diff --git a/Machine/CurrentMachine.vb b/Machine/CurrentMachine.vb
index db7bd2e..8d37380 100644
--- a/Machine/CurrentMachine.vb
+++ b/Machine/CurrentMachine.vb
@@ -1301,14 +1301,16 @@ Public Class CurrentMachine
       Dim sFilePath As String = sMachDir & "\" &  MACHININGS_DIR & "\" & WATERJETDB_FILE
       Dim Local_MaterialList = New ObservableCollection(Of EgtWPFLib5.WjMaterial)
       Local_MaterialList = EgtWPFLib5.WaterjetDbWindowVM.LoadWjMaterials(sFilePath)
-      ' definisco la lista delle qualità
-      m_Qualities.Add("")
-      m_Qualities.Add("Q1")
-      m_Qualities.Add("Q2")
-      m_Qualities.Add("Q3")
-      m_Qualities.Add("Q4")
-      m_Qualities.Add("Q5")
-      m_Qualities.Add("QExtra")
+      ' definisco la lista delle qualità (solo se è vuota)
+      If m_Qualities.Count < 1 Then
+         m_Qualities.Add("")
+         m_Qualities.Add("Q1")
+         m_Qualities.Add("Q2")
+         m_Qualities.Add("Q3")
+         m_Qualities.Add("Q4")
+         m_Qualities.Add("Q5")
+         m_Qualities.Add("QExtra")
+      End If
       ' inserisco il materiale generico di default -- IN SOSPESO
       'm_Materials.Add(New Material(0, "***", 0))
       ' costruiscoi la lista