4 min read

CAD Weeks 2+3: Learning Basics

Since I couldn't attend Week 2's class, I've been quite behind, but I'm slowly getting the hang of things. I tried three examples from last week's assignment, the final results which I show below:

I more or less followed the same steps for each model: follow the diagram to create a sketch and then extrude. For the Lego block, I cropped the image into its bottom and side views and tried to sketch over them. For all three models, I tried using constraints as much as possible, but I think I'm still having trouble being thorough with all of them. One of the tutorial videos shows how you can make a fully-defined sketch, but I don't think any of mine are.

I have the following questions so far that I hope to ask in class:

  1. How do you extrude up to the height/border of another sketch? For example, the side view of the Lego block shows a narrow section in the center that doesn't go all the way to the bottom, but when extruding from the bottom view, it's hard to tell by eye up to where I should cut.
  2. Is it possible to rotate a canvas to a different face? When writing sketches for different axes, I want to see the same diagram, but I couldn't figure out a way to move it.
  3. How do you properly align sketches of the same object that are on different planes? For example, I extruded the caps of the Lego blocks from a top-view sketch, but I had to manually move the sketch to the correct height so that the extrusion wouldn't cut through one I made for the body. Is there a more efficient way of doing that?
  4. When should you make new components? The tutorial videos mention making components to organize your work but I haven't used them yet.
  5. How do you make sure that the entire sketch/parts of the sketch won't shift when you resize a part or add a new constraint? I can show what I mean in the second example: whenever I adjust a line it moves everything at once.

After getting some practice in with last week's assignments, I tried this week's classwork again, and managed to create a vase and cup using the reference photos.

I think I got the hang of using spline and rotation, but watching the demo videos I realized there's a lot of eyeballing that has to take place in between very precise sketches. For example, when creating the cylinder that I used to cut along the outer perimeter of the cup, I had to move the sketch by hand so that it was nearly the height of the cup before extruding down.

Finally, I had a chance to build the IKEA plant stand for this week's homework. The steps themselves weren't so complicated, since given the symmetrical arrangement of each level of the plant stand meant that I only had to model one of them, create a pattern, and then adjust the heights accordingly. The execution was a little more complicated, as I ran into the following questions:

  1. How do I make two circles concentric while keeping them at different heights in my sketch? I had two circles in my sketch for the diameter of the leg and the bottom, and another two for the outer and inner perimeters of each table. I tried to place these circles at different heights, but when using concentric circles or move to point, the z-coordinate would also change.
  2. How do I use fillet to make a convex curve between two edges? As you can see in the reference image, each leg of the plant stand isn't a straight cylinder, but is round at the end. I used two circles for the bottom of the leg thinking that I could fillet the edge between them after extruding, but found that filleting made a concave curve instead of convex.