Tutorial For Making 3D MODEL of Cranial Defect Using 3D SLICERV

Is their tutorial availabel for making 3d model of cranial defect and i want to know how i can get an STL file of the model for 3D printing .

Assuming you have CT(Volume) data ,

If you are trying to reconstruct a cranial defect there are a number of ways to achieve this in 3D Slicer.
One option is

Another way of achieving this is described in detail here,

The way you can get your data as STL files can be found here,