CAD files are files that save drawings and 3D models on computers, used by engineers and architects for their designs. Just like how you use Word documents for text or JPEG files for photos, designers and engineers use CAD files to create and save their design work.
If you’re new to design software or starting a career in engineering, you’ve probably come across terms like .dwg, .dxf, or .stl.
These are all types of CAD files, each serving different design needs.
While they might seem confusing at first, understanding these files is simpler than you think. From buildings to products, CAD files are the standard format for all technical designs and blueprints.
Together, we’ll break down everything about CAD files—from formats and types to finding the viewer that works best for your needs. Soon you’ll see how straightforward they really are.
So, without further ado, let’s get to it.
What is CAD File
A CAD file is your digital design container—it holds all the geometry, dimensions, and technical details of your project.
Think of it like a digital version of traditional paper drawings, but much more powerful. While paper drawings are static, CAD files let you modify, rotate, and zoom into every detail of your design.
These files don’t just store simple lines and shapes.
They contain precise mathematical data about every element in your design—from the exact measurements of a building’s foundation to the thread pitch of a tiny screw in a mechanical assembly.
You can store 2D drawings, like floor plans, or complex 3D models of entire buildings or machine parts, all in a single CAD file.
When you work with CAD files, you’re not just drawing—you’re building a database of your design.
Want to change the size of a window in your architectural plan? The CAD file automatically updates all related views and dimensions.
Need to see how a mechanical part looks from the inside? Your CAD file lets you slice through the model and inspect internal features.
This is why CAD files have become the standard for design work across industries—they make complex design tasks simpler and more precise.
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What It Contains?
A CAD file holds information that makes up your complete design.
Each file combines different types of data that work together to create a usable digital model or drawing. From simple 2D sketches to complex 3D models, these files store every detail needed to bring your design to life in the real world.
Inside a CAD file, you’ll find:
- Geometric data that defines the shapes and dimensions, whether in 2D drawings or 3D models
- Product Manufacturing Information (PMI) with details like tolerances, surface finishes, and material specs
- Assembly structures showing how multiple parts fit together
- Metadata like object names, IDs, and layers to organize the design
- Material properties needed for manufacturing and simulation
- Rendering information including textures and colors for visual presentation
These elements combine to create a complete digital representation of your design, allowing others to view, modify, and manufacture your work exactly as intended.
Each piece of information serves a specific purpose, from showing how the design looks to providing essential details for production.
When manufacturers receive your CAD file, they can access all the specifications they need to create your product, from the basic shape to the smallest manufacturing detail.
What It’s Used For?
CAD files power the entire design-to-manufacturing process in today’s industries. From initial concept sketches to final production blueprints, these files guide every step of creating physical products and structures.
Here’s how different professionals use CAD files:
- Architects create building plans, floor layouts, and 3D models of structures
- Engineers design and test mechanical parts before manufacturing
- Product designers develop prototypes and prepare designs for mass production
- Construction teams extract measurements and material specifications
- Manufacturers set up their machines using CAD data for precise production
- 3D printing services convert CAD files directly into physical objects
Every major industry relies on CAD files to turn ideas into reality. Construction companies build entire buildings from CAD blueprints, factories produce thousands of identical parts using CAD manufacturing data, and designers share their work globally through these digital files. The ability to modify, share, and reuse designs makes CAD files essential tools in modern design and manufacturing.
What It’s Called?
CAD files use different formats that tell you what software created them and how you can use them. Each format has specific features that make it better for certain tasks, like sharing designs or preparing files for manufacturing.
Common CAD file formats include:
- .dwg: The native AutoCAD format, used for 2D drawings and 3D models
- .dxf: A universal format that works with most CAD software
- .stl: The standard format for 3D printing and rapid prototyping
- .iges: An older format still used for sharing 3D models
- .step: A modern format that preserves complex 3D design data
- .skp: SketchUp’s format, popular in architecture and interior design
- .prt: Used by programs like SolidWorks for detailed part designs
- .3dm: Rhino’s format, common in industrial and product design
Software companies often create their own file formats to take advantage of their program’s special features. When sharing files with others, designers often save their work in universal formats like .dxf or .step to ensure compatibility across different CAD programs.
CAD File Format, Types, and Extension
CAD files come in different formats that serve specific purposes.
Each format handles features, compatibility, and data preservation differently, making them suited for various tasks in the design and manufacturing process.
These CAD file formats can be broadly categorized into Native CAD Formats created by specific software vendors, Neutral Formats designed for universal compatibility, and Format Categories that serve specialized functions like 2D drafting, 3D modeling, and visualization.
Let’s examine each type in detail.
Native CAD Formats
These formats belong to specific CAD software and work best within their own systems.
They keep all design features intact and provide full editing capabilities. Native formats preserve every detail of your design, from basic geometry to complex parameters and relationships between parts.
While they offer the most complete feature set, they usually require the original software to access all capabilities:
- AutoCAD uses .dwg for drawings and .dxf for file sharing
- SolidWorks saves parts as .sldprt and assemblies as .sldasm
- CATIA works with .catpart for components and .catproduct for assemblies
- Inventor uses .ipt for parts and .iam for assemblies
- Siemens NX saves designs as .prt files
Neutral Formats
These formats work across different CAD software, making them essential for collaboration.
They act as universal translators in the CAD world, ensuring teams can share and access design data regardless of their preferred software.
While they might not carry all the sophisticated features of native formats, they reliably transfer the core design information needed for manufacturing and visualization:
- STEP (.stp, .step) handles complex 3D models and assembly data
- IGES (.igs, .iges) transfers surface geometry between systems
- STL (.stl) prepares models for 3D printing
- 3D PDF (.3dpdf) shares viewable 3D models through regular PDF readers
Format Categories
CAD files generally fall into three main types, each serving different stages of the design process.
These categories help organize files based on their primary use, whether that’s detailed documentation, 3D modeling, or sharing designs with others. Understanding these categories helps you choose the right format for your specific needs:
- 2D Formats (.dwg, .dxf, .dgn) for traditional drawings and documentation
- 3D Formats (.sldprt, .ipt, .catpart) for detailed part modeling
- Exchange Formats (.step, .igs, .stl) for sharing between different systems
Beyond formats and types, CAD files have other important aspects. File sizes may vary – native files are usually larger since they contain more information, while neutral formats tend to be more compact.
CAD files may also store extra data like creation dates, revision histories, and author details along with the design. Working with these files typically requires good computer resources and backups.
If you plan to work with CAD files, you may need to check your software compatibility and computer specifications first.
Like any digital files, keeping backups and tracking versions will help you manage your work.
CAD File Viewer
Not everyone needs expensive CAD software just to look at designs.
CAD viewers let you check and review files without the hefty price tag of full programs. This makes a big difference for construction teams, architects, and clients who need to stay in the loop without breaking the bank.
Here are some CAD file viewer options that you can use
- Autodesk DWG TrueView: A free viewer from Autodesk specifically for DWG files.
- Features: Allows viewing, measuring, and converting DWG files between different versions of AutoCAD. It provides tools similar to AutoCAD for navigation and measurement.
- Platform: Windows only; not available for Mac.
- Autodesk Viewer: A free web-based viewer that supports various file types, including DWG, DXF, and other CAD formats.
- Features: Users can view, annotate, and share designs online without needing to download software. It supports collaboration through comments and measurements.
- Platform: Accessible from any device with internet connectivity.
- Bentley View: A versatile viewer that supports over 50 file formats, including DWG and DGN.
- Features: Offers dynamic zooming, measuring tools, and the ability to print high-resolution drawings.
- Platform: Windows; free to use.
- LibreCAD: An open-source 2D CAD application that can open and edit DWG files.
- Features: Provides a user-friendly interface for viewing and editing 2D designs. It is suitable for users who need basic CAD functionalities without the cost of commercial software.
- Platform: Cross-platform (Windows, macOS, Linux).
- FreeCAD: A parametric 3D modeler that is open-source and can work with various CAD file formats, including DWG (with additional plugins).
- Features: Supports 3D modeling and allows users to create complex designs while providing tools for viewing existing models.
- Platform: Cross-platform (Windows, macOS, Linux).
Your choice really depends on how you work. If your team spreads across different locations, a web viewer might make more sense.
Need to take detailed measurements on site? A desktop viewer could serve you better. Start with the free versions and see what clicks – you might end up using different viewers for different tasks, and that’s perfectly fine.
More on Interscale Education Blog: What is CAD Drafting? A Complete Guide to Computer-Aided Design Careers
Learn More Than CAD Files
Now you know the basics of CAD files – from common formats like DWG and DXF to different viewers you can use. Ready to learn more? Turn this knowledge into practical skills with our Certified AutoCAD Online Course.
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Learn alongside fellow designers and industry experts in our supportive learning environment. With over 60 years of industry experience, Interscale Education delivers Australian-class training that prepares you for real-world success.
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