diff --git a/EgtMachKernel.rc b/EgtMachKernel.rc
index 76ccbd9..d009d28 100644
Binary files a/EgtMachKernel.rc and b/EgtMachKernel.rc differ
diff --git a/Operation.cpp b/Operation.cpp
index 30816ce..4a06dc0 100644
--- a/Operation.cpp
+++ b/Operation.cpp
@@ -819,7 +819,7 @@ Operation::ApproxWithArcsIfUseful( ICurveComposite* pCompo, bool bCareTempProp)
    Frame3d frRef ;
    frRef.Set( ORIG, vtExtr) ;
    BBox3d b3Crv ;
-   if ( ! pCompo->GetBBox( frRef, b3Crv)  ||  ! b3Crv.IsEpsilonZ( 100 * EPS_SMALL))
+   if ( ! pCompo->GetBBox( frRef, b3Crv)  ||  abs( b3Crv.GetMax().z - b3Crv.GetMin().z - dThick) > 100 * EPS_SMALL)
       return true ;
   // se posso ignorare la proprietà temporanea
    if ( ! bCareTempProp) {