Check the make solid help for specifics. If you have a convergent body, you can use the "unassociative" mode to convert it to a solid. If you have a totally closed sheet body made from features (rare, but it happens), you will need to turn on the "associative" option.
Note that this command will not work for multiple sheet bodies that enclose a volume; in this case, use the "sew" command to sew the multiple sheet bodies into a single body. If the sheets enclose a volume with no gaps, a solid will result.
You need a closed sheet body for this to work.
From help documentation:
"Use the Make Solid command to convert any facet or analytic closed sheet bodies to solid bodies."
It doesn't really matter if the body is facet or analytic (imported one or created in NX).
To make this work, you must have a 'totally closed' single sheet body, which is in one way, possible with 'sew' command. But it makes every closed set a solid. Workaround for this (after searching alot) is to force NX to not create any solid bodies. Do this by going into modelling preferences, and selecting sheet instead of solid.
Then create any closed sheet body, sew it, and MAKE SOLID will work.
In case it still doesn't work, make sure the associative option is checked.
Solid Edge 2019
"It doesn't really matter if the body is facet or analytic (imported one or created in NX)."
Well, actually, yes it does. The help file specifically states:
"Not available for NX facet or JT facet bodies."
You must convert the facet body to a convergent body or it must be a parameterized, water-tight sheet body.
This is the sample partfile..where i was trying to use Make Solid Command but i've made as shet bodies using surfacing commands and if we sew it'll become as solid body....
I'm sorry how to attach the part file in this?? i really dont know
Use the browse button at the bottom @karthik6, while posting a reply or creating a new post. Compress the part file first (zip or rar) or it will not upload (don't know why it doesn't uploads the .prt files.
By the way, I'll upload one part where MAKE SOLID works. Give me a min.
EDIT: Uploaded three files. First, I have created three sheets, making a closed section, but not sewed. Then, I sew the surfaces. At last, I use Make Solid command.
Hope it helps.
Solid Edge 2019