You have spent hours designing your part in Fusion 360. The geometry is exactly right, the dimensions are perfect and you are ready to print. The final step is exporting your design as an STL file — the format that virtually every 3D printer and slicing software in the world accepts. It sounds simple, but there are a handful of settings that make the difference between a clean, accurate print and a faceted, low-quality result. This guide walks you through the entire STL export process in Fusion 360 so you get it right the first time. What is an STL File? STL stands for Standard Tessellation Language. It is the most widely used file format for 3D printing and has been the industry standard for decades. An STL file represents your 3D model as a mesh of tiny triangles that approximate the surface of your part. The more triangles used, the smoother and more accurate the surface — but also the larger the file size. Getting the right balance between mesh quality and file size is one of the key decisions you make during STL export. Before You Export — Check Your Model Before exporting any STL file, spend a moment checking your model for issues that will cause problems during printing. Make sure your part is a single solid body with no open faces or gaps. Open shells — surfaces that do not form a fully closed volume — will confuse most slicers and may result in the part not printing correctly. In Fusion 360, a valid solid body will show as a Body in the browser panel on the left side of the screen. If you see Surface instead, your geometry is not closed and needs to be fixed before exporting. How to Export STL in Fusion 360 Step 1 — Right-Click the Body in the Browser The fastest way to export an STL in Fusion 360 is to right-click directly on the body you want to export in the browser panel on the left side of the screen. In the context menu that appears, click Save As Mesh. This opens the export dialog with all the settings you need. Step 2 — Choose the File Format In the Save As Mesh dialog, make sure the Format is set to STL. Fusion 360 also supports OBJ and 3MF formats — OBJ is used for rendering and visualization, and 3MF is a newer format supported by some modern slicers. For compatibility with the widest range of slicers and printers, STL is the safest choice. Step 3 — Choose Binary or ASCII The Structure option lets you choose between Binary and ASCII. Binary STL files are much smaller and faster to process, which is why they are the default and what you should use in almost every situation. ASCII STL files are human-readable text, which is occasionally useful for debugging or inspection, but they are significantly larger and slower to work with. Stick with Binary unless you have a specific reason to use ASCII. Step 4 — Set the Mesh Refinement This is the most important setting in the entire export process. The Refinement option controls how many triangles are used to approximate curved surfaces in your model. Fusion 360 gives you preset options — Low, Medium, High and Custom. Low produces a coarse mesh with visible faceting on curved surfaces, which is fine for very rough concept models but not for final prints. Medium is a reasonable starting point for most parts. High produces a smoother mesh that is more accurate to your original geometry and is the right choice for most 3D printing work. Custom lets you set the exact surface deviation and normal deviation values manually, giving you precise control over mesh quality for advanced use cases. For most 3D printed parts, High refinement gives you a good balance between mesh quality and file size. If your part has very large flat surfaces and few curves, Medium refinement may be sufficient. Step 5 — Preview the Mesh Before exporting, click the Preview button in the dialog to see how the mesh looks on your model. This is especially important for curved or organic shapes where faceting can be visible. If the preview shows obvious flat facets where you expect smooth curves, increase the refinement level before exporting. Step 6 — Export the File Click OK to export. Fusion 360 will ask you where to save the file and what to name it. Choose a location you can easily find, give the file a clear descriptive name and click Save. Your STL file is ready. How to Export Multiple Bodies as One STL If your design has multiple bodies that you want to export as a single STL file, you need to either combine them first or use the Export option from the File menu rather than right-clicking in the browser. Go to File → Export, choose STL as the format and make sure the selection includes all the bodies you want. This exports everything as a single merged mesh, which is what most slicers expect when printing multi-body designs as one piece. STL Export Settings for Different Use Cases The right refinement settings depend on what you are printing and how accurate you need the result to be. For functional mechanical parts like brackets, motor mounts and gears, High refinement