Creating Flexible Components in
Pro/ENGINEER Wildfire

By Michael Mongilio, Swales Aerospace

The ability to create flexible components was a popular enhancement request for many years. PTC has now implemented this functionality beginning with Pro/ENGINEER Wildfire.

A flexible component is defined as a part that is represented differently in the assembly than in its stand-alone configuration. The alternate representation is controlled entirely at the assembly in which the flexibility is established. As a result, creating or changing the flexibility state in assembly does not modify the component or change its name.

A spring is the most obvious example of a flexible component since it can exist at any extension or compression length. But flexible components can vary by more than just their dimensions. Say a part has a tab that’s used to hold it during assembly and is then cut off. Rather than use an assembly cut to achieve this, Wildfire lets you make the component flexible and then simply suppress the feature that represents the tab.

In addition, a sub-assembly can be made flexible. Several types of sub-assemblies contain components that are removed when the sub-assembly is added to the next-higher assembly. For example, a sub-assembly that has a flex circuit includes a bracket to secure the flex-circuit connector until it is installed at the next assembly. That bracket can be removed by making the installed assembly flexible. The same is true for dust covers, safe pins, or temporary fasteners that are removed or replaced at a higher-level assembly.

Significance of Flexible Components

Pro/ENGINEER has always been able to accomplish these same tasks without the need for flexible components, but with one major drawback. Until Wildfire, It was impossible to create a part variation within the assembly without creating a new model name. In many organizations, a new model name represents a new part number.

As more and more companies use the bill of material generated by the Pro/ENGINEER model in their data management applications, it is important for components in the assembly to correspond one-to-one to the final bill of material. Creating a second model to represent a part in an alternate state not only added an extra part number, but also caused the correct part number to show an incorrect quantity.  With the new flexible component functionality, you can create a variation of a model to accommodate its assembly state without modifying it. Part number and quantity in the bill of material remain correct. This also means that no new version of the model needs be checked into the data management system.

Creating Part Flexibility

Making a component flexible in Wildfire takes just a few steps. In this case, we use the example of a spring.

1.     Highlight the component in the graphics window or model tree. Click the right mouse button and choose Make Flexible from the pop-up menu. A tabbed dialog box will open (Fig. 1).

Figure 1.

2.     Select the Dimension to vary (pick on features to display dimensions) and select OK. The dimension will be added to the dialog box.

3.     Enter a New Value for the dimension and select OK. The model will regenerate and the icon for the component in the model tree will change to reflect its flexible status (Fig. 2). A bill of material will still show only one component with no change to its quantity.

Figure 2.

Computing measurements. There are many times when the exact value of the desired variation is unknown. Going back to the spring example, the extension or compression length is determined by the components to which it is attached. In such a situation, a fixed value for the variation will not do. In this case, go the Method column of the flexible components dialog box, change the field from By value to Distance. The Measure dialog box will open so that a distance measurement can be computed. This computed value will become the new value for the flexible dimension. The measurement will be re-computed each time the assembly is regenerated, keeping the component dimension up to date.

Feature variations. The flexible components dialog box also lets you create feature variations. Feature variations provide the means to model variations that can’t be expressed by simple dimensional changes. As an example, say a capacitor is used in two different locations in an assembly. The leads are not only bent but also trimmed differently in each installation. Since dimensions alone cannot capture this variability, the answer is to create two sets of lead configurations in the part model. After assembling the component, it is made flexible. The particular set of leads is resumed for the appropriate installation while the other set is suppressed. In the other installation, the feature states are reversed (Fig. 3).

Figure 3.

Creating Assembly Variation

When working with sub-assemblies, it is important to note that flexibility can be established at different levels with different results. Fig. 4 shows a simplified spacecraft assembly with two representative solar array assemblies. The solar arrays have hinge sub-assemblies that allow the solar arrays to be stowed, deployed, or something in between. If the hinge assemblies are made flexible in the context of the solar-array assembly, both solar arrays will modify together (Fig. 5).

Figure 4.

Figure 5.

But what if you want to deploy only one solar array assembly? The dimension that controls deployment exists within the lower-level hinge assembly rather than in the solar array assembly itself. With flexible components, you can select a dimension from the lower-level assembly to vary at the higher assembly level. As Fig. 6 shows, the dimension that is made flexible comes from the lower-level array_hinge assembly, even though it was the solar-array assembly that was made flexible. As a result, one solar array is deployed while the other remains stowed. In the model tree, a smaller flexible component icon denotes which sub-components of the flexible assembly have been varied.

Figure 6.

Figure 7.

Setting Up Flexibility

In a similar fashion to component interfaces, flexibility can be predefined in any model to better communicate how it should be varied when used in an assembly. All you have to do is choose Edit, Setup, Flexibility. A dialog box similar to the one for assembly flexible components opens. You can add variable items to this dialog box. When the model is made flexible in an assembly, these predefined variable items will already be populated in the dialog box. All you have to do is specify the new values.

Michael Mongilio is a senior CAE applications engineer at Swales Aerospace in Beltsville, Maryland, USA. This article is based on his presentation at the 2005 PTC/USER World Event. Mike can be reached by email at mmongilio@swales.com.