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Putting Theory into Practice: Making a Parametric Mass Family |
In the following exercise, we’ll guide you through the creation of a simple parametric mass family so that you understand some of the principles of creating a mass in the Family Editor. (In the next chapter, we’ll guide you through creation of a mass model within the project.)
The result will be the mass shape shown in Figure 7.15, which is parametrically adjustable in several dimensions. |
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Figure 7.15
The parametric mass family you’ll create in this exercise |
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| When you’re creating a new family, it’s essential to select the correct family template. In this case, you wish to create a new mass element, so you need to select Mass.rftor Metric Mass.rft. Follow these steps: |
- Choose File New Family. In the New dialog, select the template Metric Mass.rftand click the Open button.
The Family Editor opens, and the drawing area shows the plan view. There are two pre-defined reference planes: The vertical one is called Center (left/right), and the horizontal one is called Center (Front/Back). The intersection of these two planes will define the inser-tion point of the family when you later place it in the project. You want to create a parametric family, not just a fixed mass, and thus you need to create reference planes to which you can constrain dimensional parameters that will allow you to change the size of the family by changing properties
- Using the Ref Plane tool from the Design Bar, add four more reference planes in the plan view:
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These will be used to control the size of the mass in plan.
- In the front elevation, add two additional horizontal reference planes. These will be used to control the height of the mass:
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- Place dimensions between the reference planes in plan and elevation. You’ll eventually con-vert these dimensions to labels that represent the future parameters to be tweaked; you’ll do that by selecting the dimensions and clicking the Label button on the Options bar. For now, let’s keep adding dimensions.
- Select the reference plane you created in elevation and that is coincidental to the level: It isn’t easy to see it (it can be completely covered by the level geometry), so use the Tab key and verify in the tooltip or in the command line that you have selected the reference plane and not the level. Click Properties on the Options bar, and change the value of the Is Reference parameter from Not Reference to Weak Reference. This makes the bottom of the massing form display blue grip controls when selected.
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- Look at the reference planes that define the center axis, because they need to remain centered relative to the other reference planes. You’ll set an equality (EQ) dimension constraint between these three reference planes to keep the design symmetrically balanced.
Select the two reference planes that define the axis, and set their Is Reference parameter to Not Reference.
- Open the plan view Ref. Level. On the Design bar, click Dimension.
Click each reference plane to create the dimensions between them, and then click the EQ symbol:
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Repeat the same action in the other direction:
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With these steps, you’ve ensured that the axes in both the X and Y directions will always be in the middle of the element. You now need to create the parameters that will control the size of the mass element: D for Depth and W for Width.
- Still in plan view, select the Dimension tool, and place a dimension between the two outer reference planes. Don’t worry about the value of the dimension:
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- On the Design bar, click Modify, and select the dimension you just created. On the Options bar, click the drop-down list next to the label, and select Add Parameter.
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- In the Parameter Properties dialog (Figure 7.16), enter Wfor Name. In the list for Group Parameter Under, select Dimensions, and select the Instance radio button. Click OK to con-firm your selections.
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Figure 7.16
Defining the Width parameter |
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Following the same principle, create a dimension in the other direction and name it Dfor depth:
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Note that from now on the value in the dimension text has a prefix D or W |
- Open the front elevation view, and add a dimension between the reference plane that is coin-cidental with the level (again, make sure that you select the bottom reference plane and notthe level line) and the first horizontal reference plane above:
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Add another dimension between the other two horizontal reference planes:
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Following the principle previously described for labeling these, name them H1and H2:
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- You’ve created the framework that will drive the geometry, so all that is left to do is to make the geometry. But before that, you need to test the parameters you just created—what is called flexingthe model.
On the Design bar, select Family Types. In the Family Types dialog (Figure 7.17), select the parameters you just created, and modify the values. Click the Apply button to see the effects in the view (the reference planes move as you change values).
Make sure you change the parameters one by one; if you get an error message, and you’ve changed many values at the same time, you won’t know which one is the problem. If you try changing all the values and don’t get any error messages, you have done well and are ready to create the geometry
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Figure 7.17
The Family Types dialog |
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- Open the plan Ref. Plane and, on the Design bar, select Solid and then Solid Extrusion:You’re placed into sketch mode, and the Design bar changes to show only tools relevant to the extrusion sketch mode. On the Options bar, select the Rectangle shape:
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Click the intersection of the left and bottom reference planes to define the start point of the rectangle
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Click the intersection of the top and right reference planes to define the diagonal finish point of the rectangle
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Click the four padlocks that appear automatically—by doing so, you create constraints between the lines of the sketch and the reference planes on which they’re drawn. This means
that later—when you move the position of the reference planes by changing the values in the Family Types, the sketch lines of the geometry will follow the change and parametrically change.
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In the Design bar, click Finish Sketch
- Open the front elevation, and select the solid you just created. Click the blue arrow on the top of the solid, and move it up to the upper reference plane. It should snap to it.
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When the geometry coincides with the reference plane, a padlock icon appears, allowing you to constrain the relationship. Click the padlock. You’ve now defined the relationship between the top of the solid and the reference plane, so that if you change the reference-plane position (the value of the parameter) again, the top of the solid will move with it.
- Using the Family Type option from the Design bar, start changing the H1 and H2 parame-ters, and see what happens. While working with the family parameters, you can also change (flex) the values for W and D to verify how they affect the geometry. Note that to review the correct functioning of the parameters while flexing them, it’s best to be in 3D view.
- You’ll now add a void to the solid. For that purpose, you’ll use the Sweep tool. You’ll start by adding a new reference plane that will control the position of the new shape in plan view.
Open the plan view Ref. Level, and add a reference plane:
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- Add a dimension between this new reference plane and the one that defines the axis front/back, and transform this new dimension into a label as previously described. Name the new label O(for Offset).
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- Open a 3D view. On the Design bar, click Void Form Void Sweep
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- Click the Pick Path tool. This time, instead of sketching the path, you’ll use existing geome-try for the path you want to define.
Click the solid’s four top edges. For this exercise, make sure you first select the edge that is in the front:
On that first edge you picked, a cross appears, with a red spot in its center. This represents the work plane of the profile sketch. You can sketch the shape of your profile directly in 3D, but it’s easier to draw the shape in the same plane as the profile work plane—especially when dimensions are important. Switch to a view that is parallel to the sketch’s work plane—in this case, the left or right elevation
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On the Design bar, click Finish Path.
- On the Options bar, select Sketch Profile. Open the right elevation. On the Design bar, click the Line tool, and then trace three sketch lines:
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- Click the Align tool, select the vertical reference plane, and then select the vertical line of the newly created sketch. By doing so, you align the sketch line to the reference plane. To estab-lish the relationship, click the padlock icon
Note: if you ever forget to click the lock, and the next time you want to do so the lock doesn’t appear, click the sketch line, move it to the left or right, and reposition over the reference plane—the lock will appear again, and you can lock it
- Still using the Align tool, click the top horizontal reference plane and then the top horizontal line of the sketch, and again lock the padlock.
- Click the horizontal reference plane just below the lower horizontal sketch line and then click that horizontal sketch line to align. Again, lock the padlock:
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- You have one more task, and it’s more delicate. Zoom in closer in the lower-right corner of the sketch and the vertical reference plane.
Still using the Align tool, click the vertical reference plane (the second from the left, if you’re in the right elevation), and then place your cursor next to the free end of the horizontal sketch line. A little square appears at the end of the sketch line, which fades slightly. (If this doesn’t happen, try moving the cursor. Help yourself with the Tab key.) Once you see the small square at the end of the sketch line, click it to define the alignment to the vertical ref-erence plane:
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- On the Design bar, click the Line tool, and draw the last line segment to close the sketch:
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- Click Dimension on the Design bar, and select Angular from the Options bar.
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- Add an angular dimension between the diagonal sketch line and the vertical reference. Create a label out of that dimension, and name it A (for an Angle):
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- On the Design bar, click Finish Sketch and then Finish Extrusion. Don’t forget to finish both of these; otherwise, your drawing will look grayed out, indicating that you are still in the sketch mode.. Go to 3D view to see the result:
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Congratulations! You just created your first fully parametric mass family! Save it as My First Mass somewhere where you can find it again. You can open a new project and load this newly created mass. In the project environment, start to flex the parameters and see how they affect the shape of the mass
Also note that when you import the mass element in the project and select it, small blue controls appear on the edges of the solid. Using them, you can change the size of the mass element on the fly:
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To change the angle of the shape you carved out with the void, change the angle in the param-eters and see how it affects the look of your mass. The value of the angle can be positive or negative, allowing you to create variations in shape like those shown in Figure 7.15 at the beginning of this exercise.
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