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Additive Manufacturing 101-7: What is vat photopolymerization?

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Vat Photopolymerization (Image: 3D Hubs)

  Mechanical Design Engineer and Additive Manufacturing Ph.D. student

This is the eighth article in a series of original articles that will help you understand the origins of the technology that is commonly called 3D printing. First an introduction, followed by the seven main technologies categories (binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, vat photopolymerization) and then a design philosophy for additive manufacturing.

Vat Photopolymerization

ISO/ASTM definition: “vat photopolymerization, —an additive manufacturing process in which liquid photopolymer in a vat is selectively cured by light-activated polymerization.”[1]

Vat photopolymerization can also be known as (in alphabetical order):

➢ Continuous Liquid Interface Production or CLIP[2]

➢ Scan, Spin and Selectively Photocure Technology or 3SP[3]

➢ Solid Ground Curing or SGC[4]

➢ Stereolithography or SL[5]

➢ Stereolithography Apparatus or SLA® (3D Systems Corporation)

➢ Two-Photon Polymerization or 2PP[6]

Stereolithography was the first AM process to be invented. The first patent was filed in 1975 which described a two-laser 2PP process[7]. The first parts were made by Dr. Hideo Kodama of Japan using SL in 1981[8]. Additional patents followed in 1984 when in three different parts of the world, people patented the SL processes. First on May 23 in Japan by Yoji Marutani[9], then on July 16 in France by Jean Claude André, Alain Le Méhauté and Olivier de Witte[10], and lastly on August 8 in the United States by Charles W. Hull[5]. Chuck Hull was the first to commercialize the technology when he founded 3D Systems in 1986. In 1988, 3D Systems commissioned Alberts Consulting Group to create a file format that could be sliced, resulting in the STL file format[11]. In 1991, Cubital introduced the Solid Ground Curing process but later ceased operations in 1999. In 2015 Carbon3D introduced a novel concept named CLIP using an oxygen-permeable bottom plate to help speed up the printing process. As the original patents surrounding this technology have lapsed, many startups have emerged taking advantage of this original AM process.

vat photopolymerization

vat photopolymerization example

Figure 1: Vat Polymerization example setup[12]

This process involves using a liquid resin as the main type of material. Specifically, this liquid resin has the special property of being able to become solid once it is exposed to light. This light can be ultraviolet as in SL processes, or for 2PP, with two photons of near-infrared (NIR) light hit within a very short period of time (several femtoseconds)[12]. This liquid resin is held in a container or vat, in which a flat build platform is partially submerged. This platform starts near the surface of the liquid and then gets exposed to light. This light can be a UV laser(SL), a digital light processing (DLP) projector, a UV light bulb filtered through a printed mask(SGC), an LCD screen similar to home theater projectors(CLIP), or even from very quick pulses (femtoseconds in length) of near infrared (NIR) laser light tightly focused to a very small area(2PP). Once the resin is cured and made solid, the build platform either moves further into the vat, or partially comes out of the vat leaving the solid cured portion just under the surface and then the process is repeated. In the case of SGC, the uncured resin is removed and then replaced with a liquid wax that solidifies, and then both the cured resin and wax is machined flat using a cutter and prepared for the next layer. If the process involves the platform coming out of the vat the resin needs to be transparent or have the solidification process occur at the very bottom of a vat with a clear window or bottom. However, this can cause the resin to solidify to the bottom which would prevent the platform from moving, or cause it to solidify so closely to the bottom that when the build platform moves up, significant suction is created which results in very slow movements. Recent developments by Carbon3D and the creation of the CLIP process have resulted in very quick builds due to the clear bottom acting as an oxygen permeable membrane which inhibits solidification of the resin within a certain zone around the clear bottom of the vat, which eliminates this suction force. This has shown to increase build speeds from 25-100 times compared to other AM processes, including SL.

Advantages to this type of AM are that it is capable of very high detail surface finish, even down to the nano-scale level, it can be very fast compared to other processes in terms of pure volume, and it’s also able to be scaled up to build desk-sized objects in very large vats.

Disadvantages include a limited number of material properties found in UV curable resins, which are not the most robust materials in terms of durability, strength, or stability. These resins can change shape over time, potentially change colour, and usually need a post-curing UV light oven to cure the material fully in order to get the most strength out of them. Some resins are also toxic and special gloves need to be used to handle parts until they are fully cured. Depending on the geometry of the part, support structures are required and can be very complex and require manual removal afterwards.

References

[1] “ISO/ASTM 52900:2015(en), Additive manufacturing — General principles — Terminology,” International Organization for Standardization (ISO), Geneva, Switzerland, 2015.

[2] Tumbleston J. R., Shirvanyants D., Ermoshkin N., Janusziewicz R., Johnson A. R., Kelly D., Chen K., Pinschmidt R., Rolland J. P., Ermoshkin A., Samulski E. T., and DeSimone J. M., “Continuous liquid interface production of 3D objects,” Science, vol. 347, no. 6228, pp. 1349–1352, Mar. 2015.

[3] Groth C., Kravitz N. D., Jones P. E., Graham J. W., and Redmond W. R., “Three-dimensional printing technology.,” Journal of Clinical Orthodontics : JCO, vol. 48, no. 8, pp. 475–85, Aug. 2014.

[4] Levi H., “Accurate rapid prototyping by the solid ground curing technology,” in Proceedings of the 2nd Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 1991, pp. 110–114.

[5] Hull C. W., “Apparatus for production of three-dimensional objects by stereolithography,” U.S. Patent 4,575,330, 11-Mar-1986.

[6] Maruo S., Nakamura O., and Kawata S., “Three-dimensional microfabrication with two-photon-absorbed photopolymerization,” Optics Letters, vol. 22, no. 2, p. 132, Jan. 1997.

[7] Swanson W. K. and Kremer S. D., “Three dimensional systems,” U.S. Patent 4,078,229, 07-Mar-1978.

[8] Kodama H., “Automatic method for fabricating a three-dimensional plastic model with photo-hardening polymer,” Review of Scientific Instruments, vol. 52, no. 11, p. 1770, 1981.

[9] Marutani Y., “Optical Shaping Method,” Japanese Patent 60,247,515, 07-Dec-1985.

[10] André J. C., Mehaute A. Le, and Witte O. de, “Device For Producing A Model Of An Industrial Part,” French Patent 2,567,668, 17-Jan-1986.

[11] Allison J., “Re: History of .stl format,” [Online email], 15-Jan-1997. [Online]. Available: http://www.rp-ml.org/rp-ml-1997/0091.html. [Accessed: 05-Feb-2016].

[12] Gibson I., Rosen D. W., and Stucker B., Additive Manufacturing Technologies. Boston, MA: Springer US, 2010.

Additive Manufacturing 101-6: What is sheet lamination?

(Image: 3D Hubs)

Material Jetting (Image: 3D Hubs)

  Mechanical Design Engineer and Additive Manufacturing Ph.D. student

This is the seventh article in a series of original articles that will help you understand the origins of the technology that is commonly called 3D printing. First an introduction, followed by the seven main technologies categories (binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, vat photopolymerization) and then a design philosophy for additive manufacturing.

Sheet Lamination

ISO/ASTM definition: “sheet lamination, —an additive manufacturing process in which sheets of material are bonded to form a part.”[1]

Sheet Lamination can also be known as (in alphabetical order):

➢ Computer-Aided Manufacturing of Laminated Engineering Materials or CAM-LEM[2]

➢ Laminated Object Manufacturing or LOM[3]

➢ Plastic Sheet Lamination or PSL (Solidimension Ltd.)

➢ Selective Deposition Lamination or SDL (Mcor Technologies Ltd.)

➢ Ultrasonic Additive Manufacturing or UAM[4]

➢ Ultrasonic Consolidation or UC[5]

The LOM process was developed by a company named Helisys and in 1991 they started selling a machine that made 3D parts using rolls of paper and a CO2 laser[6]. The company eventually went bankrupt and later formed Cubic Technologies; however, in 1999, a company from Israel called Solidimension developed a system very similar to LOM using sheets of PVC plastic rather than paper[6]. Also in 1999, a USA company called Solidica (now Fabrisonic) patented a new hybrid method[7] which looked similar to LOM but used metal tapes and films which were joined using ultrasonic vibrations, and then a CNC machine used traditional subtractive manufacturing methods to remove material. In 2005, Japanese company Kira started production of a paper-based machine similar to LOM called the PLT-20 KATANA but using a steel cutter rather than a laser. By 2008 Mcor Technologies launched their first SDL machine called the Matrix which deposited individual sheets of A4 paper rather than rolls of paper like LOM or Kira and selectively glued down sheets which were then cut using a steel cutter. This process allowed Mcor to later develop full-colour parts by printing on the paper before being glued down.

Figure 1: Sheet lamination example setup[8]

This process starts with a single layer of solid material put across the build surface, be it paper (LOM and SDL) or PVC plastic (PSL) or metal (UAM/UC) or ceramic (CAM-LEM). This layer may or may not be bonded to the previous layers first as it depends on the process. Some processes bond the entire layer to the previous and then cut the 2D slice into the layer as with SDL or UAM, while other processes cut the 2D slice into the layer first, and then bond it onto the previous layers afterwards like CAM-LEM. The bonding between each layer occurs by a number of different methods depending on the process. For SDL and PSL, bonding is performed by applying a type of glue to the build surface. Layers are bonded together in LOM through melting a polymer that is embedded within the roll of paper. In the case of UC, the layers have an atomic migration between layers in a very small zone which fuses the layers together. The 2D slice data is either cut into the layer with a laser (LOM/CAM-LEM) or a blade (SDL/PSL) or machined away with a traditional CNC cutter (UAM/UC), and then the process starts over with a new solid layer being placed on top. In the CAM-LEM process, all the 2D layers are first pre-cut from a ceramic tape and then assembled and stacked on top of each other. Then a binder is added to give it strength before it is placed in an oven and fired to sinter the material together. With CAM-LEM, there is potential to cut the layers tangentially to the surface so that the traditional steps that are seen in AM are reduced and nearly eliminated[9], although it does not appear to have made it past the demonstration phase.

Advantages of this process tie directly to the individual processes. SDL can do full-colour prints, is relatively inexpensive since the raw material is normal office paper, can be infused with materials to increase strength or colour saturation, and excess material can be recycled. UC can do metal, and has the ability to do multi-metal layers within the overall part but not in the same layer, but can also embed other things into the part like wires, sensors, or fibres. CAM-LEM can process ceramic parts. No support material is needed since each layer is already solid and can support itself, although there are limitations to this as certain geometries like internal voids and cavities may not be possible.

A common disadvantage of all processes is that the layer height can’t be changed without changing the thickness of the sheets of material being used. Thus the layer steps and surface roughness is directly tied to sheet thickness. Regardless of the size of part being made, an entire sheet is consumed per layer, so material waste can be high if parts don’t make full use of the build volume. When layers are bonded before the 2D layer is cut out, the removal of excess material can be quite labour intensive. Excess material removal may not even be possible for some internal geometry. Even though UC creates solid metal parts, the bonds between layers are weaker than in the other directions, which could result in delamination. LOM cutting is performed with lasers and there is smoke and a chance of fire, which is why that technology was not very popular and why it moved to steel cutters instead.

References

[1] “ISO/ASTM 52900:2015(en), Additive manufacturing — General principles — Terminology,” International Organization for Standardization (ISO), Geneva, Switzerland, 2015.
[2] Cawley J. D., Heuer A. H., Newman W. S., and Mathewson B. B., “Computer-aided manufacturing of laminated engineering materials,” American Ceramic Society Bulletin, vol. 75, no. 5, pp. 75–79, 1996.

[3] Feygin M. and Hsieh B., “Laminated object manufacturing: A simpler process,” in Proceedings of the 2nd Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 1991, pp. 123–130.

[4] Sriraman M. R., Babu S. S., and Short M., “Bonding characteristics during very high power ultrasonic additive manufacturing of copper,” Scripta Materialia, vol. 62, no. 8, pp. 560–563, Apr. 2010.

[5] Kong C. Y., Soar R. C., and Dickens P. M., “Optimum process parameters for ultrasonic consolidation of 3003 aluminium,” Journal of Materials Processing Technology, vol. 146, no. 2, pp. 181–187, Feb. 2004.

[6] Wohlers T. and Gornet T., “History of Additive Manufacturing,” in Wohlers Report 2014 – 3D Printing and Additive Manufacturing State of the Industry, Wohlers Associates Inc, 2014, pp. 1–34.

[7] White D., “Ultrasonic object consolidation,” U.S. Patent 6,519,500, 11-Feb-2003.

[8] Upcraft S. and Fletcher R., “The rapid prototyping technologies,” Assembly Automation, vol. 23, no. 4, pp. 318–330, Dec. 2003.

[9] Zheng Y., Choi S., Mathewson B. B., and Newman W. S., “Progress in Computer-Aided Manufacturing of Laminated Engineering Materials Utilizing Thick, Tangent-Cut Layers,” in Proceedings of the 7th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 1996, pp. 355–362.

Additive Manufacturing 101-5: What is powder bed fusion?

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Powder Bed Fusion (Image: 3D Hubs)

  Mechanical Design Engineer and Additive Manufacturing Ph.D. student

This is the sixth article in a series of original articles that will help you understand the origins of the technology that is commonly called 3D printing. First an introduction, followed by the seven main technologies categories (binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, vat photopolymerization) and then a design philosophy for additive manufacturing.

Powder Bed Fusion

ISO/ASTM definition: “powder bed fusion, —an additive manufacturing process in which thermal energy selectively fuses regions of a powder bed.”[1]

Powder Bed Fusion can also be known as (in alphabetical order):

➢ Direct Metal Laser Remelting or DMLR[2]

➢ Direct Metal Laser Sintering or DMLS® (EOS GmbH)[2]

➢ Direct Metal Printing or DMP (3D Systems Corporation)

➢ Electron Beam Additive Manufacturing or EBAM[3]*‡

➢ Electron Beam Melting or EBM (Arcam AB)

➢ High Speed Sintering or HSS[4]

➢ LaserCUSING® (Concept Laser GmbH)[2]

➢ Laser Metal Fusion (TRUMPF Laser Technology)

➢ Micro Laser Sintering or MLS (EOS GmbH)

➢ Selective Electron Beam Melting or SEBM[5], [6]*

➢ Selective Heat Sintering or SHS[7]

➢ Selective Laser Melting or SLM[2]

➢ Selective Laser Sintering or SLS® (3D Systems Corporation)[2]

* Occasionally used in literature for describing EBM.

‡ EBAM is officially a trademarked DED process.

Powder bed fusion contains a range of technologies, all of which have core similarities, the main three are SLS, SLM and EBM. These originated from work at the University of Texas at Austin in the early 1980s which was awarded a patent in 1989[8], [9]. In 1995, SLM and DMLS were developed in Germany as part of a project between the Fraunhofer Institute, EOS and others[10]. In 1997, Arcam AB of Sweden was founded to commercialize the idea of EBM with their first machine being sold in 2001 and delivered in 2002. HSS was invented in the UK in 2003 and shows promise of being an up and coming AM technology[4].

Figure 1: Powder Bed Fusion example setup[11]

Powder bed fusion methods all start with a powder bed, another parallel to binder jetting. A thin layer of loose powder between 0.001mm (EOS) and 0.2mm (Arcam) with an average of 0.02mm to 0.1mm is smoothly spread flat over a build platform. This layer of powder is then passed over by either a laser or electron beam which supplies significant heat to the powder. The powder is then either partially melted (sintered) or fully melted, to a point where the powder fuses to itself and to the layers below. Then the build platform changes height, a new layer of powder is deposited, and the process is repeated layer by layer until the part is complete. The main differences between all these methods are the heat source that causes melting, the environment in which the melting takes place, and the degree to which things are melted. SLS, DMLS, SLM and all other methods that contain laser in the name, use a laser to provide the thermal energy. SHS uses only a thermal print head. HSS uses an infrared lamp and a radiation absorbent material to do the sintering. EBM uses an electron beam. SLS and HSS generally work only with plastics and operate in a heated nitrogen atmosphere with the powder bed at an elevated temperature. DMLS and SLM primarily work with metals, and due to the reactive nature of some powdered metals, the process takes place in an inert oxygen-free environment with the powder bed being either at room temperature or at a low-temperature set-point. EBM works with metals and takes place in a vacuum and at elevated temperatures much closer to the metals melting temperature. SLS, HSS, and SHS all sinter the material resulting in a final part that has some porosity, but low to no residual stress in the part. Residual stress is energy contained within the material itself that causes it to deform and move[12]. This lack of residual stress allows the parts do not need any type of support system as the powder bed provides the needed supports for overhangs. Although DMLS contains sintering as part of its name, its process does involve melting and not sintering of metals. SLM, DMLS, LaserCUSING and EBM fully melt the material and can result in fully dense parts. SLM, DMLS, and LaserCUSING all can result in significant residual stress depending on materials, geometry, and laser parameters, and thus need significant support structures to hold parts down. EBM utilizes its fast scan speed to preheat the entire layer with the electron beam to just below melting before actually melting the selected portions. This not only preheats the powder but also causes the powder to become loosely aggregated and reduces dust ‘smoking’ which is a repulsive reaction of the powder once it is hit with negatively charged electrons[13], [14]. EBM results in parts that have little to no residual stress and thus uses very little if any supports.

Advantages of this process are mostly about material properties. First, there is a wide range of materials that can be processed from plastic parts like Nylon to a wide range of different metals like copper and Inconel to even ceramics. Next, parts that are fully or even partially melted can have significant strength advantages over non-melted processes as the material properties can be close to that of stock material. Then, depending on the process and material, support structures may not be needed, as the powder bed becomes the support. Build speeds can also be fast depending on materials and process, with processes that preheat the powder bed to just below melting being the quickest because it allows a very fast scan speed. Electron beam scan speeds are the fastest of any process due to the lack of mechanical parts to direct the beam. Processes that use lasers result in a high level of detail and fine features. EBM can process materials that are highly reactive in oxygen, and thus can be made quicker and cheaper than subtractive methods.

Disadvantages depend on the process; however, all of these processes can only utilize a single material in the final part. Some methods require inert gases as an additional consumable material. Layer heights are a function of the powder diameter and thus have a medium resolution in the build direction compared to other processes. EBM surface finish is generally rough and will need some post-processing in order to achieve tight tolerances. Some methods require support structures that need additional manual work to be removed from the final part. EBM requires more than an air blasting to remove unsolidified material as the remaining powder no longer acts as a light metal powder but clings together more like wet sand. Thus it needs either powder blasting, ultrasonic vibration, or mechanical methods to remove the powder, with certain geometries like deep narrow cavities being especially difficult.

References

[1] “ISO/ASTM 52900:2015(en), Additive manufacturing — General principles — Terminology,” International Organization for Standardization (ISO), Geneva, Switzerland, 2015.

[2] Gu D. D., Meiners W., Wissenbach K., and Poprawe R., “Laser additive manufacturing of metallic components: materials, processes and mechanisms,” International Materials Reviews, vol. 57, no. 3, pp. 133–164, May 2012.

[3] Gong X., Anderson T., and Chou K., “Review on Powder-Based Electron Beam Additive Manufacturing Technology,” in ASME/ISCIE 2012 International Symposium on Flexible Automation (ISFA 2012), St. Louis, Missouri, USA, 2012, p. 507.

[4] Hopkinson N. and Erasenthiran P., “High Speed Sintering – Early Research into a New Rapid Manufacturing Process,” in Proceedings of the 15th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 2004, pp. 312–320.

[5] Heinl P., Rottmair A., Körner C., and Singer R. F., “Cellular Titanium by Selective Electron Beam Melting,” Advanced Engineering Materials, vol. 9, no. 5, pp. 360–364, May 2007.

[6] Lodes M. A., Guschlbauer R., and Körner C., “Process development for the manufacturing of 99.94% pure copper via selective electron beam melting,” Materials Letters, vol. 143, pp. 298–301, Mar. 2015.

[7] Baumers M., Tuck C., and Hague R., “Selective Heat Sintering Versus Laser Sintering: Comparison of Deposition Rate, Process Energy Consumption and Cost Performance,” in Proceedings of the 26th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 2015, pp. 109–121.

[8] Deckard C. R., “Method and apparatus for producing parts by selective sintering,” U.S. Patent 4,863,538, 05-Sep-1989.

[9] Bourell D. L., Marcus H. L., Barlow J. W., Beaman J. J., and Deckard C. R., “Multiple material systems for selective beam sintering,” U.S. Patent 4,944,817, 31-Jul-1990.

[10] Shellabear M. and Nyrhilä O., “DMLS – Development History and State of the Art,” in Proceedings of the 4th Laser Assisted Net Shape Engineering Conference (LANE 2004): Volume 1, Erlangen, Germany, 2004, pp. 393–404.

[11] Frazier W. E., “Metal Additive Manufacturing: A Review,” Journal of Materials Engineering and Performance, vol. 23, no. 6, pp. 1917–1928, Jun. 2014.

[12] Buchbinder D., Meiners W., Pirch N., Wissenbach K., and Schrage J., “Investigation on reducing distortion by preheating during manufacture of aluminum components using selective laser melting,” Journal of Laser Applications, vol. 26, no. 1, p. 12004, 2014.

[13] Kahnert M., Lutzmann S., and Zaeh M. F., “Layer formations in electron beam sintering,” in Proceedings of the 18th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 2007, pp. 88–99.

[14] Eschey C., Lutzmann S., and Zaeh M. F., “Examination of the powder spreading effect in Electron Beam Melting (EBM),” in Proceedings of the 20th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 2009, pp. 308–319.

Additive Manufacturing 101-4: What is material jetting?

(Image: 3D Hubs)

Material Jetting (Image: 3D Hubs)

  Mechanical Design Engineer and Additive Manufacturing Ph.D. student

This is the fifth article in a series of original articles that will help you understand the origins of the technology that is commonly called 3D printing. First an introduction, followed by the seven main technologies categories (binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, vat photopolymerization) and then a design philosophy for additive manufacturing.

Material Jetting

ISO/ASTM definition: “material jetting, —an additive manufacturing process in which droplets of build material are selectively deposited.”[1]

Material Jetting can also be known as (in alphabetical order):
➢ Aerosol Jet® (Optomec, Inc.)

➢ Ballistic Particle Manufacturing or BPM[2]

➢ Drop On Demand or DOD[3]

➢ Laser-Induced Forward Transfer or LIFT[4]

➢ Liquid Metal Jetting or LMJ[5]

➢ Multi-Jet Modelling or MJM (3D Systems Corporation)

➢ Multi-Jet-Printing or MJP (3D Systems Corporation)

➢ Nano Metal Jetting© (XJet) or NMJ

➢ NanoParticle Jetting™ (XJet) or NPJ

➢ Polyjet® (Stratasys Inc)

➢ Printoptical© Technology (Luxexcel)

➢ Thermojet Printing (3D Systems Corporation)

In 1984, Bill Masters patented one of the first AM technologies[6] and founded the company Perception Systems, Inc. He later changed its name to BPM Technology and called the technology ballistic particle manufacturing but eventually went bankrupt in 1998. The first commercialized machines were made in 1994 by a company that later became Solidscape[2]. Multi-Jet-Printing is a process from 3D Systems and was commercialized in 1996 which had a few different trade names like Thermojet and MJM. Then in 1998 Polyjet technology was developed by Objet[7], a company based in Israel which later merged with Stratasys in 2012. Then a founder of Objet started XJet in Israel and in 2015 announced a new material jetting technology that can make fully dense metal parts with a high level of surface quality.


Figure 1: Material Jetting example setup[8]

Material jetting is very similar to the type of technology that exists in a standard home-based inkjet printer and is closely related to the binder jetting process. The main difference is that rather than printing ink or a binder, it prints the specific type of material that will make up the final part. Another difference from standard 2D printing is rather than printing this material into a sheet of paper, the material gets deposited directly onto the build surface and becomes solidified by some mechanism. Then the build platform changes the height and the process is repeated until the final geometry is achieved. The material is deposited drop by drop in a very precise and fine detailed manner; however, the exact mechanism for depositing these drops varies with the type of material being jetted. Some of the print heads used are exactly the same types that exist in 2D printers, namely piezoelectric or thermal print heads. These print heads are the exact same type as described for binder jetting. However, in the case of LMJ where the temperatures involved are too high to either boil the material or have a piezo mechanism operate, a combination of magnetic and electrical forces operate and utilize Lorentz forces to propel droplets of liquid metal to be printed. In the case of LIFT, a laser pulse hits a special film consisting of the desired build material, as well as a carrier substrate, and results in a droplet being formed that falls towards the build surface. Then the film is moved so that the laser can hit a new part of the film and release additional material. Regardless of the drop creation process, once the drop is deposited, it then solidifies either through material cooling (LMJ and LIFT), external curing from a UV light source (Polyjet and Multi-Jet Printing), or by evaporating a liquid transport material by using infrared light/heat (NMJ). Research into reactive jetting using monomers and catalysts to form polymers[9] will increase the strength of parts made in this way. These polymers are generally materials that cannot be easily used in AM technologies but are highly attractive because of the long molecule chains associated with them. By being able to reactively jet these materials, the resulting plastics will have very large cross bonds that are formed within and between layers which will increase the strength of these plastic parts. Parts made this way will have a strength equivalent to injection moulded parts.

One big advantage of this technology is the ability to gang multiple print heads together. Having multiple print heads allows these machines to do unique things, such as print in different colours like traditional ink-jet printers, print faster by printing over the entire build surface in one pass, and print in multiple materials at the same time. The surface quality of these parts is usually quite high due to jetting very small droplets. Similar to how a normal inkjet printer is able to print thousands of different colours using only three different inks, a 3D printer that is able to jet multiple materials can combine these materials in different proportions in order to vary material properties in the finished part and create so-called digital materials. There is also a wide range of potential materials that can be directly jetted from plastics to metals; however, the time to develop new materials can be long. An advantage of using similar UV cured resins to those used in SL is that by incorporating the UV cure immediately after jetting, the parts come out fully cured and do not typically need any sort of post-curing.

Some disadvantages of this technology are the build time can be slow due to the nature of jetting very small amounts of material at a time over a small portion of the build area. Some machines use excess material by purging extra material through the nozzles and lines between layers or when the machine is not printing in order to preserve the print heads and prevent them from clogging up. Support structures are also required, thus one print head is dedicated to jetting only support material. This support material generally has very different material properties from that of the main part. Either it melts at a much lower temperature, is much softer, or is chemically different. Removal of the support material is then a manual step requiring one of the following methods: melting or dissolving away of the support material, spraying away the support material manually with water using a high-pressure wash, or removing them by hand.

References

[1] “ISO/ASTM 52900:2015(en), Additive manufacturing — General principles — Terminology,” International Organization for Standardization (ISO), Geneva, Switzerland, 2015.

[2] Gibson I., Rosen D. W., and Stucker B., Additive Manufacturing Technologies. Boston, MA: Springer US, 2010.

[3] Le H. P., “Progress and trends in ink-jet printing technology,” Journal of Imaging Science and Technology, vol. 42, no. 1, pp. 49–62, 1998.

[4] Visser C. W., Pohl R., Sun C., Römer G.-W., Huis in ‘t Veld B., and Lohse D., “Toward 3D Printing of Pure Metals by Laser-Induced Forward Transfer,” Advanced Materials, vol. 27, no. 27, pp. 4087–4092, Jul. 2015.

[5] Priest J. W., Smith C., and DuBois P., “Liquid Metal Jetting for Printing Metal Parts,” in Proceedings of the 8th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 1997, pp. 1–9.

[6] Masters W. E., “Computer automated manufacturing process and system,” U.S. Patent 4,665,492, 12-May-1987.

[7] Gothait H., “Apparatus and method for three dimensional model printing,” U.S. Patent 6,259,962, 10-Jul-2001.

[8] Groth C., Kravitz N. D., Jones P. E., Graham J. W., and Redmond W. R., “Three-dimensional printing technology.,” Journal of Clinical Orthodontics : JCO, vol. 48, no. 8, pp. 475–85, Aug. 2014.

[9] Fathi S., Dickens P. M., Hague R., Khodabakhshi K., and Gilbert M., “Jetting of Reactive Materials for Additive Manufacturing of Nylon Parts,” in Proceedings of the 25th International Conference on Digital Printing Technologies and Digital Fabrication (NIP 25), Louisville, Kentucky, USA, 2009, vol. 2009, no. 2, pp. 784–787.

Additive Manufacturing 101-3: What is material extrusion?

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Material Extrusion (Image: 3D Hubs)

  Mechanical Design Engineer and Additive Manufacturing Ph.D. student

This is the fourth article in a series of original articles that will help you understand the origins of the technology that is commonly called 3D printing. First an introduction, followed by the seven main technologies categories (binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, vat photopolymerization) and then a design philosophy for additive manufacturing.

Material Extrusion

ISO/ASTM definition: “material extrusion, —an additive manufacturing process in which material is selectively dispensed through a nozzle or orifice.”[1]

Material Extrusion can also be known as (in alphabetical order):

➢ Direct Ink Writing or DIW[2]

➢ Extrusion Freeform Fabrication or EFF[3]

➢ Fused Deposition Modeling‎ or FDM® (Stratasys Inc.)[4]

➢ Fused Filament Fabrication or FFF[5]

➢ Glass 3D Printing or G3DP[6]

➢ Liquid Deposition Modeling or LDM[7]

➢ Micropen Writing[8]

➢ Plastic Jet Printing or PJP (3D Systems Corporation)

➢ Robocasting or Robotic Deposition[9], [10]

In 1988, Scott Crump invented a new AM process based on candle wax and a hot glue gun while making a toy for his daughter in the kitchen. The next year he started the company Stratasys, which became one of the largest AM companies in the world. In 2005, in the United Kingdom, Adrian Bowyer at the University of Bath started the RepRap project[5] based on the technology that made Stratasys so successful. His goal was to be able to make use of expiring patents[4] that would make FFF available to everyone, and create an open source 3D printer that was capable of replicating rapidly (RepRap) itself, or at least make as many parts for itself as it could. This first open source printer was released in 2008 and inspired many companies to make their own versions based on the RepRap platform. One company, MakerBot, was founded in 2009 and later acquired by Stratasys in 2013. This open-source design along with the expired patents allowed hundreds of different printer designs and companies to emerge since then. This recent development has contributed to the public’s general awareness of AM technology, even though the core technology started over 30 years ago. Most desktop 3D printers in the world are of this type and are what most people think of when they think 3D printer.

Figure 1: Example of a material Extrusion system’s basic components[11]

The core principle of this technology is that any material that is in a semi-liquid or paste form can be pushed through a nozzle and used to draw the 2D cross-sections of a sliced 3D model. Similar to how a hot glue gun heats a rod of glue and the trigger selectively pushes the material through the nozzle, material extrusion works exactly the same way. The material that is extruded doesn’t need to be plastic or even heated. While the vast majority of these printers use a plastic like ABS (Acrylonitrile butadiene styrene) or PLA (Polylactic acid), any material that can be pushed through a nozzle (heated or not) and afterwards retain its shape can be used. Other examples include cement[12], chocolate[13], ceramic pastes or slurries[9], metal clays and metal filled plastics[14], ground-up and blended food[15], or even biocompatible organic cellular scaffolding gel[16]. The technology is scalable and is only limited by nozzle size and supporting machine structure. This supporting machine structure can take many different shapes such as a delta robot configuration or multi-jointed robot arms[17]. This printer structure can also be built using traditional scaffolding structures to create some of the largest printers in the world. Two examples are a 2014 Chinese built 12m x 12m x 12m printer in the city of Qingdao, and a 2016 12m tall delta printer in the Italian town of Massa Lombarda, both of which are large enough to print a small house. There are plans to build printers that move on a rail system enabling an almost infinite build length in one direction[18]. Multiple print heads can be installed on the same machine thus enabling multi-material printing, but there can be challenges with calibration between heads; thus, more than 2 heads on a machine is rare.The greatest advantage of this process is the extensive range of materials it can use. Almost all types of thermoplastics can be used, from the standard plastics like ABS to more engineering plastic grades like nylon, all the way up to advanced engineering plastics like polyether ether ketone also known as PEEK. These plastics have superior dimensional stability and can be used as actual end-use parts like in the Boeing 787 where many parts (mostly air ducting) are 3D printed from FDM processes. The mechanics of this type of printing are fairly simple and easy to modify especially due to the availability of open source designs; thus people have taken these principles to print anything that can fit into a syringe or that can be made into a filament.Some disadvantages are that this process is slow as only one nozzle operates at a time and the entire layer must be subdivided into actual tool paths to trace out the whole 2D slice. This tool path causes the fill factor to be less than 100% due to geometric constraints and nozzle diameter[19]. Parts generally have anisotropic material properties, and the same part can exhibit different strengths depending on how it was printed[19]. Layer heights are generally larger than other AM processes and are thus more visible and contribute to a higher surface roughness. Support materials and structures need to be used, otherwise, considerable sagging can occur depending on geometry. Removing these supports is either a manual and labour intensive process, or a process which requires dissolving and rinsing of parts in a chemical bath of some sort. Generally, only one material is used, with one main material and one support material being quite common. Anything more than one material and support is rare, it usually requires specialised print heads or specialised calibration techniques.

References

[1] “ISO/ASTM 52900:2015(en), Additive manufacturing — General principles — Terminology,” International Organization for Standardization (ISO), Geneva, Switzerland, 2015.

[2] Lewis J. A. and Gratson G. M., “Direct writing in three dimensions,” Materials Today, vol. 7, no. 7–8, pp. 32–39, Jul. 2004.

[3] Calvert P. D., Frechette J., and Souvignier C., “Gel mineralization as a Model for Bone Formation,” in MRS Proceedings, San Francisco, California, USA, 1998, vol. 520, pp. 305–401.

[4] Crump S. S., “Apparatus and method for creating three-dimensional objects,” U.S. Patent 5,121,329, 09-Jun-1992.

[5] Jones R., Haufe P., Sells E., Iravani P., Olliver V., Palmer C., and Bowyer A., “RepRap – the replicating rapid prototyper,” Robotica, vol. 29, no. 1, pp. 177–191, Jan. 2011.

[6] Klein J., Stern M., Franchin G., Kayser M., Inamura C., Dave S., Weaver J. C., Houk P., Colombo P., Yang M., and Oxman N., “Additive Manufacturing of Optically Transparent Glass,” 3D Printing and Additive Manufacturing, vol. 2, no. 3, pp. 92–105, Sep. 2015.

[7] Postiglione G., Natale G., Griffini G., Levi M., and Turri S., “Conductive 3D microstructures by direct 3D printing of polymer/carbon nanotube nanocomposites via liquid deposition modeling,” Composites Part A: Applied Science and Manufacturing, vol. 76, pp. 110–114, Sep. 2015.

[8] Morissette S. L., Lewis J. A., Clem P. G., Cesarano III J., and Dimos D. B., “Direct-Write Fabrication of Pb(Nb,Zr,Ti)O 3 Devices: Influence of Paste Rheology on Print Morphology and Component Properties,” Journal of the American Ceramic Society, vol. 84, no. 11, pp. 2462–2468, Nov. 2001.

[9] Cesarano III J., Segalman R., and Calvert P. D., “Robocasting provides moldless fabrication from slurry deposition,” Ceramic Industry, vol. 148, no. 4, Business News Publishing, Troy, Michigan, USA, pp. 94–100, 1998.

[10] Cesarano III J. and Calvert P. D., “Freeforming objects with low-binder slurry,” U.S. Patent 6,027,326, 22-Feb-2000.

[11] Gibson I., Rosen D. W., and Stucker B., Additive Manufacturing Technologies. Boston, MA: Springer US, 2010.

[12] Khoshnevis B., “Automated construction by contour crafting—related robotics and information technologies,” Automation in Construction, vol. 13, no. 1, pp. 5–19, Jan. 2004.

[13] Li P., Mellor S., Griffin J., Waelde C., Hao L., and Everson R., “Intellectual property and 3D printing: a case study on 3D chocolate printing,” Journal of Intellectual Property Law & Practice, vol. 9, no. 4, pp. 322–332, Apr. 2014.

[14] Nickels L., “Crowdfunding metallurgy,” Metal Powder Report, Nov. 2015.

[15] Periard D., Schaal N., Schaal M., Malone E., and Lipson H., “Printing Food,” in Proceedings of the 18th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 2007, pp. 564–574.

[16] Mironov V., Boland T., Trusk T., Forgacs G., and Markwald R. R., “Organ printing: computer-aided jet-based 3D tissue engineering,” Trends in Biotechnology, vol. 21, no. 4, pp. 157–161, Apr. 2003.

[17] Song X., Pan Y., and Chen Y., “Development of a Low-Cost Parallel Kinematic Machine for Multidirectional Additive Manufacturing,” Journal of Manufacturing Science and Engineering, vol. 137, no. 2, p. 21005, Apr. 2015.

[18] Khoshnevis B., Bodiford M., Burks K., Ethridge E., Tucker D., Kim W., Toutanji H., and Fiske M., “Lunar Contour Crafting – A Novel Technique for ISRU-Based Habitat Development,” in 43rd American Institute of Aeronautics and Astronautics Aerospace Sciences Meeting and Exhibit, Reno, Nevada, USA, 2005, vol. 13(1), no. January, pp. 5–19.

[19] Bagsik A. and Schöoppner V., “Mechanical Properties of Fused Deposition Modeling Parts Manufactured with ULTEM 9085,” in Proceedings of the 69th Annual Technical Conference of the Society of Plastics Engineers 2011 (ANTEC 2011), Boston, Massachusetts, USA, 2011, pp. 1294–1298.

Additive Manufacturing 101: What is it?

Image: Centre for Additive Manufacturing - The University of Nottingham

Image: Centre for Additive Manufacturing – The University of Nottingham

  Mechanical Design Engineer and Additive Manufacturing Ph.D. student

This is a series of original articles that will help you understand the origins of the technology that is commonly called 3D printing. First this introduction, followed by the seven main technologies categories (binder jetting, directed energy deposition, material extrusion, material jetting, powder bed fusion, sheet lamination, vat photopolymerization) and then a design philosophy for additive manufacturing.

Introduction

Additive manufacturing (AM) has been called the next Industrial revolution[1]–[3]. It is a recent technology that encompasses a wide range of different processes and materials. It is changing industries like aerospace by adjusting how engineers think about designing complex parts[4]–[6]. This revolution can take designs that have gone unchanged for decades and improve them.

AM was first conceived of in the 1970s with the first parts made in the 1980s and has had many names over the years.

  • Layer manufacturing or LM[7]
  • Rapid manufacturing or RM[8]
  • Rapid tooling[7]
  • Rapid prototyping or RP[8]
  • Laser rapid prototyping[9]
  • Solid freeform fabrication or SFF[10]
  • Direct digital manufacturing or DDM[11]
  • 3D printing or 3DP[12]

Initially, AM was used as a tool to create prototypes much more rapidly than could be done by other means and aided in the development of bringing new products to market[13], [14]. It then helped create tooling, tooling inserts, jigs and fixtures that were used in the manufacturing of end-use parts[7], [8]. It has continued to evolve and now is being used in making end-use parts such as low-volume production plastic casings, high-end consumer in-ear music monitors, GE LEAP jet engine fuel nozzles, and SpaceX SuperDraco rocket engine chambers and Falcon 9 main oxidizer valve bodies which have gone into space.

While AM has been around for three decades, it has yet to be utilized in the manufacturing of electric motors. Since the late 1800s, electric motors have seen only a small number of improvements, most of which have come from new and improved materials and new manufacturing techniques[15]–[18]. Yet the core design of motors has been relatively unchanged [19]–[21]. There is an evident opportunity to research how AM can change electric motor design. AM has the potential to produce new electric motors that can increase motor efficiencies and power densities.

Review of Additive Manufacturing

There are many different types of AM processes. Each has specific strengths and capabilities with unique areas of specialization. Regardless of the process, there are some fundamental principles that all follow.

Subtractive manufacturing usually starts out with a solid chunk of material that is larger than the final desired shape or part. Then using different tools, material is removed (or subtracted) until the final shape or part is achieved. It is important to note that casting is not considered additive or subtractive, but rather a formative process, as an existing mould or pattern is needed to create the final part.

Compared to subtractive, AM works in the opposite way. Instead of removing material to get the final desired shape or part, material is added to a build platform bit by bit. Most forms of AM follow these basic steps:

  1. Take a 3D model
  2. Slice model into layers and generate computer code
  3. Print first 2D slice and supports (if needed)
  4. Increment height
  5. Print next layer
  6. Repeat steps 4-5 until finished
  7. Post process (if needed)

A minor exception to these steps is when an AM process can deposit material in three-dimensional space. It is then not limited to just printing 2D layers one at a time[22]–[25]. AM can be a faster and more economical way to make parts, especially when the part is complex and/or made from an expensive material. These steps are still quite broad and have many details that can provide deeper insight.

AM process steps

Step 1: 3D model

The process begins with a computer-generated 3D model of the desired final part. The model needs to be capable of being printed, which means that it needs to occupy a defined volume. The part can’t be a single surface with a wall thickness of zero. Once it has thickness and volume, it then needs to be an enclosed watertight solid. This means that if water is put in the interior volume of the model, there are no holes from the inside volume to the outside surface. Even objects like a Möbius band or Klein bottle[26] can be printed as long as the single surface is thickened to have a defined watertight volume.

Figure 1: Klein bottle and Mobius band show a surface with no thickness[26]

Once the model is generated correctly, it needs to be saved to a specific file format. These specific file formats are needed in order for it to be prepared properly for printing. Thus it needs to be saved as either an STL file[27], AMF file[28] or 3MF file[29]. The STL file format has been the de facto standard since it was created in the late 1980s. However, it does have limitations which cause some problems. It does not store the units of measurement of the original model so they need to be assumed. Also, the file size becomes very large when trying to save a model with a high level of surface curvature. In response to these limitations, the American Society for Testing and Materials (ASTM) introduced the AMF file format in 2011. Then in 2013, Microsoft intended to do the same with its own 3MF format. This format became natively supported in all Windows operating systems since Windows 8.1. 3MF has since garnered considerable support from large companies such as HP, 3D Systems, Stratasys, GE, Siemens, Autodesk and Dassault Systems although it is unknown how many actively use this file format. Thus STL is still the file format of choice for almost all 3D printing. However, a newly signed liaison agreement between ASTM and the 3MF Consortium may bridge some differences between AMF and 3MF and create one new standard file format to replace STL.

Step 2: Prepare for printing

Secondly, special software is needed to turn that 3D model into data that a 3D printer can recognize and use. This usually involves cutting or slicing the model into many digital layers. Each layer is then converted into either a 2D image or into a set of 2D tool paths. The spacing between these slices will determine the printed thickness of the layers that will be seen in the final part. These layers partially determine the final surface quality and surface roughness of the final part, as well as how long the part will take to print. This height is an important compromise between print speed and surface quality, thus they are generally very thin. An average across several processes is around 100 µm or 0.1mm[11]. Depending on the AM process, the range of layer heights is vast. In two-photon polymerization, layer features as small as 40nm or 0.00004mm[30] can be created which is smaller than the wavelength of ultraviolet light[31]. Microwave sintering can create layers up to 5cm or 50mm in depth[32]. Regardless, when working in a process, the thicker the layer, the faster the build speed but the rougher the exterior becomes. Hence layer height is a trade-off between speed and quality.

Figure 2: T shaped structure with supports[33]

Depending on the geometry of the model and the AM process involved, support structures may be needed[11]. These support structures anchor overhanging areas of the final part to the build platform or other solid portions of the part. Imagine printing a 3D letter “T” starting from the bottom moving up to the top. The 3D printer would be able to print the main body of the letter without any issue. But as soon as it gets to the top, it would have a significant challenge to print the rest properly. The reason being there is nothing that would support the outreached arms of the letter. Thus some type of support structure is needed to be built up at the same time as the main body. When it reaches the point to print the arms, it would then be able to print on top of the main body and the support structure. An alternative option is to design the part for AM so that it does not need supports. For example, if the arms of the “T” were angled upward from the main body, the main body then becomes the support structure. The part would look more like the letter “Y”. Thus the letter Y could be considered a 3D print-optimized version of the letter T that doesn’t need support.

Steps 3-6: Printing

The specifics of printing depend on the process involved and will be described in much more detail further on in the report. Regardless, the 3D printer uses the computer code generated in the previous step to create an initial solid layer of material onto a build surface. The build surface could be a solid platform onto which the part is printed or a layer of unsolidified material that will support the part. This first layer is the first slice of the original 3D model that was calculated by the computer software in step two. Once the first layer is printed, the machine increments to the next height ready to print the next layer. This new height corresponds to the second slice of the original 3D model. The printer then creates a new solid layer based on that second slice. This new solid layer bonds to the previous layer making it one solid piece. The process repeats layer by layer until the final layer is finished. If the bonds between layers are weak, the build could fail or result in a structurally weak part. These anisotropic material properties can manifest as a weaker bond between layers than within layers[34]–[36] but can lead to beneficial properties for magnetic applications[37]. There are some processes strategies[38], [39] and research projects[40] that are addressing this concern with strength.

Step 7: Post-process

Finally, once a part is finished, it is removed from the build chamber and post-processed. This post process could take any number of forms. Some processes require removing support materials[8], [41]. A few need to post cure the material to ensure a fully solid part[42]. Laser melted parts need heat treating to relieve internal stresses that build up in the build process[43]. Binder jetted parts can be placed in an oven to remove a sacrificial binder used in printing. Others are placed in ovens and sintered to increase the strength and density of the part[44]. Infiltrants like glues or metals can be added to give more strength and higher density to the part[42], [44]. Parts can undergo a chemical reaction to change the material for different material properties[45]. Parts can be smoothed by chemicals[42], by blasting or tumbling to remove layer lines. Or parts can have some artistic flourish through hand painting, hydrographics[46], or even electroplating.

Methods and processes

Only recently was a standard designed for classifying the different ways something can be made using AM. In 2009, the American Society for Testing and Materials (ASTM) created a committee to define standards in AM technology[47]. In 2010 they defined seven main technologies used in AM. This was given the standard designation: F2792–12a[48]. As of December 2015, these ASTM standards were replaced with a new standard. ASTM joined with the International Organization for Standardization (ISO) to form ISO/ASTM 52900:2015[49]. Despite having seven uniquely defined categories, there are many different processes within each category. Regardless, the overall method and the underlying principles discussed previously still apply. Variance exists only with the materials, deposition of layers, and methods of adhesion.

These seven categories will be explored in depth with their:

  • definition
  • alternate industrial or trade names
  • a brief history
  • description of method and materials
  • advantages and disadvantages

These seven categories are (in alphabetical order):

  1. binder jetting
  2. directed energy deposition
  3. material extrusion
  4. material jetting
  5. powder bed fusion
  6. sheet lamination
  7. vat photopolymerization

The following are some common terms that are used when talking about these processes. They come from the ISO/ASTM definitions and are used throughout the seven category descriptions[49].

3D printer: the machine used for 3D printing.

Build chamber: the enclosed location within the 3D printer where the parts are fabricated.

Build platform: a base which provides a surface upon which the building of the part is started and supported throughout the build process.

Build space: the location where it is possible for parts to be fabricated, typically within the build chamber or on a build platform.

Build surface: the area where material is added, normally on the last deposited layer or for the first layer, the build surface is often the build platform.

Build volume: the total usable volume available in the machine for building parts.

References:

[1]    N. Hopkinson, R. Hague, and P. Dickens, Rapid manufacturing: an industrial revolution for the digital age. Chichester, England: John Wiley & Sons, 2006.

[2]    T. S. Srivatsan and T. S. Sudarshan, Additive Manufacturing: Innovations, Advances, and Applications. Boca Raton, Florida, USA: CRC Press/Taylor and Francis, 2015.

[3]    B. Berman, “3-D printing: The new industrial revolution,” Business Horizons, vol. 55, no. 2, pp. 155–162, Mar. 2012.

[4]    B. Lyons, Additive Manufacturing in Aerospace: Examples and Research Outlook, vol. 42, no. 1. Washington, D.C., USA: National Academy of Engineering, 2012.

[5]    A. K. Misra, J. E. Grady, and R. Carter, “Additive Manufacturing of Aerospace Propulsion Components,” Additive Manufacturing for Small Manufacturers, Pittsburgh, Pennsylvania, USA, Oct. 2015.

[6]    J. Coykendall, M. Cotteleer, J. Holdowsky, and M. Mahto, “3D opportunity in aerospace and defense: Additive manufacturing takes flight,” Deloitte University Press, Westlake, Texas, USA, Jun. 2014.

[7]    G. N. Levy and R. Schindel, “Overview of layer manufacturing technologies, opportunities, options and applications for rapid tooling,” Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, vol. 216, no. 12, pp. 1621–1634, Jan. 2002.

[8]    G. N. Levy, R. Schindel, and J. P. Kruth, “Rapid Manufacturing And Rapid Tooling With Layer Manufacturing (LM) Technologies, State Of The Art And Future Perspectives,” CIRP Annals – Manufacturing Technology, vol. 52, no. 2, pp. 589–609, Jan. 2003.

[9]    M. Shiomi, A. Yoshidome, F. Abe, and K. Osakada, “Finite element analysis of melting and solidifying processes in laser rapid prototyping of metallic powders,” International Journal of Machine Tools and Manufacture, vol. 39, no. 2, pp. 237–252, Feb. 1999.

[10]  J. J. Beaman, J. W. Barlow, D. L. Bourell, R. H. Crawford, H. L. Marcus, and K. P. McAlea, Solid Freeform Fabrication: A New Direction in Manufacturing. Boston, Massachusetts, USA: Springer US, 1997.

[11]  I. Gibson, D. W. Rosen, and B. Stucker, Additive manufacturing technologies: Rapid Prototyping to Direct Digital Manufacturing. New York, New York, USA: Springer, 2014.

[12]  J.-P. Kruth, M. C. Leu, and T. Nakagawa, “Progress in Additive Manufacturing and Rapid Prototyping,” CIRP Annals – Manufacturing Technology, vol. 47, no. 2, pp. 525–540, 1998.

[13]  G. N. Levy, “SLS-Layer Manufacturing a Powerful Complementary Technology In the RPD (Rapid Product Development) Cycle,” Journal for Manufacturing Science and Production, vol. 3, no. 2–4, pp. 159–166, Jan. 2000.

[14]  A. Bernard and A. Fischer, “New Trends in Rapid Product Development,” CIRP Annals – Manufacturing Technology, vol. 51, no. 2, pp. 635–652, Jan. 2002.

[15]  W. Tong, Mechanical design of electric motors. Boca Raton, Florida, USA: CRC Press/Taylor and Francis, 2014.

[16]  A. Hughes and B. Drury, Electric motors and drives: fundamentals, types and applications, 4th ed. Oxford, United Kingdom: Newnes Press, 2013.

[17]  R. C. O’Handley, Modern Magnetic Materials: Principles and Applications, vol. 830622677. New York, New York, USA: Wiley-Blackwell, 2000.

[18]  O. Gutfleisch, M. A. Willard, E. Brück, C. H. Chen, S. G. Sankar, and J. P. Liu, “Magnetic Materials and Devices for the 21st Century: Stronger, Lighter, and More Energy Efficient,” Advanced Materials, vol. 23, no. 7, pp. 821–842, Feb. 2011.

[19]  W. J. King, “The development of electrical technology in the 19th century,” United States National Museum Bulletin, vol. 228, pp. 233–407, 1962.

[20]  M. Doppelbauer, “The invention of the electric motor 1800-1854,” [Online], 25-Sep-2014. [Online]. Available: http://www.eti.kit.edu/english/1376.php. [Accessed: 04-Dec-2015].

[21]  B. Drury, Control techniques drives and controls handbook, 2nd ed. London, United Kingdom: The Institution of Engineering and Technology, 2009.

[22]  P. F. Yuan, H. Meng, L. Yu, and L. Zhang, “Robotic Multi-dimensional Printing Based on Structural Performance,” in Robotic Fabrication in Architecture, Art and Design 2016, D. Reinhardt, R. Saunders, and J. Burry, Eds. Cham, Switzerland: Springer International Publishing, 2016, pp. 92–105.

[23]  X. Song, Y. Pan, and Y. Chen, “Development of a Low-Cost Parallel Kinematic Machine for Multidirectional Additive Manufacturing,” Journal of Manufacturing Science and Engineering, vol. 137, no. 2, p. 021005, Apr. 2015.

[24]  F. B. Coulter and A. Ianakiev, “4D Printing Inflatable Silicone Structures,” 3D Printing and Additive Manufacturing, vol. 2, no. 3, pp. 140–144, Sep. 2015.

[25]  R. J. A. Allen and R. S. Trask, “An experimental demonstration of effective Curved Layer Fused Filament Fabrication utilising a parallel deposition robot,” Additive Manufacturing, vol. 8, pp. 78–87, Oct. 2015.

[26]  K. Polthier, “Imaging maths-Inside the Klein bottle,” plus magazine, vol. 26, Cambridge, England, 2003.

[27]  J. Allison, “Re: History of .stl format,” [Online email], 15-Jan-1997. [Online]. Available: http://www.rp-ml.org/rp-ml-1997/0091.html. [Accessed: 05-Feb-2016].

[28]  J. D. Hiller and H. Lipson, “STL 2.0: A Proposal for a Universal Multi-Material Additive Manufacturing File Format,” in Proceedings of the 20th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 2009, no. 1, pp. 266–278.

[29]  “What is 3MF?,” 3MF Consortium, 2016. [Online]. Available: http://www.3mf.io/what-is-3mf/. [Accessed: 11-Jan-2016].

[30]  L. Li, R. R. Gattass, E. Gershgoren, H. Hwang, and J. T. Fourkas, “Achieving λ/20 Resolution by One-Color Initiation and Deactivation of Polymerization,” Science, vol. 324, no. 5929, pp. 910–913, May 2009.

[31]  D. Halliday, R. Resnick, and J. Walker, Fundamentals of physics extended, 10th ed., vol. 1. Hoboken, New Jersey, USA: John Wiley & Sons, 2014.

[32]  L. A. Taylor and T. T. Meek, “Microwave Sintering of Lunar Soil: Properties, Theory, and Practice,” Journal of Aerospace Engineering, vol. 18, no. 3, pp. 188–196, Jul. 2005.

[33]  D. Buchbinder, W. Meiners, N. Pirch, K. Wissenbach, and J. Schrage, “Investigation on reducing distortion by preheating during manufacture of aluminum components using selective laser melting,” Journal of Laser Applications, vol. 26, no. 1, p. 012004, 2014.

[34]  B. E. Carroll, T. A. Palmer, and A. M. Beese, “Anisotropic tensile behavior of Ti–6Al–4V components fabricated with directed energy deposition additive manufacturing,” Acta Materialia, vol. 87, pp. 309–320, Apr. 2015.

[35]  A. Bagsik and V. Schöoppner, “Mechanical Properties of Fused Deposition Modeling Parts Manufactured with ULTEM 9085,” in Proceedings of the 69th Annual Technical Conference of the Society of Plastics Engineers 2011 (ANTEC 2011), Boston, Massachusetts, USA, 2011, pp. 1294–1298.

[36]  W. Cooke, R. Anne Tomlinson, R. Burguete, D. Johns, and G. Vanard, “Anisotropy, homogeneity and ageing in an SLS polymer,” Rapid Prototyping Journal, vol. 17, no. 4, pp. 269–279, Jun. 2011.

[37]  M. Garibaldi, I. Ashcroft, M. Simonelli, and R. Hague, “Metallurgy of high-silicon steel parts produced using Selective Laser Melting,” Acta Materialia, vol. 110, no. MAY, pp. 207–216, May 2016.

[38]  B. A. Fulcher, D. K. Leigh, and T. J. Watt, “Comparison of AlSi10Mg and Al 6061 Processed Through DMLS,” in Proceedings of the 25th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 2014, pp. 404–419.

[39]  P. Mercelis and J. Kruth, “Residual stresses in selective laser sintering and selective laser melting,” Rapid Prototyping Journal, vol. 12, no. 5, pp. 254–265, Oct. 2006.

[40]  S. Fathi, P. Dickens, R. Hague, K. Khodabakhshi, and M. Gilbert, “Jetting of Reactive Materials for Additive Manufacturing of Nylon Parts,” in Proceedings of the 25th International Conference on Digital Printing Technologies and Digital Fabrication (NIP 25), Louisville, Kentucky, USA, 2009, vol. 2009, no. 2, pp. 784–787.

[41]  S. S. Crump, J. W. Comb, W. R. Priedeman Jr, and R. L. Zinniel, “Process of support removal for fused deposition modeling,” U.S. Patent 5,503,785, 02-Apr-1996.

[42]  S. Upcraft and R. Fletcher, “The rapid prototyping technologies,” Assembly Automation, vol. 23, no. 4, pp. 318–330, Dec. 2003.

[43]  E. Brandl, U. Heckenberger, V. Holzinger, and D. Buchbinder, “Additive manufactured AlSi10Mg samples using Selective Laser Melting (SLM): Microstructure, high cycle fatigue, and fracture behavior,” Materials & Design, vol. 34, pp. 159–169, Feb. 2012.

[44]  J.-P. Kruth, G. Levy, F. Klocke, and T. H. C. Childs, “Consolidation phenomena in laser and powder-bed based layered manufacturing,” CIRP Annals – Manufacturing Technology, vol. 56, no. 2, pp. 730–759, Jan. 2007.

[45]  A. E. Jakus, S. L. Taylor, N. R. Geisendorfer, D. C. Dunand, and R. N. Shah, “Metallic Architectures from 3D-Printed Powder-Based Liquid Inks,” Advanced Functional Materials, vol. 25, no. 45, pp. 6985–6995, Dec. 2015.

[46]  Y. Zhang, C. Yin, C. Zheng, and K. Zhou, “Computational hydrographic printing,” ACM Transactions on Graphics (TOG) – Proceedings of ACM SIGGRAPH 2015, vol. 34, no. 4, pp. 131:1–131:11, Jul. 2015.

[47]  W. E. Frazier, “Metal Additive Manufacturing: A Review,” Journal of Materials Engineering and Performance, vol. 23, no. 6, pp. 1917–1928, Jun. 2014.

[48]  “ASTM F2792-12a, Standard Terminology for Additive Manufacturing Technologies, (Withdrawn 2015),” ASTM International, West Conshohocken, Pennsylvania, USA, 2012.

[49]  “ISO/ASTM 52900:2015(en), Additive manufacturing — General principles — Terminology,” International Organization for Standardization (ISO), Geneva, Switzerland, 2015.

LLNL researchers first to 3D print aerospace-grade carbon fiber composites

Lawrence Livermore National Laboratory (LLNL) researchers have become the first to 3D print aerospace-grade carbon fiber composites, opening the door to greater control and optimization of the lightweight, yet stronger than steel material.

The research, published by the journal Scientific Reports online on March 6, represents a “significant advance” in the development of micro-extrusion 3D printing techniques for carbon fiber, the authors reported.

“The mantra is ‘if you could make everything out of carbon fiber, you would’ — it’s potentially the ultimate material,” explained Jim Lewicki, principal investigator and the paper’s lead author. “It’s been waiting in the wings for years because it’s so difficult to make in complex shapes. But with 3D printing, you could potentially make anything out of carbon fiber.”

3D

A carbon fiber composite ink extrudes from a customized direct ink writing (DIW) 3D printer, eventually building part of a rocket nozzle.

Carbon fiber is a lightweight, yet stiff and strong material with a high resistance to temperature, making the composite material popular in the aerospace, defense and automotive industries, and sports such as surfing and motorcycle racing.

Carbon fiber composites are typically fabricated one of two ways — by physically winding the filaments around a mandrel, or weaving the fibers together like a wicker basket, resulting in finished products that are limited to either flat or cylindrical shapes, Lewicki said. Fabricators also tend to overcompensate with material due to performance concerns, making the parts heavier, costlier and more wasteful than necessary.

However, LLNL researchers reported printing several complex 3D structures through a modified Direct Ink Writing (DIW) 3D printing process. Lewicki and his team also developed and patented a new chemistry that can cure the material in seconds instead of hours, and used the Lab’s high performance computing capabilities to develop accurate models of the flow of carbon fiber filaments.

“How we got past the clogging was through simulation,” Lewicki said. “This has been successful in large part because of the computational models.”

Computational modeling was performed on LLNL’s supercomputers by a team of engineers who needed to simulate thousands of carbon fibers as they emerged from the ink nozzle to find out how to best align them during the process.

“We developed a numerical code to simulate a non-Newtonian liquid polymer resin with a dispersion of carbon fibers. With this code, we can simulate evolution of the fiber orientations in 3D under different printing conditions,” said fluid analyst Yuliya Kanarska. “We were able to find the optimal fiber length and optimal performance, but it’s still a work in progress. Ongoing efforts are related to achieving even better alignment of the fibers by applying magnetic forces to stabilize them.”

The ability to 3D print offers new degrees of freedom for carbon fiber, researchers said, enabling them to have control over the parts’ mesostructure. The material also is conductive, allowing for directed thermal channeling within a structure. The resultant material, the researchers said, could be used to make high-performance airplane wings, satellite components that are insulated on one side and don’t need to be rotated in space, or wearables that can draw heat from the body but don’t allow it in.

“A big breakthrough for this technology is the development of custom carbon fiber-filled inks with thermoset matrix materials,” said materials and advanced manufacturing researcher Eric Duoss. “For example, epoxy and cyanate ester are carefully designed for our printing process, yet also provide enhanced mechanical and thermal performance compared to thermoplastic counterparts that are found in some commercially available carbon fiber 3D printing technologies, such as nylon and ABS (a common thermoplastic). This advance will enable a broad range of applications in aerospace, transportation and defense.”

The direct ink writing process also makes it possible to print parts with all the carbon fibers going the same direction within the microstructures, allowing them to outperform similar materials created with other methods done with random alignment. Through this process, researchers said they’re able to use two-thirds less carbon fiber and get the same material properties from the finished part… more

SOURCE – Lawrence Livermore National Laboratory