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Constraints are a way to add intelligence to sketches, and in turn, parts in Autodesk Inventor. I want to talk a little bit about constraints before we get into creating geometry, because if you don't understand what a constraint is, you may become confused when you first start creating geometry. Because Auto Disk Inventor will automatically try to apply certain constraints to certain geometry as you're creating it. A constraint, by definition, is something that limits or restricts something. In this case, we're limiting or restricting the motion of sketch geometry.
We're essentially, adding intelligence to the model that instructs it how it can and can't move, as we make changes to our design. What I've done is setup a sketch practice part, which will allow you to very easily see what constraint do to geometry as it's been applied. To begin, we're going to edit this sketch that I've created. In the browser, you can see Sketch one, and you can double click on this icon, or right click and select Edit Sketch, to begin editing the geometry. For those who are new to Inventor, I want to call out one feature that can come in quite handy while you're learning what constraints are.
And that's the ability to right click in the graphics window, and select Show All Degrees of Freedom. What this does, is shows all of the available motion inside geometry in a sketch. What I mean here, is this arrow is pointing in all four directions, which means, if I click on this end point, and left click it and drag, you can see that I can move in all directions. I'm going to hol-, go ahead and use Control Z to undo that. But what you'll see here, is as we add geometric constraints, you will see some of these arrows be removed, indicating that something is being restricted.
Now as you get better with inventor and you understand this, you probably aren't going to use this feature that much. But it's nice while you're getting started. Constraints come in a couple of different forms, they come in geometric constraints and dimension constraints. We're going to start with geometric constraints. Here you can that see we need to apply a horizontal constraint to this piece of geometry. We're going to go the sketch tab, under the constrain panel and select the horizontal constraint. Once that's been enabled, we can select the piece of geometry we want to add the constraint to, and, you'll see that the line becomes horizontal.
I can right click and select cancel or okay, to get out of the command. Now that we've done that, you can see some of the arrows have changed, and now, if I left click and drag on that endpoint, my line will change length, but with, and it and it will change horizontally. But, if i move my cursor up and down, I'm locked into a horizontal position, which is exactly what we want. Now before we move on to the other constraints, let's talk a little bit real quickly about dimensional constraints. While geometric constraints control how a shape can change, the dimensional constraint or the dimension, lets you define how big that your piece of geometry can be.
For example, if I left-click on the line and then left-click to place the dimension, I can enter two, and control the exact size of this line. I can always go back and edit that by clicking on the two, and changing it to something else like 1.5. Now that I've applied a geometric and dimensional constraint, I want to show you how you can see the geometric constraints. I'm going to hit Escape to get out of the dimension command. And then I'm going to right click on the graphics window. And in the right click menu, I have an option that says, show all constraints, or F8 on my keyboard.
What that does is brings up all the constraints that have been applied to the geometry in this sketch. You'll see lots of locks, those are the locks that I use to pre-define some locked in positions, so that you could actually do this exercise. If I zoom in on our horizontal line, you might see a little blurriness here. This is essentially a couple of constraints, and if you left click and drag, you can move them around for clarity's sake. But what you'll see here is I have a lock, which, when I hover over it, highlights this center point, or this mid-point, and I have this horizontal constraint, which, when, when I hover over it, highlights the line itself.
This allows you to see what geometry is being affected by this specific constraint. Now, I have these two here, and I don't really need to see this lock anymore, so I'm going to hit this x next to it. What that does, is temporarily turns off the visibility of that constraint, just to clean up the display a bit. If I want to actually delete the constraint, like for example this horizontal, I can hover over it, left-click, and then right-click on the geometry to get the option to delete it.
With it highlighted, I could also just hit E+Del on the keyboard to delete it. But what I'm going to do is right click on this and select Delete, which now you can see I get new degrees of freedom based on the fact that I deleted that constraint. And, if I want to test that, I can left click and drag on that end point, and you can see that while I maintain my dimensional 1.5 constraint I am no longer locked into a horizontal position. I'm going to go ahead and hit Crtl+Z to undo that, and put things back to the way they were.
Now as we continue on, I'm going to clean up the display a little bit by right-clicking, and selecting Hide All Constraints, which is also F9 on your keyboard. And I'm also going to right click again and select hide all the grades of freedom, because I always just want to clean up the display if we walk through the rest of this. The next few constraints we need to add we're going to do fairly quickly. You've seen most of the instructions, but what you need to do now is walk through and apply the appropriate constraint based on the description here. So I'm going to go ahead and real quickly apply a vertical constraint by clicking on the button first, and then selecting on the line that I want to make vertical.
I can then right-click and select okay to get out of that command. Next, I want to make these two lines co-linear, which means make 'em perfectly in line with each other. And I can do that by using the co-linear constraint on the tool bar in the constrain panel. And I can select each piece of geometry to make it co-linear with each other. Now constraints are bi-directional as well, rather than selecting the button then selecting geometry, I could chose to select the geometry first if I wanted to. I'm going to go ahead and continue by adding a concentric constraint, which essentially lines the two center points of these circles up, by selecting each of the pieces of geometry.
If I don't want to get out of the command, I can simply go select a different constraint. The next one we need to apply is the tangent constraint and you can see on my, by my cursor, I'm still seeing the concentric icon. If I simply go up and select the tangent icon from the tool bar, you'll see I now have a tangent icon next to my cursor, and I have the ability to select the circle, and this line, to make sure that they only touch at that one point, making them tangent. Finally, I'm going to add a perpendicular constraint. You can do this by selecting the perpendicular icon in the constraint panel, and then selecting each piece of geometry, which will lock the two pieces of geometry 90 degrees from each other.
This should provide a basic overview, of what constraints are and how they work so that when we get into creating geometry, you understand how Inventor is automatically applying some of these constraints.
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