This being the first blog entry, what better way to start than by reviewing the steps that have been taken to reach the current ecosystem of technology. Under the same name of Additive Manufacturing or 3D Printing, we have different ways of transforming matter that may or may not share scientific principles between them. How were they originally formulated? How has each process evolved? What companies have been born from each technology?
We divide the entry into three parts coinciding with important milestones. The first part explores the foundations on which the technologies are built. The second part deals with the commercialisation of the machines and the creation of major players in the industry. The third part is about democratisation and opening up the world of additive manufacturing thanks to the end of patents.
Part I. Prehistory.
The decade 2010-2020 has been the decade in which 3D printing has leapt into the limelight, leaving the workshops of industrial companies to the world: today it is found in homes, architecture and design studios and even on our streets, giving us the feeling that it has just been invented. However, the scientific community agrees in referring the beginning of this path to the middle of the 19th century . We are therefore talking about 150 years of experimentation and development.
The origins and the first experiments.
We could say that the first device for creating three-dimensional objects dates from the middle of the 19th century and was the work of the French sculptor and photographer François Willème. 24 cameras equidistant from the element to be sculpted took the images which, once their silhouettes had been cut out and arranged on a common axis, gave us a 360º outline over the whole height on which to work with a material.
This development is interesting as it is an analogue way of scanning objects and making them volumetrically from a reverse engineering approach, with the very goal that we use technology for today: to gain accuracy and save time.
In 1864 he was granted a patent in the United States , although the technique was not of great commercial interest and was not developed for other fields beyond the sculpture of people. Nevertheless, his obituary refers to his invention.
In 1890, cartographer Joseph E. Blanther filed a patent for a method of producing three-dimensional relief maps . The new military strategies required a more accurate knowledge of the terrain than that provided by a 2D map, which, while giving an idea of the geography, was not as visual.
It was based on layering, one at a time, by cutting contoured wax plates that were melted in layers and then smoothed on the outer surfaces. Now we are talking about working in layers, but as in Willème’s patent, we need to carry out certain manual operations to obtain the final result.
Moreover, in both cases, the object of the invention is oriented towards specific fields: sculpture and cartography, so that other sectors could hardly apply these techniques for their purposes. From these two disciplines, a number of patents arise that delve into the concept of successive layers. This timeline is described in depth by Beaman et al .
Already in the 20th century, we find a development to manufacture objects by adding successive layers, by R. Baker in the year 1920 with a patent application for electric arc metal deposition technology . This already refers to “decorative articles”, giving us an idea that a wide range of objects can be manufactured, with a greater potential for further development.
It was chemistry that came into play in the 1950s, when the DuPont company invented the photopolymer resin , which served as the basis for the development of different techniques based on lasers during the 1950s, 1960s and 1970s. It can be said that it is in this period that the first attempts were made to polymerise a resin, although the degree of development of the technology and its commercialisation were still primitive and served above all to lay the scientific foundations for what was to come later.
In 1951, Otto John Munz invented a technique consisting of stacking a series of 2D photographs printed on a photosensitive emulsion . Each of these projected images, corresponding to a cross-section of the object to be printed, is selectively exposed to the photosensitive medium. 
The breakthrough is that the system already has a piston that gradually descends in Z with each layer that is added, one of the operating principles of modern machines. One of the disadvantages was that precisely this piston had to be removed along with the entire medium and either carved or subjected to a photochemical process to obtain the shape of the object in question.
A series of experiments by W. K. Swainson in the late 1960s at the Battelle Memorial Institute, called “photochemical machining”, aimed to solidify the resin in a tank at the point of intersection of two lasers of different wavelengths by means of cross-linking or polymer degradation . This is the beginning of the work on the subject with lasers. In the 1971 patent , terms such as galvanometer-controlled mirror or laser scanning strategies are already mentioned.
In 1971, the Frenchman Pierre Ciraud applied for a patent  for a method of manufacturing “any meltable material” by solidifying it using a source of energy from a laser beam. This is the first development based on the transformation of materials from powder form, and can be considered as a precursor of Laser Cladding of the DED family.
Ciraud himself describes it as an invention that makes it possible to manufacture parts with extremely complex shapes without the need for casting moulds .
R. Housholder applied for a patent in 1979  which included the description of a system and method that can be considered as the forerunner of selective sintering technology. The stated object of the invention was “to provide a new and unique moulding process for forming three-dimensional articles three-dimensionally in layers and whose process can be controlled by modern technology such as computers”. We continue with powder as the raw material but in this case the laser, controlled by a computer, performs an x-y path along an added layer of powder.
Due to the very high cost of lasers at the time, and the fact that computers were still being developed, his invention did not attract much attention. It was only later, when the DTM company discovered it and licensed the patent, that it began to be marketed under the name SLS .
We come to 1981 with one of the key names. Hideo Kodama of the Nagoya Municipal Industrial Research Institute published an article  in which he experimented with the solidification of a photosensitive resin with an x-y plotter guiding the optical fibre as a source of UV rays.
Shortly afterwards, still in 1981, he published a second article  in which he described the technology in more detail with three different methods.
(a) Using a mask for UV exposure control. The platform is lowered.
(b) Using a mask for UV exposure control, but positioned below. The platform descends.
(c) With the platform descending but using an x-y plotter and fibre optics for the exposure of a new layer.
He mentions familiar parameters such as wavelength, focal diameter, layer height, exposure time, resin viscosity and even substrates. He emphasises the possibilities of creating quite complex structures in a short time and at low cost, without excessive manual labour. The image shows a 20 x 20 x 12.5 mm piece made with 5 layers of 2.5 mm thickness. 96 minutes per layer, total 8h.
In April 1980, Hideo Kodama had already filed a patent application  which was later stalled, according to some sources, due to a lack of funding to ensure further testing and development. Nevertheless, he is considered a pioneer in the approach of stacking successive layers solidified with an ultraviolet source, to the extent that he received recognition from his colleagues at the IECE (Institute of Electronics, Information and Communication Engineers) in Japan in 2014 for his work in the early development of 3D printing technology .
Throughout the 1980s this idea would take shape in other heads in Europe and the United States to give birth to the commercialisation of additive manufacturing technology and serve industry beyond experimentation.
 J. Breuninger, R. Becker, A. Wolf, S. Rommel, A. Verl, et al. Generative Fertigung mit Kunststoffen: Konzeption und Konstruktion fr selektives Lasersintern, Springer Vieweg, Berlin (2013)
 D.L. Bourell, J.J. Beaman, Jr., M.C. Leu, and D.W. Rosen, A Brief History of Additive Manufacturing and the 2009 Roadmap for Additive Manufacturing: Looking Back and Looking Ahead (US, Turkey Workshop on Rapid Technologies, 2009).
 F. Wilème. Photographing sculpture US43822. Aug. 9, 1864
 J E. Blanther. Manufacture of contour relief maps. US473901. May. 3, 1892
 R. Baker. Method of making decorative articles. US 1,533,300, Filed Nov. 12, 1920
 O. J. Munz. Photo-glyph recording. US2775758. Filed May. 25, 1951.
 O. Diegel, A. Nordin, D. Motte. A Practical Guide to Design for Additive Manufacturing. Springer (2019)
 W.K. Swainson. Method, medium and apparatus for producing three dimensional figure product. US4041476. Filed Jul. 23, 1971
 A. Ciraud, Process and Device for the Manufacture of any Objects Desired from any Meltable Material, FRG Disclosure Publication 2263777. Filed Dec. 28, 1971
 M. Shellabear & O. Nyrhilä, DMLS – “Development History and State of the Art,” presented at LANE 2004 conference, Erlangen, Germany, Sept. 21-24, 2004
 R. Housholder. Molding process. US4247508. Filed Dec. 3, 1979
 Hideo Kodama. “A Scheme for Three-Dimensional Display by Automatic Fabrication of Tree-Dimensional Model” .IEICE Transactions on Electronics, Vol.J64-C No.4, pp.237-241, April 1981.
 H. Kodama. “Automatic method for fabricating a threedimensional plastic model with photo hardening polymer”. Rev. Sci. Instrum, Vol. 52, No. 11, pp 1770-1773. Nov. 1981
 H. Kodama. Stereoscopic figure drawing device. JPS56144478A. Filed Apr. 12th, 1980