Keyur Kanade
Ansys Employee

You can use manual approach. Auto skin will work if shape is very nicely defined. Otherwise you can use manual approach. 

You can convert faceted data to solid in SpaceClaim. There are different ways to convert stl to solid.

The first one is using Right Click on the body in the structure tree and select Convert to solid option. This option is useful for planner surfaces and simple bodies. If your body has some fillets or curved surfaces, this option should not be used.
 
The other option is using Skin tool. You can find more information about Skin tool in help manual at following link.
 
In SpaceClaim different commands can be used to create solids from faceted data. Various options are shown in following video.
Whether you need a rough or accurate construction of a model, or tooling based on mesh-scanned data, Discovery SpaceClaim's easy-to-use reverse engineering tools will autosurface any STL data to get your job done faster. Learn more: https://www.ansys.com/discovery
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Please go through help manual for more details