Hi Jimbo2,
The only mechanisms for creating 3D plots in LabVIEW are using the 3D Surface Graph, 3D Parametric Graph, and 3D Curve Graph. I don't know if these graphs will fit your application, you could probably better determine that than myself. Also, to my knowledge there is nothing inherent to LabVIEW to directly handle .stl files. However, you might be able to find a 3rd party program that will display .stl files. If the 3rd party package has an ActiveX control, you can embed it into the front panel of your VI using an ActiveX Container and call methods and properties to the control using the property nodes and invoke nodes in the ActiveX palette in LabVIEW.
I hope this gives you a couple of ideas,
Travis H.
LabVIEW R&D
National Instruments