Tangency Weight and other options in the Fusion Fillet command

Creating smooth, professional edges in CAD models is both an art and a science. The Fillet command in Fusion plays a key role in refining your designs, especially when you master its advanced features. Learning to control how edges blend together can transform your models from basic to stunning. This guide explores those powerful tools—like tangency weight, curvature options, chord length, and different corner styles—that give you full control over your fillets.

Understanding the Fusion Fillet Command

What Is a Fillet in CAD?

A fillet is a rounded edge added between two surfaces or faces. It’s commonly used to remove sharp corners, improve aesthetics, or prepare parts for manufacturing. While a simple fillet just rounds the edge, Fusion offers many ways to make this transition as smooth or sharp as needed.

The Default Fillet Functionality

Normally, creating a fillet involves just selecting an edge and setting a radius. It’s quick and easy for basic needs. But what if “more” is required—like smooth transitions between curved surfaces or variable edge profiles? That’s when the advanced features come into play.

Exploring the Fillet Options in Fusion

Adjusting the Radius with the Blue Arrow

To modify the size of a fillet in Fusion, you drag the blue arrow that appears after selecting an edge. This provides quick control, but you can also type in a number for the radius value.

Utilizing Tangency Weight for Better Surface Transitions

Tangency weight allows you to control how the fillet blends with neighboring surfaces. Think of it like setting how strong or gentle the connection is. Increasing this weight makes the fillet extend further along the adjacent surface, creating a smoother or more dramatic transition.

• How it works: Dragging the tangency weight arrow adjusts the "pull" of the fillet. A higher value gives a more gradual jump between surfaces.

• Practical use: When designing parts with curved and flat faces, adjusting tangency weight helps avoid sharp or awkward transitions.

  
  

Radius Types: Constant vs. Variable

The default is a fixed radius, but you can change it to create a more complex edge.

• Constant radius: Same size all along, perfect for simple shapes.

• Variable radius: Allows different sizes along the edge.

To set a variable radius, choose the radius type, then input different values at each end. Clicking along the line allows you to enter different radius values along the edge. You can also adjust tangency weight again to fine-tune transition smoothness.

Using the Dot Shortcut to Recall Settings

When working on multiple fillets, it’s handy to reuse previous values. Clicking the three dots next to the input fields quickly recalls your last radius and tangency weight. This saves time and helps keep your design consistent.

Advanced Fillet Techniques

Simulating Variable Chamfers with Fillets

Even though Fusion doesn’t have a dedicated variable chamfer option, tweaking the tangency weight can create a similar effect. Set the radius to vary along an edge and then lower the tangency weight. The result looks like a chamfer that tapers from larger to smaller, perfect for adding detail to mechanical parts.

Enhancing Surface Transitions with Curvature Options

Fusion offers a “curvature” setting instead of simple tangent (G1). Choosing curvature (G2) makes the surface flow even smoother.

• Why matter? Especially on reflective or high-precision parts, a G2 transition looks cleaner and helps avoid visible edges.

• How to tell if you’re doing it right: Use Zebra analysis, which shows lines aligning perfectly across joins. If the stripes are smooth and continuous, your surface transition is high quality.

  
  

Specialized Fillet Options for Complex Shapes

Chord Length Mode for Precision Filleting

When working with angled or transitional surfaces, setting a fixed radius sometimes creates uneven results. Chord length mode keeps the distance between points constant along the fillet, resulting in a uniform shape.

• When to use: On cylindrical or angled faces where evenness matters.

• How to set it: Change from radius to chord length, then specify the length for even distribution.

  
  

Corner Styles: Rolling Ball vs. Setback

Choosing the right corner method influences how the fillet looks, especially at intersections.

• Rolling ball: Imagine sliding a ball over the edges—this smooths out sharp corners naturally. It’s perfect for rounded aesthetics or smooth joints.

• Setback: Think of it as creating a surface patch connecting fillets. It gathers multiple edges into a smooth surface rather than a single rounded curve.

Which to pick? Use rolling ball for organic, flowing shapes. Setback suits mechanical parts where a flat transition is preferred.

Practical Tips for Better Filleting Results

• Preview your transition with Zebra analysis. It shows if the surface flow looks smooth.

• Experiment with tangency weight to fine-tune how edges blend.

• Use variable radius for complex profiles, like chamfers or aesthetic edges.

• Combine curvature controls with tangency settings for the best surface finish.