From the course: Learning CATIA v5

Types of sketches - CATIA Tutorial

From the course: Learning CATIA v5

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Types of sketches

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- [Instructor] I'd like to take a moment and step back and talk about two different types of sketches that V5 offers you. Now, when we go to the sketch icon, you'll notice I have this little black arrow, and as I mentioned before, that is indicating that there are additional functions located underneath that icon. So I'm just going to select it, and I'm going to drag out that toolbar, and what I want you to notice is that there's a sketch and position sketch. By default, you have what's called "sketch," and when you look at this, the system defines the absolute, as well as the horizontal axis, based off of the plane or the face that you select to draw your sketch on. This is called a sliding sketch. So when I select on the icon, you'll notice that no menu pops up, nothing appears. If you read down below, you'll notice that it says "Select a plane, planar face, or a sketch." Now, if I pick a plane or a planar face, it's going to create a new sketch. If I select an existing sketch, it enters into that existing sketch and allows you to modify it or do any edits that you want to. So here, I'm just going to simply select my plane. And once again, I can pick the plane either in the graphics window, or I could pick it in the tree. Once I select it, you'll notice that the sketch orients to the horizontal and vertical, as well as you're looking straight down the Z axis of the sketch. Here, this sliding sketch determines the horizontal based off of the plane or the face that you selected. When I look at the sketch here in the tree, you'll notice that I have this large S sitting beside that. I'm just going to generate some curves, and exit out of the workbench. And it's important to pay attention to this. This is one of those features that, if you're not careful, can potentially cause problems in the future, and I'll explain why in a moment. But before I do that, I'm going to create a position sketch. I'm going to select the position sketch icon. And here, what you'll notice is that the menu actually pops up, and you have several options within the sketch positioning. I'm going to pick the same plane as I did previously. And you'll notice that the origin or the axis of that sketch comes in and overlays exactly on the previous sketch, 'cause I picked the same plane. The difference between a sliding sketch, and in this case, the positioning sketch or the position sketch, is that I have the capability now to specify the origin. So, if I have a point, or a datum point, or a reference out in space that doesn't sit at absolute, which is quite frequent when you're designing something. You may have a datum, datumae, that you have to reference over and over again. This allows you now to attach the sketch to that reference origin point out in space. You also have an orientation. Orientation is very important in that it allows you to control the horizontal or the vertical of the sketch, whichever is easier for you to maintain. Now, in some instances you may have a tooling direction, which would be a vertical in your sketch. So you can come in here and specify I want something to be parallel to a line, or based off of a vector, or through a point. So you would have a tertiary piece of geometry determining what your aiming at, or determining what your horizontal is aiming at, or your vertical is aiming at. Once you have those elements selected, you can move further on down and reverse, let me orient this to the screen, the horizontal and the vertical. You can also swap out the horizontal and vertical. So, using the position sketch, you have full control over the origin, as well as the orientation of the sketch, whereas with a sliding sketch, the system determines the origin based off of absolute. It also determines the horizontal reference and the vertical reference. Positioning sketch gives you a lot more options, but it also allows you to fully control that sketch, and in a lot of cases, that's very important. Sometimes, when you make a modification to some geometry, let's say a plane, or a solid and the face somehow changes, that modification could potentially affect the surface or the plane normal, and if it reverses, there's a good potential that the sketch has issues and could potentially fail in the future, or may drop a reference, or decides to pick up a reference that's unknown, and your sketch orientation gets a little wacky. So, for someone just coming in and making widgets, tiny pieces, something where the orientation control isn't that critical, a sliding sketch is more than acceptable. Great tool, very powerful. But, if you really want to fully realize the capabilities of a sketch, getting to understand a positioning sketch is going to be critical for you in the future.

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