Polymer-Based Additive Manufacturing Recent Developments

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