If you need to make a quick patch to a model in Fusion 360, it is often easier to use the Brep functionality located in the Surface tab.
The commands of this workspace work similarly to the features of both the Solid tab and the Form contextual tab, but with a couple of notable differences. A Brep, or Boundary Representation patch, allows you to use curves to generate more free-form and flowing surfaces.
Expand the Create panel and you will notice that, unlike the Sculpt and Model environments, there are initially no included tools to allow you to create primitives in Patch. You will, however, see tools like Extrude, Revolve, Sweep, and Loft that allow you to create a 3D form from a 2D sketch. If, however, you are importing an existing shape into Fusion, you will find the same basic primitive shapes that are available in the Solid tab and the Form contextual tab.
To form a surface in the Patch environment, you can start by first clicking Create Sketch, selecting a plane, and sketching a rectangle that is 100 mm x 100 mm. Click Finish Sketch. Then, use the Extrude command to create a surface that is 50 mm high. Notice that the box is open at both ends. This is because an object created in the Surface environment is a surface, not a solid. Like a T-Spline extrusion, the Brep does not have any mass. Look in the Timeline, and you can see that the shape has been created with Sketch and Extrude icons.
The Create panel also features some surface creation features specific to the Surface tab: Patch, Offset, and Boundary Fill.
Offset is used to create an offset copy of an existing surface, face, or quilt. The copy is generated so that all surfaces are offset at an equal distance from the original. Start the Offset command and choose one of the faces. This instantly creates a copy that can be offset to any distance you desire. You can also select multiple faces to offset. Select each of the four sides and drag them out to create a larger box surrounding your original box.
Notice that you can move offset faces independently of the original. The new surface is not associated with the original and will not update if the original is changed. The new surface is listed as a new body in the browser, which means that you can right-click it in either the browser or Timeline and edit the offset at a later date.
Patch is used to create a boundary patch surface, which is extremely useful for closing open faces in your model. The biggest advantage is that you can select a series of existing edges and Fusion will determine the patch to create.
Select the Patch tool and the Patch dialog opens. Before making your selections, make sure that you toggle ON Enable Chaining. This allows you to click a single edge and all adjacent edges are selected simultaneously. When this option is disabled, you will need to pick all of the edges that are required. Now, select the top edge of the smaller open box in the middle of your model.
The Continuity drop-down controls the transition between the new patch and the selected edges. There are three types: Connected, Tangent, and Curvature.
Connected creates a G0 surface, which means that no transition occurs. The patch surface will be created based on the selected edges, with no consideration to the surfaces around it.
Tangent creates a G1 surface. This means that the patch is tangential to the surfaces around it.
Curvature creates a G2 surface, which means that it is blended with continuous curvature.
Leave the Continuity set to Connected and click OK to create your patch.
Using the Boundary Fill tool can help you to create a complex shape by using surface model geometry in conjunction with solid geometry and work planes. It gives you the control to define shapes based on the intersections of solids and surfaces.
To create a boundary fill, expand the Create panel, click Boundary Fill, and the Boundary Fill dialog appears.
Then, use a window to select all of the geometry in small box in the center of this model. Once all the features are selected, the option to select cells becomes available.
The cells are the regions that are defined by the intersection of the selected solids and surfaces. These cells can be joined together, deleted, or used to create new components. Depending on the selection in the Operation drop-down, such as Cut or Join, picking the cells will represent different procedures. For example, selecting Cut will result in the selected cells being deleted. Selecting Join will mean the selected cells will be joined together. Alternatively, by selecting New Component, you will be able to choose which cells you wish to keep and create into new components.
Choose one of the cells, set the Operation to New Body, and click OK to complete the feature. The selected cell will now be listed in the browser as a new body.
To edit the boundary fill at a later date, right-click the Boundary Fill icon in the Timeline and select Edit Feature. A dialog box appears that contains the same options as before.