Can some one advise on how to extract from an assembly of imported solids one component?
Delete all the other solids.
Ok, your terminology is kind of confusing.
You said, "Can some one advise on how to extract from an assembly of imported solids one component?"
With regards to Solidworks, an Assembly is a file that is made up of different components, some can be other assemblies and some can be parts.
A Part is a file that is made up of different surface bodies, sketches and solid bodies.
If you have an assembly that is made up of solids (parts with solid bodies), then that is all you need to do is select the component and then select "Open Part"
If, however, you really mean that you have a single part with many solid bodies in it, then that is a different ball of wax entirely.
There are a couple of ways to extract 1 single body.
1) What Steve Calvert already said and expand your solid bodies folder and select all the other bodies and delete them. (maybe run a Save as... first.
2) You can select the single body (from the solid bodies folder) that you want and RMB on it, then select "Insert into New Part..."
I tend to try and get there the easiest way first so for me save-as and delete what I don't want.
If you have one assy from CATIA for eg import to SW2018, export the file like *.XT and import again from de *.XT file you can choose any part or export each part as you wish only from a XT file.
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