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AutoCAD has two types of parametric constraints: geometric and dimensional. Geometric constraints are the relationships that hold your geometry together and Dimensional constraints are much like handles that can be used to push and pull that geometry into different shapes. If you happen to be working with a complicated part, you may have so many constraints that it becomes difficult to keep track of the function of each of the handles. AutoCAD 2011 simplifies the use of constraints by letting us sort them into logical groups. In this lesson, we are going to learn how to use filters to organize our dimensional constraints.
On my screen I have a simple mechanical part and this part has several geometric and dimensional constraints assigned to it. By default, they are all turned off. To turn these on, I am going to move up to the Parametric tab and it will turn the Geometric Constraints on first. Now, the button for that is in the Geometric panel. Let's click Show All. And at first glance this looks pretty busy. Let me explain what's going on. First of all, each of these entities around the outside of the part has a coincident constraint that connects it to the next entity.
Each of my circles is concentric to the outer arc, all of my vertical lines are parallels to all the others. Likewise, all of my horizontal lines are parallel to the others. Each of my fillets is tangent at either end and any common fillets are set to be equal to each other. So while this looks rather complicated, it's really nothing we haven't seen already. Since my geometric constraints are set and my geometry is tied together. Let's turn these off. I can do that by clicking the Hide All button and we will take a look at our dimensional constraints.
To see those, I will go to the Dimensional panel and click Show All. Let's back up a little bit so we can see these on screen. Now, dimensional constraints are used to drive the geometry of our part, and as you can see, I have several constraints already. I would like to add another one. I would like to add a dimensional constraint to control the length of this tab. So I am going to come up to the Dimensional panel and select Linear, and I would like to create my linear constraint from the endpoint here to the center here.
I will pull this up and click to set its location and then I will hit Enter. And I can see that the distance is 4 and AutoCAD has created a variable called d1 and assigned it this length. I would also like the length of this tab to always equal the length of this one. So let's create another dimensional constraint. Once again, I will click the Linear icon, and I will create this constraint from the endpoint here to the center here. I will pull this one down and click. And before I hit Enter, since I would like this constraint to equal this one, I will place my pointer over this variable and click and then I will hit Enter.
As you can see, AutoCAD took this dimensional constraint called d2 and assigned it the value of d1. Also note the fx prefix. This is a visual cue that shows us the value of this constraint is dependent on another parameter. Let's try it out. To change the length of the tab, I will double-click the value of d1 and I am going to set this to a new length of 7 and I will hit Enter. Notice my geometry changes. Let's double-click the value again and I will set this back to 4. All right. Let's pan this geometry over and I would like to open up the Parameters Manager.
We can do that by clicking the icon right here in the Manage panel of our ribbon. Now, the Parameters Manager is where I can go to see all of the parameters that have been assigned in this drawing. As you can see, I have several. Now, when the Manager first comes up, these columns may be a little bit too narrow to read. If you place your cursor between the columns and click and hold, you can drag these guys and make them a little bit wider. There we go. That looks better. Let me pull this slider down to the bottom so we can take a look at these user parameters.
Personally, when I am doing parametric drafting, I create several user parameters, because it makes it much more intuitive when I edit my geometry later. Let me show you what I mean. I am going to create a new user parameter. To do that, I will click the New User Parameter icon and we will call this parameter tab_length and I will hit Enter. I will then double-click in the expression area and I will set its value to 4 and hit Enter. 4 happens to be the current length of this tab.
Now I will grab my slider, we will move to the top, and we will find the d1 constraint. Let's double click on this value and I will set d1 equal to tab_length. Notice the change in my constraint. Also notice the fx. This constraint is now dependent on a parameter. Once again, I am going to grab the slider and pull it down, and let's make some changes to our geometry using the user parameters. To change the length of my tabs, I can go to tab_length, once again very intuitive.
I will double-click right here, and let's set its value to 8, and I will hit Enter. My part updates instantly. Let's double-click and we will set this back to 4. I also have a user parameter that controls the size of the holes in this part. Let's double-click this value and we will set each hole_radius to be .25. Right here I have a user parameter called fillet_min. This stands for fillet minor. This guy controls the small common fillets on this part. Right now I can see that they are set to a value of .5.
I am going to double-click and we will change this to a value of 1 and I will hit Enter. Now, take a look at this part. It's really not that complicated. As your geometry becomes more involved, this list of parameters is going to get longer and it quite possibly could become unwieldy. Let me show you how we can organize our parameters into group filters. To do that, I need to open up the filter area. I can do that by clicking this chevron, and if the Group Filter panel is a little bit too narrow, we can always grab the slider and drag it back and forth to scroll.
Or I can place my cursor over this bar and I can click down and I can drag this guy left or right to change its size. To create a new group filter, I will click the Group Filter icon. I am going to call my filter "length" and I will hit Enter. This group will hold all of the parameters that are associated with lengths on this part. Let's click All so we can see all of our parameters, and then I will select this one and I will hold my Ctrl key. I will select this one, this one, I am still holding my Ctrl key.
Let's select this one and this one. When I am finished, I will release the Ctrl key, I will click and hold on a selected parameter, and I will drag these into my group. That doesn't remove them from the All list. It just associates them with this group. Let's create one more. Once again, I will click the New Group Filter. We will call this group "rounds." In this group I would add all of the round geometry. This would include fillets and circles. Once again, I will Select All and I will select this parameter. I will hold my Ctrl key and I will select this one and this one, this one and this one.
We will grab my major and minor fillets, hole radius, and this tab round. I will release my Ctrl key, I will click and hold on this selected parameter and I will drag it into my group. So no matter how large this list of parameters gets, I can always simplify the amount of parameters I see by selecting my groups. These groups don't have to remain static, I can always add parameters later, and if you would like to remove a parameter from a group, you can simply right-click on it and select Remove From Group Filter.
No matter how many dimensional constraints and user parameters you may have, you can always keep your parameters organized and simplify your work using the new parameter filters in AutoCAD 2011.
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