The feature lines of a model are the lines imported from the solid modeler program that define the surfaces in a model. There are two possible configurations of feature lines that will make it impossible for the model to be meshed.
Unmatched Feature Lines: An unmatched feature line is one that is not shared by two surfaces. It means that one surface ends in the middle of space and does not connect with another surface. This configuration does not enclose a volume and will therefore not allow the solid mesh engine to create a solid mesh. If you view the model with either View Appearance Visual Style Edges or Shaded with Edges options, and if View AppearanceCAD Surfaces is active, then unmatched feature lines will appear orange.
Multi-Matched Feature Lines: A multi-matched feature line occurs when more than two surfaces on one part share an edge. To enclose a continuous volume, only two surfaces can meet at an edge. This configuration does not enclose a continuous volume and will therefore not allow the solid mesh engine to create a solid mesh. If you view the model with either View Appearance Visual Style Edges or Shaded with Edges options, and if View AppearanceCAD Surfaces is active, multi-matched feature lines will appear blue.
Alternatively, use View Appearance Only Bad CAD Features along with View Appearance Visual Style Edges or Shaded with Edges to show only the feature lines that are unmatched or multi-matched. (If there are no problems, then no feature lines will be shown.)
Specify the Stitching tolerance and click the Apply button. The goal is to eliminate all multimatched and unmatched features by trying different tolerances. A larger tolerance eliminates most unmatched feature lines while a smaller tolerance eliminates most multi-matched feature lines.
How the value is used will depend on the option selected in the Type drop-down box. If the Percentage of automatic option is selected, the feature matcher automatically calculates a mesh size based on the percentage entered times the default mesh size (the size when the slider is at the middle position). The slider can be used to specify the value when this option is active. The number in the Stitching tolerance field will be the percentage value. The default mesh size is one sixth of the cube root of the volume. If the Absolute mesh size option is selected, then the feature matcher tries to match the feature lines in the model using approximately the specified mesh size. The number in the Stitching tolerance field will be the approximate length of the sides.