Wireframe and Surface Analysis Techniques #3
Joe Costa, MSC Software Corporation

This is the Last in a series of articles discussing the tools available within CATIA to analyze the quality of surfaces and curves. The first article discussed just wireframe analysis techniques. The second article focused on analyzing the continuity and the quality of surfaces. This article will continue to focus on tools that will analyze surface quality.

The first tool to look at is the inflection Analysis Tool. It will identify the areas of the surface where the curvature direction changes (bump in the surface). In the blue area, curvature is the same in both directions (positive). In the green area, curvature is reversed (negative). In the yellow, the curvature is 0, which represents a transition area. Sometimes inflection areas in a surface are needed, but many times this represents an unwanted bump in the surface.

Figure 1: Inflection Analysis

Try to avoid areas of one color embedded inside the other color. If this occurs, investigate the area for possible defects. In the following example (figure 2), there are two green pockets surrounded by blue. These green areas dip below the rest of the surface. This tool does not quantify how big this problem is. It only points out that a problem exists. A Further analysis using some of the other tools we have already discussed, such as Gaussian Analysis, would determine the severity of the problem.

Figure 2: Inflection Analysis – Problem areas

The intersection planes command cuts the surface to create cross sectional curves of the surface. Use the compass to define the direction of the cuts. This tool allows you to control where the cuts are taken, how many there are and how far apart they are. A Curvature Analysis can then be performed on each of these cross sectional curves.

Figure 3: Intersection Planes Analysis

The next two tools will analyze the manufacturability of the surfaced part.

The limited radius analysis tools is used to identify the areas of the part where the radius of curvature in either direction is too small, making it impossible to manufacture the part. For example, in figure 4 we want to know if a 2mm tool can be used to machine the part. Anywhere where the part is colored red indicates a radius of curvature of less than 2mm, which means it is impossible to machine this area with a 2mm tool. So for the red areas, we will need a smaller tool size.

Figure 4: Limited Radius Analysis

The last tool to look at is the draft analysis tool. This tool quickly reveals if the part has enough draft to be removed from a mold. Use the compass to specify the pull direction, which is the direction the mold will be removed from the part. Select the surface to analyze and specify the draft angle to analyze. The surface is then color-coded based on the results. Green shows areas that have the minimum required draft. Red indicates the area where the draft is less than the minimum but greater then 0 degrees. Blue areas represent an undercut. At any location on the surface, you can obtain exact draft angle information.

Figure 5: Draft Analysis

All of these analysis results are captured in the specification tree. This means they can be easily modified, renamed, or hidden. They are also fully associated to the parent geometry. So if the original curve or surface is modified, the analysis results will be updated, removing the need to recreate the analysis on the new surface. In the following example (Figure 6), notice how the cutting plane analysis is automatically updated when the surface is modified.

Figure 6: Modifications

In Summary, CATIA has the tools that can help you analyze not only the quality of a surface, but also the functionality of a surface. Hopefully, this series of articles has provided you with techniques that you will be able to use to be more efficient and effective in your daily design work with CATIA V5.

To receive a PDF version of the complete presentation covering this curve and surface analysis techniques, send an email to info@mscsoftware.com include your contact information and ask for the "WireFrame and Surface Analysis Techniques" presentation by Joe Costa.