DigiKey - Introduction to FreeCAD Part 3: Shape Binders, Expressions, and Spreadsheets | DigiKey
The tutorial guides users through creating a parametric box with a lid in FreeCAD, emphasizing the use of spreadsheets for global parameters. It starts by setting up a spreadsheet to define dimensions like length, width, and thickness, which are then used to create sketches and features in the Part Design workbench. The video explains how to create a box body, add fillets, and use constraints to ensure dimensions are consistent. It also covers creating a lid using a subshape binder to reference the box's geometry, ensuring the lid fits snugly. The tutorial highlights the importance of parametric design, allowing easy adjustments to dimensions via the spreadsheet, which automatically updates the model. It concludes with exporting the model for 3D printing and tips for using slicer software to prepare the print.
Key Points:
- Use spreadsheets in FreeCAD to manage global parameters for consistent and adjustable designs.
- Create a subshape binder to reference geometry from other bodies, ensuring parts fit together accurately.
- Utilize constraints and expressions to maintain consistent dimensions and relationships in sketches.
- Export models as STL files for 3D printing, ensuring parts are oriented correctly in slicer software.
- Adjust transparency and use clipping planes to visualize internal structures and ensure proper fit.
Details:
1. 🛠️ Introduction to Assembly Creation
- The session transitions from creating simple parts to building simple assemblies, focusing on a box with a lid that fits by sliding onto a lip.
- It involves importing a step file for reference geometry to create a mounting plate or enclosure, showcasing practical application.
- Parts created can be 3D printed if a 3D printer is available, adding a hands-on component to learning.
- Prerequisite skills include sketch creation and feature definition in the part design workbench, ensuring participants are prepared for assembly tasks.
- The process emphasizes understanding the transition from individual parts to cohesive assemblies, enhancing project versatility.
2. 📊 Creating a Parametric Spreadsheet
2.1. Creating a New Spreadsheet
2.2. Setting Up Variables
2.3. Using Aliases
2.4. Best Practices and Naming Conventions
3. 📐 Designing the Box Base with Sketches
3.1. Setting Up the Design Environment
3.2. Creating and Modifying Sketches
3.3. Using the Fillet Tool
3.4. Defining Dimensions with Parametric Modeling
3.5. Utilizing Global Variables and Expressions
3.6. Error Handling and Constraint Management
3.7. Finalizing the Sketch
4. 🔧 Building the Box Lid
- Begin by using the expression editor to automate design dimensions, ensuring consistent and easily editable parameters like base height.
- To prevent topological naming problems, create sketches on the XY plane instead of directly on faces, and adjust the Z position through the expression editor for proper alignment.
- Use the rounded rectangle tool for consistent fillets and edges, and implement symmetry constraints with smart dimension tools for precise alignment.
- Assign aliases to dimensions such as lip width, lip length, and lip fillet to simplify future references and adjustments.
- Calculate dimensions using the smart dimension tool by subtracting global thickness from width and length, ensuring the sketch is fully constrained.
- Extrude the sketch to a specific thickness, e.g., 3mm, for the lip to complete the box lid design.
5. 📦 Completing the Box Assembly
- Start with a chunky rounded cube or rectangle design for the box with limited capacity.
- Use external geometry tools and view section buttons for accurate sketching and visualization.
- Apply the rectangle tool with fillets, equality constraints, and symmetry tools for precise alignment and fully constrained dimensions.
- Carve out a pocket by reducing a 10mm thickness by 2mm, achieving an 8mm depth for effective material subtraction.
- Manually adjust pockets using camera views for simple shapes, ensuring precise adjustments.
- Export the body with set tips to include specific features, using resetting tips to view all features.
- Finalizing involves renaming the body to 'base', marking the completion of the current modeling stage and preparing for further development.
6. 🧩 Using Subshape Binder for Lid Design
6.1. Subshape Binder Overview and Benefits
6.2. Step-by-Step Usage Instructions
7. 🎨 Finalizing the Lid Design
- Advanced parametric editing was employed to adjust the z-axis through global variables, ensuring that the lid maintained a critical gap of just above 10 mm for optimal fitting during assembly. This adjustment was vital to accommodate potential imperfections during the 3D printing process.
- External geometry was incorporated to align the sketch accurately, with a focus on symmetry and concentric constraints. These constraints were crucial in maintaining design consistency, especially when dealing with complex geometries.
- The design incorporated a small gap to improve fitting accuracy, particularly essential when working with tight tolerances. This gap was strategically planned to address common 3D printing inaccuracies, enhancing the overall assembly process.
8. 🔄 Using Shell Tool for Hollowing
- The shell tool, also known as the thickness tool, automatically determines bounds for creating pockets, enhancing efficiency in design.
- Users should reference a pre-defined spreadsheet for thickness settings to ensure precision, emphasizing the integration of data-driven approaches.
- For simple designs, the default shell tool settings are often sufficient, but it may not handle complex shapes well, requiring alternative methods.
- Designers should be flexible, using manual methods for intricate designs when the shell tool is inadequate, illustrating the need for adaptability.
- For example, the shell tool can effectively hollow out straightforward geometries but struggles with intricate patterns, necessitating manual intervention or different tools.
9. 📏 Adjusting and Measuring Fit
- The Expression Editor allows designers to reference base object dimensions and constraints, effectively eliminating manual calculations and streamlining the design process.
- Design dimensions such as width, length, and fillet are precisely controlled through a combination of sketch constraints and spreadsheet values.
- A parametric approach is employed, enabling automatic updates across related elements when base dimensions are modified, such as changing the box's width to 100 millimeters.
- Symmetry constraints and smart dimension tools enhance efficiency by ensuring equal and proportional dimensions are set accurately.
- Global variables and the expression editor within the design framework provide high customization and adaptability, demonstrated by defining the lip width and length with added gap space.
- The design's adaptability is highlighted by its ability to revert changes while maintaining original dimensions, as shown when reverting to 60 and 40 millimeters for a keepsake box.
- An example of using the expression editor is adjusting the fillet radius in real-time based on the overall design changes, ensuring consistent aesthetics and functionality.
10. 🔍 Visualizing Internal Structure
10.1. Identifying Visualization Challenges
10.2. Changing Appearance for Clarity
10.3. Identifying and Measuring Gaps
10.4. Fixing Errors in Design
10.5. Verification through Clipping and Measurement
11. ✂️ Adding Fillets and Chamfers
- Fillets can be challenging for 3D printers, especially on the bottom where angles exceed 45°, potentially requiring support structures. To mitigate this, use fillets cautiously and consider the printer's capabilities.
- Chamfers, set at a 45° angle, are recommended for edges printed on the bed as they provide better results and are easier for 3D printers to manage compared to fillets.
- To preserve design integrity, apply chamfers and fillets at the end of the modeling process, ensuring that other features are added first to prevent structural issues.
- Include illustrations of fillets and chamfers to enhance understanding and provide practical examples for when to use each in various design scenarios.
12. 🖨️ Exporting for 3D Printing
12.1. Exporting STL Files
12.2. Slicing and Printer Preparation
12.3. Printing and Troubleshooting
13. 🌐 Importing and Referencing External Designs
13.1. Accessing CAD Designs Online
13.2. Importing Models into FreeCAD
13.3. Manipulating and Using Imported Models
14. 🎯 Challenge and Next Steps
- Design a mounting plate for a development board such as an Arduino or Raspberry Pi without using screws, utilizing pegs for the board to rest on the plate.
- For an advanced challenge, design a lid that snaps onto the mounting plate.
15. 📢 Conclusion and Invitation
- Encourage participants to share their work by tagging Digi, whether it is a screenshot or a 3D printed part.
- Invite participants to learn about creating mounting holes and using heat set inserts in future sessions.