CATIA V5: Focusing on Design Intent

September 26, 2023 Joshua Sands

Design intent plays a vital role in the CAD Design process. It is the concept that your design not only satisfies the initial specification, but also behaves appropriately when modifications are made. We’ll dive into how to maintain design intent in CATIA V5, focusing on dimensional and geometric constraints, integrating equations into parameters and created parameters for easy access in your design tree.

Before we even start in CATIA, it’s helpful to sketch out our design. This step lets us quickly visualize our design and can get us thinking about what dimensions are vital, and which ones could be turned into geometric constraints.

You can see that I’ve got this block here and it has quite a few dimensions on it. I don’t think they’re all needed and some don’t represent the design intent. For example, is the 25 mm dimension needed, or is the design intent that this cutout be half the height dimension? By making that line coincident to the midpoint, we can eliminate that dimension and maintain the design intent without needing to remember to update it any time the height dimension changes. Similarly, the design intent for the hole is that it be centered on our part, so we can implement geometric constraints in our CATIA Sketch and not worry about those dimensions. At first glance, it looks like we can use the mid-point for the two 35.5 mm dimensions, but those are going to depend on a locating peg. It would make sense to make a parameter for PEG Length and PEG Width, that way we can modify those in the tree, just like we would with our Main dimensions. The 29 mm dimension looks a little odd, and after some investigation, we find out that it meets up to a face that is 40 degrees. Now that we have our sketch, we can make this in CATIA.

Creating Parameters in the Design Tree

Creating parameters so they appear in your design tree is a vital step in making your design more manageable and intuitive. These parameters can represent critical design intent elements such as key dimensions, distances, or angles.

Having parameters easily accessible in your design tree allows for quicker edits and provides a clear overview of the defining elements of your design. This is particularly beneficial when collaborating with a team, as it enables others to understand and modify your design more effectively.

First, let’s create some parameters and publish them so they can be modified in our Specification Tree. From our sketch, we know we’ll need 5, the main Length, Width and Height, along with the Peg Length and Peg Height. We might as well give these parameters the values from our sketch.

Dimensional and Geometric Constraints

Dimensional and geometric constraints are essential in establishing and maintaining design intent in CATIA V5. Dimensional constraints define the size and location of a shape, while geometric constraints determine the shapes' relational characteristics, such as being parallel, perpendicular, tangent, concentric or coincident with other shapes.

By applying these constraints, you ensure that your design retains its intended form and functionality, even when dimensions change. In CATIA V5, these can be added using the ‘Constraints’ tool in the ‘Sketcher’ workbench.  Remember, judicious use of these constraints facilitates predictable changes, reducing the time for rework.

Integrating Equations into Parameters

This is another robust way to preserve design intent. By using mathematical equations to drive dimensions and positions of your design elements, you introduce a level of intelligence into your model. Changes to a single parameter can reflect across multiple dimensions, maintaining proportionality and design relationships.

To integrate an equation into a parameter in CATIA V5, go to the ‘Knowledge’ toolbar. Here, you can define your variables, write your equations, and link them to the relevant dimensions in your design.

While the Length needs to remain independent, we can control its ratio to the width and height using an equation. This makes the length our driving dimension, controlling the other two. We click on the 'Formula' tool and select the Width parameter. Select the length and at a multiplier of .75 to maintain that ratio. We can repeat that with the height parameter, this time, dividing the length by 2. You can make these equations as simple or as complicated as you want, but make sure they work.

Maintaining design intent is crucial for efficient CAD design. It requires an understanding of dimensional and geometric constraints, equations integration, and effective parameter management. By mastering these in CATIA V5, you pave the way for designs that are robust, flexible, and easy to manipulate, enhancing your productivity and reducing design iteration time.

About the Author

Joshua Sands

Technical Training Engineer<br><br>Joshua is a resident instructor for a large automotive OEM, working out of their Advanced Development Center. He implements customer specific training and brings eight years of industry experience to his classes. Joshua’s areas of expertise include Advanced Part and Generative Shape Design, VPM Navigator and Generative Drafting.

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