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Additive Manufacturing is the process of creating objects by adding material as opposed to Subtractive Manufacturing which is the process of taking away material in order to create said objects. After the invention of Stereolithography by Chuck Hull, the C.T.O of 3D Systems, 3D printing took off into a race to become the most economic and innovative form of prototyping.
The exponential progress in additive manufacturing is partially accredited to the power behind its’ availability for open-source hardware and software. 3D printers are now so widely available that even today’s students are being taught how the process of Additive Manufacturing works , which can lead to newer, younger minds employing never thought of solutions with potentials that will ultimately lead to increased efficiencies in the user interfaces for open source 3D printers. Instead of a slow corporate approach to remodeling the infrastructure and layout of a system, open-source hardware allows for a faster more natural evolution that is more closely tethered to the likes or dislikes of the primary users. In this form of thinking, the system technically employs thousands of engineers and coders for no charge and only with the goal of creating a more streamlined and efficient design .
Such is the integration of complex infills for 3D printing. Infills make up the area between walls in additive manufacturing which would range from being completely solid or with a complex geometry in the case of a load-bearing structure, or empty in the case of a lightweight, topologically optimized device.
In the image shown above, you can see a gyroid structure. Recently, they are being used as infill material due to their geometric properties. Gyroid structures were discovered by NASA scientist Alan Schoen and contained a minimal surface area geometry that, at the same time, had a high strength and toughness factor. Gyroid structures are said to be the future of combining mechanical engineering and turning it into biomechanical engineering. Gyroid structures are difficult to replicate using traditional manufacturing, yet with the ability that a 3D printer has, it can now be easily created down to the nanoscale level. They are nano-porous and nano-hybrid which reduce the creep and breaking of the material in order to create a longer material life. Human bodies accept these structures more so than the standard alloys such as titanium implants because of a gyroids connection to nature. They are being found all over nature and allow for the integration between bone and other organic materials, to all of these other alloys.  The integration of gyroid and other structures into 3D printing are paving a new era of what could be done with what is currently known about additive manufacturing.
With all of the capabilities that Additive Manufacturing possesses, the predecessor, Subtractive Manufacturing still holds the commercial industry’s attention with a tight grasp. The reason for this is the ability to create a vast amount of products, quickly, and at a low cost. Injection molding is the industry leader for outputting products while hitting all those marks. One of the largest drawbacks however, is the cost of using Subtractive Manufacturing to create the molds in which different materials such as steel, aluminum, or the more common nylon  are injected into. Today’s 3D printing technologies allow for printing materials that are high enough over the melting temperature of the injected material that a sort of relationship can be created between subtractive and additive manufacturing. The problem of rough surfaces and features after printing could be where traditional subtractive manufacturing steps in, or where newer printing technologies pave the way  and lead the commercial industry in a new highly efficient and zero waste environment.
Lego injection molds. Photo taken at Mannheim State Museum for Engineering and Work
Environmental impacts also happen to be a leading trend in today’s world and with the help of Additive Manufacturing, the impact should be nothing short of positive. While printed metals and plastics are not absorbed back into an ecosystem, the progress in 3D printing builds a theoretical scaffold that can, in turn, build a literal organic scaffold that can be absorbed back into the earth. Such is the case with newer technologies  that employ the use of laser-based two-photon polymerization for bioprinting.
Bio-additive manufacturing is recently receiving an ever-increasing amount of funding and thus leading the research of newer materials for all forms of applications . There are certain materials (polyetheretherketone polymer, Cobalt-Chrome alloy, Magnesium) that resonate exceptionally well with tissue and musculoskeletal systems and with the help of directed energy deposition, or other covering techniques such as tomographic printing to encompass solid materials, they're able to be added as a coating onto structural titanium prosthetics and other metallic implants for a synergistic effect on integration. Increasing knowledge of newer materials , their different applications, and how different structures including surface finish can affect their intended outcome, is how AM technologies are rapidly progressing in the scientific/maker community and affecting the industrial world.
One of the few ways that AM technologies are ever-changing, is the new form tomographic printing  which prints all at once by rotating the workpiece in a vat along the vertical axis and using photopolymerization in order to cure/harden the material instead of layer by layer. This method of printing is not only faster than traditional 3-D printing but much more versatile when it comes to coupling a pre-existing solid material with cured resins. This will prove to be a monumental cornerstone for bioprinting tissues, organs, or other devices for biomedical implementation. Whilst the new method is optimal for small parts, It faces challenges with making larger-scale parts due to the curing process and might result in deformed material properties. Yet advances in additive manufacturing has proven time and time again that complications are just another name for future opportunities for progress.
The traditional model for manufacturing has been incredibly fruitful. The time is quickly approaching where traditional manufacturing will be rendered obsolete and the costs for production will outweigh the return of investment. A new form of manufacturing will have to take place one way or another. Therefore a relationship between the solid foundation of Subtractive Manufacturing and the newer technologies that are being discovered every day from Additive Manufacturing will instill a highly efficient and revolutionary form of manufacturing.
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