Pattern & Mirror 3D Features

1. Types of Patterns and the Objects We Can Pattern

In Fusion 360, the Pattern and Mirror tools are found under the Create menu. They operate on 3D geometry, distinguishing them from their 2D sketch counterparts you've used before.

There are three primary pattern commands for 3D objects:

• Rectangular Pattern: Duplicates objects in a grid (rows and columns).
• Circular Pattern: Duplicates objects around a central axis.
• Pattern on Path: Duplicates objects along a custom curve or edge.

And, of course, the Mirror command, which creates a symmetrical copy across a plane.

Before we use these tools, it's crucial to understand what you can pattern. The dialog for each tool will ask you to select a Pattern Type. The choice you make here has significant implications for how your model behaves.

To summarize the key idea:

• Patterning Features: Replicates a specific operation from your timeline (e.g., an extrude, hole, or fillet). This is best for adding repeated details to a single body.
• Patterning Bodies: Duplicates an entire solid body. This is useful when you need multiple, separate copies of a solid volume within the same component.
• Patterning Components: Creates instances of an entire component. This is the standard for assemblies. If you change the original component, all instances in the pattern will update automatically. This is analogous to using multiple identical bolts in a physical assembly.

2. Creating Patterns

Now let's see these tools in action. We'll use a single comprehensive video that demonstrates all three pattern types.

The Compute Option (Optimized, Identical, Adjust) for patterning features is a particularly important detail. As a general rule:

• Start with Optimized for the best performance.
• If the result is incorrect (e.g., a hole doesn't cut through a curved surface properly), switch to Adjust. This mode is "smarter" as it re-evaluates the end condition for each instance but can be slower to compute.
• Identical is a middle ground, useful when you know each instance should be an exact copy of the source.

3. Creating Symmetrical Designs with Mirror

The Mirror command is essential for any design that requires symmetry. It's conceptually simpler than patterning but just as powerful.

One excellent use case for mirroring features is in designing snap-fit enclosures, like the Raspberry Pi case in the LINK resource. The designer models one snap hook and its corresponding cutout, then simply mirrors those features to the other side to ensure perfect symmetry and alignment.

4. Your Turn: Practice Task

Let's apply these skills to a practical design. We'll model a simple mounting plate that could be used for a gaming headset holder or a camera mount.

Task: Design a Symmetrical Mounting Plate (15 minutes)

1. Create the Base:

   • Start a new design. Create a sketch on the top plane.
   • Draw a Center Rectangle that is 100mm wide and 50mm tall.
   • Finish the sketch and Extrude it up by 5mm to create the base plate body.

2. Create a Mounting Hole:

   • Use the Hole tool (Create > Hole).
   • Place a hole on the top face of your plate.
   • Set the hole type to Counterbore.
   • Enter some reasonable dimensions: a counterbore diameter of 8mm, a counterbore depth of 2mm, and a main hole diameter of 4mm. Set the extent to Through All.
   • Position the hole 10mm from the top edge and 10mm from the left edge.

3. Pattern the Hole:

   • Go to Create > Pattern > Rectangular Pattern.
   • Set the Pattern Type to Features. Select the Hole feature from your timeline at the bottom of the screen.
   • For Directions, select the two perpendicular edges of your plate.
   • Set the Quantity for the first direction to 2 and the Distance to 80mm.
   • Set the Quantity for the second direction to 2 and the Distance to 30mm.
   • Click OK. You should now have four identical counterbored holes.

4. Add and Mirror a Feature:

   • Create a sketch on the top face of the plate.
   • On the left side only, sketch a small circular or rectangular cutout for a cable pass-through.
   • Extrude this sketch downwards to cut through the plate.
   • Now, use the Create > Mirror tool.
   • Set Pattern Type to Features and select the extrude-cut feature you just made.
   • For the Mirror Plane, select the origin plane that runs vertically through the center of your part (it should be the YZ or XZ plane, depending on your initial sketch orientation).
   • Click OK. The cutout should now be perfectly mirrored on the right side.

You've now efficiently created a symmetrical, manufacturable part using patterns and mirrors.

Conclusion

You've now added two of the most significant time-saving toolsets to your modeling arsenal. By mastering patterns and mirroring, you can create complex, repetitive, and symmetrical geometry with minimal effort, allowing you to focus more on the creative aspects of your design.

Key Takeaways:

• Use Rectangular, Circular, and Path patterns to duplicate geometry in organized arrangements.
• Use the Mirror command to create perfect symmetry across a plane.
• The Pattern Type is critical: use Features for details on one body, Bodies for separate lumps of material, and Components for assembly instances.
• The Timeline is paramount. The order of operations determines what gets patterned or mirrored. Features must exist before the pattern/mirror feature in the timeline to be included.

Next Lesson Preview:
In our next lesson, we will explore the Split Body and Combine tools. While Pattern and Mirror are used to create new geometry, Split and Combine are used to manage and modify existing solid bodies. These tools are the key to designing multi-part objects, like enclosures with lids or complex parts that need to be broken down for 3D printing, bringing us one step closer to your goal of designing custom accessories.