تولید افزودنی مبتنی بر پلیمر: تحولات اخیر

"Additive manufacturing (AM) is a potentially disruptive technology, revolutionizing not only traditional industries but generating entirely new ones through rapid innovation, the democratization of manufacturing, and unprecedented freedom of design. Furthermore, the development of AM technologies has practical implications for economic growth, healthcare, national security, space exploration, and sustainability. For military and space agencies, AM offers the possibility to transform the traditional supply chain system through manufacturing at-point-of-demand, recycling, and indigenous sourcing of raw materials. Similarly, these concepts are being leveraged by remote communities across the globe through efforts such as Fab Labs, which provide low-cost access to manufacturing technologies. AM is transforming healthcare in unexpected ways: doctors and patients have access to high-quality physical 3D models generated directly from computerized tomography (CT) scans. These surgical guides have proved invaluable in surgical preparation and patient consent. In the lab, researchers are developing medical devices or implants which mimic the patient's physiology, are pre-loaded with therapeutics, and are replaced with the patient's cells through natural tissue repair pathways. Pushing the limits of resolution, multi-photon technologies, which allow subdiffraction-limited resolution, are revolutionizing the development of micro-optical components. Unfortunately, adoption of AM technologies by industry has been slow; and while there are numerous success stories and commercial adoption is steadily increasing, AM is hampered by weak parts, incomplete certification methods, and empirical materials development. Regulatory and standards bodies are working to update or develop new standards and policies to deal with the unique material and production issues posed by AM. Many of the challenges facing the industry stem from our limited understanding of structure-process-performance relationships. These challenges fall into many categories and require a broad range of skills to address. For the researcher, AM processes offer unique challenges in materials development, metrology, and modeling, as well as opportunities to combine all three. What makes a polymer printable? What process parameters are important? How should parts be tested? These are all active areas of investigation. This book was inspired by the 2017 ACS Symposium "Additive Manufacturing of Structures and Functional Devices: Materials, Methods, Models, and Testing" and is supplemented by additional experts in the polymer AM field. The chapters discuss the technologies, measurement challenges, manufacturing opportunities, and fabrication potentials. We begin with an introduction to polymer additive manufacturing, identifying the measurement needs and technical challenges facing the industry. A chapter reviewing polymer powder bed fusion follows, providing a complete discussion on methods, materials, and applications. The bulk of the book covers thermoplastic material extrusion, with chapters discussing recycling-based feedstocks, composites materials, and multi-physics modeling linking experimentation and theory. Moving from thermoplastics to conductive inks, a chapter on in situ monitoring and control of direct-ink-write provides a clear example of how theory and modern machine vision can be used to create a practical and responsive control system. The last chapter provides a state-of-the-art review of multi-photon printing, discussing methods, materials, and the stunning capabilities of the technique"-- Provided by publisher Polymer-Based Additive Manufacturing: Recent Developments......Page 2 Polymer-Based Additive Manufacturing: Recent Developments......Page 4 Library of Congress Cataloging-in-Publication Data......Page 5 Foreword......Page 6 Subject Index......Page 8 Preface......Page 10 Introduction......Page 12 Figure 1. Annual worldwide sales of industrial polymer AM machines separated into companies that sell only polymer-based AM printers (“Polymer”), companies that sell both polymer and nonpolymer AM machines (“Polymer+”), and the sum of Polymer and Polymer+ (“Total”). Adapted with permission from ref 9. Copyright 2017 Terry Wohlers.......Page 13 Advantages and Challenges in Polymer AM......Page 14 Measurement Needs in AM......Page 15 References......Page 16 1.1 Current Benefits and Limitations of Additive Manufacturing......Page 18 2.1 Strengths and Weakness of PBF/P......Page 19 Figure 1. Example of 250 mm wide part assembly produced by LS PBF/P from polyamide 12 (PA12).......Page 20 2.2 Comparison of PBF/P to Other AM Technologies......Page 21 Figure 2. Schematics of PBF/P technologies: (a) LS, (b) HSS, (c) MJF, and (d) MPD.......Page 22 2.4.1 Materials......Page 23 Figure 3. Overview of polymer LS. (a) Process schematic including automated recycle blending with 3D Systems MQC feeding ProX500 LS machine. (b) The U.S. Army Research Lab’s MQC and (c) ProX500. (d) PEKK powder bed during LS. (e) Sintered PEKK parts being broken out from completed powder bed. (f) PEKK parts after breaking out and cleaning. Color variations are due to a range of laser energy densities used.......Page 24 Figure 4. Polymer LS feedstock properties: SEM images of (a) 3D Systems Duraform ProX PA12 LS powder, (b) EOS HP3 PEK LS powder, (c) DSC traces of PA12, poly(phenylene sulfide) (PPS), PEK, and 60:40 terepthaloyl/isopthaloyl poly(ether ketone ketone) (PEKK 60/40 T:I) tested at 10 K/min. Dashed lines indicate the LS bed temperature setpoint for each powder. (d) Several engineering thermoplastics plotted in terms of their melting peak temperature Tm as a function of their glass transition temperature (Tg). Polymers shaded in green fall within an ideal window characterized by high enough Tg for structural performance and low enough Tm for economical processability.......Page 26 2.4.2 Consolidation and Mechanical Properties......Page 27 Figure 5. Mechanical properties of LS polymer parts: (a) tensile stress–strain curves of PA12, PPS, PEK, and PEKK versus conventionally processed analogs, (b) SEM image of PPS LS part fracture surface showing internal porosity, (c and d) photographs of ballistic impact penetration in extruded PEEK (front and back faces, respectively), (e and f) LS-printed HP3 PEK (front and back), (g) SEM image of LS HP3 PEK ballistic fracture surface, and (h and j) high magnification details of the circled regions in g (color coded).......Page 29 2.5 High Speed Sintering......Page 30 2.7 Multi-Powder Deposition......Page 31 3.1 Aircraft......Page 32 Figure 6. Representative applications of polymer LS: (a) glass-filled PA12 microvanes being installed on C-17 Globemaster fuselage 109; (b) U.S. Army RQ-16 T-Hawk m-UAV featuring LS PA12 control pods 111; (c) glass-filled PA12 LS intake runners (dyed black) fitted to 960-horsepower supercharged Porsche 928 engine (reproduced with permission from 928 Motorsports, LLC 112); (d) SEM image of copper-filled LS PA12 3D mechatronic integrated device (3D-MID) with conductive patterns formed by laser direct structuring (reproduced with permission from Elsevier 113); (e) Pyros small tactical munitions containing LS parts (reproduced with permission from Raytheon Company 114); (f) topology-optimized LS PA12 ankle-foot orthosis (reproduced with permission from IEEE 115); and (g) lightweight PA12 drop tower impactor used to develop and test ballistic clay replacement material.......Page 33 3.3 Electronics......Page 34 3.4 Weapons......Page 35 3.5.2 Footwear......Page 36 4 Conclusions......Page 37 References......Page 38 Introduction......Page 48 Material Considerations for Material Extrusion AM......Page 50 Figure 1. Select material extrusion printing parameters.......Page 51 Figure 2. Global plastic usage (Adapted from reference 23). PUR, polyurethane......Page 52 Figure 3. Schematic of conventional (white) and distributed (grey) plastic recycling. (Adapted from reference 1).......Page 53 Recycling of Commercial Filaments......Page 54 Recycling of Consumer-Grade Plastics for Material Extrusion AM......Page 55 Figure 4. Mechanical testing of recycled and PET. (A) Representative stress strain curves from die-cut, injection molded, material extrusion printed recycled PET, and material extrusion printed commercial PET. (B) Fracture surface of material extrusion printed tensile bar. (C) Testing apparatus for 3D-printed vehicle radio bracket. (D) 3D-printed vehicle radio bracket. (E) Load at failure for testing of (D). Adapted with permission from reference 44. COTS, commercial off-the-shelf; rPET, recycled polyethylene terephthalate. Copyright 2018 Elsevier.......Page 56 Barriers to Recycling......Page 57 Future Outlook......Page 58 References......Page 59 Introduction......Page 64 ABS Characteristics and Selection......Page 65 Figure 1. MWD of Trinseo Magnum 347EZ ABS resin.......Page 66 Sample Fabrication......Page 67 Melt Viscosity Results......Page 68 Filament Examination......Page 69 Notched Izod Impact Toughness......Page 70 Tensile Test Results......Page 71 Figure 6. Optical photomicrographs of notched Izod fractures of ABS and ABS/graphene samples. Each sample is 12.7 cm wide . (a.) 0° raster angle samples with (from left to right) 0 wt %, 5 wt %, and 10 wt % M5 graphene; (b) 45°–45° raster angle samples (with ~20° fractures) with (from left to right) 0 wt %, 5 wt %, and 10 wt % M5 graphene.......Page 72 Figure 7. Tensile modulus of 3D-printed ABS versus M5 graphene content for 0° and 45°–45° bead raster angles.......Page 73 Figure 8. Tensile peak stress of 3D-printed ABS versus M5 graphene content for 0° and 45°–45° bead raster angles.......Page 74 Dynamic Mechanical Spectroscopy......Page 75 Figure 10. Optical photomicrographs of fracture surfaces of tensile bars printed-to-shape and milled-to-shape 3D-printed with graphene-containing ABS composites. Delamination of the circumferential MatEx printing layers is associated with the defects thus formed resulting in lesser properties (e.g., tensile elongation). The upper two samples are 2.38 mm thick and the lower two samples are 3.18 mm thick. All tensile bars and their fracture surfaces are 12.7 mm wide.......Page 76 Conclusions......Page 77 References......Page 78 Characterization and Analysis of Polyetherimide: Realizing Practical Challenges of Modeling the Extrusion-Based Additive Manufacturing Process......Page 80 Introduction......Page 81 Rheology Measurements......Page 82 Governing Equations......Page 83 Analysis of IR Temperature Data......Page 84 Shear Rheology......Page 85 Complete Re-Entanglement Time......Page 86 Figure 3. Relationship between the complete re-entanglement time of Ultem 1010 and isothermal temperature.......Page 87 Figure 4. Cross-section image of a single road width wall (SRWW) displaying ovular shape. (a) The bottom layer of a 10-layer SRWW. (b) The top layer of the SRWW, illustrating differences in shape and weld width as a function of distance from the print bed.......Page 88 Development of Representative Mesh Geometry from SEM Cross-Section Data......Page 89 Thermal Model......Page 90 Figure 7. Measurements used to describe the representative shape of the individual layers in a single road width wall. (a) Corresponds to dimension A, (b) corresponds to dimension B, and (c) corresponds to dimension E from Figure 5.......Page 91 Figure 9. Image depicting node density used in the heat transfer finite element analysis of a single road width wall based on the parametric model.......Page 92 Conclusions......Page 93 References......Page 94 Introduction......Page 96 Sample......Page 98 Printing Conditions......Page 99 MatEx Process Model......Page 100 Figure 2. Shape of the deposited filament from four perspectives. The melt exits a circular nozzle, radius RN, at speed UN and traces a smooth elliptical arc. The melt is deposited onto a build plate transformed into an elliptical cross section of height H. In a frame fixed with the nozzle the build plate moves at speed UL. The shape of the deposit is parameterized by angle θ. Adapted with permission from ref 20. Copyright 2017 AIP.......Page 101 Constitutive Model......Page 102 Deposition Flow......Page 103 Figure 3. Polymer stretch profile Λ in the nozzle cross section (left) and the deposited filament cross section (right). This stretch profile provides the initial condition for the crystallization calculation.......Page 104 FIC......Page 105 Stretch Relaxation and Surface Cooling......Page 106 Figure 4. Cooling profile of filaments L9 and L8 measured using infrared imaging technique. The temperature profile at the weld is given by the average. The boundary condition imposed at the free surface of the filament is given by the line.......Page 107 Quiescent Nucleation and Crystal Growth Rate......Page 108 Saturation Limit......Page 109 Figure 7. Isothermal, quiescent nucleation kinetics for three crystallization temperatures and corresponding temperature-dependent saturation limit Nq,max.......Page 110 Figure 8. Images of the cross sections of the printed filament (pre-annealing) under bright-field illumination. The cross sections are dark in cross-polarized light. The scale bar is 200 μm.......Page 111 Figure 9. Predicted cross-sectional nucleation density for nine printing conditions. A boundary layer of flow-enhanced nuclei can be observed in each case, which becomes more distinct at lower print temperatures and faster print speeds.......Page 112 Figure 10. Evolution of the temperature, polymer stretch, number of nuclei and degree of space filling at the top (a), middle (m) and bottom (b) of the cross section for two printing conditions. The initial stretch profile is shown as an inset. Flow-enhanced crystallization occurs only at the surface of the filament in both cases.......Page 113 Spherulite Size Distribution after Annealing......Page 114 Figure 13. Images of the annealed cross sections of the prints using cross-polarized illumination. The cross sections are dark in cross-polarized light, with the polarizer and analyzer oriented at 45° to the image. The scale bar is 200 μm.......Page 115 Figure 15. Normalized birefringent intensity loss at the weld versus feed rate. The error bars indicate the standard deviation based on measurements of four welds at each printing condition.......Page 116 Figure 16. Average spherulite diameter measured from optical imaging versus feed rate. Filled symbols indicate spherulites measured towards the middle of the filament, and open symbols indicate spherulites within 50 μm of the weld. The error bars indicate the standard distribution from an average of five spherulites.......Page 117 Figure 17. Predicted cross-sectional spherulite diameter after annealing for 1 h at 140 °C for each of the nine printing conditions. A flow-enhanced boundary layer of smaller spherulites can be observed in each case, which becomes more distinct at lower print temperatures and faster print speeds.......Page 118 Discussion......Page 119 Conclusion......Page 120 References......Page 121 Introduction......Page 126 Figure 1. Despite the vast differences in scale, the principles of FFF and BAAM are the same. In both forms of thermally-driven MatEx, a molten thermoplastic is extruded onto a build plate as a structure is formed layer-by-layer.......Page 127 Significance of Temperature Profiles......Page 128 Material Considerations......Page 129 1D Modeling Approaches......Page 130 2D Modeling Approaches......Page 132 3D Modeling Approaches......Page 133 Parameterization of Material, Processing, and Geometric Parameters......Page 136 References......Page 137 Introduction......Page 142 System Requirements......Page 143 Figure 1. DIW schematic, not to scale. Camera and light B are only present when measuring focusing in the channel. (A) Example frame for measuring rotational flows in the filament. Nozzle and filament outlines are superimposed. (B) Example frame for measuring focusing in the channel. Channel edges are superimposed. (C) Example frame for monitoring filament stability. Nozzle outline, substrate position, surface tangents, contact points, and points of maximum curvature are superimposed.......Page 144 Calibrating Machine Geometry......Page 145 Figure 2. Nozzle and substrate detection. (A) Initial frame. (B) Number of pixels in product of image and reflection for a range of probed reflection planes. (C) Edge detection. (D, E) Linear regression of bottom edge for two frames. Gray points are the front nozzle corner, black points are bottom edge points, and the gray area is the extracted nozzle.......Page 146 Lubrication Theory To Guide Image Processing......Page 147 Extracting Stability Parameters......Page 148 Figure 4. (A) Measured Laplace pressure differential and (B) measured contact angle for varying flow and stage speeds. For droplets, maximum and minimum values are connected by dotted lines. (C) Contact line position as a function of flow and stage speed. For droplets, maximum and minimum values are represented in striped boxes. Bold lines correspond to Equation 2. (D)–(I) Example frames, annotated with nozzle contact point SiL, substrate contact point SL, channel position C, points of maximum curvature U and D, and contact point tangents.......Page 149 Extracting Surface Points......Page 150 Extracting Contact Points and Points of Maximum Curvature......Page 151 Figure 6. Meniscus point fitting examples. Nozzle, substrate, and plotted regions are annotated. (A), (B) Droplets. (C) Balanced filament.......Page 152 Utility of Extracted Parameters......Page 153 Figure 7. Contact line to channel distance lSL, contact angle θSL, wetting length lSiL, upstream Laplace pressure ΔPU,L, downstream Laplace pressure ΔPD,L, and Laplace pressure differential ΔPUD,L collected from a video. Left: A filament is extruded and then breaks into droplets. Gridlines indicate local maxima in contact line position. Images on right belong to highlighted region. Right: a new contact line forms, draws downstream, and another new contact line forms. Nozzle and contact line tangents are superimposed.......Page 154 Figure 8. (A) Dense particles move toward a node. (B) Silver-coated glass microparticles flowing through a dark channel and image intensity, averaged over the image height. (C) Particle displacements averaged over 30 frames. (D) One frame used to produce (C). Glare on the left side of the filament induces perceived backward flows.......Page 155 Rotational Flows......Page 156 References......Page 157 Introduction......Page 162 Figure 1. Illustration of the process of MPL. The structure is patterned in a photoactivatable material, such as a photopolymer, via point-by-point scanned exposure using tightly focused ultrashort laser pulses. After exposure, the sample is “developed” by immersing in a solvent that removes the unexposed material, leaving behind a freestanding 3D structure that is a replica of the photopattern.......Page 163 Principles of MPL......Page 164 Figure 2. (a) During MPL, initiators in the photopolymer are activated by MPA, the simplest case of which is 2PA. Because of the kinetics of polymerization, the degree of monomer conversion varies nonlinearly with local irradiance, which introduces a threshold for polymerization. (b) Monomer is converted to cross-linked polymer at points within the vocal volume where the local irradiance exceeds the polymerization threshold. The dimensions of the polymerized volume element, or “voxel,” are determined then by the size of the focal spot and the nonlinear response of the material to the irradiance profile within the focal volume.......Page 165 Implementation of MPL......Page 166 Materials for MPL......Page 167 Lenses on Optical Fibers......Page 169 Waveguides......Page 170 Figure 4. SEM images of straight and curved waveguides fabricated by MPL in SU-8. (a, b) top views and (c, d) side views of the waveguides. Images (b) and (d) are zoomed-in views of waveguides having a turn radius R = 19 μm.......Page 171 Metallodielectric Photonic Crystals......Page 172 SVPCs......Page 173 Figure 8. SEM images of an SVPC fabricated in SU-8. (a) Perspective view of the SVPC. The arrows indicate where scanned optical fibers are positioned to couple a source beam into the device and to characterize light exiting along the straight-through and bent-beam paths. (b) Top view of the SVPC.......Page 174 References......Page 175 Chad R. Snyder......Page 184 Indexes......Page 186 Author Index......Page 188 F......Page 190 P......Page 191 "Additive manufacturing (AM) is a potentially disruptive technology, revolutionizing not only traditional industries but generating entirely new ones through rapid innovation, the democratization of manufacturing, and unprecedented freedom of design. Furthermore, the development of AM technologies has practical implications for economic growth, healthcare, national security, space exploration, and sustainability. For military and space agencies, AM offers the possibility to transform the traditional supply chain system through manufacturing at-point-of-demand, recycling, and indigenous sourcing of raw materials. Similarly, these concepts are being leveraged by remote communities across the globe through efforts such as Fab Labs, which provide low-cost access to manufacturing technologies. AM is transforming healthcare in unexpected ways: doctors and patients have access to high-quality physical 3D models generated directly from computerized tomography (CT) scans. These surgical guides have proved invaluable in surgical preparation and patient consent. In the lab, researchers are developing medical devices or implants which mimic the patient's physiology, are pre-loaded with therapeutics, and are replaced with the patient's cells through natural tissue repair pathways. Pushing the limits of resolution, multi-photon technologies, which allow subdiffraction-limited resolution, are revolutionizing the development of micro-optical components. Unfortunately, adoption of AM technologies by industry has been slow; and while there are numerous success stories and commercial adoption is steadily increasing, AM is hampered by weak parts, incomplete certification methods, and empirical materials development. Regulatory and standards bodies are working to update or develop new standards and policies to deal with the unique material and production issues posed by AM. Many of the challenges facing the industry stem from our limited understanding of structure-process-performance relationships. These challenges fall into many categories and require a broad range of skills to address. For the researcher, AM processes offer unique challenges in materials development, metrology, and modeling, as well as opportunities to combine all three. What makes a polymer printable? What process parameters are important? How should parts be tested? These are all active areas of investigation. This book was inspired by the 2017 ACS Symposium "Additive Manufacturing of Structures and Functional Devices: Materials, Methods, Models, and Testing" and is supplemented by additional experts in the polymer AM field. The chapters discuss the technologies, measurement challenges, manufacturing opportunities, and fabrication potentials. We begin with an introduction to polymer additive manufacturing, identifying the measurement needs and technical challenges facing the industry. A chapter reviewing polymer powder bed fusion follows, providing a complete discussion on methods, materials, and applications. The bulk of the book covers thermoplastic material extrusion, with chapters discussing recycling-based feedstocks, composites materials, and multi-physics modeling linking experimentation and theory. Moving from thermoplastics to conductive inks, a chapter on in situ monitoring and control of direct-ink-write provides a clear example of how theory and modern machine vision can be used to create a practical and responsive control system. The last chapter provides a state-of-the-art review of multi-photon printing, discussing methods, materials, and the stunning capabilities of the technique."-- Résumé de l'éditeur