diff --git a/MachMgrRawParts.cpp b/MachMgrRawParts.cpp
index 7257355..7a3b617 100644
--- a/MachMgrRawParts.cpp
+++ b/MachMgrRawParts.cpp
@@ -414,9 +414,22 @@ MachMgr::AddRawPart( int nSurfId, Color cCol)
      // ne calcolo la silhouette secondo Z+
       POLYLINEVECTOR vPL ;
       bool bSilh = false ;
-      if ( pStm->GetSilhouette( Z_AX, vPL)  &&  vPL.size() == 1) {
+      if ( pStm->GetSilhouette( Z_AX, vPL)  &&  vPL.size() > 0) {
+        // cerco il contorno esterno
+         int nInd = - 1 ;
+         double dMaxArea = 0 ;
+         for ( int i = 0 ; i < int( vPL.size()) ; ++ i) {
+            double dArea ;
+            if ( vPL[i].GetAreaXY( dArea)  &&  abs( dArea) > dMaxArea) {
+               if ( dArea < 0)
+                  vPL[i].Invert() ;
+               dMaxArea = abs( dArea) ;
+               nInd = i ;
+            }
+         }
+        // ne deduco la curva
          PtrOwner<ICurveComposite> pCrvSilh( CreateCurveComposite()) ;
-         if ( pCrvSilh->FromPolyLine( vPL[0])  &&  pCrvSilh->IsClosed()) {
+         if ( nInd >= 0  &&  pCrvSilh->FromPolyLine( vPL[nInd])) {
             pCrvSilh->SetExtrusion( Z_AX) ;
             Plane3d plProj ;
             plProj.Set( b3Srf.GetMin(), Z_AX) ;