What does offset do on bottom 3D layer?

[dbur]

I have some Ultiboard parts with feature on top and bottom.  I am wondering what the part height offset does for bottom layer parts.  Is it referenced to the top layer, or does it look up the board thickness and factor that in?

I set a stud nut to offset 62.5mils for standard board thickness, but it appears somewhat below the bottom of the board in the part editor.  In the design with a 62.5mil board it seems to be in the right place.

Do I need to edit the part to change that offset for each board thickness I want to use the part on?  Or is there some way for bottom side 3D features that reference to the bottom of the board to take into account the board thickness?

Thanks.

[Tien_P]

Hi Dbur,

The "offset"  field is to how high above the board you want to component while the "height" field is to set the component height.  Have a look at the attached file for visual. The board thickness doesn't affect this setting.

[Tien_P]

Hi Dbur,

The "offset"  field is to how high above the board you want to component while the "height" field is to set the component height.  Have a look at the attached file for visual. The board thickness doesn't affect this setting.

[dbur]

So if I put something on the part's 3D bottom layer that is the same as specifying an offset on the top as negative minus the height and is still referenced to the top of the board?

If so how is board thickness taken into account in the final 3D design presentation?

I guess I could mock up a bunch of test cases and figure it out.

[dbur]

I did do a test and it works as I assumed.  You can do a bottom side feature with negative offsets on the 3D top layer or normal offsets on the 3D bottom layer.  Niether method takes into account the board thickness in the design.  For bottom side features you must add the board thickness as an offset to each feature in the library part.

This should be considered a bug since not all boards are the same thickness.  Parts are displayed as if the board thickness is 0.  This could cause problems for the unwary, especially on a project like I am working on now with many complex 3D parts on both board sides.  The ME design team is using my 3D export as a part in their design space to make sure the mechanical design is correct.