This section explains how to create a parametric part from within TurboCAD.

Note: You can also create a parametric part using a script. For details on creating scripts, check the "Docs" folder of the TurboCAD installation disk.

There are four basic steps in this process:

1. creating the object(s) themselves
2. saving the objects as a part and defining parameters
3. defining relationships between parameters
4. inserting the part

Step 1- Creating the Object(s)

In this example, a part will be created from a polyline with holes, made 3D by extruding it. The objects will be created using different sizes than the actual part that will be saved, to show that parameters can be used for accurate sizing.

1. In this example, Auto Constraints is turned on. This is so that dimensions can be used as parameters, and so that geometric relationships between objects will be maintained when parameters are changed.

1. Create a polyline using two identical linear segments and two tangent arc segments.

1. Create two circles concentric with the polyline arcs. The circles can be different sizes now, but in the eventual parametric part, the circles will be identical.

1. Apply Concentric constraints so that the circles will remain concentric with the polyline arcs.

1. Add a Linear Dimension and a Radial Dimension to measure the polyline.

1. Activate Simple Extrude, and make sure Use Compound Profile is active. Select the polyline, then press Shift and select two circles. Click to define the height, or enter an exact value.

Step 2- Defining the Part and its Parameters

Now a part will be created from this object. There will be five parameters defined for this part: H1 = radius of one internal circle H2 = radius of the other internal circle R = radius of the polyline arc W = length of the linear polyline segment D = extrude depth

1. Select Parametric Part Manager.

2. Use a selection window to select all of the objects.

1. The Selection Info palette opens, and the part is temporarily called "Part Candidate." Expand this item to see what the part contains.

1. The parameters H1 and H2 are for the two internal circles. Highlight the first Circle in the palette.

The circle is also highlighted on the model.

1. The radius of this circle is found under "Metrics," at the bottom of the palette. Right-click on the Radius field.

1. Enter the parameter name "H1," then click OK.

Note: You are not restricted to defining only geometric parameters. You can also define material, pen color, line width, etc. as parameters.

1. Next, highlight the other Circle.

The other circle is now highlighted on the model.

1. Right-click on the Radius field.

1. Enter the parameter name "H2."

1. For the next parameter, highlight the Radial Dimension.

The dimension of the polyline arc is now highlighted.

1. The Value field of this dimension is found under "Constraints." Right-click on this field.

1. Name this parameter "R."

1. Next is the Linear Dimension.

1. This value is also found under "Constraints." Name its parameter "W."

1. The last parameter is the depth of the part. Highlight "Simple Extrude."

1. This parameter is called "Height" and is found under "Simple Extrude." Right-click on this field.

1. Name this last parameter "D."

1. Now that all five parameters are defined, select Finish from the local menu or Inspector Bar.

Note: There are other options in the local menu and Inspector Bar. Relocate Reference Point enables you to define the point by which the part will be inserted. For circular parts, Set Assembly Axis can be used to set an axis for assembly using Assemble by Axis

Step 3- Defining Relationships between Parameters

1. The Parametric Part window is now open, in which you can define relationships between the parameters you've defined. First, enter a name for the part.

1. The eventual part will be defined by only three parameters: the hole radius, distance between hole centers, and depth. All other parameters will be functions of these three.

2. The names of the parameters currently listed don't tell the user exactly what they are for, so we can add parameters with more obvious names. To do this, right-click on the first parameter on the list, and select Insert Parameter.

1. "HoleRad" is now first parameter on the list. Under "Value," enter the default radius that will be used when you first insert the part.

1. Under "Type," specify "Linear."

1. Create another parameter for the center-to-center distance between the holes. This parameter can be named "CenToCen". Specify an initial "Value" and "Type."

1. Under "Value" next to "H1," replace the number with "HoleRad." Do the same for "H2."

1. Define"R" as twice the hole radius.

1. Set "W" as equal to "CenToCen."

1. Now the three controling parameters needed for the part are defined. They are "HoleRad," "CenToCen," and "D." Click Finish to close the Parametric Part window.

Step 4- Inserting the Part

1. Continue in the file in which you defined the part. Select Draw / Parametric Part. Select the part you just defined.

You may get a warning:

If you don't. want to see the message again , check the "Don't show this message again." box. Then click OK.

Note: Load from File can be used to insert parametric parts saved in other files.

1. Click to insert the part. The inserted part is shown to the right of the original geometry. Note that the two holes are equal, and that the polyline arc's radius is twice as large as the hole radius.

1. Select the part, and it appears in the Selection Info palette, with its three parameters available for editing. The initial values are the ones you set in the Parametric Part window.

The internal holes updates, as well as the overall radius of the part, which was set to be twice as large as the hole radius. In some instances you may get a warning message "Compound Profile is not up-to-date" when inserting the part.

1. Increase the "CenToCen" parameter value.

The distance between holes updates, while the radius values remain the same.

1. The last value to change is "D."

This changes the depth of the extruded part.

Editing a Parametric Symbol

With the edit tool active you can save all of the Parametric parts in a *.SLW file.

You can also Load Parametric parts from an *.TCW file. To Edit an exiting part. Click the local menu option Edit Existing Symbol. You can edit either the content or the parameters. Content is the physical geometry. When finished, click OK and the part is saved with the changes.