accomplish preferred cell attachment, growth, and differentiation depending on the target tissues. In this study, we propose a new strategy for fabricating hierarchical structures consisting of microfibrous collagen/poly(ε-caprolactone) (PCL) bundles obtained using a 3D printing process supplemented with a unique bioink, plasma treatment, and collagen coating process. To obtain the hierarchical fibrous PCL structure, we used an alginate matrix hydrogel to form a microfibrous bundle of dispersed PCL components using elongational and shear stresses within a printing nozzle. By controlling various mixture ratios of alginate and PCL, processing temperature, pneumatic pressure, and nozzle moving speeds, a stable hierarchical structure consisting of PCL microfibers was obtained. To demonstrate the feasibility of hierarchical PCL-based structures coated with type I collagen, we investigated whether the construct affects the alignment and differentiation of myoblasts. The hierarchical fibrous biocomposite constructs presented a higher degree of myogenic activity than the control, which was fabricated using normal printing/collagen coating processes. Furthermore, the hierarchical PCL structures were further elaborated using 10 × simulated body fluid (SBF) resulting in a scaffold consisting of a hydroxyapatite (HA) layer. The hierarchical collagen/PCL/HA structures were evaluated with the aim of obtaining a functional scaffold that could efficiently induce osteogenesis to the human adipose stem cells (hASCs). These in vitro results suggest that the fibrous composite structure can provide enhanced osteogenic activity compared to the normally printed control (collagen/PCL/HA).

An Investigation of Printing Parameters of Independent Extrusion Type 3D Print Continuous Carbon Fiber-Reinforced PLA

Fused filament fabrication (FFF) technology is highly favored by various industries as the simplest and most commonly used technology in additive manufacturing. The embedding of continuous fiber-reinforced thermoplastic composites (CFRTC) is a great help to compensate for the mechanical properties of FFF-printed specimens. In this paper, the optimal printing parameters of printed specimens containing continuous carbon fiber-reinforced PLA were investigated by the Taguchi method, full factorial analysis, and the tensile test. Fiber printing layer thickness and fiber printing speed are significant factors. After excluding the influence of fiber overlap, the optimal printing parameters were obtained. When the thickness of the fiber printing layer is 0.05 mm, the speed of the fiber printing nozzle is 250 mm/min, and the temperature of the fiber printing nozzle is 210 °C, the maximum tensile stress of the sample is 189.52 MPa. In this paper, the maximum tensile stress of the specimen printed by different printing parameters can be doubled, which shows the influence of printing parameters on the mechanical properties of the specimen. Compared with the specimen using pure PLA printing, the increase was 703.5%. Then the failure mechanism of 3D-printed CFRTC specimens with different layer thicknesses was investigated by using microstructural morphology and tensile fracture interfacial property analysis. The influence of layer thickness parameters on the interfacial bonding force was revealed. Through analysis, it is found that the lower the thickness of the specimen printing layer, the better the interface bonding force of the specimen, and the minimum layer thickness suitable for FFF independent extrusion printer is found.

Three-Dimensional Printed Highly Porous and Flexible Conductive Polymer Nanocomposites with Dual-Scale Porosity and Piezoresistive Sensing Functions.

Highly flexible, deformable, and ultralightweight structures are required for advanced sensing applications, such as wearable electronics and soft robotics. This study demonstrates the three-dimensional (3D) printing of highly flexible, ultralightweight, and conductive polymer nanocomposites (CPNCs) with dual-scale porosity and piezoresistive sensing functions. Macroscale pores are established by designing structural printing patterns with adjustable infill densities, while the microscale pores are developed by phase separation of the deposited polymer ink solution. A conductive polydimethylsiloxane solution is prepared by mixing polymer/carbon nanotubes with non-solvent and solvent phases. Silica nanoparticles are utilized to modify the rheological properties of the ink, making direct ink writing (DIW) feasible. 3D geometries with various structural infill densities and polymer concentrations are deposited using DIW. The solvent is evaporated during a stepping heat treatment, leading to non-solvent droplet nucleation and growth. The microscale cellular network is developed by removing the droplets and curing the polymer. Up to 83% tunable porosity is achieved by independently controlling the macro- and microscale porosity. The effect of macroscale/microscale porosity and printing nozzle sizes on the mechanical and piezoresistive behavior of the CPNC structures is explored. The electrical and mechanical tests demonstrate a durable, extremely deformable, and sensitive piezoresistive response without sacrificing mechanical performance. The flexibility and sensitivity of the CPNC structure are enhanced up to 900 and 67% with the development of dual-scale porosity. The application of the developed porous CPNCs as piezoresistive sensors for detecting human motion is also evaluated.

Effects of FDM parameters and annealing on the mechanical and tribological properties of PEEK

In this paper, the effects of FDM parameters (nozzle temperature, platform temperature, layer thickness, and printing speed) as well as annealing temperature on the mechanical properties of poly(ether ether ketone) (PEEK) were investigated through orthogonal experiments. And the tribological properties of PEEK were also studied before and after annealing. Results show that nozzle temperature and printing speed were main factors affecting the mechanical properties of PEEK, which was optimized to be 440 ℃ and 40 mm/s, respectively. The mechanical strength of PEEK was increased with increasing annealing temperature and reached the maximum at 300 ℃ with the sacrifice of elongation at break, and the ultimate tensile, flexural and compressive strength was increased by 36%, 54% and 21%, respectively. As for the tribo-properties, there appeared a minimum wear rate(1.37 × 10−6mm3/Nm) in 200 °C annealed PEEK when tested in parallel manner, combined influences of annealing and filament orientation were revealed, and appropriate annealing temperature was found to help enhance the formation of uniform and homogeneous transfer films on the counter steel surfaces.