Stereolithography / 3D Printing / Additive Fabrication
Stereolithography is an imaging process in three dimensions. Some synonyms used for stereolithography include 3D printing, optical fabrication, photosolidification, solid freeform fabrication, solid imaging, optical shaping, steric polymerization, desk-top manufacturing, additive manufacturing, automatic modeling, electron beam melting, digital part materialization, freeforming etc. Besides 3D printing, commonly accepted term for this process is additive manufacturing (AM). We propose the term “additive fabrication” since manufacturing connotes mass production and current 3D printing is anything but that
The U.S. Patent 2,775,758 issued to John Munz in 1956 disclosed a process to produce three-dimensional reproductions using a light-sensitive “emulsion” in a container. The process was referred to as “photo-glyph recording”. In 1950s and 1960s, DuPont Company was awarded a number of patents for making solid printing plates using a variety of photopolymers and UV light exposure. Subsequently, a number of inventors attempted to make solid objects using photopolymers and UV lasers. However, it was Charles W. Hull who commercialized his invention in 1980s by setting up 3D Systems
The term “stereolithography” was coined by Chuck Hull, in his US Patent 4,575,330, entitled “Apparatus for Production of Three-Dimensional Objects by Stereolithography” issued in 1986. Stereolithography was defined as a method and apparatus for making solid objects by successively “printing” thin layers of the curable material, e.g., a UV-curable material, one on top of the other.
In Hull’s patent, a concentrated beam of ultraviolet light is focused onto the surface of a vat filled with liquid photopolymer. The light beam, moving under computer control, draws each layer of the object onto the surface of the liquid. Wherever the beam strikes the surface, the photopolymer polymerizes/crosslinks and changes to a solid. An advanced CAD/CAM/CAE software mathematically slices the computer model of the object into a large number of thin layers. The process then builds the object layer by layer starting with the bottom layer, on an elevator that is lowered slightly after solidification of each layer.
Non-photopolymer-based rapid prototyping processes include fusion deposition modeling (FDM®), laser sintering, an inkjet system, electron beam melting and the new Arburg Plastic Freeforming. The FDM process developed by Stratasys extrudes a thin thermoplastic filament layer by layer. Laser sintering process uses data from a CAD/CAM/CAE system and laser technology to transform a variety of powdered materials into three-dimensional prototypes. Selective laser sintering (SLS ®) involves the use of a high power laser to fuse small particles of plastics, metal, ceramic or glass powders into a solid object. An inkjet equipment marketed by Z Corp. (now part of 3D Systems) builds models by depositing a binder solution through an inkjet print head onto layers of a plaster-based powder. A US company is developing a desk top 3D printer using liquid metal jet printing technology. Objet Geomeries’ (now merged with Stratasys) 3D printers use inkjetters of photopolymers. In laminated object manufacturing (LOM), layers of adhesive-coated paper, plastics or metal laminates are successively bonded together and cut to shape with a knife or a laser.
A variety of liquid photopolymers are available for stereolithography. Epoxy-based systems and hybrids are now preferred to older acrylates because of former’s higher green strength, higher temperature resistance, lower moisture absorption and lower shrinkage. Radiation-cured acrylates also suffer from oxygen inhibition. The hybrids cure under light by cationic as well as free radical polymerization. Photopolymer resins with mechanical properties similar to engineering plastics such as ABS, nylon and polycarbonate are available.
Besides rapid prototyping, 3D printing is now used for rapid manufacturing of small production runs. Both photopolymer-based as well as non-photopolymer-based processes are now used for short run manufacturing. Our forecast made six years ago that “Soon desktop 3D printers will be available to consumers to make small appliance parts or toys at home!” has materialized. A proliferation of 3d printer manufacturers has made printers now available for DIY-ers, teachers, artists, hobbyists and consumers. A list of printer manufacturers, large and small, include those shown below:
Manufacturers of 3D Printers/Additive Fabricators
|USA||Germany||Netherlands||Rest of World|
|3D Systems||Arburg||Cartesio||3D Stuffmaker, Australia|
|Afinia||EnvisionTEC||Leapfrog||3D Robotics, Singapore|
|Airwolf 3D||F&S Stereolithographietechnik||Mauk Custom Creations||3Dfactories, Czech Republic|
|Aleph Objects||SLM Solutions||Azuma Machinery, Japan|
|Cubic Technologies||Concept Laser||Beijing Tiretime Technology, China|
|DeltaMaker||bq witbox, Spain|
|Isis 3D||Makism 3D Corp., UK|
|MakerBot||Marcha Technology, Spain|
|MakiBox||Mcor Technologies, Ireland|
|Organovo Holdings||Omni3D, Poland|
|Pop Fab||Rapide 3D, Hong Kong|
|QU-BD||Robot Factory, Italy|
|RoBo 3D||Solido 3D, Israel|
|Stratasys||Ion Core, UK|
|Type A Machines|
|Old World Labs.|
An initiative known as RepRap (short for replicating rapid prototyper) has brought together a community of hobbyists to build a 3D printer which prints copies of its own parts. The initiative has an open-source policy. The project calls its process Fused Filament Fabrication (FFF) to avoid trademark issues around the “fused deposition modeling” term. As of 2013, the RepRap project has released four official 3D printing machines. The project envisions the possibility of cheaply distributing RepRap units to people and communities, enabling them to create (or download from the Internet) complex products without the need for expensive industrial infrastructure. RepRaps prints objects from filaments made of ABS, PLA, nylon, HDPE and other thermoplastics. RepRap was the first of the low-cost 3D printers, and the RepRap Project started the open-source 3D printer revolution.
Estimated worldwide 2013 desktop/personal printer sales are in the range of 80,000 units worldwide. These are used by teachers, students, consumers, designers, hobbyists and do-it-yourselfers to imagine, design and print their ideas at their desks. In addition, about 10,000 industrial printers were sold for making prototypes, aerospace and automotive components, molds, parts for dental and hearing aid applications, body prosthesis, jewelry etc.
The U.S. President Obama in his State of The Union Address in early 2013stated that “A once-shuttered warehouse is now a state-of-the art lab where new workers are mastering the 3D printing that has the potential to revolutionize the way we make almost everything”. The Economist magazine dated August 21st, 2012 has predicted that ‘factories of the future will have 3D printers working alongside milling machines, presses, foundries and plastic injection molding equipment in the business of making things.’ These statements have caused a lot of hype about 3D printing and some new products fall on the border line to be called 3D-printed. For example, a new disposable underwear produced by a UK company is claimed to be made by 3D printing. It is produced by spraying textile fibers along with binders in an automated process. The process, however, would have significant overspray of raw materials. By that reasoning, all composite/FRP structures such corrugated sheets, bath tubs etc. made by automated spraying of chopped glass fibers and a resin binder can be claimed to be made by 3D printing! Also, process of making filament-wound FRP containers which uses continuous glass filament and a binder may qualify to be called continuous 3D printing!
In 2012, Voxeljet’s first commercially available continuous 3D printer VXC800 was launched. This innovation establishes a completely new generation of machines that allows the building and unpacking process steps to run at the same time, without having to interrupt the operations of the system.
In late 2013, the German plastics machine manufacturer, Arburg, with more than $650 million in annual sales, introduced its first 3D printing machine called freeformer using its own Arburg Plastic (kunststoff) Freeforming (AKF) process which produces parts directly from plastics granules. The discharge unit, incorporating an extruder and a nozzle, remains steady and the component carrier moves. This new additive manufacturing process could be a game changer in 3D printing and may bring about a revolution in small volume thermoplastic parts production. The machine uses all kinds of thermoplastics including thermoplastic elastomers except fiber-reinforced types.
3D printing is thriving and will continue to thrive for the foreseeable future. Only time will tell whether the major growth will come from manufacturing or in fabrication of parts, products and things not possible to make otherwise economically such as body parts, food items in space, one-of-a-kind art objects, personalized shoes, personal clones etc.
A recent CNN video clip describes the process briefly on the following Youtube link:
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