Join Dave Schultze for an in-depth discussion in this video Surface analysis tool: Draft Angle Analysis, part of Rhino: Tips, Tricks & Techniques.
- [Narrator] Next up we check out a surface analysis tool called Draft Angle Analysis. This tool is far more specialized than the other surface analysis tools we've looked at in other videos. It is used to evaluate geometry for potential issues on injection molded parts. We'll start of by taking a look at a couple of very simple objects. This cone and vase shape here in the front. I'm going to go ahead and launch the command by going going up to the analyze toolbar, go to surface, and then draft angle analysis.
We'll pick both of these, one after the other, and right click to complete. Now we'll kind of examine some of the options here. I'll zoom in to this first one on the left. I'm noticing it's kind of got jagged edges here, so what you want to do, when possible, is adjust the mesh. The term mesh can be confusing, but all this is referring to is the display or viewport mesh. Just to make it smoother and give you better feedback. I'm just going to select that option there. Crank the slider all the way up.
You can go ahead and preview it and you'll notice the difference. So the mesh becomes much tighter and the edges are smoother. Hit ok, and now we are seeing how this command really works. We basically have several colors that identify a range of angles. These angles as set right now range from zero, which indicates red, and then blue, which indicates 5 degrees. So in relation to what you might ask? Well, we are using the construction plane, and going straight up vertically.
So if you think about it, if this form were to be pulled in that direction vertically, this red angle indicates an undercut that would be a problem with tooling. Now the blue is exposed to the air above. That will be fine. And then we have a transition zone here, which is the in between green color. That's getting close to vertical and then red again is either zero or an undercut. Let's go check out the cone shape, and this is a little bit confusing.
Why is it red? It looks like it should work just fine for a tool that is pulling vertically straight up. However, there is one thing you got to watch out for and that is the surface normals, or direction of the geometry. Let's exit this command here just for a moment. I'm going to select this object and then there is a command called direction here on the main toolbar, analyze direction with a left click. And these arrows, which have been covered actually in some other lessons, but for now, we're just going to flip them going the opposite direction and then right click to exit the command.
Okay, let's revisit the command and see what difference we've made. Analyze, surface, draft angle analysis, select this cone. Right click to accept. And now it's a totally different color, so you can see that it is all blue, so therefore we're going to have minimal or no problems with injection molding. So a basic strategy I would recommend for using this command is if you are having a little bit of trouble understanding this, you might want to check some of your forms early in the process just to get a feel for it. But typically I don't really worry about them until much later in the process.
Let's go ahead and add the entire spacecraft over here. We're going to select add objects, click the whole of the spacecraft, and then right click. Looks like the mesh is pretty nice and clean there. We're going to do something that's a bit of a hack. This is not surprising, the fact that the blue section, or greater than zero degrees would be facing up, but I like to do every once in a while is just kind of crank these values down to the exact same number. So I'm going to put zero for the blue and zero for the red.
And immediately you can see that there is just those two colors. But this is actually fairly useful if you'd like kind of a recommended location for your parting line. So that makes a lot of sense. It's kind of right there almost down the center, or equator of that form. Let's go ahead and close out the command and mention that if you thought the other surface analysis tools were nerdy, then this one is yet another degree up the nerd chart. Draft angle may not be used very often, but it's a very useful tool if you need to double check for manufacturing.
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Skill Level Intermediate
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