The 3D part file – STEP and Parasolid X_T
STEP and Parasolid X_T are the most important exchange formats for 3D parts between CAD and CAM systems – structure, properties and benefits at a glance.
The 3D part – the 3D file – is the interface between CAD and CAM. It is not only used to exchange data between CAD and CAM, but also to exchange information between different CAD systems. Two formats have become widely established for this: STEP as a vendor-neutral standard and X_T through the widespread use of the Parasolid kernel.
STEP / STP file
The STEP format (Standard for the Exchange of Product Data) is an industrial file format for exchanging 3D models and product information between different CAD systems. It has been standardized by the International Organization for Standardization (ISO) and is based on a neutral, platform-independent data model.
Beyond geometry data, STEP also transfers information about materials, assemblies, properties, tolerances, layers and more. Its data structure is based on the “EXPRESS” modeling schema, which defines the elements of a 3D model and their relationships. The data is stored as ASCII text, which makes it easy to read and exchange.
The great advantage of STEP is its broad support among CAD vendors: since STEP is an international standard, most CAD systems can read and write STEP files. This enables seamless data exchange between platforms and applications and makes STEP the most important tool for collaboration between companies using different CAD systems.
X_T file
The X_T format – also called the Parasolid text format – is the file format of the Parasolid kernel. Because Parasolid is used as the kernel in many CAD products, the X_T format is also widespread in industry.
An X_T file contains both the geometric shapes and the structural information of a CAD model: precise 3D geometry data such as points, lines, curves, surfaces and solids, plus additional information such as colors, materials, layers and properties. Transfer works between different CAD systems – regardless of whether they themselves use Parasolid as their kernel.
The X_T format offers two key advantages: it is supported by many CAD vendors, so models can be exchanged without additional conversion steps or data loss, and it preserves the precision of the geometry data, ensuring the model is reproduced accurately in other CAD systems.
The X_T format has a binary counterpart: the X_B file. While X_T is a text-based representation of the model, X_B is a binary representation. Both formats contain the same geometry data, but X_B files are usually more compact and load faster.