Objective : Clean up the geometry of the component i.e. Housing and extract the mid   surface for another component i.e. Plastic by using different midsurface extraction options 
 and use of ruled, spline and options in the quick panel to clean the surface.

 Procedure For Model 1 (Housing) :

• Open HyperWorks and choose "OptiStruct" as user profile .
  
  
• Now go to File > Import > Geometry. 
  
  
• Select STEP as file type and import the model.
  
  
  
  
• Go to geom > autocleanup > surfs (select all ) > autocleanup.
  
  
  
  
• Now we have to create the missing surface as shown in above figure and for adding  the surface we will use to spline / filler tool .
  
  
• Geometry > Surface > Spline / Filler and select the lines to make the surface as 
  shown in figure. 
  
  
  
  
• Now for the another surface creation , we are going to use filler surf tool. 
  
  
• Geometry > Quick Edit > filler surf and then select the red line  to make the surface      as shown in figure.     
     Now we had cleanup the geometry
  
  
  Procedure for Model 2 (Plastic) :
  
• Open HyperWorks and choose "OptiStruct" as user profile .
  
  
• Now go to File > Import > Geometry. 
  
  
• Select STEP as file type and import the model.
  
  
  
  
• See all the error and study them. 
  
  
  
  
• Now Select "By Topo" in geometry color mode .
  
  
  
  then select display fixed point .
  
  
• Now Press F11 to go to quick edit menu and use the option as per requirement.
  
  
  
  as toggle edge is used to suppress unwanted lines and filler is used to fill the surface and delete surf is used to delete the particular surface. 
  
  
• Similarly, replace point is use to replace the point from one location to another .
  
  
• add/remove point is use to add and remove the point. 
  
  
  
  
• After eradicate all the errors , we will get such result as shown in figure.
  
  
  

        Now, we will do midsurface of this component and again eradicate all the error from              the mid surface using same tools by using proper tool by understanding the errors. 


       

Conclusion / Result : By using different tools, like spline , ruled , toggle etc. we came to know how to clean up the geometry and create the mid surface using both automidsurface and extraction options and also where to use surface edit and other tools to get the finest result as much can be achieved.