TechTip: Avoiding incorrect calculations of the surface normals
Especially for paths on curved surfaces, it is usually desired that the TCP orientation adapts to the shape of the surface as well as that other criteria are met, for example, that the Z-axis of the TCP is orthogonal to the surface at all times (e.g. for polishing applications). This can be set in step 2 of the CAD2Path tool (“Change Curve Parameters”) with the option “Z-Axis normal to 3D Surface”. After selecting this option, the CAD2Path tool automatically calculates the surface normals of the 3D object. Depending on the shape of the object, however, errors may occur if the automatic calculation assumes an incorrect reference surface. In the example of Figure 6, by mistake the resulting surface normals (visualized as small purple arrows) are pointing in positive Y-direction.
Selection Mode “Faces”
This problem can be solved with the help of the selection mode “Faces”, which can be found in the drop-down menu at the top of the window (Fig. 2). This selection mode allows to select entire surfaces of the 3D object (see Fig. 3 & Fig. 4). With the option “Recalculate Normals from Selected” the surface normals can now be recalculated relative to the selected surface (Fig. 5).
Adapting Surface Direction
Next, the direction of the surface normals must be adapted to the orientation of the Z-axis of the TCP. This can be done by using the option “Toggle Orientation Normal” (see Fig. 6, Fig. 7) so that the surface normals point in positive Z-direction.
After exiting the CAD2Path tool, the path can now be traversed as long as every point along the path is in the working space of the robot (see Fig. 8).
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