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CAD Drafting Basics: A Beginner's Guide to Creating Engineering Drawings


CAD Drafting Basics: A Beginner's Guide to Creating Engineering Drawings

What is CAD Drafting?


CAD, or Computer-Aided Design and Drafting, is the use of specialized software and computing technology to create and edit technical drawings used in engineering and manufacturing. CAD software allows users to draft 2D drawings as well as 3D models of products and assemblies by utilizing a digital workspace and a full suite of drawing and editing tools.


The purpose of CAD drafting is to produce clear, accurate and detailed technical drawings that can communicate the specifics of a design to all stakeholders in the manufacturing process. It enables engineers and designers to create schematics, blueprints, architectural plans, engineering drawings, prototypes and more. Since CAD files are electronic, they make collaboration and sharing of designs highly efficient.


CAD drafting has many applications across engineering disciplines. It is used to create detailed part drawings for machined or manufactured components. Assembly drawings that provide instructions for putting together multiple component parts into a final product are also drafted in CAD. Electrical engineers use it to design circuit schematics and wiring diagrams. Architects employ CAD software to draft building plans and convert their visions for structures into technical drawings. CAD is an indispensable tool across manufacturing, construction and engineering.


By utilizing the power of computers, CAD allows for greater precision, higher accuracy, enhanced collaboration and increased productivity versus manual drafting techniques. CAD drawings can be quickly edited and iterated upon, while maintaining consistent standards. The automated features of CAD make repetitive drawing tasks much simpler and faster. CAD has streamlined and modernized the entire technical drawing and design process.


CAD Software Options


When getting started with CAD drafting, one of the first decisions you'll need to make is which CAD software to use. There are many options available, with the most popular being:


AutoCAD


AutoCAD by Autodesk is one of the most widely used CAD software programs. It offers 2D drafting as well as 3D modeling capabilities. Some key features include:


  • Powerful 2D drafting tools for creating detailed technical drawings

  • Ability to create detailed 3D models and renderings

  • Customizable interface to optimize workflow

  • Works with DWG and DXF files, common CAD file formats

  • Extensive learning resources available


AutoCAD has a steep learning curve but it's a great choice for complex drafting and design work. There's a free trial available to test it out.


SolidWorks


SolidWorks by Dassault Systèmes is a 3D CAD program focused on mechanical design. Key features include:


  • Intuitive 3D modeling and assembly design tools

  • Simulation and analysis capabilities

  • Specialized tools for drawings, sheet metal, weldments

  • Tight integration between 2D drawings and 3D models

  • Can open AutoCAD DWG files


For those interested in mechanical engineering and product design, SolidWorks is a leading choice. The learning curve is still significant.


DraftSight


DraftSight by Dassault Systèmes is a free and lightweight 2D CAD option. Key features:


  • Similar interface and commands to AutoCAD

  • Capable 2D drafting tools for floor plans, schematics, etc.

  • Support for DWG files

  • Significantly lower learning curve than AutoCAD or SolidWorks


DraftSight is a great starting point for beginners to get a taste of CAD drafting and create 2D drawings without the complexity of 3D tools.


For new CAD users, either DraftSight or AutoCAD with ample time set aside for learning would be good options. The investment for SolidWorks may be best after gaining proficiency with 2D drafting fundamentals. Most skills will translate between CAD platforms.


CAD Interface Basics


The CAD interface is made up of various components that allow you to create and edit drawings. Getting familiar with these key elements will help you navigate the software efficiently.


Title Block


The title block sits at the bottom or right side of the drawing area. It contains important information like the drawing name, creator, revision number, date, and scale.


Toolbars


Toolbars contain buttons and menus to access the various drawing and editing tools. Common toolbars include Drafting, Modify, Draw, and Dimension. Toolbars can be customized to show only the tools you need.


Drawing Area


The drawing area is the large blank space where you create the drawing. It can contain multiple viewports to show different views of the model.


Navigating the Interface


You can zoom in and out of the drawing using the mouse scroll wheel or view tools. Panning allows you to move around the drawing area while zoomed in. Regenerating the display refreshes the view when changes are made.


Customizing the Interface


Many settings like grid visibility, snap spacing, and colors can be customized. Toolbars can be shown, hidden, or moved to suit your workflow. Default templates allow you to optimize the interface for different drawing types.


Starting a New Drawing


When you first open your CAD software, you will need to set up a new drawing file. This involves configuring the page size, units, scale, and other settings before you can start drafting.


Page Size


Most CAD programs allow you to select from a range of standard page sizes such as ANSI, Architectural, ISO, etc. Common sizes are ANSI full bleed (11x17 inches), ANSI A (8.5x11 inches), and Architectural D (24x36 inches). Choose the page size appropriate for your industry and drawing type.


Units


You'll need to determine the unit system for your drawing. The most common options are decimal units such as inches or millimeters. However, some CAD programs allow you to work in fractional inches as well (such as 1/4", 1/2" etc). Pick a unit that allows you to work precisely and avoids unit conversion errors.


Drawing Scale


Set an appropriate drawing scale like 1:1, 1:2, 1:5, 1:10 etc. The scale indicates how dimensions on paper relate to real-world dimensions. For example, in a 1:2 scale drawing, 1 inch on paper equals 2 inches in reality. Pick a scale suitable for the size of objects you'll be drawing.


Title Block


A title block provides important information about your drawing like project name, designer details, date, revision number etc. Most CAD software have pre-made title block templates you can insert. Make sure to fill in the necessary details in the title block fields.


Templates


Leverage title block templates and drawing templates in your CAD software to optimize starting a new drawing. Templates have predefined settings which saves time and ensures consistency. You can also create and save custom templates for your drawing standards.


Basic Drawing Tools


CAD software provides a variety of basic drawing tools for creating the objects that make up your drawing. Getting familiar with these tools and how to use them efficiently is essential for CAD drafting.


Some of the most common basic drawing tools include:


  • Lines - Straight lines are the most basic object and are used to create outlines for designs as well as edges, axes, and dimensions in drawings.

  • Circles - Circles allow you to draw arcs and rounded shapes. You can specify the radius or diameter to control the size.

  • Arcs - Arcs are a portion of a circle and are defined by their radius, start angle, and end angle.

  • Rectangles - Rectangles have four straight sides and 90-degree corners. You can draw rectangles by specifying length and width or two corner points.

  • Polylines - Polylines are connected line and arc segments that act as a single object. Useful for outlining complex shapes.

In addition to drawing tools, CAD software provides aids to allow for precision and efficiency:


  • Object Snaps - Snap to key geometric points on existing objects like end points, midpoints, intersections etc.

  • Grid - Display grid lines at set increments to use as a visual aid for alignment.

  • Layers - Organize objects on different layers to manage and control visibility.


Using the right tools and proper technique is crucial for fast and accurate CAD drafting. Take time to practice and become proficient with the basic drawing tools in your chosen CAD software. This will help you work more efficiently as you create CAD models and drawings.


Advanced Drawing Tools


CAD software provides several advanced tools for creating more complex geometry and annotations in your drawings. Getting comfortable with these tools will allow you to work more efficiently and produce higher quality drawings.


Polylines


Polylines are continuous lines or polygons made up of multiple segments. Polylines are useful for creating contours and outlines with multiple straight and curvilinear segments while maintaining it as one object. This makes editing faster since you can move or modify the entire polyline at once.


Some key things to know about polylines:


  • Create polylines by converting existing objects like lines, arcs, circles into one polyline using the PEDIT command

  • Edit vertices and segments of the polyline using PEDIT

  • Set width, color, linetype for the entire polyline at once

  • Use closed polylines to create filled polygons and apply hatch patterns


Spline


Splines allow you to draw smooth, flowing curves through a series of fit points. Splines are useful for organic and free-form shapes.


To create splines:


  • Specify the start and end points

  • Add additional fit points to control the shape

  • Set tolerance to determine how closely the spline follows the fit points


Splines create smooth curves without many vertices like polylines. You can convert splines to polylines as needed.


Hatches


Hatches, also called hatch patterns or fills, are used to fill defined boundaries with repeating patterns. This can help clearly differentiate between materials or objects.


Some tips for working with hatches:


  • Apply hatch patterns to bounded areas like closed polylines

  • Use ANNHATCH command and pick a pattern, scale, angle

  • Set boundary using picking points or selecting objects

  • Modify pattern properties like scale and angle after placing hatch

  • Create custom hatch patterns if needed

Hatches improve readability of drawings by visually differentiating objects and materials.


Blocks and Symbols


Blocks allow you to create reusable symbols by combining multiple objects into a single named block. This helps improve efficiency.


Key uses of blocks:


  • Insert common symbols like doors, windows, furniture, etc.

  • Represent repeated elements like nuts, bolts, crystals, trees

  • Maintain consistency by editing the block definition, and changes update everywhere the block is inserted


Steps for working with blocks:


  • Combine objects into a block using BLOCK command

  • Insert blocks by name and set base point and scale

  • Modify block definitions to update all instances automatically

  • Explode blocks to convert back to individual objects


Using blocks for common elements in your drawings will save significant time.


Dimensions and Annotations


Dimensions and text annotations provide critical information for manufacturing and assembly.


Best practices for dimensions:


  • Use aligned, angular, radial and diameter dimension types appropriately

  • Dimension objects soon after drawing to avoid omissions

  • Modify dimension text, leaders, and styles for clarity

  • Set dimension units and precision formatting as needed


For annotations:


  • Add text, leaders, and multiline text objects

  • Use appropriate text heights, fonts and styles

  • Place notes strategically using leaders and text boxes

  • Update annotations as the drawing evolves to avoid mismatches


Double check all dimensions and text before finalizing drawings to prevent errors or ambiguity for those using your drawings.


View Management


One of the key skills in CAD drafting is being able to create different views of a model and manage how they are displayed on the drawing. There are two main types of views - orthographic and perspective.


Orthographic vs Perspective Views


Orthographic views show a 3D object from different angles using projection lines that are perpendicular to the plane being viewed. This allows for precise, measurable drawings. The most common orthographic views are the top, front, side, and isometric views.


Perspective views show a 3D object from a fixed viewpoint, displaying how it would look in real life. Lines converge towards vanishing points, giving a realistic depth effect. Perspective drawings are less technical and more for visualization purposes.


In most CAD programs, orthographic views are the default and provide the accuracy needed for engineering drawings. Perspective views can be used occasionally for a better visual representation.


Creating Multiple Views


With CAD, multiple views of a model can be generated automatically from your chosen angle and layout. This allows you to quickly visualize the object from all necessary sides without having to redraw it.


Common practices are to include a front, top, and right side view arranged together on the drawing. Isometric views are also frequently used. Any additional views needed to show hidden features and dimensions can be created as required.


Layout Tabs


Layout tabs in CAD allow you to easily organize and manage your different views on the drawing. You can designate separate tabs for the individual orthographic views, isometric views, detailed views, and even perspectives if required.


This enables you to quickly switch between the different views without them overlapping. You can also use layouts for different drawing scales or versions. Managing views across layouts is key for creating clear, legible drawings.


Editing Objects


One of the most fundamental CAD skills is being able to efficiently edit the objects in your drawings. Whether you need to adjust the size, orientation or location of an object, CAD software provides various editing tools. Here are some of the key object editing functions:


Selecting Objects


Before you can edit an object, you need to select it. This is easily done using the SELECT command, clicking the object, or windowing a group of objects. Selected objects are highlighted for easy identification. You can also remove objects from the selection with CTRL+click.


Moving Objects


Use the MOVE command to reposition an object to a new location in the drawing area. Simply select the object(s) and specify the displacement distance and direction. Make sure to use object snaps for precision.


Rotating Objects


The ROTATE command rotates objects around a specified base point. Select the object(s), define the base point, and enter the rotation angle. Positive angles are counterclockwise.


Scaling Objects


To uniformly scale selected objects up or down, use the SCALE command. Pick the base point and enter the scale factor as a percentage. A value greater than 1 enlarges the object, less than 1 shrinks it.


Trimming and Extending


The TRIM command removes unwanted portions of objects so they end precisely at other geometric features. EXTEND lengthens objects to meet other features. Just select cutting edges and objects to trim or extend.


Breaking Objects


The BREAK command allows you split an object into two parts at a specified point. Simply pick the object, specify the break point, and the object is divided.


Grouping Objects


Grouping combines objects while maintaining their individual properties. This allows them to be moved, copied, rotated etc. together as one unit. Use the GROUP command to create object groups.


Ungrouping Objects


Ungrouping separates a group back into individual objects. The UNGROUP command restores objects' independence for editing flexibility.


Printing and Plotting


When you are done creating your CAD drawing, you will need to either print it or export the file to share with others. Unlike printing a regular document, CAD drawings require special consideration regarding scale, size, orientation, etc. Here are some key factors to keep in mind:


Page Setup


Before printing or plotting a drawing, you need to configure the page setup which includes settings like paper size, orientation (landscape or portrait), and print margins. Most CAD software has presets for common paper sizes like ANSI, Architectural, ISO, etc.


Print vs. Plot


In CAD, printing refers to sending a drawing to a regular printer just like you would print a Word doc or PDF. Plotting refers to large-format printing where drawings are scaled and printed on specialty plotters. Plotters allow much larger paper sizes.


Plot Scale


Since CAD drawings are created at real-world scale, you need to set a plot scale when printing to fit the drawing on a sheet of paper. Common scales are 1:1, 1:2, 1:4, etc. The scale impacts the size - a 1:4 scale prints the drawing at 1/4th its actual size.


Plot Orientation and Style


Orientation refers to printing landscape or portrait. Plot style includes settings like color vs monochrome, line weights, and more. These impact the final look of the printed drawing.


Exporting File Formats


CAD drawings can also be exported as PDFs, DWG files, and image formats like JPEG instead of printing. This allows them to be shared digitally while maintaining the drawing fidelity.


Modeling in 3D


CAD software allows you to create 3D models in addition to 2D drawings. With 3D modeling, you can visualize and analyze designs more completely before manufacturing.


Intro to 3D Modeling


To create 3D models, CAD software uses special features like extrude, revolve, loft, sweep, and more. These tools allow you to take 2D shapes and turn them into 3D objects. 3D modeling is based on creating sketched profiles and trajectories and then using CAD tools to give them depth and form.


Basic 3D Tools


Some of the most common 3D tools are:


  • Extrude - Extends a 2D profile along a straight path to create a 3D object.

  • Revolve - Rotates a 2D profile around an axis to form a 3D object.

  • Loft - Creates a smooth object transitioning between 2D cross sections.

  • Sweep - Forms a 3D object using a 2D profile shape moved along a trajectory.


Rendering and Animation


Once you have created a 3D model in CAD, you can create realistic visualizations using rendering and raytracing. This applies colors, textures and lighting effects. You can also animate the model to show how different components move. Renderings and animations help others visualize the design before manufacture.

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