I'm not new to ACAD but I am new to 3d modelling. I downloaded an item from thingyverse to 3D print but I need to modify it slightly as some of the dimensions could be tighter. So I converted STL to DXF and then converted all the 3D faces to solid via 'convert to faceted surface' and 'sculpt' commands. I now have an entire 3D solid model which I want to edit but am now stuck as nothing I have tried seems to work. A picture of the item is attached (in top down view) with arrows indicating where I want to modify the dimensions. Basically I want to offset the inside edges by a couple of mm. Can anyone help?

Many thanks in advance!

I've been using ACAD for 14 years, so I have quite a lot of experience in 2D anyway! I do work in 3D, just not with solids - I work a lot with pointclouds so I am used to switching between coordinates systems and views. I have access to versions from 2017 to present.

If it's too difficult as 3D AutoCAD is not easily modified or whith parameters we ( I ) could do the solid if you give all the dimensions defined in the very first step that I think are enough to define the part.

You said that you work in 3D with coordinate systems and views and that's very good; do you want to "learn" 3D AutoCAD or modifying this object is enough ?

Maybe my AutoCAD study is too shortly explained.

I will have a go at drawing the object from scratch and then extruding the regions as you suggest, and we'll see how I get on with it. At the moment I just want to edit this object but long term I do want to acquire 3D CAD skills as I want to be able to create objects myself to 3D print.

Cheers, Ken.