CAD File

What is a CAD file?

A CAD file is a digital file format of an object generated using CAD software, containing a blueprint, technical drawing, schematic, or 3D rendering of an object. Computer-aided design (CAD) or computer-aided design and drafting (CADD) denotes a 3D graphics file format consisting of 2D or 3D designs. 2D CAD files are usually drawings, while 3D files are models, parts, or assemblies.

The .cad file extension is used for a 3D graphics file format, often associated with CAD projects. These files generated using CAD tools are also called CAD drawing files. Besides digital 2D and 3D graphics, these files may contain other data used to create a CAD project, such as information on materials, dimensions in an architectural plan, construction processes, etc.

Logiciel CAD File

Logiciel mentionnant cad file comme fonctionnalité ou terme.

SolidWorks eDrawings

AutoCAD

DWG Viewer 2.0

SketchUp

KeyShot

Ansys Mechanical

Types of CAD files

CAD files provide a design preview within particular CAD software. CAD file formats can primarily be classified into two categories:

• Proprietary or native: Some CAD programs utilize proprietary file formats created exclusively for use on that program alone. The proprietary CAD file format stores every aspect of the original design. Such files are created and coded in a way that only the program used while generating it has access. If one tries to open a proprietary file in another program, they receive an error message. This type of file is convenient for sharing designs within a group where each user has access to the program.  
• Non-proprietary or neutral: Contrary to a proprietary file format, a neutral or non-proprietary file format is vendor agnostic and can be accessed using various programs that can read it. A non-proprietary CAD file format typically uses general information and standardized protocols to ensure that multiple programs can comprehend the information within. This type of CAD file format is used while sharing documents with external stakeholders, such as customers who may not have access to a particular CAD program but can still view the file.

Benefits of using a CAD file

• Design creation: CAD files are used in creating detailed 3D models and 2D drawings of physical components in a technical drawing. A digital document is created when one uses CAD software. This document is then saved in a particular file format: a CAD file.
• Information repository: The CAD file format helps decide the type of program one can use to view the digital document. Each CAD system has its methodology of describing the topology representation as well as the structural and mathematical geometry of a design. CAD files hold information about these processes and drafting.

Basic elements of a CAD file

The format for a CAD file may vary, but a typical CAD file will consist of the following elements:

• Representation of geometry and topology: CAD models are illustrated using the boundary representation (B-Rep) method in which shapes are described using limits. A B-Rep model consists of two components: 
• Geometry: This defines the shape of elements. Geometric objects store details about dimensions and geometric properties of parts, i.e., surface area, volume, and center of mass.
• Topology: This outlines how elements are connected and bounded. Topological shapes comprise bodies such as solid, sheet, wireframe, acorn, and elements like shells, faces, edges, etc.
• Product structure: Product structure is a hierarchical representation of single objects and groups. The single objects are also known as parts, and groups of interlinked objects are known as assemblies. The product structure data provides a directory hierarchy on the left side of the screen in most CAD software packages. One can broaden the tree or its groups, create duplicates of the assemblies, check the boxes to conceal or show model components, and explore the interdependence of the parts in the CAD file.
• Representation of visual attributes: CAD files contain visual attributes such as colors, light, textures, materials, etc. Visual attributes come into play when presenting the model to stakeholders and are very important. These properties make the CAD model stand out and vividly enhance its structure and functionality. 
• Metadata: Metadata refers to data that offers information about other data. It enhances the data with details, making it more simple to locate, apply, and manage. Metadata in a CAD file consists of object names and IDs, layers, product and manufacturing information (PMI), and user-defined and validation properties. When 3D CAD models have metadata built in, each download will consist of the part number, information on how to purchase the physical product, and the manufacturer's name. It ensures that the manufacturer’s information is stored in the product when it’s downloaded and helps the customer with the next step to buy the product. Without metadata, all information related to the part will be lost once it goes into the design. 

CAD file best practice

To make a CAD file work, one should follow this best practice:

• Use a suitable file format: Losing crucial data contained within a CAD file while circulating it among internal and external stakeholders will have an adverse impact on any CAD project. Therefore, it is essential to use suitable CAD file formats compatible with existing software packages. Below is a list of commonly used extensions and their advantages and disadvantages: 
• Initial graphics exchange specification (IGES) file format: This file format uses the extensions .igs and .iges. This vendor agnostic file format supports assembly structure, colors, and names. However, there may be limitations due to its large size.
• ACIS-SAT file format: This file format uses the extensions .sat and .sab. ACIS-SAT file format provides complete B-Rep geometrical and topological entities support. Furthermore, it requires no translation when read by ACIS-based applications. The downside of using this file format includes limited visual support and low suitability for applications that are not ACIS based.
• Standard for the exchange of product model data (STEP) file format: This file format uses the extensions .stp and .step. The best feature of this file format is its interoperability with a broad range of CAD, CAM, and various 3D modeling software packages. However, there may be round-off errors in numerical values due to the usage of text format in the file. Moreover, some contents may not be readable in certain workflows.