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In this section of the tutorial, we modify the model to create a casting pattern. We simplify the model, add draft, and then add fillets and rounds.
Before we can start modifying the model, we need the parting line, pull direction, minimum section thicknesses. We also need to know which surfaces are machined. For this part:
- The bottom of the part is the parting line, so the pull direction is vertical.
- The bottom of the part is machined.
- The width at the top of the extrusions cannot be reduced.
- The inside faces of the extrusions are machined.
- Open the tutorial file Body Constraints and Dimensions.dwg, and save it as Advanced Modeling Tutorial- casting pattern.
- Start the Simplify command from the Simulation Panel. It automatically selects all fillet, chamfer, and hole features.
We need the chamfered faces, so deselect the Chamfer filter. Confirm the Action is set to Delete, and click the check mark.
- Before we add draft, we should capture the current size and shape of the model. Since Fusion does not create a link between sketches and the model, projected geometry in sketches does not update. Create sketches on the Left, Front, and Bottom faces, and project geometry as necessary. Rename the sketches to match the views, and turn off the visibility.
- Start the Draft command and select the top face of the base for the neutral plane. Select the inside faces, enter 2 for the draft angle, and then press Enter. The taper makes the extrusions narrower, so we need to increase the width.
- Use the ViewCube to rotate the model to the Left face. Expand the Sketches folder in the browser and edit the sketch for the left face. Project the inside edge of an extrusion so we can measure how much material was removed. Start Measure and select the endpoints- the gap is 1.9 mm. We also need a 2 mm machining allowance, so we will increase the width by 4 mm.
Start Press/Pull, and 4 mm to each inside face.
- The draft on the outside cannot remove material. If we use the bottom of the model as the neutral plane, we have to add material. A simpler method is to create a work plane tangent to the top of the extrusions, and use it as the neutral plane.
Click the drop-down arrow next to Plane and select Plane At Tangent. Select one of the rounds, and then select the top face of the base to provide an angular reference.
- Start Press/Pull and add 2 mm to the bottom face of the part for a machining allowance.
- Start Draft and select the work plane, and then select the outside faces. When you enter a draft angle, the error symbol displays. Press the Ctrl key, click a face to remove it from the selection set, and then release the Ctrl key to update the preview. The error does not display when you remove the Left face. Since that face is tangent to the round, the taper cannot be added from the neutral plane. Add the other faces, if necessary, and create the 2.0 degree draft.
- Rotate the model and click the Top-Left-Front corner of the View Cube. Since the left face is tangent to the round, we cannot use the Draft command to add the taper. The solution is to use Move to rotate the face at the tangent. Start Move and select the Left face. Click the Reorient Triad button, select a tangent edge on the face, and then click Finish Reorient. Select the arc manipulator and rotate the face 2.0 degrees.
- Now that all of the faces have draft, we can add fillets and rounds to finish the pattern. Create 8 mm fillets on the short edges, and 2 mm fillets on the rest of the edges.