Alex Raymond Renner 6/29/16

Transcript

Additive Manufacturing Technology and Trends MCA Session Topic: Generalizing Fundamental AM Principles Alex Raymond Renner 6/29/16 [email protected] Eight 1 Steps in Additive Manufacturing 1. Conceptualization and CAD Processes: Rapid? • • Users: Have the solution! Expenses: High • 2. Conversion to STL/AMF 3. Transfer to AM Machine and STL File Manipulation • Processes: Iterative • Users: Have some solutions. • Expenses: Hidden 4. Machine Setup 5. Build 6. Removal and Cleanup 7. Post-Processing 8. Application Processes: Slow • •Users: Might have a solution? • Expenses: Over budget 1) Gibson, Ian, David W. Rosen, and Brent Stucker. Additive manufacturing technologies. Vol. 238. New York: Springer, 2010. MCA Session 4 Activity Review 1. Where in a G-code file does a heated MakerBot component get information? 2. Where in a G-code file does a moving MakerBot component get information? 3. What type of data conversion occurs for the motor(s) used in the following Gcode commands: • G1 X9.202 Y15.578 Z0.600 F9000; Travel Move • G1 X8.962 Y15.888 Z0.600 F5400 A47.05344; Inset Machine Movement Overview ๏ Machine component movements and material bonding methods must work together ๏ A machine with specific movements can use different materials ๏ Material properties are part of designing an AM machine ๏ - This makes AM fundamentally different than any other manufacturing technology - The machine component movement capabilities are always better than the tolerances of the produced part - Analogous to designing a Quality Assurance device Non-linear relationship between machine movement accuracy and final part accuracy AM Machines LeBigRep (FFF) Zcorp 3D Printer MakerBot 2X (FFF) Stratasys (FDM) Delta RepRap(FFF) Stratasys (PolyJet) KickStarter Tiko (Delta FFF), $180 EOS (SLS) Materials & Bonding Methods Overview cont… ๏ Poor quality materials can cause good machines to make make really bad parts (and vice versa) - As the quality of the material increases, the machine approaches its full potential - Expensive and inexpensive can degrade in quality for many reasons Materials & Bonding Methods Overview ๏ High quality materials can cause good machines to make really bad parts (and vice versa) - Some materials present unique challenges that depend more on the part’s features than on the machine’s capabilities - Geometric features and machine processes require extra attention when using materials with “special” material properties - Example: DMLS machines can produce Titanium and Ceramic parts FDM AM Processes Polyjet SLA Passive Supports Post-Processing DMLS SLS AM Machine Specifications Machine Type Tolerance Range (in.) FFF 0.0000X -> 0.0X FDM Fused Powder SLA 0.001 -> 0.010 0.0001 -> 0.005 0.0001 -> 0.003 Polyjet 0.00005 -> 0.0005 SLS 0.0001-> 0.001 DMLS 0.0001 -> 0.001 SLM, LENS, EBM > 0.0001 Materials Material & Part Properties Typical Applications Thermoplastic filament Varies based on user Function of Cost ABS filament Thermoplastic & thermoset powders UV cured polymers UV cured polymers, plastics, rubber > 60% of other mfg. processes Poor, requires postprocessing Fair Good Fit, and some function Fit, Form, Function, Communication 3D shape and Small features, multi-material prototypes Ceramics, Thermoplastics Good Wide variety, based on material Ceramics, Metals Very Good, semiporous Industrial use, complex internal geometric features Fully Dense When it can’t be made or repaired in any other way Metals Active vs. Passive ๏ Support Material moves with part - ๏ Support (if needed) created simultaneously with part - StereoLithography 3D printed (glued powder, Zcorp) Thermo and Multi-Jet Printing Sintering - ๏ Deposition: - FFF, FDM, MEMS - 3D printed (glued powder, Zcorp) - Thermo and Multi-Jet Printing Melting Purpose/Use-case priority - - Aesthetics / Display - Feel - Function ๏ SLM, LENS, EBM Purpose/Use-case priority - Function - Feel - Aesthetics / Display “3D Printer” ๏ ๏ Layers are formed through fusing powder using a liquid binder - Liquid binder is added via an ink-jet type printing process - Un-fused powder serves as passive support structure Process Sequence: - Sweep powder from source to build chamber - Glue powder using inkjet head - Move down a layer - Sweep and repeat “3D Printer” ๏ ๏ Binder-Particle Interaction Considerations - Different droplet technologies affect part quality - Droplet and particle size are related, they both affect part quality Layer Generation Deposition Methods - Continuous Ink Jet - Drop-on-Demand - Piezoelectric - Thermal inkjet Piezoelectric Continuous Ink Jet Thermal Inkjet “3D Printer”: Machine Examples ๏ ๏ Zcorp Z310 - Envelope:8” X 10” X 8” Layers: 0.0035”-0.008” Monochrome
 Cheap: ~$25,000 - “Concept modeler”, but can be used to make rapid castings Newer Systems - Z450, 650, 850 - 8x10x8 to 20x15x9 - Increased automation - Post processing chambers - Full color “3D Printer” Example Parts FDM/FFF: Method Overview ๏ Extruder nozzles moved via x-y device ๏ Traversal speed is regulated by the desired beadwidth (bead width varies ~ 0.010”-0.040”) ๏ Combination of material feedrate and traversal speed (for a given nozzle diameter) controls the bead width ๏ Bead width affects the ability of the process to fill the interior region completely (raster filling) ๏ Also dependent on raster orientation and contour shape FDM/FFF: Part Shape Approximation ๏ Part “raster” fill types ๏ Raft/Base/ Support styles FDM/FFF: Materials ๏ Materials used in FDM are closer to functional materials, ABS and Polycarbonate - ABS (Acrylonitrile-Butadiene-Styrene) - Good strength, good hardness, available with water soluble supports - Tg:212°F - Tensile strength (2000psi-7000psi) ๏ Polycarbonate ๏ (“Lexan”) - Better strength, better hardness, not currently available with water soluble supports - Tg:293°F - Tensile strength (10,500psi) Anisotropic properties (inter laminate strength) - machine movements’ affect on bead shape assumes material is heated “just right”… - Material properties are a function of material, process temp and movement precision - Tg: 428°F FDM Machine Examples ๏ Build speed is average to slow ( < 200mm/s) ๏ Layer thicknesses are limited (0.004”to 0.013”) ๏ Large price range in machines, ~$20,000, up to $400K PolyJet ๏ Stratasys trade name for multi-jet technology for UV cured photopolymers ๏ Cannot be used with Thermoplastics which require FDM/FFF processes StereoLithography (SLA) ๏ A build platform moves down ๏ Passive since surrounded by resin ๏ Overhanging features still need support ๏ Layers are formed by curing photosensitive resin using a laser ๏ Resin is contained in a vat ๏ A build platform in the vat is used to position the next layer just below the surface of the resin ๏ Each layer is cured and fused to the preceding layer, forming a solid part SLA: Laser Solidified Shape Considerations ๏ In addition to the material considerations the system must be able to accurately focus the UV light (where accuracy may depend on the users needs) ๏ Laser spot diameter (0.010in 0.030in) or (0.254mm 0.762mm) for borders and interior filling, respectively (as available) Selective Laser Sintering ๏ ๏ Sintering is not melting - Laser power dependent on material, 25-100W laser is typical - Chamber is heated to below melt temperature of material - Nitrogen used to avoid oxidation and/or explosion Process Steps: - Laser beam directed through use of galvanometric mirrors - Un-fused powder serves as passive support structure - Supply platform raises and build platform lowers - Counter-rotating roller sweeps powder layer from supply - One layer thickness of powder ready for sintering - Laser sinters a layer - Platform moves down after sintering - Fresh new powder layer (slow step, compared to laser sintering step) - Build Platform raises out of the build chamber Direct Metal Laser Sintering (DMLS) ๏ Higher power lasers and chamber temperatures allow direct sintering of metal powders or selective melting ๏ Lasers 200W + ๏ Slower scan speed (~ 118 ips) versus 300-400 ips for SLS ๏ Layer thickness (~0.001”-0.004”) DMLS: Materials and Processing ๏ Polyamide (Nylon) ๏ Glass filled Polyamide ๏ Polycarbonate ๏ Elastomeric materials (rubber like) ๏ Zircon (ZrSiO4) and Silica (SiO2) sand (coated) ๏ Metal powders (coated) Melting: Selective Laser (SLM), Electron Beam (EBM) ๏ EBM uses electron beam for power and must have conductive materials (lasers can heat others) ๏ Surface finish in all processes can be a challenge ๏ Shrinkage and distortion of parts can be a problem ๏ SLM and EBM can make fully dense parts in metal ๏ All machines are relatively expensive, EBM and SLM being the most ๏ Relatively small build envelopes for metal parts Hybrid ๏ Support (if needed) created simultaneously with part ๏ Deposition: ๏ - Laser Engineered Net Shape (LENS) - Thermo and Multi-Jet Printing - Shape Deposition Manufacturing (SDM) Purpose/Use-case priority - Function - Feel - Aesthetics / Display Thermojet / Multi Jet ๏ Very high accuracy and good surface finish ๏ Niche application in jewelry making and dental/medical ๏ Great for investment casting small parts ๏ Deposits molten material which solidifies on contact ๏ Low viscosity molten thermoplastic ๏ Active support structures using different material ๏ Low melt temperature, low viscosity ๏ Intended for investment casting ๏ Support Material: Natural and Synthetic waxes and Fatty Esters ๏ Melt temp 120°F-158°F Shape Deposition Manufacturing (SDM) ๏ A hybrid method using both additive and subtractive manufacturing ๏ Decompose complex shape into layers (arbitrary depth) such that the part can be made with simple operations ๏ Either machine a cavity and deposit material, or deposit material and machine the shape Laser Engineered Net Shape (LENS) ๏ Uses a focused laser to melt powder and build layers ๏ Powder is supplied via nozzles around the laser ๏ Laser, typically Neodymium Yttrium Aluminum Garnet (Nd:YAG) focused with a lens to the build location ๏ Several nozzles supply metal powders to focal point of laser ๏ Creates fully dense metal parts and tooling ๏ Laser power: 500W to 20kW ๏ Materials - Titanium - Stainless Steel – Inconel ๏ Can process reactive materials because of inert environment ๏ LENS process is good for depositing expensive and/or difficult to machine metals Laser Engineered Net Shape (LENS) cont… ๏ It is expected that LENS parts/tooling will be machined ๏ Extra material purposely deposited for this reason ๏ Substrate may need to be removed ๏ Post processing alone could exclude LENS from “rapid” category... ๏ Large use of the LENS process is repair of existing parts ๏ Cracked/Brokenparts filled with metal in selective regions using LENS process ๏ Saves costly replacements ๏ Repair is as strong or stronger than original material Post Processing, Maintenance, & Quality Assurance ๏ “I’m melting”: water soluble supports ๏ “I’m not melting but I am feeling a bit hygroscopic”: help control the wet filament population, have your filament stored and adsorbed ๏ “I think I’m melting”: FDM vs. FFF (why your extruder is probably clogged) ๏ “I wish I was melting”: you can’t “print metal” but you can sinter it ๏ “I overcooked it”: laser power and angle of incidence in a heated build chamber ๏ “I wasn’t roughhousing”: post-processing steps non-AM quality assurance inspection standards applied to AM parts ๏ “I’m not done with it, but it printed”: the often forgotten but beneficial post-processing steps ๏ “I’m for sure melting”: how to make fully dense metal parts using AM processes/techniques Post Processing: 3D Printers ๏ Inkjet binder is not very strong ๏ Infiltration with other liquids ๏ - Wax 100% infiltration, not very strong, improves surface - Cyanoacrylate, lower quality but better strength than wax, < 1/8” penetration depth - Elastomeric Urethane, higher strength and flexibility, < 1⁄2” penetration depth - Epoxy, best strength, may be machinable, < 1⁄2” penetration depth Infiltration by - Dipping (wax) - Spraying, Brushing, Dripping Post Processing: FDM / FFF ๏ Traditionally Polyvinyl Acetate (PVA) ๏ Stratasys: “Water Works” PVA for ABS ๏ 3D Systems: Infinity Rinse Away Post Processing: SLA Post Processing: Sintering ๏ Parts must be extracted from contents of the build chamber, parts must be found in a “block” of material and cleaned ๏ Cost increases with part complexity and quantity of parts (very little material can be recycled) ๏ “The Shapeways Factory is a Modern Santa Klaus’ FabLab” That’s not a multi-tool! This is a multi-tool Emerging AM Methods ๏ ๏ Self-Propagating Photopolymer Waveguides (SPPW) - Lattice-based open-cellular materials - shorter manufacturing time vs. SLA Layer-Less AM processes - Could be applied to multiple AM system types - Borrows concepts from CNC machining Emerging AM Methods ๏ In-situ FFF painting ๏ CMYKW FDM