Mirror Command Not Working in Fusion 360

Beginners often face a common issue when trying to mirror objects in Fusion 360.

Several things could be preventing the mirror command from working. In this post, I’ll be answering the following questions and statements:

• Why is the mirror function not activated in Fusion 360?
• Why won’t my sketch objects select to mirror?
• Mirror tool not available to use
• Cannot select lines which I want to mirror in mirror command
• Can’t get mirror command to work
• Fusion 360 mirror not working

Each problem or question is due in part that there are two different mirror commands. Fusion 360 has a Sketch Mirror command and a Model Mirror Command.

The Sketch Mirror command is to be used only with sketch geometry. Both Fusion 360’s native sketch geometry, as well as inserted SVG lines, can be mirrored.

Contrary, the Model Mirror command is to be used only with faces, 3D bodies, features, and components.

These features do not work with one another. It’s necessary to pay close attention to the location and icon of each mirror command.

The Sketch Mirror command looks like two hollow triangles. The original triangle on the left is black, while the mirrored triangle on the right is blue.

The Model Mirror command looks very similar to the Sketch Mirror command – which is why it’s so easy to select the wrong one. The Model Mirror command is filled-in. It has a gray triangle on the left and a blue triangle on the right.

Fusion 360 Sketch Mirror Command

The Sketch Mirror command mirrors the selected sketch curves about a selected mirror line.

Important: You must be in an active sketch environment to use the Sketch Mirror command.

1. Create a new sketch or enter an existing sketch environment.
2. Activate the Sketch Mirror command from the toolbar or Create dropdown (while in the Sketch tab)

3. Select all Sketch objects (curves) that you want to mirror. Be sure to avoid selecting your desired mirror line.

4. Select the Mirror Line selector in the dialog > Select the desired Mirror line (which can be a construction line)

5. Click OK in the dialog

The sketch objects will then be copied. Symmetry constraints will appear next to all sketch objects that have been mirrored. Any changes to the original side will be automatically updated to the mirror side.

Fusion 360 Model Mirror Command

The Model Mirror command makes a mirrored copy of selected faces, features, bodies, or components at equal distances across a plane.

Important: The Model mirror command does NOT work with Sketch geometry.

1. Select the Model Mirror command from the Create dropdown

2. Select a Pattern Type – Faces, Bodies, Features, Components

3. Select the Objects selector in the dialog > Select the object(s) based on your Pattern Type

4. Select the Mirror line selector in the dialog > select an origin plane, construction plane, or face to mirror by

5. Set the Compute Option – Optimized, Identical, Adjust

Take note of the Model Mirror command (icon) displaying in the parametric timeline (at the bottom). To edit the mirror command simply double-click on the icon in the timeline.

Pattern Types in Fusion 360 Mirror Command

The model mirror command has the following four pattern types. Each pattern type lets you select a different type of object to mirror. Remember, the modeling mirror command is parametric, meaning you can edit the feature at any time – which means you can always change the pattern type selection.

• Faces – mirror only the face(s) of 3-dimensional objects
• Bodies – mirror 3D solid bodies or a single body
• Features – mirror a model feature or selection of model features in the parametric timeline
• Components – mirror component(s), which can contain several bodies and other modeling features

Compute Option in Fusion 360 Mirror Command

The compute option lets you choose how the mirror command will be calculated by Fusion 360. The option selected can impact the performance, as outlined below.

Important: If your mirror is not showing up, try using a different compute option.

• Optimized (fastest) – Just mirrors the faces of the feature, which optimizes performance.
• Identical (moderate) – This method just extracts the pattern type selection, mirrors that selection, making it identical to the original part.
• Adjust (slowest) – This method recomputes each mirror instance almost as if it were a separate feature. This allows you to do alter parts of the mirrored object, and have each instance of the mirror compute differently.

Fusion 360 Mirror Best Practices

• When possible use the Model Mirror command over the Sketch Mirror command – It’s easier and faster for Fusion 360 to render bodies
• Avoid using either Mirror Command when copying and pasting components provides the desired result
• Never mirror threads or other components that work in a singular direction. Remember, they’ll be mirrored, causing them to be backward
• Use minimal mirror features in a single design file. Otherwise, performance will be greatly impacted. Considering inserting a component (with mirrors) into a new design file (the larger assembly file)