The multitude of different file formats encountered in the world of 3D printing is a source of uncertainty and confusion. The file formats used to depend on the design software used, the 3D scanner used and the 3D printer to be used. The following article introduces the most popular file formats and is intended to help you navigate through the confusion. Since we cannot cover all formats here, we have limited ourselves to the following 9 file formats (STP; IGES; STL; X3D; COLLADA; WRL; OBJ; PLY; AMF), but there are dozens more.

Mesh Formats

STL

STL stand stands for ‘Standard Tesselation Language or Stereolithography’ (the first 3D printing process). It is also known as the standard “language” in the field of computer-aided systems. Nearly all CAx systems support this file format. The object data is stored as a grid (based on triangles). STL is the 3D printing format par excellence; virtually all 3D printers, from hobby 3D printers to industrial machines, work with this format.

X3D

The ‘EXtensible 3D’ format is based on XML and has one major advantage: the files can be displayed in a browser with the help of a plug-in. The X3D format can also be used with NURBS. According to the W3C (World Wide Web Consortium), X3D is intended to replace the WRL format and will be a new standard in this area. At present, however, X3D plays only a minor role in 3D printing because many printer control programs cannot work with this format, or can only work inadequately.

COLLADA

Just like X3D, ‘COLLAborative Design Activity’ is XML-based. The corresponding file extension is.DAE. It is an open exchange format among 3D applications. A big advantage of the format is the possibility to display animations. There are efforts to establish this format everywhere, but at the moment it plays only a very minor role.

Full Color Formats

OBJ

OBJ is an open file format for displaying 3D geometries. It can use both polygons and curves and surfaces (NURBS), and the vertex positions are also stored. The textures and UV positions are saved in a separate file, usually in .jpg (“texture”) format. This file format is often used because many design programs can export their data to the.OBJ format. Most 3D printers are capable of printing objects from an.OBJ file. OBJ is the standard format for color 3D printing.

VRML (WRL)

The file format is popular when working with color 3D models that are to be printed. The ‘Virtual Reality Modeling Language’ is a description language for 3D scenes and is indicated by the file extension.WRL. A grid is used to represent the geometries. The format is to be superseded by X3D at the will of the W3C. Currently, WRL is the second most popular format for color 3D printing besides OBJ.

PLY

The ‘PoLYgon’ file format files are usually generated by 3D scanners and must be converted by 3D design software to be used for 3D printing. In addition to the geometry of a 3D object, data such as edges, color values, and materials are stored as well.

AMF

The ‘Additive Manufacturing File Format’ is an open, XML-based standard for the description of 3D objects. The format contains information about the shape and composition of the object (color, material, gridlines). A conversion to STL is possible without data loss. The big advantage of AMF is that it is highly compressible. The format is intended to replace STL in the future but has not been established as the new standard yet.

CAD Formats

STP

The .STP file format is the file name extension of a standard for the transmission of product data (STEP) and was developed to replace IGES. STP can do everything IGES can do, but it also stores tolerances, material properties, textures, material types, and topologies. While IGES is still widely used for hobby applications, the STP format is preferred for professional applications.

IGES

The file format ‘Initial Graphics Exchange Specification’ was developed in the 1970s by the US Air Force in cooperation with Boeing. It was designed to facilitate data exchange between the Air Force’s systems and their suppliers. The format can also display colors, but no textures. It is a bit outdated and is no longer being developed further, but still enjoys considerable popularity among hobby users.