By Michael A. Brattoli and Steve R. Norgrove, Moen Incorporated
While software applications are available to produce curves and surfaces that are exportable to the mechanical designer, many industrial designers still create their concepts manually, generating hand sketches, renderings, and physical models. Pattern makers interpret these ideas, capturing them in 3D using a variety of techniques (foam models, etc…) for review and sign-off by management and/or customers.
These 3D models provide visualization of the overall concepts, but capturing the mechanical reality of the product is the challenge. The Reverse Engineering Extension (REX) within Pro/ENGINEER, also known as the “Restyle module” is one of a variety of solutions available to the designer/engineer to insure this process is as painless as possible.
Why Restyle?
The 2D Trace Sketch functionality found in the Pro/ENGINEER Style module (ISDX) is extremely useful. Unfortunately, because of the limitations of 2D sketches, additional information may be needed to complete the CAD model. Using the faceted feature function within the Restyle module, you can import scan data in the form of a point cloud into a model, wrap a surface around the points, and create a faceted solid. This can then be used as a “3D Trace Sketch” to capture the industrial designer’s intent accurately and ensure the end product conforms to the aesthetics of the initial concept.
Here’s how to do it.
1. Create a new part using Restyle.
Start Pro/E with REX and select Insert/Facet Feature. Depending on the orientation of the scan data, you’ll probably need to add a coordinate system to orient and locate the point cloud correctly. Figure 2 uses the default coordinate system while Figure 3 is oriented using a created coordinate system.
Figure 1.
Figure 2.
Figure 3.
2. Select the point cloud file. The following file types will bring up the points menu within the faceted feature: .acs, .ibl, .igs, .pts, .vda, and .vtx. Note that only datum points will be read and all other geometry ignored when using an IGES file. In addition, .stl, .wrl, and some .acs files will bypass the point menu and proceed directly to the facet menu.
Figure 4.
3. Select the coordinate system. Pick OK and the point cloud will appear on the screen.
Figure 5.
4. Clean up the point cloud. The following tools are available:
Reverse Selection. Reverses selection of currently selected points.
Hide Selected. Hides all selected points.
Unhide All. Displays previously hidden points.
Crop Selected. Deletes all points outside a selected region.
Delete Selected. Deletes all points inside a selected region.
Delete Outliers. Deletes stray points offset from the main cluster of points. You can adjust the sensitivity in the popup menu.
Reduce Noise. Relocates points using free-form (preserving more organic shapes) or mechanical mode (preserving sharp edges).
Sample. Samples the point set and removes points while preserving or improving the accuracy. (See Figure 6 for sample types.)
Fill Holes. Fills gaps and holes by adding new points.
Add. Adds another point set to the current one and merges the two.
Save. Saves the point data to a .pts file.
Wrap. Wraps a triangulated mesh around the point cloud and proceeds to the Wrap menu.
Quit. Exits faceted feature creation.
These tools are also available in the Points dropdown menu. Experiment with the various tools and options to achieve optimum results, using the preview feature until you are sure of your changes.
Figure 6.
5. Wrap the point cloud data. The Wrap command essentially wraps a surface (or triangulated mesh) around the point cloud (Figures 7 and 8) and takes you to the Wrap Edit menu to finish creating the faceted feature.
Figure 7.
Figure 8.
6. Clean up the wrap. The following tools are available:
Select by Length. Selects facets with an edge greater than or equal to the specified value.
Push Shallow. Removes triangles through a selected area.
Shoot Through. Deletes triangles straight through a selected area (similar to drilling a hole).
Push Deep. Removes triangles through the model until the point density changes.
Remove Webs. Removes triangles in open areas.
Fine Tune. Proceeds to the Fine Tune menu.
Facets. Proceeds to the Facets menu.
Quit. Exits faceted feature creation.
These tools are also available in the Wrap dropdown menu. Again, experiment to achieve optimum results.
7. Fine tune the wrap. The following tools are available:
Select by Length. Selects facets with an edge greater than or equal to the specified value.
Push Shallow. Removes triangles through a selected area.
Shoot Through. Deletes triangles straight through a selected area.
Remove Webs. Removes triangles in open areas.
Fill Edges. Adds volume to the selected facets to define sharp features.
Fill Up. Adds volume to selected concave areas.
Fill Layer. Adds a single layer of volume to the selected area.
Facets. Proceeds to the Facets menu.
Quit. Exits faceted feature creation.
These tools are also available in the Fine Tune dropdown menu.
8. Modify the facets. The following tools are available:
Select by Length. Selects facets with an edge greater than or equal to the specified value.
Reverse Selection. Reverses selection of currently selected facets.
Delete. Deletes selected facets.
Fill Holes. Fills gaps to create a continuous faceted surface.
Clean. Modifies the faceted geometry by creating sharp edges or smooth surfaces.
Decimate. Reduces the number of facets.
Refine. Increases density of facets and modifies facet vertices.
Relax. Smoothes faceted surfaces.
Make Manifold. Creates a manifold representation of the faceted model.
Add Facet. Adds facets using specified vertices.
Flip Edge. Reverses facet orientation.
Split Edge. Adds facets by splitting selected edges.
Done. Completes the faceted features.
Quit. Exits faceted feature creation.
These tools are also available in the Facets dropdown menu.
The finished faceted feature (Figure 9) acts like a true solid protrusion so sections can be created, but not cut features (Figure 10). Note that because the scanned points are from a physical model, the faceted feature will not be completely symmetric (Figure 11).
Figure 9.
Figure 10.
Figure 11.
8. Review the faceted model. Review the faceted model to determine which half you will use to create your modifiable Pro/ENGINEER part file. Using the cross-section tools, create the desired sections (symmetry, cutting planes along the part, etc…) and then create datum curves through the cross-sections (Figure 12). You can use these curves as a visual guide when constructing your modifiable geometry, allowing direct comparison between the finished “symmetrical” model and the original scanned item. Continue creating reference profile curves as needed for definition of the overall model (Figures 13, 14 and 15)
Figure 12.
Figure 13.
Figure 14.
Figure 15.
9. Create the part features. You can now choose the half of the faceted model that best captures the design intent of the product. The designer/engineer, through the creation of modifiable curves and surfaces, can create a part file that closely matches the scanned data (Figure 16). Solidify the surface model after merging the surfaces and add any required solid features to complete the model.
After the part file has been completed, delete the scan data from the Model Tree to eliminate any potential parent/child relationships.
Figure 16.
Summary
Using the Restyle module, the designer/engineer can accurately capture the design intent of a hand-sculpted model while dramatically reducing the time it takes to “recreate” the product. The time savings generated by this approach can allow additional design iterations and/or reduce the time to market for the part. Creatively capturing a design is a win-win situation for everyone involved in the product development process.
Mike Brattoli is the engineering systems administrator at Moen Incorporated in North Olmsted, Ohio. Steve Norgrove is a senior product design technician.
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