Designing a Pulley for a D-Shaft Motor
I want to walk you through a quick Fusion 360 tutorial where we’ll design a pulley that perfectly fits the D-shaft of a motor. This is a task I often find myself needing to tackle, so I’ve developed a reliable approach that I’m excited to share with you. Let’s jump right in!
Overview of the Pulley Design Process
Above is the completed pulley design. As you can see, the hole for the D-shaft is perfectly aligned with the shaft of the motor. The goal is to ensure a snug fit that’s secure but also allows for easy removal without damaging the motor shaft.
Before diving into the D-shaft design specifics, let me briefly walk you through how I approached the overall pulley design. We’ll start with the first sketch:
Creating the Profile: In the front view, I sketched the top portion of the pulley profile. Once the top was complete, I mirrored it about a central line to generate the bottom half.
Revolving the Profile: With the full profile complete, I used the Revolve Tool to revolve it around the central axis. This gave me the basic pulley shape.
If you’re interested in a more detailed tutorial on creating this initial sketch, let me know in the comments. For now, let’s focus on designing the D-shaft hole.
Designing the D-Shaft Hole
To ensure the pulley fits securely onto the motor, precision is key. Here’s how I created the D-shaft hole in Fusion 360:
Step 1: Measuring the Shaft Dimensions
Using a pair of digital calipers, I measured the dimensions of the motor shaft:
Diameter of the shaft: 3 mm
Distance from the flat of the shaft to the outer edge: 2.5 mm
Step 2: Creating the Sketch
Starting with the Circle: Open a sketch on the top surface of the pulley. Use the Circle Tool (shortcut: C) to draw a circle at the center of the sketch. Set the diameter to 3 mm, matching the motor shaft.
Adding the Flat Edge: To define the flat part of the D-shaft, I drew a horizontal line. Here’s the key:
Use the Coincident Constraint to attach one endpoint of the line to the perimeter of the circle.
Attach the other endpoint to the opposite side of the circle.
Setting the Dimension: This is where a neat trick comes in:
Select the line and press D for the Dimension Tool.
Right-click and choose Pick Circle Arc Tangent instead of the default Arc Center option.
Hover over the top of the circle until you see a small X, then click and set the dimension to 2.5 mm.
By using the tangent measurement, the flat edge is placed precisely where it needs to be.
Step 3: Cutting the D-Shaft Profile
Finish the Sketch: Once the D-shaft profile is complete, finish the sketch.
Extrude the Profile: Select the D-shaft profile and use the Extrude Tool (shortcut: E) to cut through the pulley. Set the distance to the desired depth.
Step 4: Adding Clearance
To ensure the pulley fits snugly but not too tightly:
Go to Modify > Offset Face.
Select the two inner faces of the D-shaft hole.
Set the offset to -0.1 mm (negative to slightly enlarge the hole).
Different 3D printers may require different clearance values, so adjust based on your setup.
Fine-Tuning the Fit
After printing the initial design, I tested the fit. The pulley was too tight, so I made a slight adjustment:
Reopened the Offset Face feature.
Changed the offset from -0.1 mm to -0.15 mm, adding an extra 0.05 mm of clearance.
The result? A perfect friction fit. The pulley slides onto the shaft with slight resistance, ensuring it stays in place but can still be removed without excessive force.
Key Takeaways
Use Digital Calipers: Accurate measurements are crucial for a perfect fit.
Tangent Dimensions: The Pick Circle Arc Tangent feature in Fusion 360 comes in very handy. Keep this one in your back pocket.
Test and Adjust: Always test your prints and fine-tune the clearance for your specific 3D printer.
Wrap-Up
That’s it for today’s Fusion 360 tip! Designing a pulley for a D-shaft motor may seem daunting at first, but with these techniques, you’ll achieve a professional fit every time. If you found this tutorial helpful, let me know in the comments. Have questions or topics you’d like me to cover next? Drop them below.
Until next time, keep creating and happy making!
By the way, I'm currently running a half-off promotion to my online Weekly Live Fusion Class. Click here for more info
— Vladimir
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