Creating and managing constraints
Video: Creating and managing constraintsNow that we've got all our components placed into our Assembly file, we are ready to begin the assembly process. Before we begin, I wanted to talk a little bit about the different ways to create constraints. Under the Assemble tab in the Position panel, there are two different options I want to call out, there is the Constrain option and the Assemble option. The Constrain option is the default way to create constraints in Inventor; the Assemble option is a slightly more advanced version of that, that allows you to create multiple constraints in a single action. I don't recommend this option for those who are just starting out with Inventor.
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This course introduces you to the interface and key processes of Inventor, the parametric design system from Autodesk. Author John Helfen covers sketching, part modeling, assemblies, and drawings. These tasks work in conjunction, allowing you to create parts and assemblies and document them in a way so that the manufacturing process proceeds faster and more efficiently.
- Navigating drawings with the View Cube and other navigation tools
- Sketching geometry
- Dimensioning parts
- Creating parameters
- Drawing circles, squares, and other shapes
- Creating extrusions
- Creating and managing constraints in assemblies
- Setting basic drawing dimensions
Creating and managing constraints
Now that we've got all our components placed into our Assembly file, we are ready to begin the assembly process. Before we begin, I wanted to talk a little bit about the different ways to create constraints. Under the Assemble tab in the Position panel, there are two different options I want to call out, there is the Constrain option and the Assemble option. The Constrain option is the default way to create constraints in Inventor; the Assemble option is a slightly more advanced version of that, that allows you to create multiple constraints in a single action. I don't recommend this option for those who are just starting out with Inventor.
I think it's important for everybody to understand what constraints are, how they work, how to edit and manage those constraints, and once you have that solid foundation, then you can begin exploring the Assemble command. In this movie, we are going to focus on a couple parts that we'll use to explain how constraints work and how to edit and manage them. Once we have that foundational understanding, then we'll move forward with assembling the remaining parts. The parts we're going to be focusing on are the Piston Shaft and the Engine Block. I am going to zoom in a little bit on those so we can get a better view.
Now I am going to launch the Constrain dialog box and begin the constraint process. Within the Place Constraint dialog box there is a few different settings you need to understand. First is the Type Section. There are four major types of constraints in Inventor: there is a Mate constraint, an Angle constraint, a Tangent constraint, and an Insert constraint. For this video, we are going to focus on the Mate constraint. It's the most commonly used constraint, and once you understand how it works you'll have a solid understanding of how the other constraints work as well. Next is the Selections area. The whole purpose of constraints in the first place is to assemble two parts together, or connect those parts.
The Selections set area allows you to see whether or not parts have been selected. A red arrow indicates that nothing has been selected and Inventor is waiting for an input. A white arrow indicates that a selection has been made and Inventor is ready to continue. Next we have the Offset section. This allows you to determine the distance between two faces or two objects that you have connected with a constraint. We'll go over that in a moment. The Solutions area allows you to select between two different solutions of the same type of constraint. For example, in the Mate constraint, you have a Mate option, and you have a Flush option.
I'll show those in a minute, because once you see, it's very easy to understand. To begin, the system is ready for the first selection. We are going to select the center axis of this part by hovering over the part and left-clicking. After making that selection, you'll notice that the Selections set has changed a bit, we now have a white arrow on Selection 1, indicating that the selection has been made and Inventor is ready to continue at that point. It also move to Selection 2 and is waiting for us to pick an input. For that item, we are going to select the center component of the Engine Block, and you'll notice that we receive an audio indication that the constraint has been made, and we get a preview of the constraint result.
At this point we can Apply the constraint and continue on, or we can select OK to apply that constraint and close the dialog box. That's what we are going to do in this case, because I want to show you what actually just took place. If we left-click and drag on the Piston Shaft, you'll notice that as I move my cursor right and left, the component spins, and it can move up and down, but it remains locked to the center axis of the Engine Block. That's exactly what the constraints do. They're rules that tell parts how they connect and how they can interact with each other. The problem we have here is the part is upside-down, and that happens from time to time and is perfectly acceptable and expected.
We are going to go a head and use the Marking menu by right-clicking and select the Constraint option to bring up the Constraint dialog box. We are now ready to create a second constraint here. This time rather than selecting the axis, I'm going to select the bottom face of the Piston Shaft and the top face of the Engine Block, because I want those two parts connected. Now you'll notice from the preview the part has remained in the Engine Block but now it's been flipped over and positioned properly. If I zoom in a bit and orbit just a hair, you can see that these two faces are touching each other now.
This is a point I want to show you the two different Solution options. Right now we have the two faces touching each other. The Flush option allows me to just flip that option over, and if I zoom in a bit you can see the two faces are perfectly flushed with each other. Again, you can toggle back and forth between these to see the result. I do want to go ahead and continue with the Mate constraint, so I'll go ahead and leave that as it is. The next item I want to mention before we continue on is the Offset. The Offset in the dialog box allows you to determine how far apart the two faces are.
For example, if I enter .25, you'll notice that the preview updates to show that result, if I make it .5, that moves up even further. In this case, I do want to go ahead and leave it at zero, so I'll return that, and now I am going to click OK to accept that constraint and close the dialog. Now that we have the part constrained, I am going to rotate it around and show you one more time what just took place. If we left-click and drag on the part, it now will rotate, but it won't move up and down because the bottom of the Piston Shaft and the top of the Engine Block are connected, and the axis of the Piston Shaft and the axis of the Engine Block are locked together.
Now you'll notice as I move this around we do have an Exhaust port down here, and this is important, because if we rotate around to the other side, you'll notice that there is corresponding Exhaust port on the side of the Engine Block. In the Piston Shaft component, you'll also notice that there's a little notch here. As we drag the component around, you'll notice a little notch on the top of the Engine Block. The purpose for that is to align the two components so that the Exhaust Ports match up. So the final constraint we need on this component is an axis-axis constraint between these two components.
I am going to right-click and select Constraint from the Marking menu, and this time I'm going to select the axis on the Piston Shaft and the axis on the Engine Block, and those two components align, and now I can select OK, and that constraint is created. This time if I go to click and drag that part I get a no-go symbol, essentially it's telling me that there is enough constraints on this, that it's permanently positioned, and the only way I can move it at this point would be to remove a constraint or edit an Offset.
Now that we've created a few constraints, let's look at the browser to see what's actually happened. If we expand the Engine Block, you'll see a couple of things. You see some hidden work planes and then you see the constraints that have been applied to the Engine Block. Let's zoom back in on the Engine Block so we can see this in the Graphics Window. If you hover over the first Mate, you'll see that it highlights in the graphic screen. This is the Mate between the axis of the Piston Shaft and the axis of the Engine Block. Because there are two components involved in this constraint, sometimes you might want to find the other half of that constraint or what part is contained in that other half of the constraint.
To do that, you can right-click on the constraint in the browser and select other half, and you notice the browser expands the Piston Shaft part and highlights the other half of the Mate constraint. This is just a nice way to find out how components are interacting with each other, and it comes in handy if you ever run into a problem and you need to interrogate the model a little bit closer. The next item we have is this Mate here. This is the Mate between the top of the Engine Block and the face on the bottom of the Piston Shaft. Finally, we have the last Mate we just created, the axis between the pin and the corresponding notch on the Piston Shaft.
At any point we can go back and right-click on any constraint and make some edits to it. For example, if we wanted to update the offset, we could go back and hit Edit and change that after the fact. Here we have a .05 offset, we can set that to .25, and you see the preview updating as well. In this case, we don't want to make that change so we'll leave it at zero, but you can always go back and make changes. Now that we have a solid understanding of what constraints are, what they do, how we can edit and manage them, we're ready to move on and continue assembling parts.
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