3D PRINTING EXPLAINED
Additive manufacturing, 3D printing & rapid prototyping are all terms for the same process of building a three-dimensional object from a digital (CAD) model. However there is a difference – in 2010 the ASTM International (F42) committee defined additive manufacturing as: “… making objects from 3D data, usually layer upon layer…” and 3D Printing as “… fabrication of objects through the deposition of a material using a print head, nozzle or other printer technology.” These terms are published in ASTM F2972 and are now accepted internationally by ISO, clearly positioning 3D Printing as a process within the Additive Manufacturing industry.
3D Printing does appear to be the term which has achieved wider public recognition as the range of Additive Manufacturing technologies have become more visible in the general marketplace. Most recently ‘Rapid Prototyping’ has been dropped by many companies that can produce end-use parts.
There is a large variety of different types of 3D printer that function in different ways and produce an equally wide variety in the finish of the end product. At Zeal3DPrinting we build using Fused Deposition Modeling (FDM), Stereolithography (SLA) and Selective Laser Sintering(SLS) technologies and offer a range of different materials and finishes.
Fused Deposition Modeling (FDM) :
Fused deposition modeling (FDM) is an additive manufacturing technology commonly used for modeling, prototyping, and production applications.
FDM works on an "additive" principle by laying down material in layers; a plastic filament or metal wire is unwound from a coil and supplies material to produce a part.
FDM begins with a software process which processes an STL file (stereolithography file format), mathematically slicing and orienting the model for the build process. If required, support structures may be generated. The machine may dispense multiple materials to achieve different goals: For example, one may use one material to build up the model and use another as a soluble support structure, or one could use multiple colors of the same type of thermoplastic on the same model.
The model or part is produced by extruding small beads of thermoplastic material to form layers as the material hardens immediately after extrusion from the nozzle.
Stereolithography (SLA) :
The SLA process uses a vat of UV-curable liquid resin which is cured by a laser to build parts one thin layer at a time. The laser ‘draws’ a single layer cross-section of the part on the top surface of the liquid resin, curing and solidifying it whilst joining it to the layer below.
Once a layer has been drawn and cured, the SLA machine’s platform is lowered by an amount equal to the depth of one layer. This then allows the re-coater blade to sweep across the vat, spreading another layer of fresh resin, ready for the laser to draw on. In this way a whole three dimensional part is built up. Once completed, the build is drained, parts are washed in a chemical bath to remove the excess resin and are then finished to a client’s specification.
Selective Laser Sintering (SLS) :
The SLS process uses a bed of powdered material which is fused a layer at a time by a high power, CO2 laser. The laser ‘draws’ a single layer cross-section of the required part on the surface of the powder bed, accurately creating the part layer and joining it to the layer below.
When each layer has been completed the powder bed lowers and the process is repeated, one layer at a time until the required object is complete. During construction, an object being built by SLS is supported by the surrounding powder – it is possible therefore to build very complex geometries without any need for interfering support structure. In this way the SLS process allows previously impossible shapes to be built.