Printing has come a long way from as early as woodblock printing to offset printing to screen printing, inkjet printing laser printing to now Additive manufacturing / 3D printing and digital printing. Additive manufacturing is an appropriate name for the technologies that are used to build 3D objects by adding layer upon layer of material. Initially, 3D objects were only made by some special materials and plastic but nowadays plastic, metal, concrete, or even one-day human tissue can be 3D printed. It uses 3D modeling computer software like Computer-Aided Design (CAD), machine equipment, and layering material.
The CAD sketch is made initially and then the additive manufacturing machine or the 3D printer reads data from the CAD file and lays downs or adds successive layers of liquid, powder, sheet material or other, layer by layer to create a 3D object. This technology includes layered manufacturing and additive fabrication, 3D printing, Direct Digital Manufacturing (DDM), and Rapid Prototyping (RP). The application of 3D printing is getting wider and wider so there is not any limit to this technology being confined to a few places.
In the beginning times, it was used in the form of Rapid Prototyping that is focused on preproduction visualization models. However in recent times 3D printing / Additive manufacturing is being used to fabricate end-use products for aircraft, medical implants, automobiles, dental restorations, and even fashion products as well. So we can see the wide use of 3D printing everywhere. Even human organs to replace after the operation are being made from 3D printers or with the use of additive manufacturing.
History of Additive Manufacturing / 3D printing
The concept of additive manufacturing / 3D printing was first described by Raymond F. Jones in his story, “Tools of the Trade,” which was published in November of 1950. It was an issue of Astounding Science Fiction magazine. 3D printing was referred to as “molecular spray” in his story. Additive manufacturing has been around since the early 1950s where it was considered something only suitable for the production of functional or aesthetic prototypes, which was known as rapid prototyping then. Only in the 2000s additive manufacturing became popular which was because it is inspired by the theme that material was being added together. Later in the years around 2019 the precision of them, repeatability and material range of printing have become so good that they are considered as a viable industrial production technology. The reason why 3D printing was introduced was to be able to produce very complex shapes and geometries that would be almost impossible or very hard for humans to construct by hand. It is also able to create hollow parts with internal truss structures that help in reducing weight and saves up some extra material as well. As of recent times in 2021, Fused deposition modeling (FDM) is the most common 3D printing process in use.
General principles of Additive manufacturing
There are mainly three general principles of Additive manufacturing or 3D modeling
With the help of computer-aided design (CAD), one can create 3D printable models. Besides, that one can also use a 3D scanner, or a plain digital camera and photogrammetry software. However, using CAD is the best way to have minimum errors.
The file of the model that we will print will be an STL file which must be examined before printing so that there are no errors or as little as possible. Most of the time CAD applications produce errors in the output modeled STL file like holes, self-intersections, noise shells, faces normal and manifold errors. Using the repair function in a step in STL generation fixes such problems to minimize the errors. The checked error less file is processed by a piece of software called “Slicer”. Slicer converts the model into a series of thin layers and produces a G-code file for the printer. Now the model can be printed using 3D printing client software. The determination of the layer thickness in dots per inch (dpi) or micrometers is done. Layers from as thin as 250 dpi to 1600 dpi can be printed in nowadays modern printers. One drawback of 3D printers is the time it takes to print. Although it is not any simple thing but printing can take anywhere from several hours to several days depending on the complexity of the model, size and method used.
Although people try to minimize as much error as possible but still creating a thicker layer first and then later removing the material using a higher-resolution subtractive process is efficient and more precise. There are some printable polymers that allow the finished surface to be smoothed and improved using chemical vapor processes that are based on acetone and similar solvents. Even aluminum and steel are removed with GMAW 3D printing as it allows for substrate surface modifications for such hard objects as well.