Creating a clutch case with the Loft command in Fusion
- Brad Tallis
- Apr 15
- 3 min read
Creating complex parts like a gear housing or clutch case can seem hard at first. You might try to use a simple revolve tool, but that doesn't always work. If your part moves from a circular base to a rectangular top, you need a different plan. This guide shows you how to use the loft command and guide rails to build professional 3D models in Autodesk Fusion.
Getting Started with the Loft Command
The loft command is the best way to connect two different shapes. To use it, you need two separate planes. Start by creating a new component and naming it something like Clutch Case.
First, draw a circle on the first plane. For this example, let's make it 12 inches wide. Next, you need a second plane sitting above the first one. Use the offset construction plane tool to move up 6 inches. On this new plane, draw a rectangle. Use the center rectangle tool so it lines up perfectly with the circle below.
Adding Fillets to Your Sketch
While you usually add rounded corners in 3D, doing them in the 2D sketch helps with lofts. Select the corners of your rectangle and add a 1-inch fillet. This makes the transition between the circle and the rectangle much smoother.
Using Guide Rails for Better Shapes
If you just loft the circle to the rectangle, the sides might look strange. The software just takes the shortest path between the shapes. To get a specific curve, you must use guide rails. Guide rails tell the loft exactly which path to follow.
The Intersect Command
To make guide rails that actually touch your shapes, use the intersect command. This is found under the create and project menus. It finds where your existing profiles intersect with the sketch plane. This gives you exact points to snap your lines to.
Create a sketch on a side plane.
Use Create-->Project/Include-->Intersect to find the edges of the circle and rectangle.
Draw lines connecting these points.
Use fillets to round the corners of your guide lines.
Repeat this process on all four sides of your model. Having a guide rail for every major side prevents wrinkles in the 3D surface. When you run the loft command again, select your two profiles and then select all four rails.
Refining the Housing Design
Once you have the main lofted shape, you can start to modify it. Use the extrude tool on the top face to give it some height. Then, use the shell tool to hollow out the inside. A thickness of 0.25 inches is a good starting point for a sturdy housing. This removes the solid middle and leaves you with a realistic casing.
Creating Bolt Holes and Bosses
Most gear housings need a way to bolt together. You can create a ring around the bottom for these bolts.
Draw a circle on the bottom face.
Extrude it to create a mounting flange.
Draw a small circle for a bolt hole.
Use the horizontal/vertical constraint to line the hole up with the center.
Extrude the hole through the flange.
When cutting holes for bolts, select both the hole area and the surrounding material. This prevents "sliver faces," which are tiny, annoying pieces of leftover 3D geometry.
Advanced Modeling Techniques
Instead of drawing every single bolt hole, use the circular pattern tool. This saves time and makes changes easier later. Change the pattern type to "Features" so you can pick the hole, the cut, and any fillets all at once.
The Power of Rule Fillets
Rounding every edge on 14 different bolt holes would take forever. Instead, use the rule fillet command. This tool lets you select a "source" feature, like your circular pattern. It will automatically find and round every edge created by that pattern. This keeps your timeline clean and saves you from clicking a bunch of lines.
Adding Side Features with Tangent Planes
If you need to add a square box or a mount to the curved side of your housing, use a tangent plane.
Select the curved face.
Create a tangent plane at that spot.
Draw your square on this plane.
Use Extrude to Object to make the square grow until it perfectly meets the curved housing.
By using "Extrude to Object" instead of a set distance, the part will always fit perfectly even if you change the size of the housing later.
Conclusion
Building a gear housing in Fusion requires more than just basic shapes. By mastering the loft command and guide rails, you can create smooth transitions between different shapes. Using smart tools like rule fillets and tangent planes makes your modeling faster and more professional.
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