Introduction to CAD Software
Computer-aided design (CAD) software is used by engineers, architects, designers, and draftsmen to create precise 2D drawings or 3D models of physical components and systems. CAD has largely replaced traditional hand drafting techniques for engineering design and technical illustration.
CAD provides several key benefits:
Accuracy - CAD allows you to create scaled drawings and models to exact specifications. Measurements, angles, positions, and alignments are very precise.
Efficiency - CAD software automates and speeds up much of the drawing process. Editing and modifying designs is fast and simple.
Flexibility - CAD files are easy to change or manipulate. Engineers can quickly iterate on designs to evaluate different options.
Standardization - CAD uses common standards for measurements, annotations, file formats, and other conventions. This facilitates collaboration and sharing.
Some of the most popular CAD platforms used for engineering design include:
AutoCAD - 2D/3D CAD from Autodesk, the industry standard for over 30 years.
SolidWorks - 3D CAD with powerful solid modeling capabilities, widely used by engineers.
CATIA - High-end 3D CAD/CAM from Dassault Systems, popular in automotive and aerospace.
PTC Creo - Full suite 2D/3D CAD with parametric and direct solid modeling modes.
Siemens NX - Integrated CAD/CAM/CAE software with advanced simulation tools.
FreeCAD - Open source, free CAD for Linux, Windows, and Mac platforms.
Choosing the right CAD software depends on your specific design needs, budget, and operating system. Most platforms offer student versions for learning.
Choosing the Right CAD Platform
When starting any engineering design project, one of the first decisions is choosing which CAD (Computer-Aided Design) software you will use to create the technical drawings and 3D models. There are many CAD platforms available, so it's important to take the time upfront to select the one that best fits your specific needs and preferences. Here are some key factors to consider when evaluating CAD software options:
Compare Top Options
The most popular CAD platforms used in engineering include:
AutoCAD - The industry standard for 2D drafting and detailing. Owned by Autodesk.
SolidWorks - Leading 3D CAD package, also by Autodesk. Integrates well with AutoCAD.
Creo - Powerful 3D CAD and product design software from PTC.
CATIA - High-end 3D software focused on aerospace and automotive industries. By Dassault Systemes.
NX - Integrated CAD/CAM/CAE software with advanced simulation. From Siemens.
Do your research to see which one offers the functionality, features, and compatibility you require for your projects. If working with external teams, consider which platform they use.
Evaluate 2D vs. 3D Needs
Determine whether you mainly need mature 2D drafting capabilities or advanced 3D modeling functions. AutoCAD excels at 2D while SolidWorks and Creo are focused on 3D. Some software like NX blend both 2D and 3D tools.
Consider if you need to generate detailed 2D drawings from 3D models or vice versa. This interoperability is important.
Consider Cost and Learning Curve
Look at the pricing structure (one-time, rental, free trial) and evaluate the learning curve. Entry-level packages from AutoCAD and SolidWorks are more affordable and usable for beginners. CATIA and NX are costlier and have steeper learning curves.
Select a CAD platform that fits both your current and future needs. Don't sacrifice key functionality to save money in the short-term. Invest time to properly evaluate all aspects before committing to a particular CAD software for your projects.
CAD Interface and Settings
Each CAD software has an interface that allows you to customize and optimize your workspace. Setting up your interface properly will allow you to work efficiently and access the necessary tools with ease. Here are some key settings and customizations to focus on when configuring your CAD interface:
Customize Toolbars
Most CAD platforms allow you to customize the toolbars by adding, removing, or rearranging tools based on your needs. For example, you may want to add frequently used commands like Trim, Extend, and Fillet to your main toolbar for quick access. Take time to organize your toolbars in a way that matches your workflow.
Create Shortcut Menus
You can create custom menus that only contain the specific tools or commands you use most often. Place these shortcut menus in an easy to access location. This avoids having to dig through layers of menus to find the function you want.
Set Up Templates
Templates allow you to define drawing settings, styles, layers, etc. that will apply by default to new drawings. Set up templates for different drawing types you create to save time on reformatting the same settings repeatedly.
Adjust User Preferences
Dive into the user preferences and modify settings to optimize your interface. For example, you can change the default colors, cursor size, display resolution, auto save frequency and location, and much more. Set preferences tailored to your workflow needs.
Save Interface Settings
Once you have your interface configured properly, be sure to save your toolbars, menus, templates and preference settings. This allows you to restore your custom interface anytime across different computers. A consistent interface helps reinforce workflows and mouse memory.
Taking the time to optimize your CAD interface will boost your efficiency and productivity. A well-configured workspace can save you significant time during the course of a project.
Creating Geometry in CAD
CAD software provides various tools to draw the basic geometric shapes and forms that make up your design. Here are some of the key features:
Lines
Use line tools to create straight line segments.
Set start and end points to define the length and position.
- Change line properties like color, thickness, and line type.
Circles
Draw circles by defining their center point and radius.
Draw arcs by specifying start and end angles.
- Use snap tools to connect lines to circles precisely.
3D Features
Create 3D wireframe geometry with lines, circles, rectangles and polygons.
Add surfaces by connecting and filling in wireframe profiles.
Construct solids by extruding 2D profiles into 3D objects.
Constraints
Apply geometric constraints to lock objects together.
Use constraints to control sizes, angles, positions, tangency, parallels and more.
Modify your design while maintaining constraints.
Following these steps allows you to accurately construct the underlying geometry for any CAD drawing or model. Take advantage of the various CAD tools to efficiently draw the shapes, curves, and 3D structures required in your designs.
Adding Dimensions
Dimensions are a critical part of any engineering drawing. They precisely indicate the measurements and geometry of the design. In CAD software, you can easily add different types of dimensions to your drawings.
To add a basic linear dimension in CAD:
1. Select the Dimension tool from the toolbar. This may be called Dimension, Smart Dimension, or Linear Dimension depending on your software.
2. Click on the first point you want to dimension, like the endpoint of a line.
3. Click on the second point to dimension. An angled line will appear between the points as you drag your mouse.
4. Position the dimension line outside of the object you are dimensioning.
5. The measurement value will appear. You can edit the text if needed.
The basic process is the same for other types of dimensions like diameter, radius, and angular dimensions. Simply select the specific tool before picking points on the drawing.
When adding dimensions, it's important to follow standard conventions:
Place dimensions outside the object, with the text parallel to the dimension line
Arrange dimensions in a clear, organized manner and avoid crowding
Dimension to hidden edges with dashed lines and indicate them as "phantom"
For diameters, place the measurement text above the dimension line
Indicate the radius with an R before the value
Use <<>> around angular dimensions
You can also add geometric tolerances like +/- .005 to indicate an acceptable variance. Include these after the primary dimension measurement.
Always double check your dimensions for accuracy and clarity. Dimensions are necessary for manufactured parts to be created correctly.
Organizing with Layers
One of the most important organizational tools in CAD software is layers. Layers allow you to logically separate the different elements in your drawing. For example, you may want to put all the parts on one layer, dimensions on another layer, annotations on another, etc.
Proper use of layers gives you much more control over your drawing. You can turn layers on and off to hide or view just certain elements. You can also control properties like color, line type, and thickness on a per-layer basis.
When creating layers, it's best to think about the major components of your drawing and group related items together. Here are some common layering strategies:
Parts: Create separate layers for individual parts or assemblies. This allows you to hide certain components and work on others independently.
Dimensions: Put all dimensions on a dedicated layer. This makes it easy to toggle dimensions on and off for clarity.
Annotations: Use a layer for text, labels, notes, and other written information. Keep this separate from parts and dimensions.
Centerlines: Centerlines often go on their own layer for emphasis.
Documentation: Additional information like title blocks, borders, and revision info can go on a documentation layer.
The key is to logically organize your layers so you can control visibility and properties. Don't overload layers with too many different elements. Give thoughtful names to layers so their contents are clear. Taking the time to layer properly will make your CAD drawing much easier to edit and manage over time.
Annotations and Notes
Annotations are critical elements in CAD drawings that provide additional information through text, symbols, and other markings. They allow you to specify important details that are not clearly conveyed by the drawing geometry alone.
Adding Text
Use text in your CAD drawings to label parts, provide instructions, indicate measurements, describe processes, and more. Here are some tips:
Place text on separate layers from the drawing geometry for easy editing
Use standard fonts like Arial, Helvetica or Times New Roman
Add leader lines to connect text labels to the relevant drawing elements
Inserting Symbols
Include common symbols in your CAD drawings such as:
Surface finish symbols (e.g. roughness, machining marks)
Weld symbols
Feature control symbols (roundness, runout, etc)
Datum identifiers
Revision clouds to highlight changed areas
Symbols clearly communicate design specifications without using extensive text.
Specifying Measurements
Although dimensions precisely indicate measurements in drawings, you can further clarify by adding measurement callouts with specific values. For example:
4X Ø6mm THRU
LENGTH 8.25in
6deg DRAFT ANGLE
Providing Instructions
Use text and symbols to indicate any special instructions for manufacturing or assembly. Common examples include:
REMOVE ALL BURRS AND SHARP EDGES
MACHINE TO WITHIN 0.005" TOLERANCE
ASSEMBLE WITH LOCTITE ADHESIVE
Clear instructions prevent errors and support proper fabrication of the design.
Checking for Errors
Once you've completed your CAD drawing, it's critical to thoroughly check it for any errors before finalizing. Here are some tips on verifying accuracy and meeting standards:
Review drawing accuracy - Zoom in and visually inspect every detail of the drawing. Check for gaps, misalignments, incorrect dimensions, etc. Verify the accuracy of curves, angles, and hole positions. Double check any complex geometry.
Run diagnostics - Most CAD programs have built-in tools to diagnose problems. In AutoCAD, run the AUDIT command to check for errors like duplicate objects, small gaps, zero-length geometry, etc. Fix any issues it detects.
Check against requirements - Review your drawing against any client requirements or industry standards like ISO, ANSI, or ASME. Make sure you meet all expectations for dimensions, symbols, layout, annotations, etc.
Use a checklist - Develop and follow a checklist to methodically verify every component of a drawing before release. Include items like title block, border, line styles, hole callouts, and part naming.
Perform test prints - Print hard copies at different scales and in black and white to reveal any hidden flaws. Check for elements that overlap, text that's difficult to read, missing information, etc.
Request peer review - Have a colleague familiar with CAD and your industry review the drawing to catch mistakes you may have overlooked. Implement any feedback.
Investing time in meticulous error checking will prevent costly mistakes down the line. Establish robust review processes to ensure your CAD drawings are perfectly accurate before use.
Exporting and Printing CAD Files
After completing your CAD drawing, you'll need to export the files to shareable formats and print hard copies for review, documentation, and fabrication purposes. Here are some tips:
Export to Common File Formats
PDF - The PDF format allows anyone to view the drawing electronically while preserving the formatting. PDFs can be password protected and are widely supported.
DWG - DWG is the native file format for AutoCAD drawings. It maintains full editing capabilities if further changes are required. Share DWGs when collaborating with other AutoCAD users.
DXF - DXF is an open CAD file format that can be read by most CAD platforms. Use it for sharing drawings with third parties using different software.
JPG/PNG - For simple file sharing, JPG and PNG image formats allow you to export drawings for electronic viewing only.
3D Formats - For 3D CAD, you can export to STL and other common 3D file types for 3D printing or use in advanced simulations.
Print Hard Copies
Print full size plots of drawings for in-person design reviews, marking up changes by hand, and creating master documentation copies.
Print scaled reductions of large drawings to conserve paper and allow easier handling.
Print to PDF for combined electronic and print copies.
Use large format plotters for very large drawings like architectural plans or mechanical assembly diagrams.
Following industry best practices for exporting and printing will facilitate collaboration, documentation, and fabrication from your CAD drawings. Maintain both digital and print copies for redundancy.
Tips for CAD Best Practices
To create professional engineering drawings, follow these best practices that focus on accuracy, efficiency, flexibility and standardization:
Double check all dimensions, measurements, angles, and tolerances to ensure total accuracy. CAD allows you to be precise, so aim for perfection.
Use sheet templates, title blocks, and reuse content like standard notes or symbols to maximize efficiency. Save time with automation.
Build flexibility into your drawings by using constraints, relationships and lightweight geometry. This makes edits and adjustments quick and easy.
Follow industry and company drafting standards for text fonts, line weights, dimensioning, file formats, and documentation. Consistent standards are key.
Organize with layers, blocks and libraries so you can find, control and reuse content. A clean structure improves workflow.
Keep CAD skills sharp through regular practice and learning new techniques. Employ shortcuts and power tools to speed up work.
Take advantage of CAD's capacity for iterations by exploring design options virtually before final documentation.
Run audit checks and pre-print tests in CAD to identify errors early on when they are easier to fix.
Back up files frequently to avoid data loss. Use version control for complex projects.
Consult experienced drafters or mentors to learn conventions, get project checks, and refine your CAD craft.