Units - export STL - 3d printing.

[bashment]

Hi, I am trying to 3D print a rotating turntable using a headset lower bearing for smoothness. 

I did some test rings to check the ID and OD of the bearing. The OD was spot on. The ID needed tweeking. However, knowing I had to deal with real world size, I went into the units settings and without looking deep, set it to Metric as bearings are measured in mm. And somehow it failed and worked :

At this point I need everything working in mm. The slicing software (anycubic) is in mm by default. 

When I import the rings, the slicer complains : The object is too small

If I say no, the model is less than 10% size required. When I scale up 1000% it is still a bit too small.
If I say yes, the model is perfectly sized. 

Bemused I went on to try making the model. When I import the base, I get the complaint, do the same thing and it prints correct size. But when I import the top plate of this model which is bigger, it seems too big to trigger the complaint and doesn't offer to convert it. 

For now I am doing a test print, using the scale tool to upscale it to the correct diameter, trusting it will be the right proportions but I don't know if this will work. 

I assume I have done something wrong in the settings although I can't think how you can set it to metric and this is the outcome when exporting to another software. I see other people have suffered similar but the said solution didn't work for some people. 

If anyone knows exactly what has gone wrong here I'd appreciate some help. Thank you

[VincentSheehan]

I have a Bambu Lab printer and I get this from time to time. Did you set the Display Unit Scale to Metric or did you set the System Unit Setup Scale to Millimeters?