contour on my print

[Lisberg]

close-up 3d printed insole with contours

Hi everybody,
i am 3d printing insoles, and as you can see from the attached pictures, the insole top has contours, which I would like to get rid off. The 3D stl file do not have any contours. They emerge when I prepare the model for print in S3D. Any idea how I can get qa smooth surface without contours?

[CompoundCarl]

You could try changing the external fill pattern to concentric. Lowering the layer height will also help.