Just one thing to add to Dave’s replies.
If your model is too small, faces may fail to form. Try scaling up by x1000 and using the Dave method
That is, start with your component(s) at ‘real’ size as you have them, roughly 50mm diameter. Copy the component, scale up the copy by 1000, zoom extents to see it all, then edit the large copy.
When done with the editing, delete the copy, zoom extents again to zoom in on the original, and it should have the the edits in it.
Alternatively, model it in metres instead of mm as you have done.
Then when you export it to stl format for 3D printing, tell the program that the units are mm instead of metres.