diff --git a/libsrc/stlgeom/stlgeom.cpp b/libsrc/stlgeom/stlgeom.cpp
index 34ef9d8a..b34f38c5 100644
--- a/libsrc/stlgeom/stlgeom.cpp
+++ b/libsrc/stlgeom/stlgeom.cpp
@@ -3521,6 +3521,75 @@ void STLGeometry :: SmoothGeometry ()
     }
 }
 
+void STLGeometry :: WriteChartToFile( ChartId chartnumber, string filename )
+{
+  PrintMessage(1,"write chart ", int(chartnumber), " to ", filename);
+  Array<int> trignums;
+
+  if (chartnumber >= 1 && chartnumber <= GetNOCharts())
+  {
+    const STLChart& chart = GetChart(chartnumber);
+
+    for (int j = 1; j <= chart.GetNChartT(); j++)
+      trignums.Append(chart.GetChartTrig1(j));
+
+    for (int j = 1; j <= chart.GetNOuterT(); j++)
+      trignums.Append(chart.GetOuterTrig1(j));
+
+    QuickSort(trignums);
+    STLGeometry geo;
+    NgArray<STLReadTriangle> readtrigs;
+    const auto & first_trig = GetTriangle(chart.GetChartTrig1(1));
+    auto normal = first_trig.Normal();
+    Box<3> box{Box<3>::EMPTY_BOX};
+
+    for(auto j : trignums)
+    {
+      const auto& trig = GetTriangle(j);
+      Point<3> pts[3];
+      for(auto k : Range(3))
+      {
+        pts[k] = GetPoint(trig[k]);
+        box.Add(pts[k]);
+      }
+      Vec3d normal = Cross( pts[1]-pts[0], pts[2]-pts[0] );
+      readtrigs.Append(STLReadTriangle(pts, trig.Normal()));
+    }
+    auto dist = box.PMax() - box.PMin();
+    auto extra_point = GetPoint(first_trig[0]) - dist.Length()*normal;
+
+    NgArray<int> acttrigs(GetNT());
+    acttrigs = -1;
+    for (int j = 1; j <= chart.GetNT(); j++)
+      acttrigs.Elem(chart.GetTrig1(j)) = chartnumber;
+
+    for (int j = 1; j <= chart.GetNT(); j++)
+    {
+      auto t = chart.GetTrig1(j);
+      const auto & tt = GetTriangle(t);
+      for (int k = 1; k <= 3; k++)
+      {
+        int nt = NeighbourTrig(t,k);
+        if (acttrigs.Get(nt) != chartnumber)
+        {
+          STLPointId np1, np2;
+          tt.GetNeighbourPoints(GetTriangle(nt),np1,np2);
+
+          Point<3> pts[3];
+          pts[0] = GetPoint(np2);
+          pts[1] = GetPoint(np1);
+          pts[2] = extra_point;
+          Vec3d normal = -Cross( pts[2]-pts[0], pts[1]-pts[0] );
+          readtrigs.Append(STLReadTriangle(pts, normal));
+        }
+      }
+    }
+
+    geo.InitSTLGeometry(readtrigs);
+    geo.Save(filename);
+  }
+}
+
 
 
   class STLGeometryRegister : public GeometryRegister
diff --git a/libsrc/stlgeom/stlgeom.hpp b/libsrc/stlgeom/stlgeom.hpp
index f7157eb8..76796cd2 100644
--- a/libsrc/stlgeom/stlgeom.hpp
+++ b/libsrc/stlgeom/stlgeom.hpp
@@ -394,14 +394,14 @@ namespace netgen
     int TrigIsInOC(int tn, int ocn) const;
  
     //get chart number of a trig or 0 if unmarked
-    ChartId GetChartNr(STLTrigId i) const;
+    DLL_HEADER ChartId GetChartNr(STLTrigId i) const;
     ChartId GetMarker(STLTrigId i) const  { return chartmark[i]; }
     void SetMarker(STLTrigId nr, ChartId m);
     size_t GetNOCharts() const { return atlas.Size(); }
     //get a chart from atlas
     const STLChart& GetChart(ChartId nr) const { return *atlas[nr];};
     STLChart & GetChart(ChartId nr) { return *atlas[nr];};
-    int AtlasMade() const;
+    DLL_HEADER int AtlasMade() const;
   
     void GetInnerChartLimes(NgArray<twoint>& limes, ChartId chartnum);
 
@@ -460,6 +460,9 @@ namespace netgen
     int GenerateMesh (shared_ptr<Mesh> & mesh, MeshingParameters & mparam) override;
     
     virtual const Refinement & GetRefinement () const override;
+
+    // Add additional Point to chart to close the surface and write the resulting stl to a file
+    DLL_HEADER void WriteChartToFile( ChartId chartnumber, string filename="chart.slb" );
   };
  
 
diff --git a/libsrc/stlgeom/stlpkg.cpp b/libsrc/stlgeom/stlpkg.cpp
index 0858fa68..3d234bbb 100644
--- a/libsrc/stlgeom/stlpkg.cpp
+++ b/libsrc/stlgeom/stlpkg.cpp
@@ -395,6 +395,16 @@ namespace netgen
 	  {
 	    stlgeometry->STLDoctorConfirmedToCandidateEdges();
 	  }
+	else if (strcmp (argv[1], "writechart") == 0)
+	  {
+            int st = stlgeometry->GetSelectTrig();
+
+            if (st >= 1 && st <= stlgeometry->GetNT() && stlgeometry->AtlasMade())
+            {
+              auto chartnumber = stlgeometry->GetChartNr(st);
+              stlgeometry->WriteChartToFile(chartnumber, "chart.stlb");
+            }
+	  }
       }
 
     return TCL_OK;
diff --git a/ng/dialog.tcl b/ng/dialog.tcl
index e47cbaaa..3a7706dd 100644
--- a/ng/dialog.tcl
+++ b/ng/dialog.tcl
@@ -944,8 +944,14 @@ proc viewingoptionsdialog { } {
 	    -textvariable stloptions.chartnumberoffset -validate focus -takefocus 0 \
             -validatecommand "my_validate %W 0 1e9 %P 0" \
             -invalidcommand "my_invalid %W"
+
+        ttk::button $f.fn.btn_write_chart -text "Write selected chart to chart.stlb" -command {
+            Ng_STLDoctor writechart
+        }
+
 	grid $f.fn.lab -sticky ne -padx 4
         grid $f.fn.ent -sticky nw -padx 4 -row 1 -column 1
+        grid $f.fn.btn_write_chart -padx 4 -row 2 -column 1
         grid anchor $f.fn center 
         
 	ttk::labelframe $f.advstl -text "Advanced STL options" -relief groove -borderwidth 3
diff --git a/ng/onetcl.cpp b/ng/onetcl.cpp
index 4aabb669..2a9585d5 100644
--- a/ng/onetcl.cpp
+++ b/ng/onetcl.cpp
@@ -1996,8 +1996,12 @@ const char * ngscript[] = {""
 ,"-textvariable stloptions.chartnumberoffset -validate focus -takefocus 0 \\\n"
 ,"-validatecommand \"my_validate %W 0 1e9 %P 0\" \\\n"
 ,"-invalidcommand \"my_invalid %W\"\n"
+,"ttk::button $f.fn.btn_write_chart -text \"Write selected chart to chart.stlb\" -command {\n"
+,"Ng_STLDoctor writechart\n"
+,"}\n"
 ,"grid $f.fn.lab -sticky ne -padx 4\n"
 ,"grid $f.fn.ent -sticky nw -padx 4 -row 1 -column 1\n"
+,"grid $f.fn.btn_write_chart -padx 4 -row 2 -column 1\n"
 ,"grid anchor $f.fn center\n"
 ,"ttk::labelframe $f.advstl -text \"Advanced STL options\" -relief groove -borderwidth 3\n"
 ,"pack $f.advstl -fill x -pady 15\n"