Explore advanced sketching techniques used to create a 3D model of a power cord, including strategic hiding of unnecessary components, the use of projected geometry, and the importance of constraining and dimensioning features accurately. Understand the downside of using a single spline for complex shapes and the benefits of using a series of splines, arcs, and lines to create a parametric model that can be updated when the model is moved.
Key Insights
- Advanced sketching includes hiding unnecessary components in the model to ensure a clear focus on necessary components such as the power cord.
- Rather than using a single spline for complex shapes, it's better practice to use a series of splines, arcs, and lines to create a parametric model. This allows the model to be updated parametrically when certain sections are moved or changed.
- The use of projected geometry and the careful constraining and dimensioning of lines are crucial for accurate and professional 3D modeling.
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In this video, we will use some advanced sketching techniques to create the power cord for our model. If you will, please scroll down, find Step 13, and open it.
Once your file is open, you can go ahead and hide your data panel, and let's look at our Power Cord component. I need to add a component inside of my Power Cord component for the cord. So I will right-click > New Component, and I will name this “Cord.”
Also, I want to hide some features in my model because they are not necessary—specifically the Fastener Assemblies component and the Lampshade. I will still need the Lampshade Cap Assembly, as that's where my cord is going into.
I’ll need my arms here and here, but I don’t need this arm or the base. So I will go into the Arm Assembly, hide the Lampshade Arm and the Lower Arm, and hide the Base component. Now that I have all the components I need, I can begin sketching.
I’ll create a new sketch and host it directly to my middle plane. This is because my lamp is symmetrical, and I’m only creating the first part going through the middle of the arm. Once the sketch is active, I’ll zoom in and explain the sketch layout.
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For now, I’ll demonstrate a spline—but please do not use this as the final approach. We are going to run the cord through this arm, up through the next arm, and around like this. This shows the rough path for our model, but using one long spline like this is poor practice.
Splines with too many points are not parametric and cannot be easily updated. Instead, I will use a combination of splines, arcs, and lines to create a parametric model that updates when we move the lamp. So I will delete this spline—just remember the shape—and let's begin sketching properly.
Notice that there is no projected geometry in view, so the first thing I want to do is create projected geometry to snap to. You’ll notice that I cannot directly select the hole in the model. I will go to the Sketch Palette and enable Slice. This will slice the model down the middle, revealing the interior of the Lampshade Cap Assembly.
Now I will press P for Project and zoom in to grab the top and bottom edges of the holes. I’ll do the same for the lower hole. Now we’ll be able to snap to the midpoints of those lines.
I also want to snap to specific parts of the Lampshade Cap, but instead of using Slice, I’d prefer to grab the outside edges. So I will uncheck Slice, press P for Project, and grab the horizontal lines here. I can also click directly on the face to grab all surrounding geometry.
Once that’s done, I no longer need the Lampshade Cap Assembly, so I can hide it. The projected geometry will remain visible. I’ll keep one arm component visible for context while sketching. If you accidentally hid the Lampshade Cap Assembly while still in the Project command, you may need to hide it again.
Let’s begin drawing. I want to start down here because all of my lines and arcs will begin from this point, which is easiest to draw. I’ll select Line and zoom in, then draw a line from this endpoint to this endpoint.
Notice that the Line command finishes, and the two endpoints are black, meaning the line is fully constrained. I’ll select Line again and repeat the process for the next pair of endpoints.
Again, fully black lines are fully constrained. Now I’ll draw a line into empty space and press Escape. Let’s constrain and dimension this line.
I’ll apply a Parallel constraint between this line and the bottom edge of the arm, then press D for Dimension and set the distance to 10 millimeters.
Next, I want to connect these lines with arcs. I’ll go to Sketch > Fillet, select the first pair of lines, and set a radius of 5. Your value may vary depending on your zoom level.
Notice that adding the fillet has unconstrained the line. This is because the endpoint is no longer coincident with the midpoint of the line. Apply a Perpendicular constraint from the arc to the nearby edge to fully constrain it. Let’s do that one more time.
I’ll go to Sketch > Fillet, select the next pair of lines, set the radius to 5, and accept the warning that constraints were removed. Again, I’ll apply a Perpendicular constraint to restore stability.
Notice that the projected edge created a profile—this is okay. I’ll select it with a crossing window and change it to Construction geometry to remove the profile.
Let’s review. I now have a rough shape for the lampshade arm cord. I’m happy with the result, so I’ll click Stop Sketch and save the file.
Before ending the video, let’s do one more thing. I’ll double-click to edit the sketch again and add small helper geometry we’ll use in the next video when placing our splines.
I’ll draw a new line, ensure that it is blue and unconstrained. Then, I’ll press P for Project and project this circle into the sketch. I’ll apply a Coincident constraint from the new line to the circle’s center point.
Now one end of the line is constrained, and the other is free to move. I’ll change this line to Construction geometry and apply an angular dimension of 10 degrees.
That’s all for this geometry. I’ve placed a helper line constrained at one end and unconstrained at the other so it can rotate freely. This will help us create a spline that connects to that endpoint and follows the lamp’s path.
We’ll do that in the next video. For now, zoom out, click Stop Sketch, and save the file.
I’ll see you in the next video.
