Even though almost everyone likes to use 3D Printing synonymous for all the different Additive Manufacturing processes, in real life there are many individual processes which vary in method of manufacturing layer. Those processes can differ and that depends on the machine technology and material used. However there are major differences between additive manufacturing technologies and the most common types of technologies are explained in this blogpost.
Vat polymerisation applies liquid photopolymer resin, out of which the desired model is printed. This occurs layer by layer and will display some visual layering in the printed product. With VAT Photopolymerisation an ultraviolet light is used to harden or cure the resin, whilst the object being made is being moved downwards by a platform after each new layer is finished. Because this process uses liquid instead of powder to form objects, there is no structural support by the material in the build phase, like there is with powder based additive manufacturing methods.
Material jetting has a technique similar to a 2D ink jet printer. The material is jetted onto a stage. It uses either a Drop on Demand (DOD) or continuous approach of jetting material. It gets solid and the model is built layer by layer. The material lands from a pipe which moves horizontally over the platform. There is variety in the complexity of the machines around and in their ways of controlling the deposition of material. The layers deposed get hardened with the help of ultraviolet light.
Binder jetting technology makes use of two components: a binder and a powder based material. Usually the binder is in liquid form and the material to build your 3D design is in powder form. The printhead which moves horizontally along the x and y axes sets various layers of the binding material and the building material. The object being printed gets lowered on its build platform after each new layer is set. Because of the method of binding, the characteristics of the material are not always suitable for structural parts. Also, even though the quite good speed of printing, additional post processing can add a lot of time to the total process.
Fuse deposition modelling (FDM) is a widespread Material Extrusion process. The company Stratasys has it trademarked. Material is pulled through a pipe, where it gets heated up and after it is built up layer by layer. The pipe itself can move from left to right and there is a platform which moves up and down after each new layer is set. This technique is commonly used in many domestic environments, for people who have 3D printing as a hobby or who like to keep things rather inexpensive. The process for this category has many factors influencing the quality of the final model. However, it has great potential if these factors are controlled in a successful manner.
Powder Bed Fusion
The Powder Bed Fusion process involves these commonly known printing techniques: Selective laser sintering (SLS), Direct metal laser sintering (DMLS), Selective heat sintering (SHS), Selective laser melting (SLM) and Electron beam melting (EBM). Powder bed fusion (PBF) methods either make use of an electron beam or a laser to melt and then fuse material powder together. In this way the 3d file can be printed.
Directed Energy Deposition
Directed Energy Deposition (DED) is a more complex printing process which is widely used to repair or add extra material to existing parts. A typical DED machine has a pipe mounted on a multi axis arm. It deposits melted material onto the wished for surface, where the material then solidifies. The process of directed energy deposition can be compared to material extrusion (ME), however in DED the pipe can move in multiple directions (in contrary to ME) and the nozzle is not fixed to a specific axis point. The material is melted upon deposition by either an electron beam or a laser. It can be deposited from any angle because of four and five axis machines. DED can be done with ceramics, polymers and metal but it is normally done with metal, either in powder or wire form. Applications for the creations made by DED include maintaining and repairing structural parts.
Sheet lamination processes list laminated object manufacturing (LOM) and ultrasonic additive manufacturing (UAM). It is most commonly applied with metal materials. It makes use of ribbons of metal which are welded together. It requires removal of the unbound metal and additional CNC machining to create a smooth printed product. This is often needed during the welding process. LOM has a kind of similar layer by layer approach, however it uses sheets of paper instead of metal and adhesive instead of welding. In the LOM process a cross hatching method is used during the printing process as it allows for easy removal after building has finished. The laminated objects are often used for visual and aesthetic models but are not suitable products for structural use.