By Jan H. Schut
The first two pellet-fed 3-D printers take the spotlight at the Society of Plastics Engineers (www.4spe.org) ANTEC 2015 Annual Technical Conference March 23-25 in Orlando, FL. Both are based on existing machine technology—one on extrusion, the other injection molding. They aren’t brand new–they were announced and demonstrated over the past two years at several major international shows. But they’re going commercial now, which is where they get interesting.
Oak Ridge National Laboratory in Tennessee (www.ornl.gov) partnered with machine builder Cincinnati Inc. in Ohio (www.e-ci.com), to develop the first Big Area Additive Manufacturing machine (BAAM) with enough build space for car bodies. It’s based on Cincinnati’s gantry-style laser cutting machine, but replaces the articulated cutter with a 1-inch 14:1 L/D extruder.
Arburg GmbH + Co KG in Germany (www.arburg.com) is also presenting its pellet-fed Freeformer additive manufacturing in the U.S. for the first time, based on injection molding. Build area is only 9 x 5.1 x 9.8 inches, but with two pellet-fed components, it targets complex functional production parts. (For news on smaller 3-D printers, see this blog Oct. 27, 2014.)
Other news at ANTEC includes co-ex films with unusual micro features, nanofoams of engineering polymers, potential algal route to flame retardancy, and new ways to recover high-value plastics from durables. Because ANTEC is collocated this year with the triennial NPE 2015: The International Plastics Showcase, March 23-27 (www.npe.org), processors can first learn about new technology at ANTEC and in several cases see it running next door.
The letter and number in brackets after the title of an ANTEC paper indicate the day of the week and session when it’s given, e.g., [M8] is session 8 on Monday, March 23. Session papers are available to non-attendees from the SPE for $200 to members and $250 to nonmembers. Plenary speeches, new technology forums, and graduate posters, however, aren’t on the CD, so you’ll have to go and listen up!
FIRST PELLET-FED 3-D PRINTERS
Breaking Barriers in Additive Manufacturing [T29 New Technology Forum] by Lonnie Love, senior research scientist for automation, robotics and manufacturing at Oakridge National Lab. The first BAAM machine deposited 10 lb/hour of plastic with a build area of 157.5 x 78.75 x 34 inches. The next size deposits 38 lb/hour with a whopping 240 x 93 x 72 inch build area, and it’s planned to go up to 100 lb/hour. BAAM’s gantry-mounted x,y moving extruder is fed pellets by a flexible pneumatic hose and deposits a continuous bead of semi-molten plastic onto a build table with z movement up and down. BAAM was launched last September at the IMTS 2014 show in Chicago, building a small concept car during the show. Next ORNL “printed” a reproduction Shelby Cobra sports car for the North American International Auto Show in Detroit in January with a body of 20% oriented carbon-fiber-filled ABS. Cincinnati has sold four machines already.
Modeling of Large Scale Fused Deposition Modeling with Reinforced Plastics [W29] by Vlastimil Kunc, research staff at ORNL, describes how large functional parts are simulated. The design starts as a CAD file, is converted into horizontal slices in sterolithography, and finally converted into instructions for the tool path that deposits the plastic bead to build a part. The deposition process is simulated using a finite element tool developed in collaboration with AlphaSTAR Corp., Long Beach, CA (www.alphastarcorp.com), because existing FEM software couldn’t handle the massive calculations. Simulating thermal stresses to prevent cracking and warping of such large parts during cooling is especially complex.
Injection Molding without a Mold: Arburg Plastic Freeforming for Additive Manufacturing of One-of-a-Kind Parts and Small Batches, plenary speech by Heinz Glaub, managing director of technology and engineering at Arburg presents its Freeformer, which plasticizes pellets based on injection-molding. Freeformer feeds two components to a stationary discharge unit with special nozzles that deposit tiny droplets of plastic using high-frequency piezo technology (at 60-200 Hertz). Droplets fuse to form a part on a precisely controlled x,y,z moving carrier. At NPE 2015, two two-component Freeformers are expected to mold a TPU part and a part with an articulated joint using a water soluble support polymer that’s removed easily afterward in a water bath.
Arburg Plastic Freeforming–New Industrial Additive Process [T29 New Technology Forum] by Oliver Kessling, manager of the plastic freeforming department at Arburg, explains the process with focus on materials and applications. The two-component Freeformer can build parts with hard and soft materials, two colors, or a primary and support polymer, allowing complex part geometries with overhangs and undercuts that couldn’t be injection molded. Five published patent applications give an idea of how complex 3-D parts could be produced.
NOVEL FILMS AND OTHER EXTRUSION NEWS
Effect of Rheology on the Morphology of Coextruded Microcapillary Films [M8] by Wenyi Huang, associate research scientist, The Dow Chemical Co., Midland, MI (www.dow.com). A new patent-applied-for die (WO2013009538) coextrudes micro channels in the machine direction filled with a second polymer in a matrix polymer layer. Size and shape of microcapillary threads varies by the comparative speeds of the two extruders and the viscosities of the two materials. If the microcapillary resin is much lower viscosity than the matrix, initially round capillaries become square. A decade ago the University of Cambridge in the U.K. patented film with hollow microcapillary channels, but not a second polymer.
Triple Shape Memory Materials Fabricated by Forced Assembly Multi-Layer Film Extrusion Technology [M26] by Shanzuo Ji, doctoral student at Case Western Reserve University in Cleveland, OH (www.case.edu). Case’s nanolayer multiplication die technology forces the assembly of three polymers with different thermal transition temperatures (PU/EVA/PVAc) to make a 257-nanolayer, triple-shape-memory film with better properties than traditional shape memory alloys. Case previously produced dual shape memory materials by forced layer assembly.
Integrated Waste Heat Utilization for Extruder Barrels by Interconnection of Fluid Streams [M28] by Christoph Ketteler, research assistant, University of Duisburg-Essen, Germany (www.uni-due.de). Instead of heating an extruder with electric heater bands and cooling with fans, this energy-saving concept simulates a barrel with two discrete oil loops, one heated, the other cooled, and bypasses for each temperature zone, thus applying heat and cooling directly into the barrel. The next step is to build a lab model.
NANO FOAM AND NANOFEATURE MOLDING
Solid-State Thermoplastic Nanofoams via a Novel Low-Temperature Saturation Pathway [M36] by Huimin Guo, doctoral student at the University of Washington in Seattle (www.washington.edu). Few polymers allow nanocellular foams with cells >100 nm, but new patent-applied-for technology (WO2014210523) nanofoams PC, PMMA, and PSU by saturating the polymer in liquid CO2 at very low temperature (-30 °C) under high pressure, then molding it at over its Tg. This makes PC and PSU nanofoams with 20-30 nm cells and 60% and 48% void space respectively, and PMMA nanofoam with 30-40 nm cells and 86% void space. The university previously commercialized solid-state microcellular foamed PET by saturating it in gaseous CO2 at room temperature under high pressure and molding it at over its Tg.
Injection Molding of Nano-Features: a Study on Filling and Birefringence [M9] by Srini Vaddiraju, senior project engineer at Corning Inc., Corning, NY (www.corning.com), reports an unconventional injection molding technique for optical parts with very low birefringence for Corning’s Epic sensor, used to test sensitive living cell reactions. Injection molding of the sensor substrate replaces a more expensive multi-step coating process on glass. The patent-applied-for injection molding (WO2013148630) is described as using “a fan gate that spans the entire length of the substrate” and 30% of the width. The unheated runner also has a dish-like melt reservoir to keep injection pressure uniform across the wide fan.
NEW BIO-BASED MATERIALS AND COMPOSITES
Development of Eggshell Powder Masterbatch for Food Trays [T2] by Yoshihisa Sumita, CEO, Hinode Resin Industry Co. Ltd., Tokyo, Japan (firstname.lastname@example.org). Egg shell powder is a source of calcium in food supplements. But when waste eggshells were tested as a 30% mineral filler for molded PP food trays, the compound smelled of sulfur. Hinode found that compounding and molding at the lowest possible temperature for PP avoided the odor problem.
Novel Fire-Resistant Renewable Materials Derived from Freshwater Algae [W25] by Gary E. Wnek, professor at Case Western Reserve University, Cleveland, OH (www.case.edu). The first presentation based on four years of R&D on a species of inherently fire-resistant algae found in Lake Erie. The algae are cellulose-based, but coated with silica diatoms. The next step is to use this discovery to develop environmentally friendly flame retardants for commodity plastics.
Vegetable-Based Copolymers Based on Blend of Acrylated Epoxidized Soybean Oil and Tung Oil [M1] by Samy Madbouly, professor at Iowa State University in Ames (www.iastate.edu). Soy bean oil modified with methacrylates and blended with tung oil as a reactive diluent makes a highly cross-linked copolymer. Described in a 2014 master’s thesis by Harris Handoko, copolymers range from brittle with no tung oil to tough and rubbery with 50%.
Compatibilizing and Toughening of an Immiscible Polyphenylene Blend via Reactive Mixing [M19] by Sayantan Roy, research scientist at Baker Hughes Inc., Houston, TX (www.bakerhughes.com). A patent-applied-for reaction (WO2013077956) combines immiscible PPS and PPSU into a hybrid polymer blend with a single glass transition temperature and the toughness of PPSU. The new material targets downhole sealing applications in oil wells.
NEW TECHNOLOGIES TO RECYCLE DURABLES
Rubber Devulcanization Using a Planetary Extruder [T32] by Michael Batton, process manager, Entex GmbH, Bochum, Germany (www.entex.de). Entex owner Harald Rust’s new technology (U.S. Patent Applic. # 20130023639) uses a specific configuration of planetary spindles around a central spindle with precise heating and cooling profiles to break the cross-links in recycled rubber mechanically, so it can be processed again.
Devulcanization of Waste EPDM Rubber from Post Industrial Scrap Using an Ultrasonic Twin-Screw Extruder: Effect of Screw Design [graduate poster] by Hui Dong, graduate student, University of Akron, Akron, OH (www.uakron.edu), presents the first ultrasonic twin-screw devulcanizing of EPDM. When a twin-screw extruder is tested at zero to 13 um of sonic amplitude, it recycles EPDM with higher tensile strength and elongation at break, but lower modulus and viscosity with 13 um of vibration than with none.
Plastics Recovered from Shredded End-of-Life Vehicles [W26] and Plastics Recovered from Shredded Waste Electrical and Electronic Equipment [W26], both by Brian Riise, R&D director at MBA Polymers Inc., Worksop, Nottinghamshire, U.K. (www.mbapolymers.com). MBA’s U.K. plant uses the latest patent-applied-for multi-stage technology (U.S. Patent Applic. # 20140231557) to recover plastics from shredded automobiles. MBA plants in Austria and China recover plastics from shredded waste electrical and electronic equipment for sale into high value products. Only a handful of other plants in the world do anything similar.