Making 3D renders of CAD models like this robot is actually pretty easy. The way I like to do it is by using a software called “CAD Assistant” by Open Cascade. It allows you to convert between a wide variety of different file formats and does it in a relatively clean manner (clean geometry, no duplicated vertices, etc.)
First you need to get CAD assistant from here. Then, you can export your CAD file into .STEP, which is the standard export format for most CAD software (including Onshape and Solidworks).
Using CAD assistant, import the .STEP file and take a look at it to see if it’s imported correctly. If it is, then just hit the export button and select “.glb” as your file format. .GLB imports very well into Blender, but you can try the other file formats based on your specific need.