1. Prepare Your CAD Model
Before you can generate drawings from your CAD model, you first need to make sure the model itself is properly prepared. Any issues in the CAD model will carry through to the drawings, so getting the model right is crucial. Here are some tips for setting up a CAD model that is ready for drawing creation:
Ensure the model is fully defined. Make sure all sketch geometry, extrusions, features, and components are fully constrained and defined in the model. Any ambiguous or underdefined geometry can lead to problems down the line.
Assign appropriate materials and colors. Properly define materials for parts and assemblies. Apply realistic colors and textures to help the model visualize. This will transfer to the drawings.
Run model diagnostics. Most CAD packages provide tools to diagnose the model for problems. Fix any issues like gaps, misalignments, lightweight components, etc. before moving to drawings.
Organize the model tree. Structure your parts, assemblies, and features in a logical hierarchy in the model tree. Use configurations to manage design iterations. A clean model tree makes it much easier to navigate.
Simplify large assemblies. Turn off visibility or suppress unimportant components. Remove fasteners and small parts if not critical. This simplifies the model topology and improves performance.
Confirm units. Ensure your CAD model is using your desired system of units like inches or mm. This will dictate units on the drawing.
Spending time upfront to prep and optimize your CAD model pays dividends when you begin making drawings. It helps avoid introducing errors and improves the quality of the resulting drawings.
2. Set Up the Drawing Template
Before generating views of your 3D CAD model, you first need to set up the 2D drawing template in your CAD software. This establishes the correct paper size and orientation, imports any title blocks or borders, and configures the styles and layers you will use in the drawing.
The first step is to choose the appropriate paper size and orientation for your drawing. Common engineering drawing sizes include ANSI sizes like ANSI B (11x17 in) or ANSI D (22x34 in), as well as ISO A-sizes like A3 (297x420 mm) or A1 (594x841 mm). Consider the amount of detail in your model and required views when picking a paper size. Also decide whether you need landscape or portrait mode - landscape offers more width while portrait has more height.
Next, import any title blocks, borders, logos, or other templates into the drawing. Many CAD programs include libraries of title blocks and drawing templates to start from. Customize these to match your company standards. Properly formatted title blocks are essential to provide the necessary drawing information.
Finally, set up the layers, styles and other drawing settings that control the look of entities in the drawing. For example, create layers for dimensions, notes, section lines, etc. Define line styles for different line weights and types. Configure text styles, arrow sizes, and any other CAD drawing settings needed. Taking the time to set up the template will pay off when generating the drawing views.
The drawing template serves as the foundation to build your engineering drawing on top of. With the paper size and orientation, title block, and styles in place, you are ready to begin generating the model views.
3. Generate Drawing Views
Once you have a template set up, you can start generating drawing views from your 3D CAD model. The key at this stage is deciding what views you need to fully convey the design, and positioning them appropriately on the sheet.
Common options for view types include:
Orthographic views - These are flat 2D views showing the object as projected onto a plane. Orthographic views represent the true shape and size of the part, so they are ideal for dimensioning and manufacturing. Common orthographic views used in technical drawings include front, top, side, rear, and section views.
Isometric views - An isometric view shows the object in isometric projection, where the three axes create equal 120° angles. This view helps visualize the 3D form. Details like dimensions would not be included in an isometric view.
Detail views - These are enlarged views of a small area of the model, to show features clearly.
Section views - These show an imaginary cut through the object to reveal internal features. Section views are annotated with hatching, section lines, and a section symbol.
Auxiliary views - An auxiliary view is projected onto a secondary plane that is not parallel or perpendicular to the main views. This helps show inclined or curved surfaces in true size and shape.
Position your views to make best use of the sheet space, aligning them as appropriate. Add centerlines and hidden lines to improve clarity. You can also apply hatching and shading to differentiate components or material types. Always double check that your views are showing the necessary features clearly and accurately. The goal is to generate drawing views that unambiguously convey design intent.
4. Add Dimensions
Accurate dimensions are critical for ensuring your engineering drawings convey the design intent and can be correctly interpreted for manufacturing or fabrication. When adding dimensions to your drawing:
Dimension all features, distances, angles, radii, hole diameters, etc. that are important to defining the part or product. Focus on critical dimensions needed for function or assembly.
Use appropriate dimension styles and settings. Aligned, unidirectional, chain, baseline, and ordinate dimensioning all have specific purposes. Consult your CAD software's documentation to apply them correctly.
Format dimensions consistently with standards. Include units, tolerances, limit markings, etc. per ISO or ASME standards for example. This ensures uniformity.
Use leaders and reference dimensions where appropriate. Leaders help associate dims with specific features. Reference dims call out non-critical info.
Arrange dimensions clearly without clutter. Space them appropriately and avoid crossing object lines. Align text horizontally for readability.
Dimension from established datums whenever possible. This reduces compounding tolerance errors.
Double check accuracy of all entered values. Incorrect dims can lead to scrapped parts.
Thoughtful dimensioning requires time and attention but is essential for a professional drawing that conveys the precise design requirements. Follow industry standards and refer to examples to apply dimensions for maximum clarity and utility.
5. Include Notes and Tables
Notes and tables are important elements to incorporate into your engineering drawings. They provide critical information for understanding the drawing and manufacturing the part.
General Notes
The general notes section is used to indicate information applicable to the entire drawing. This may include:
Material specifications
Required finishes or coatings
Manufacturing notes
General tolerances
For example:
```
MATERIAL: 6061 Aluminum Alloy
SURFACE FINISH: 125 μin (3.2 μm)
REMOVE ALL BURRS AND SHARP EDGES
```
Specific Annotations
Annotations are used to call out specific features directly on the drawing. They can indicate:
Surface finishes
Welds
Required processes
Critical characteristics
Annotations are placed close to the feature and use a leader line to connect to the feature.
Tables
Tables allow you to consolidate information in an organized manner. Common examples include:
Bill of materials
Revision history
Hole chart
Weld table
Surface finish callouts
Tables should have clear headings and data that references the drawing views.
Linking to Separate Documents
For extensive information, reference separate documents like specifications rather than including all details on the drawing. For example:
```
MATERIAL PER AMS-QQ-A-225
```
This keeps your drawing clean while providing access to more details.
6. Specify Tolerances
Tolerances are a critical component of engineering drawings that indicate the allowable variation in the dimensions and geometry of a part. Specifying tolerances lets manufacturers and fabricators know the acceptable limits for features of your design.
When adding tolerances to your engineering drawing, focus on indicating tolerances for any critical dimensions in your part. These are dimensions that directly impact the fit, form, or function of the part. For example, you may need tight tolerances for the diameter of a shaft that needs to fit precisely inside a hole.
For critical tolerances, also reference any geometric controls or datums you have defined in the drawing. Datums establish the primary reference points for dimensions and tolerances. Referencing datums helps ensure the toleranced features relate properly to the established datum geometry.
When indicating tolerances, follow standard conventions like using a symmetry symbol for concentricity and perpendicularity tolerances. This makes the drawing easier for others to understand. You can also include notes to provide additional clarification on tolerances when needed.
By properly specifying tolerances for critical features and following standard tolerance indications, your engineering drawings will clearly communicate the acceptable variance in your design to those responsible for fabrication and inspection. This helps ensure your parts are manufactured accurately and function as intended.
7. Add Additional Details
Often your drawing requires more than just the standard orthographic views to fully convey all the important design details. This is where additional views like section views, blowups, and detailed callouts come into play.
A section view shows an internal feature of the part as if it has been cut along a plane. Section views are useful for revealing internal geometry, features, and dimensions that wouldn't be visible otherwise. To indicate a section view, draw a section line on the main view showing where the cut is made. Then draw the section view beside it, and add hatch marks or shading to indicate the portion that has been "cut away".
Blowups and detail views let you isolate and zoom in on crowded or complex areas of your drawing. This is helpful when you need to show components that are too small or dense to dimension and annotate clearly on the main view. Create blowups by "exploding" a section of the main view and displaying it at a larger scale on the sheet.
Callouts with leader lines are used to point out and provide extra information on specific part features. For example, you may use a callout to specify details for a hole, surface finish, weld, or other important characteristic. Make sure callouts are labelled clearly and tied unambiguously to the feature with a leader line.
The goal is to incorporate any additional views required to thoroughly and unambiguously convey the part's features, measurements, materials, and tolerances according to your chosen manufacturing process. The time spent adding appropriate section views, blowups, and callouts will pay off by preventing errors and delays in manufacturing.
8. Finalize the Drawing
Once you've completed adding all the necessary views, dimensions, notes, and details to your engineering drawing, it's important to take the time to finalize it properly before release. This helps ensure that the drawing accurately communicates all the critical design information needed for manufacturing or fabrication.
Double check the accuracy and completeness of the drawing by reviewing the following:
Are all necessary views included to fully convey the part?
Are all critical dimensions shown?
Is the scale indicated correctly?
Are the line weights, styles, and annotative text clear and legible?
Have all relevant notes, tables, and specifications been added?
Do the tolerances adequately specify the required manufacturing precision?
Has the title block been fully completed with drawing info?
Next, add any important title block information that may be missing, such as:
Drawing title
Part name or number
Scale
Units
Date
Revision number
Engineer name and approval
Company name
Include a revision table to track any changes made to the drawing over time.
Lastly, run through a pre-release checklist to catch any final errors or omissions:
Spelling and grammar check
Confirm nothing overlaps or obscures other elements
No unintended line breaks or formatting issues
All information clear and legible when printed
Following these tips will help you finalize a professional engineering drawing that accurately conveys your design and is ready for release. With practice, this process will become second nature and ensure your CAD models translate smoothly from 3D into 2D technical drawings.
9. Export and Share
Once you have finalized your engineering drawing, the next step is to export it and share with your team and stakeholders. Choosing the right file format and including key information will ensure it can be accessed and utilized properly after you send it out.
When exporting your drawing, you'll want to save it in an appropriate file format based on how it will be used. Common options include:
PDF - This format is great for sharing as it preserves the drawing and allows for printing, zooming, and measuring. PDFs can be viewed easily across devices.
DXF - This CAD file format is useful if others need to edit or work with the drawing in their CAD programs. DXF retains drawing information like layers and blocks.
DWG - Another CAD format, DWG is the native file type for AutoCAD drawings. Use DWG if you or others need to edit the original CAD file.
PNG/JPEG - These image formats allow you to export the drawing as a high-quality graphic that can be easily viewed.
When saving the file, give it a descriptive name that identifies the part, project, and version. For example: "Motor Mount Plate v1".
In the drawing area, make sure to include the file name, version number, your name, and the date. This information will help track the drawing and any updates made over time.
Once exported, the drawing can be distributed to team members and stakeholders through email, file sharing services, or collaboration platforms like Slack or Teams. Be sure to share with anyone involved in the design, engineering and manufacturing process.
Storing a copy of the drawing in a central location like a shared drive also gives everyone access to the latest version. Be sure to notify the team when updates are made and provide the new version.
Following best practices for exporting and sharing your engineering drawings will streamline collaboration and ensure the right people can access the information they need for the next steps in the project.
10. Make Updates as Needed
Engineering drawings are not set in stone. Changes often need to be made even after a drawing is formally released. Proper change management ensures everyone is on the same page.
To handle updates smoothly:
Store the master drawing file in a secure location where authorized users can access it. Don't allow unauthorized changes.
Formally track all revisions with a revision table on the drawing. Log the date, change made, and approver for each revision.
When changes are required, modify the master file accordingly. Make sure to update the revision table and revision number.
Notify all relevant stakeholders of drawing changes. They'll need the latest revision.
Re-release and re-distribute the modified drawing files. Ensure the old revision is replaced everywhere. Destroy any obsolete prints.
Archive and store previous revisions in case you ever need to refer back to them. But clearly mark old versions to avoid confusion.
Following a rigorous change process ensures all users have the most current engineering drawing revision. This prevents errors from working off outdated information.
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