How to Modify a Mesh in Fusion

You've printed a cool 3D model, but it comes out droopy and weak in one spot. That happened to me with a portable battery tray for the Starlink Mini. The design looked great, yet the print sagged along an edge. Let's fix that without starting over.

Identifying the Print Failure: Sagging on a Complex Geometry

This project came from Everlanders, a guy who shared a free design on YouTube for a battery tray that fits the Starlink Mini. It's a handy holder for off-grid setups, like camping or remote work. But my first print failed as it sagged right at a horizontal edge, leaving a messy blob instead of a clean line.

The issue stemmed from the model's mesh file. It had a built-in sacrificial support that prints at an angle and gets removed after the print. That support worked fine on the sides, where tiny sawtooth marks held things up. However, there were no supports for that long horizontal edge, so the plastic drooped during printing.

We all hit these snags in 3D printing. But with Fusion, there's an easy fix.

The Goal: Non-Destructive Mesh Modification Workflow

My aim was clear: add those sawtooth supports to the mesh without having to convert the original file. Having to convert the whole thing to a solid body sounds like hours of headache and possible errors. Instead, I wanted a quick way to tweak the STL file and keep it as a mesh for easy slicing.

This method saves time and keeps the design intact. You add new bits as solids, then combine them into the original mesh body. No full remodel needed. It's perfect for fixing sagging 3D prints on imported models.

Think of it like patching a roof leak. You don't rebuild the house—you just seal the spot.

Section 1: Initial Model Inspection and Orientation for Precision Work

Importing and Analyzing the Unoriented Mesh File

Start by pulling in the mesh file. It loads into Fusion at a weird tilt, making orientation somewhat confusing.

Reorienting the Mesh for Easier Sketching and Alignment

Fix the angle first. Go to the Mesh tab, pick Direct Edit, then Mesh Align. Click the mesh body.

Select the flat bottom face and align it to the bottom origin plane. Preview it and the mesh will now be aligned to the bottom origin plane, however, it may be flipped. Hit the flip button. Run the Mesh Align command again and select a side face and align to the right view plane. Preview again. Front, top, and right all make sense now.

Section 2: Preparing the Mesh for Feature Addition Using Conversion

The Pitfall of Direct Mesh Sketching vs. Solid Conversion

Meshes are great for imports, but they're picky. You can't select edges or points like on a solid. Full prismatic conversion to a solid? It might take forever and fail on complex shapes. This tray is pretty complex with lots of surfaces and blends, so I doubt it would convert easily. I skipped that trap. Instead, I just copied the existing mesh as a Faceted Mesh.

Creating a Workable Solid Copy via Faceted Conversion

Make a backup copy right away. Right-click the mesh, move/copy it in place. Name the original "backup" so you don't lose it.

Now convert the copy. Select Convert Mesh, pick Faceted mode. It turns mesh faces into solid ones. Hit OK. The icon changes to a solid body.

You can now use this converted body to measure, apply sketches on, etc, and it is an exact copy of the original mesh. This copy lets you build without touching the raw mesh.

Section 3: Designing and Implementing the Custom Support Features

Establishing the Sketch Plane for the New Support Geometry

Focus on the sagging edge. Create a plane at an angle: pick an edge on the support ledge, set it to 90 degrees vertical. This plane hugs the angled print path.

Now sketch on that plane. It positions your new teeth right where they need to grip. Turn off other bodies for a clean view.

Reverse-Engineering the Required Sawtooth Profile

Project lines first. From the solid copy, grab height lines onto your sketch. They define the tooth bounds.

Measure the side teeth for a match. Width is 0.082 inches. Draw a rectangle that size, center it on the projected line. Make the top of the rectangle collinear with the other projected line.

Add a three-point arc for the tooth curve. Start at the lower-left corner, then click near the top right corner, leaving a little segment about 0.06 inches wide.

Section 4: Integrating New Geometry with the Existing Mesh Model

Extruding the Profile as a New Body

Select the sketch profile and Extrude it out. Set to New Body so it doesn't cut the other bodies. Go 0.02 inches thick—enough to support without bulk.

Thin extrudes work best for sacrificial bits. They break off clean post-print.

Patterning the Support Structure Across the Flawed Section

Select the tooth body. Use Rectangular Pattern. Pick the horizontal axis along the edge. Switch to Symmetric as it patterns teeth both directions. Drag to cover the length of the support shelf.

Change the quantity to 11. The preview shows even spacing. Hit OK. Now you've got a row of teeth holding that edge.

Section 5: Finalizing the Combined Mesh for Slicing

Converting Temporary Solid Bodies Back into Meshes (Tessellation)

Solids won't slice with the mesh, so we need to Tessellate them. Select all patterned teeth, and select the Tessellate command from the Mesh Create menu. They turn to meshes.

The Crucial Step: Merging Meshes with the Merge Command

Go to Modify, then Combine for meshes. Pick Merge—not Join. Join would try and mathematically calculate the combining of the meshes. We don't need that.

Target= original mesh. Tools= all new teeth meshes. Uncheck Keep Tools. It blends all of the support teeth into the original mesh.

Conclusion: Achieving a Flawless Print Through Targeted Mesh Modification

This video showed how you could modify a mesh without actually having to modify the mesh. Instead, you created the 3D models in Fusion like you are used to, then converted those into meshes and just merged them into the original mesh. Much quicker, easier, and smoother.