Plastics commonly used in injection molding have been developed to work with thermoplastic 3D printing technologies like Fused Deposition Modeling (FDM).
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INTRODUCTION 3D printing material achievements have skyrocketed over the past ˜ve to ten years. Today, the 3D printing processes available are substantial for creating prototypes and end-use production parts in hundreds of plastic and metal materials. The advancements in additive manufacturing technology coupled with corresponding advancements in material evolutions have hugely impacted the way 3D printing is viewed and relied upon by engineers, designers and manufacturers during product development and production. Materials in additive manufacturing technology systems are de˜ned by the technology. Each 3D printing technology transforms material through external heat, light, lasers and other directed energies. The ability of a material™s mechanical composition to react positively to a certain directed energy marries that material to a technology which can deliver the desired change. These material-technology partnerships will expand as materials are advanced and material chemistry explored. Advancing technologies encourages more positive material reactions, layer by layer, to directed external energies. The mechanism of material changeŠunique to individual 3D printing technologies and processesŠde˜nes the material in terms of state changes, ˜nal mechanical properties and design capabilities. By extension, developments in 3D printing materials correspond with developments in 3D manufacturing; as the build process improves to encourage more positive reactions from materials, material selections will expand. Today, 3D printing is substantial for creating prototype and end-use production parts in hundreds of plastic and metal materials. 3D PRINTING MATERIALS: CHOOSING THE RIGHT MATERIAL / 3

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3D printing offers many of the thermoplastics and industrial materials found in conventional manufacturing. Plastics commonly used in injection molding have been developed to work with thermoplastic 3D printing technologies like Fused Deposition Modeling (FDM). Traditionally machined metals, such as stainless steel and titanium, have been created as powdered metals for manufacturing with Direct Metal Laser Sintering (DMLS) 3D printing. Biocompatible materials like ULTEM 1010 and polycarbonate have been developed to deliver 3D printed parts using Laser Sintering and FDM technologies. These materials exhibit highly bene˜ cial mechanical properties while delivering complex designs impossible to achieve using conventional manufacturing. The most popular 3D printing manufacturing technologies to date include PolyJet, Stereolithography (SL), Laser Sintering (LS), Fused Deposition Modeling (FDM) and Direct Metal Laser Sintering (DMLS) 1. These technologies develop plastic and metal designs layer by layer using unique processes. PolyJet is a technology which deposits photopolymer resins layer by layer; the resin is cured simultaneously as it deposits using UV laser energy. Stereolithography also uses photopolymers and UV energies, however its photopolymer resins are held in a vat of liquid resin. UV energy is directed via dynamic mirrors to cure parts in precise designs. FDM, also a material MATERIAL SELECTION CONSIDERATIONS APPLICATION Certain 3D printing materials offer biocompatibility, sterilization capabilities, FDA certi˜ cations for skin contact, heat smoke toxicity certi˜ cations, ˜ re retardant certi˜ cations, chemical resistance or other certi˜ cations which may be critical for your project. When choosing a material and 3D printing process for your project it is important to ensure your material can deliver on these certi˜ cations. A 3D printing service provider with ISO 9001 and AS 9100 certi˜ cations like Stratasys Direct Manufacturing can ensure strict material and engineering requirements are met. FUNCTION 3D printing materials are subjected to rigorous testing in order to answer the kinds of stresses it can endure and the level of taxing environment the material will excel in. The ability of a material to function in a desired application relies partly on design. GEOMETRY As we mentioned before, 3D printing materials are often inseparable from their corresponding technology. Additionally, each technology, whether it™s FDM, Stereolithography or Laser Sintering, excels in delivering unique geometric executions. Consider the dimensional tolerances, minimum feature execution and wall thicknesses of your design when choosing a material and 3D printing technology. POST PROCESSING 3D printed designs can result in beautifully ˜ nished products with the right post-processing. Some materials may be better suited to certain post-processing methods than others Œ heat treating stainless steel versus post-curing a photopolymer, for example. 3D PRINTING MATERIALS: CHOOSING THE RIGHT MATERIAL / 4

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depositing process, extrudes heated thermoplastics layer by layer through a precise nozzle. Laser Sintering and Metal Laser Sintering are powder based processes which use IR lasers and a heated, enclosed build chamber to melt plastic or metal materials. These processes, tailored to the materials they utilize, bring unique and varied offerings to the 3D printing industry. When beginning material selection for your next 3D printing project, it will be necessary to consider the application, function and design of your product. Materials available with 3D printing technologies range in heat de˚ ection, chemical resistance and durability and material viability greatly depends on design, application and desired product life. To determine the material and 3D printing process which will best support your application, consider the materials and technologies below 2.3D PRINTING MATERIALS: CHOOSING THE RIGHT MATERIAL / 5

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PHOTOPOLYMERS Photopolymer materials in 3D printing begin as liquid resins which are cured and hardened with ultraviolet (UV) energy to result in plastic prototypes and parts. Photocurable materials range in colors, opacities and rigidities. In 3D printing, two widely adopted technologies use photocurable materials in their manufacturing processes: Stereolithography (SL) and PolyJet. SL materials deliver ˜ne feature details with dimensional tolerance implementations between 0.020fl or ± 0.004fl/fl (whichever is greater) in X/Y and ± 0.005fl or ± 0.002fl/fl (whichever is greater) in Z. SL materials react to UV laser energy in independent and unique ways based on the mechanical properties of each material; these variances in reaction can determine the tolerance and feature, or it may determine the shrinkage rate and speed of print among other factors. The choice of SL material best suited to a particular design will factor speed, shrinkage and feature detail requirements for optimum design execution. SL materials with lower shrinkage and higher print speeds include, or are similar to, SC 4500, SL7810, Accura25, Next and Somos 18420; we refer to these materials as SLA White. In addition to SLA White materials is a category of clear or transparent and colorless SL materials, which we™ll refer to as SLA Clear materials. SLA Clear materials include, or are similar to, Somos 10122, Accura 60 and Somos 11122. Materials used speci˜cally for their micro or high de˜nition feature abilities include Somos NeXT and the Stratasys Direct Manufacturing proprietary material SC 5500. 3D PRINTING MATERIALS: CHOOSING THE RIGHT MATERIAL / 6

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As we mentioned in our introduction, PolyJet technology deviates from SL technology in that PolyJet deposits and cures photopolymer materials simultaneously rather than curing materials in a vat of liquid resin. PolyJet materials are capable of manifesting the highest resolution of any 3D printing technology or material, with layer thicknesses as thin as 16 microns (on the Z axis). PolyJet™s ˜ ne resolution eliminates the need for extensive surface post-processing; the thin layer thicknesses result in designs with a smoother texture than other 3D technologies. PolyJet is also the only 3D printing process to currently print in multiple materials with ranging durometers. There are hundreds of photopolymer composites available with PolyJet, but we™ll focus on seven standard materials that give the widest example of what PolyJet photopolymers are capable. PolyJet VeroWhitePlus, VeroBlue, VeroGray, Amber Clear, GreenFire, Endur and Flex comprise the mechanical properties found in the more popular PolyJet material options. VeroWhitePlus, VeroGray and Amber Clear sit around a ˚ exural strength of 93 MPa while VeroBlue, GreenFire and Endur afford ˚ ex strengths between 52 and 67. These materials are capable of 16 micron layer thicknesses and 300 micron feature details. GreenFire and Endur are PolyJet materials with a slightly higher heat de˚ ection and higher elongation at break. GreenFire HDT ranges between 124° and 131° (at 264psi) while Endur HDT ranges between 120° and 129°. The elongation for both materials hit 20% – 40% ranges, with GreenFire falling higher on the scale than Endur. PolyJet Flex materials range between shore 27A and shore 95A hardness for elastomeric material simulations. This material has the added bene˜ t of printing in conjunction with rigid PolyJet materials; this is termed PolyJet Over-Mold and can be used to develop prototype models with critical design reveals. To create PolyJet Over- Mold, PolyJet Flex is infused with PolyJet VeroWhitePlus to create durometer variations. PolyJet Flex materials print in slightly thicker layers, at 30 microns, with similar feature details to PolyJet rigid materials. PolyJet Over-Mold Parts use ˚ exible and rigid materials to reveal design features and textures. 3D PRINTING MATERIALS: CHOOSING THE RIGHT MATERIAL / 8

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COMMON APPLICATIONS PolyJet and SL materials are commonly used to create high resolution concept models, master patterns for urethane casting processes and as form and ˜ t prototypes for a multitude of industries during early product development. Both photopolymer materials, with their corresponding processes, have been used as medical device models, anatomical educational pieces, industrial design reveals for consumer products, show models, among many other applications. PolyJet offers smooth surfaces and a variety of colors while SL offers easily sanded surfaces for cosmetic paint ˜ nishes. Both processes have been used to answer to niche and widespread needs during product development. SPECIAL CONSIDERATIONS PolyJet and Stereolithography (SL) have a much lower HDT than other 3D printing processes and are more susceptive to warp when exposed to heat or prolonged UV rays. Their market spotlight isn™t in the functional end-use product but rather the end-use or prototype model that helps relay a product™s critical design features, feel and form to new and existing markets. > PLEASE REFERENCE CHARTS I & II ŠIN THE APPENDIX. 3D PRINTING MATERIALS: CHOOSING THE RIGHT MATERIAL / 9

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Plastic nylons used in 3D printing begin as powdered composites. These powdered nylons are then fisinteredfl, or heated and fused, layer by layer via a CO2 laser to form dense plastic designs. Nylon materials in 3D printing are relied upon for their heat de˜ection, high strength and excellent elongation properties. The process does not require support materials and is therefore capable of more complex designs and geometric executions than any other 3D printing technology. Laser Sintering (LS) nylon composites mainly derive their base from two nylon powders: Nylon 12 and Nylon 11. These two nylons are then enhanced or reinforced with different ˜llers, including aluminum, glass and even carbon-˜ber, to deliver speci˜c mechanical properties. LS materials typically build at 0.004fl Œ 0.006fl layer thicknesses with tolerances around ± 0.020fl or ± 0.003 fi/fl (whichever is greater). There are a wide variety of nylon powder composites available to Laser Sintering technologies. Some pass smoke and toxicity certi˜cations and many offer higher heat resistance. We™ll focus on general purpose powders on one end of the spectrum and the nylons which perform well within taxing environments on the other end, though there are a range of durable materials which fall in-between. Nylon 12 is a general-purpose un˜lled nylon. This material™s heat de˚ection lands around 187°F (@264psi) with a ˚exural strength around 47 MPa. Its decent strength and HDT have made it a staple in functional prototyping, architectural modeling and even ˜ne arts. Nylon 12 has an elongation between 4-15%, which lands it on the more brittle end of nylons; however certain ˜llers can heighten elongation. To reinforce strength and heat de˚ection, Nylon 12 can be ˜lled with glass and carbon. Nylon 12 Glass Filled (GF) has an HDT of 273°F (@264psi). Carbon ˜ber ˜lled Nylon 12 results in similar HDT with higher ˚exural strength 3D PRINTING MATERIALS: CHOOSING THE RIGHT MATERIAL / 10

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than un˜ lled nylon. Aluminum is an additional ˜ ller used in nylon. Nylon 12 Aluminum Filled (AF) has a higher ˚ exural and tensile strength, but its lower elongation makes it more applicable for prototyping or models when compared to other nylons. Its striking appearance has made it popular for nonfunctional units. Aside from these general nylon composites, there is a more ˚ exible nylon available. Flex TPE is an elastomeric nylon which has the highest elongation of any other 3D print nylon. Flex TPE can be in˜ ltrated with additives to increase the durometer of the material (from shore 40A to shore 70A). Unin˜ ltrated, Flex TPE has an elongation at break of 110%. It™s excellent for stretchy applications. In addition to the above general use nylon materials are FAR 25.853 certi˜ ed for ˜ re, smoke and toxicity performance nylons for 3D printing. FAR 25.853 nylons are used in commercial, corporate and civil aircraft interiors. These materials pass 15 and 60 second vertical burn tests as well as smoke and toxicity requirements for aerospace or similar applications. Nylons available to the 3D printing industry today which meet these standards include reinforced Nylon 12 (also called 606-FR or NyTekŽ4 1200 FR) and enhanced Nylon 11 (also called FR-106). The most notable difference between these highly heat and toxic-resistive materials lies within their elongation properties. Nylon 12 FR (NyTek 12 FR) has an elongation at break similar to regular Nylon 12 while Nylon 11 FR (FR-106) has a much higher elongation, around 21 – 38% at break. Nylon 12 FR has also proven to have a lower shrink rate than Nylon 11 FR, which is important when considering the build of larger part volumes; lower shrink rates results in more accurate parts. 3D PRINTING MATERIALS: CHOOSING THE RIGHT MATERIAL / 11

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