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In this lesson we're going to create the front axle plate for our wagon, and while modeling the part we're going to learn how we can use one surface to trim another. We'll also learn that surfaces cannot only be trimmed, they can be extended as well. On my screen, I have some polyline geometry, I am going to orbit my view, such that you can see its orientation in 3D space. Pretty much what I've done is created the front-view cross-section and the top-view cross-section of my axle plate. Let's return the view to about where we started, and I'm going to begin my model by extruding this polyline.
So I'll launch the Extrude command, I'll select my geometry and hit Enter, and I'm going to pull this up a distance of 5 units and I will hit Enter. Next, I'll re-launch the Extrude command, I'll select these two sections and hit Enter, and I'll pull these back a distance of 14. Now as I orbit my geometry, you can see I have multiple intersecting surfaces. At this point, I'd like to use the Trim command to clean up these surfaces and create a composite surface model.
Let's launch the Trim command, and then I am going to select the surfaces that I'd like to trim. That would be this one, this one, and this one, and I'll hit Enter. Now I'll select the surfaces I'd like to use as cutting objects. That would be this one, this one, and this one, Enter. Finally, I'll select the parts of the model that I'd like to remove. I'd like to remove the top here. I'd like to remove the outside portion of this surface, the outside portion of this surface, and the lower portion of this surface, and I'll hit Enter.
Let's zoom in a little bit. I'll orbit this around. Notice by trimming those intersecting surfaces, I can very easily create a more complex shape. Now I am going to tip this up again, because I would like to remove this surface on the bottom. I actually don't need this because the front axle plate is going to be stamped out of a piece of sheet metal. So this bottom surface is unnecessary. To remove it, I'm going to select it and then I will hit the Delete key on my keyboard, and notice what happens. My extruded surface comes back.
That's because of the Surface Associativity setting. This extruded surface was tied to this lower surface that passed through it. When I remove the lower surface, my extruded surface had no place else to go, but back where he started. Keep that in mind, when you're working with Surface Associativity turned on. Now I want to keep my Surface Associativity so I am going to work around this. I am going to orbit this back down a little bit. Let's go to a front view. I'll zoom in and I'm going to trim this lower half off using this 2D line work.
I'll launch the Trim command, I'll select my surface and hit Enter, and we'll then select this geometry and hit Enter. Finally, I'll select the part of the surface I want to remove and I will hit Enter, there we go. Now I have exactly what I needed, and all of my surfaces are still dynamically linked to the geometry that created them. Let's do a little layer maintenance. I don't need my section geometry visible on screen anymore, so I am going to open up the Layer Properties Manager, and I am going to turn off layer surface_section1.
Let's zoom in on this front portion of the model. I would like to change the shape of this area. This is where the handle is going to be bolted onto my axle plate. Let's turn on another layer. I will go back to the Layer Properties Manager and we'll turn on surface_section2. If I back up a little bit you can see I have drawn an arc in the top-view plane. Let's come over and click the top-view hot spot, so we can see where that arc is in relation to our part. Notice if that arc was projected straight up, it would cut the front off of this surface.
Let's actually make that modification. We'll do it by using the Trim command. I am going to orbit this up, so I can see both of my objects. We'll launch Trim and I would like to trim this top surface and this side surface and I'll hit Enter, and we'll then select my cutting edge and hit Enter, and notice that AutoCAD projects that geometry perpendicular to the drawing plane, such that it passes through my surface. I can then click this portion to trim my top surface and I'll click this portion to trim off the side surface and I will hit Enter.
So if you are trimming a surface based on 2D geometry, your trim is not based on your point of view. It's based on the drafting plane in which your line work was created. It will always be projected perpendicular from that plane. Let's zoom in a little bit closer on this area. I would like to pull these edges out and create some tabs, such that I have a place to put the bolt through to hold the handle. Not only can we trim surfaces, we can also extend them. To extend a surface, I'm going to move up to the Edit panel and launch the Surface Extend command.
I will then select the edge of this surface and hit Enter and I'll pull this out a distance of .5. Now if I hover over this you can see that the surface that I created is an independent surface. It's actually not tied to the original. That's the way things work by default. We don't have to have it that way. If we want our extension to be a part of the original surface, let me show you how we can do that. I am going to launch the Extend command again. I'll select this edge and hit Enter and then I'll right -click and select Modes.
From here I'll select Extend from the menu and then I will change this from Append to Merge. Once again I'll enter a distance of .5 and hit Enter. The extension that I created is a part of the original surface. Let's switch to our right side view. I'm going to click that hotspot on my ViewCube. We'll zoom in on the same area and we'll turn on another layer. This time we'll turn on layer surface_trim. This layer contains the geometry that I'd like to use to trim these tabs that we just created.
Once again, we'll use the Trim command, and remember we don't have to maintain that right side view to get our trim. I'll launch the command. I would like to trim this tab and this one, Enter. I would like to use this arc and this circle is cutting objects, Enter, and then I will click the areas that I'd like to trim. When I'm finished I'll hit Enter. Let's go back to our right side view. We'll zoom in on the back portion of our axel plate. I am going to turn on another layer.
Let's turn on surface_trim2 this time. This layer contains the circle that represents the hole where my axle is going to pass through the plate. Once again I am going to trim this out using the Trim command. Let's select our surface, Enter, select our geometry, Enter, and then we'll click to remove the hole. Finally, I'll hit the Enter key when I am finished. If I orbit this around, you can see the hole was punched through both sides. Let me tip this up a little bit. I have another hole on top.
I am going to click the top-view hot spot, such that were oriented in that view. There we go, let's launch Trim again. I'll select the surface, Enter, the geometry, Enter, and the part I want to remove, Enter. Okay, let's back up. We'll adjust our view on screen and we'll zoom in. I'd like to do a little bit more layer maintenance. Let's get rid of some of these things that we don't need anymore. We'll go back to the Layer Properties Manager and I am going to turn off my section2 layer, my surface_ trim, and my surface_trim2 layer.
Let's turn on surface_trim3 and return to our drawing. Now if you've ever used a wagon before, you know that the front axle plate has to pivot so that the wagon can steer. I would like to create a circular recessed pivot area on top of this plate and I'm going to do that by revolving this circle around this axis. So let's launch the Revolve command, I'll select my circle and hit Enter, and I'd like to define my axis of revolution by this endpoint and this endpoint, and my angle will be 360, and I'll hit Enter.
Now the revolution I just made is a surface. Let's now create the recessed pivot area by trimming this surface and this one. I'll launch my Trim command and then I'll select the surfaces I'd like to trim. Both of these, I'll hit Enter,. I will then select the surfaces I'd like to use as cutting objects. Once again, the same two surfaces. Finally, I'll select the portions I'd like to remove. We'll remove the top of this doughnut shape and then I'll remove this area right between my score lines.
There we go, and that creates a nice circular recessed area for my pivot. Finally, we have one more thing. We need to create our front axle. Let's turn on another layer. This time we'll turn on the solid_extrude layer. Let me orbit this around. We'll do it from the backside. Also note that I'm still in the Trim command. Let me hit Enter to exit that, there we go. To create my axle I am going to extrude this circle along this path, but I would like my extrusion to be a solid.
So let's launch the Extrude command. I will then right-click and select Mode and I'm going to select Solid from the menu. I'll then select my circle and hit Enter. Now I don't want to create a straight extrusion, so I'm going to right-click and select Path from the menu and I'll select my path to create the solid geometry for my axle. Finally, we'll orbit this around. We'll center it on screen. Let's turn off any of the layers that we don't need. We don't need the solid_extrude layer. We don't need the surface_trim layer. I'm going to leave wagon_front_axle turned on.
We'll save this geometry, so we can use it later in our final assembly. Let's go to the application menu and I'll click Save As. We'll save this in the exercise files folder inside the finished_parts directory. I'm going to call this frontAxle _finished, and I'll click Save. This completes the geometry for the front axle plate. In this lesson, we learned that trimming intersecting surfaces is a great way to create complex surface models. We also learned that if we trim a surface using 2D geometry, our cutting objects are projected perpendicular from the plane on which they were created.
Finally, we learned that surfaces cannot only be trimmed, they can also be extended.
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