You can refine your STL output by selecting the Options setting in the Save dialog box. You use the Max Deviation options. As far as the distance and angle settings in Max Deviation, These are relative numbers that are used to refine the facets that are used in the display of your parts. You can test this, by building a cube. Check the part properties and look at facet refinement. There will be no options, because there are no curves to generate. Add a hole to your cube, and check again. It is probably easier to refine the facets on your model BEFORE you save an STL. Open the Part and Assembly menu. At the bottom, select properties. Select a part, and the Part Properties dialog box will open. Bring the Facets tab to the front. Now you have another option to use that is much simpler. You can select a factor to refine your facets by. An STL file is generated from what you see on the screen not the actual geometry of the model. The distance and angle numbers will vary depending on the geometry you have created. If you look closely at a feature of your part, such as a hole, you will see that it does not display as a circle, but actually, a number of small straight lines. (facets) The distance and angle settings represent the relative size of these facets. The more you refine these facets, the better looking your model is on the screen. (and the worse your graphics performance will be) The STL file has a direct relationship to these facets. The more you refine the facets, the more triangles you calculate in your STL model. Do not refine too far, as the file size can get huge. Your STL machine usually has a limit in how thin a layer of material it can build. This is the usually the limitation when it comes to building a smooth looking prototype part. I have had best results when I ignore the numbers, and refine the facets by a factor of two. Then I look at it on the screen, and if the curves look good when I zoom in, I generate the STL file. If it does not look good enough, I refine it again. When it comes to STL files, what you see is what you get. It is important to note that you are ONLY converting graphics data to STL data, you are not exporting actual model geometry. This is why you can export your data from CoCreate Modeling PE to STL, but other export functions that export actual model geometry (like IGES STEP or SAT) are turned off.