diff --git a/EXE_Exchange.cpp b/EXE_Exchange.cpp
index 0b2b413..853c666 100644
--- a/EXE_Exchange.cpp
+++ b/EXE_Exchange.cpp
@@ -449,8 +449,11 @@ ExeImport3dm( const string& sFilePath)
 {
    GseContext* pGseCtx = GetCurrGseContext() ;
    VERIFY_CTX_GEOMDB( pGseCtx, false)
-   bool bOk = true ;
+  // se necessario, carico libreria exchange 3dm opzionale
+   if ( ! IsLoadedExch3dmDll()  &&  LoadExch3dmDll( GetLogger(), ExeGetKey(), ExeGetNetHwKey()))
+      LOG_INFO( GetLogger(), MyGetEE3Version())
   // importo il file 3dm
+   bool bOk = true ;
   // preparo l'importatore
    PtrOwner<IImport3dm> pImp3dm( MyCreateImport3dm()) ;
    bOk = bOk && ! IsNull( pImp3dm) ;
@@ -678,8 +681,11 @@ ExeExport3dm( int nId, const string& sFilePath, int nFilter)
 {
    IGeomDB* pGeomDB = GetCurrGeomDB() ;
    VERIFY_GEOMDB( pGeomDB, false)
-   bool bOk = true ;
+  // se necessario, carico libreria exchange 3dm opzionale
+   if ( ! IsLoadedExch3dmDll()  &&  LoadExch3dmDll( GetLogger(), ExeGetKey(), ExeGetNetHwKey()))
+      LOG_INFO( GetLogger(), MyGetEE3Version())
   // esporto il file 3dm
+   bool bOk = true ;
   // preparo l'esportatore
    PtrOwner<IExport3dm> pExp3dm( MyCreateExport3dm()) ;
    bOk = bOk && ! IsNull( pExp3dm) ;
diff --git a/EXE_General.cpp b/EXE_General.cpp
index 29cd10a..8e6280e 100644
--- a/EXE_General.cpp
+++ b/EXE_General.cpp
@@ -118,9 +118,8 @@ ExeInit( int nDebug, const string& sLogFile, const string& sLogMsg)
    if ( LoadExchangeDll( s_pGenLog, s_sKey, s_bNetHwKey))
       LOG_INFO( s_pGenLog, MyGetEExVersion())
 
-  // carico libreria exchange 3dm opzionale
-   if ( LoadExch3dmDll( s_pGenLog, s_sKey, s_bNetHwKey))
-      LOG_INFO( s_pGenLog, MyGetEE3Version())
+  // la libreria exchange 3dm opzionale viene caricata solo al momento del bisogno
+  // (è molto lento il caricamento di OpenNurbs)
 
   // carico libreria di lavorazione opzionale
    if ( LoadMachKernelDll( s_pGenLog, s_sKey, s_bNetHwKey))
diff --git a/EgtExecutor.rc b/EgtExecutor.rc
index 56c1f62..417933e 100644
Binary files a/EgtExecutor.rc and b/EgtExecutor.rc differ