diff --git a/tools/adaptive-isogrid/src/nx/import_profile.py b/tools/adaptive-isogrid/src/nx/import_profile.py
index 37025034..deb18f98 100644
--- a/tools/adaptive-isogrid/src/nx/import_profile.py
+++ b/tools/adaptive-isogrid/src/nx/import_profile.py
@@ -637,8 +637,8 @@ def _extrude_sketch(part: Any, sketch: Any, thickness: float,
             lister.WriteLine(f"[extrude] Expression warning: {exc}")
             half_expr = str(float(thickness) / 2.0)
 
-        # Symmetric extrude: ±thk/2 from sketch plane
-        builder.Limits.StartExtend.Value.RightHandSide = half_expr
+        # Symmetric extrude: -thk/2 to +thk/2 from sketch plane
+        builder.Limits.StartExtend.Value.RightHandSide = f"-({half_expr})"
         builder.Limits.EndExtend.Value.RightHandSide = half_expr
 
         builder.BooleanOperation.Type = NXOpen.GeometricUtilities.BooleanOperation.BooleanType.Create