Collapse Material Boundaries
The Collapse Material Boundaries 
option gives users the ability to unite adjacent solids that have the same material assignment over all stages in a project. To use this function:
- Select Geometry > Repair Tools > Collapse Material Boundaries.
This option is useful when unnecessary splits occur to a unified solid that breaks up into small pieces. These small pieces increase the complexity of the model and reduces the speed of simulation. Use this function to have the program quickly merge all touching solids that have the same material assignments over all stages.