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Additive Manufacturing 101-7: What is vat photopolymerization?
Vat Photopolymerization (Image: 3D Hubs)
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 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?
Material Jetting (Image: 3D Hubs)
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?
Powder Bed Fusion (Image: 3D Hubs)
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?
Material Jetting (Image: 3D Hubs)
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?
Material Extrusion (Image: 3D Hubs)
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]
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 101-2: What is directed energy deposition?
Directed Energy Deposition (Image: 3D Hubs)
Directed Energy Deposition
ISO/ASTM definition: “directed energy deposition, —an additive manufacturing process in which focused thermal energy is used to fuse materials by melting as they are being deposited. “Focused thermal energy” means that an energy source (e.g., laser, electron beam, or plasma arc) is focused to melt the materials being deposited.”[1]
Directed Energy Deposition or DED can also be known as (in alphabetical order):
➢ 3D Laser Cladding[2]
➢ Cold Gas Dynamic Spray[3]*
➢ Cold Spray[4]*
➢ Direct Laser Deposition or DLD[5]
➢ Direct Laser Fabrication[5]
➢ Direct Metal Deposition or DMD® (DM3D Technology, LLC)[5]
➢ Directed Light Fabrication or DLF[5]
➢ Electron Beam Additive Manufacturing or EBAM ™ (Sciaky, Inc.)
➢ Electron Beam Freeform Fabrication or EBF3[6]
➢ Focused Ion Beam Direct Writing or FIBDW[7]
➢ Metal Powder Application or MPA (Hermle Maschinenbau GmbH)
➢ Laser Chemical Vapor Deposition or LCVD[8]
➢ Laser Consolidation or LC [9]
➢ Laser Deposition Welding[10]
➢ Laser Engineered Net Shaping or LENS® (Sandia National Labs)[5], [11]
➢ Laser Metal/Melting Deposition or LMD[5]
➢ Laser Powder Forming[12]
➢ Laser Rapid Forming[5]
➢ Powder Fusion Welding[13]
➢ Shape Welding[14]
➢ Shape Deposition Manufacturing or SDM[15]
➢ Three-Dimensional Welding[16]
➢ Wire Arc Additive Manufacturing or WAAM[17]
*An additive manufacturing process in which kinetic energy is used to fuse materials by plastic deformation as they are being deposited. “Kinetic energy” means the energy contained by the material that is being deposited at high velocity and is released at the time the material contacts a solid surface.
From 1994-1997 in New Mexico USA, Sandia National Laboratories developed a new AM technology which they called LENS. It differed quite a bit from all other AM technologies at the time and spawned a number of similar processes like DMD, which was commercialized in 2002 by POM Group based in Michigan USA. These other processes use many different names in an attempt to differentiate themselves; DLD, LC, LMD, DLF and more, but can be understood the same as LENS. LCVD is a completely different process from LENS and has its origins in the 1980s, but it wasn’t used to build actual 3D parts until the early 1990s. Three-dimensional welding has its roots in 1960s Germany where parts were built up using welders, but it wasn’t specifically used in AM until in the 1990s[14]. In 2002, engineers at NASA developed a system that uses electron beams and solid wire feedstock to create parts that could potentially be made in space without gravity called EBF3. Since 2013 researchers have been investigating the use of cold spray techniques in AM as an alternative to thermally based fusion methods.
Figure 1: Example of a directed energy deposition system’s basic components, LENS (top) and EBF3 (below)[18]
Directed energy deposition processes look very different between each method, but the premise is the same in each case. First, there is a focused area of intense energy, usually a thermal energy source like a laser, electron beam, or TIG welding torch. A feedstock material is introduced into that intense energy area causing it to bond to the surrounding material. This feedstock can be introduced either through blowing powder into that area like with the LENS or cold spray process, by pushing a solid wire into that area like with EBF3 and WAAM, or by introducing a special gas into the build chamber like with LCVD or FIBDW. The bonding mechanism varies in each process as well. In LENS and related methods, the powder enters into a melted pool of material and initially sticks to it and then melts to join the melt pool which will then cool and solidify. With EBF3 and WAAM, the wire melts and binds to the previous layers and then cools and solidifies. With LCVD and FIBDW, either a laser or an ion beam heats a spot on the build surface to a high enough temperature to thermally decompose a halide gas compound. This special gas then deposits half of itself onto the build surface, while the other half combines with a reducing chemical in the air like hydrogen to form a secondary gas compound. With the cold spray process, material is deposited at very high velocities onto the build surface and then plastically deforms and bonds onto the part.
Several different processes fall into this category, so advantages depend on the process. With the powder blowing method, powders can be changed or mixed mid-build thus creating multiple materials in a build, even creating a gradient between two different materials in the same build. This can also occur in LCVD or FIBDW by evacuating the build chamber from one gas, and putting in a different one thus making multiple materials possible. LENS type processes are able to aid in the repair of damaged parts that normally could not have been repaired using traditional methods. It can roughly add material to the damaged areas which are then cleaned up and machined to tolerance afterwards. Some of these processes like EBF3 and WAAM can also be used to develop near net shape parts that can then be machined to final tolerance without the traditional waste associated with subtractive manufacturing from a solid block. Some of these processes can also be used in space without the need for gravity like EBF3 and cold spray.
Again disadvantages range between processes. All of these processes require material to be deposited one spot at a time, and cannot do entire layers all at one time; tool paths are needed to complete each layer. Consequently build speeds are limited and somewhat slow. LCVD is especially slow due to the decomposition process and limited material deposited by it. These processes do not lend themselves to create support structures, so certain geometries with overhangs may not be created. Resolutions are generally very low and have a rough surface finish that may need post-processing like machining to get tight tolerances.
References
[1] “ISO/ASTM 52900:2015(en), Additive manufacturing — General principles — Terminology,” International Organization for Standardization (ISO), Geneva, Switzerland, 2015.
[2] Murphy M. L., Steen W. M., and Lee C., “The Rapid Manufacture of Metallic Components by Laser Surface Cladding,” in Proceedings of the Laser Assisted Net Shape Engineering Conference (LANE’94), Erlangen, Germany, 1994, vol. 2, pp. 803–814.
[3] Sova A., Grigoriev S., Okunkova A., and Smurov I., “Potential of cold gas dynamic spray as additive manufacturing technology,” The International Journal of Advanced Manufacturing Technology, vol. 69, no. 9–12, pp. 2269–2278, Dec. 2013.
[4] Lupoi R. and O’Neill W., “Deposition of metallic coatings on polymer surfaces using cold spray,” Surface and Coatings Technology, vol. 205, no. 7, pp. 2167–2173, Dec. 2010.
[5] 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.
[6] Taminger K. M. and Hafley R. A., “Electron Beam Freeform Fabrication for Cost Effective Near-Net Shape Manufacturing,” in Specialists’ Meeting on Cost Effective Manufacture via Net Shape Processing (NATO/RTO AVT-139), Amsterdam, The Netherlands, 2006, p. 16:1-10.
[7] Matsui S., Kaito T., Fujita J., Komuro M., Kanda K., and Haruyama Y., “Three-dimensional nanostructure fabrication by focused-ion-beam chemical vapor deposition,” Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, vol. 18, pp. 3181–3184, 2000.
[8] Williams K., Maxwell J., Larsson K., and Boman M., “Freeform fabrication of functional microsolenoids, electromagnets and helical springs using high-pressure laser chemical vapor deposition,” in Proceedings of the 12th IEEE International Conference on Micro Electro Mechanical Systems (MEMS ’99), Orlando, Florida, USA, 1999, pp. 232–237.
[9] Xue L. and Islam M. U., “Laser Consolidation – A Novel One-Step Manufacturing Process for Making Net-Shape Functional Components,” in Specialists’ Meeting on Cost Effective Manufacture via Net Shape Processing (NATO/RTO AVT-139), Amsterdam, The Netherlands, 2006, p. 15:1-14.
[10] Kaierle S., Barroi A., Noelke C., Hermsdorf J., Overmeyer L., and Haferkamp H., “Review on Laser Deposition Welding: From Micro to Macro,” Physics Procedia, vol. 39, pp. 336–345, 2012.
[11] Griffith M. L., Keicher D. M., Atwood C. L., Romero J. A., Smugeresky J. E., Harwell L. D., and Greene D. L., “Free Form Fabrication of Metallic Components Using Laser Engineered Net Shaping (LENS),” in Proceedings of the 7th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 1996, pp. 125–132.
[12] Liu Q., Leu M. C., and Schmitt S. M., “Rapid prototyping in dentistry: technology and application,” The International Journal of Advanced Manufacturing Technology, vol. 29, no. 3–4, pp. 317–335, Jun. 2006.
[13] Bohrer M., Basalka H., Birner W., Emiljanow K., Goede M., and Czerner S., “Turbine blade repair with laser powder fusion welding and shape recognition,” in Proceedings of the 2002 International Conference on Metal Powder Deposition for Rapid Manufacturing, San Antonio, Texas, USA, 2002, pp. 142–150.
[14] Dickens P. M., Pridham M. S., Cobb R. C., Gibson I., and Dixon G., “Rapid Prototyping Using 3D Welding,” in Proceedings of the 3rd Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 1992, pp. 280–290.
[15] Fessler J., Nickel A., Link G., Prinz F., and Fussell P., “Functional gradient metallic prototypes through shape deposition manufacturing,” in Proceedings of the 8th Solid Freeform Fabrication Symposium (SFF), Austin, Texas, USA, 1997, pp. 521–528.
[16] Spencer J. D., Dickens P. M., and Wykes C. M., “Rapid prototyping of metal parts by three-dimensional welding,” Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, vol. 212, no. 3, pp. 175–182, Jan. 1998.
[17] Wang F., Williams S., Colegrove P., and Antonysamy A. a., “Microstructure and Mechanical Properties of Wire and Arc Additive Manufactured Ti-6Al-4V,” Metallurgical and Materials Transactions A, vol. 44, no. 2, pp. 968–977, Feb. 2013.
[18] Frazier W. E., “Metal Additive Manufacturing: A Review,” Journal of Materials Engineering and Performance, vol. 23, no. 6, pp. 1917–1928, Jun. 2014.
Management Issues Survey 2016
Shaping the future of Canadian manufacturing and exporting
Dear Colleague:
The world of manufacturing and exporting is undergoing a transformation. Innovation and new technologies have not only changed the nature of industrial activity in Canada, they have dramatically altered the very definition of what it means to be a manufacturer.
At the same time, Canadian businesses are struggling with profound economic uncertainty. Lower oil prices, exchange rate and equity market volatility, a slowing global economy, and new government policies aimed at pricing carbon are all impacting business and casting a shadow over future investment plans.
To effectively meet these challenges, we must first understand the core priorities of businesses and explore their outlook for the future.
I invite you to join Canadian Manufacturers & Exporters (CME) and the Canadian Manufacturing Coalition, as well as our partners Food & Consumer Products of Canada (FCPC), BDO Canada LLP, Bombardier and Tenaris in developing a common vision and strategy for the future of Canadian manufacturing and global business.
Our bi-annual Management Issues Survey asks you about your company¹s current operations, your top challenges, and how you are addressing them in the current business environment. We want to know about the issues that are keeping organizations from growing, becoming more innovative, attracting and retaining skilled employees, and reaching new markets.
Your responses are central to informing our engagement strategies with governments as we work to build a world-class business environment for Canadian industry and strengthen our ability to compete globally.
This year we need your support more than ever. CME has undertaken an ambitious initiative called Industrie 2030. Its goal is to create a roadmap to double value-added manufacturing output and exports in Canada by 2030. The Management Issues Survey is a critical component of that initiative. Survey results will be published in combination with our Industrie 2030 action plan during Manufacturing Month in October.
Please help us help you by filling out the survey and sharing it with your network. The survey will take only 30 minutes to complete and your responses will be held strictly confidential. The deadline for completion is August 15, 2016. By submitting your email address, you will receive a copy of the follow-up report when it is published later this year.
Take the survey today, visit: www.surveymonkey.com/r/6VRP77V
Thank you in advance for your input and support.
Sincerely,
Jayson Myers
President & CEO
Canadian Manufacturers & Exporters (CME)
Thank you to our National Partners:
