diff --git a/CustomWidgets/ExportPrintItemWindow.cs b/CustomWidgets/ExportPrintItemWindow.cs
index 996df5885..d6324356c 100644
--- a/CustomWidgets/ExportPrintItemWindow.cs
+++ b/CustomWidgets/ExportPrintItemWindow.cs
@@ -398,7 +398,7 @@ namespace MatterHackers.MatterControl
         {
             if (ActivePrinterProfile.Instance.DoPrintLeveling)
             {
-                GCodeFile unleveledGCode = new GCodeFile(source);
+				GCodeFileLoaded unleveledGCode = new GCodeFileLoaded(source);
                 if (applyLeveling.Checked)
                 {
                     PrintLevelingPlane.Instance.ApplyLeveling(unleveledGCode);
diff --git a/PartPreviewWindow/ViewGcodeWidget.cs b/PartPreviewWindow/ViewGcodeWidget.cs
index 6a3c2a351..cbdcad6ea 100644
--- a/PartPreviewWindow/ViewGcodeWidget.cs
+++ b/PartPreviewWindow/ViewGcodeWidget.cs
@@ -264,11 +264,11 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 
 				if (firstExtrusionIndex > 0)
 				{
-					for (int i = 0; i < loadedGCode.NumChangesInZ; i++)
+					for (int layerIndex = 0; layerIndex < loadedGCode.NumChangesInZ; layerIndex++)
 					{
-						if (firstExtrusionIndex < loadedGCode.IndexOfChangeInZ[i])
+						if (firstExtrusionIndex < loadedGCode.GetInstructionIndexAtLayer(layerIndex))
 						{
-							activeLayerIndex = Math.Max(0, i-1);
+							activeLayerIndex = Math.Max(0, layerIndex-1);
 							break;
 						}
 					}
@@ -481,7 +481,7 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 
 		public void Load(string gcodePathAndFileName)
 		{
-			loadedGCode = new GCodeFile(gcodePathAndFileName);
+			loadedGCode = GCodeFile.Load(gcodePathAndFileName);
 			SetInitalLayer();
 			CenterPartInView();
 		}
@@ -497,7 +497,7 @@ namespace MatterHackers.MatterControl.PartPreviewWindow
 			backgroundWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(initialLoading_RunWorkerCompleted);
 
 			loadedGCode = null;
-			GCodeFile.LoadInBackground(backgroundWorker, gcodePathAndFileName);
+			GCodeFileLoaded.LoadInBackground(backgroundWorker, gcodePathAndFileName);
 		}
 
 		public override void OnClosed(EventArgs e)
diff --git a/PrintQueue/OptionsMenu/ExportToFolderProcess.cs b/PrintQueue/OptionsMenu/ExportToFolderProcess.cs
index ffad912f2..97fca6de8 100644
--- a/PrintQueue/OptionsMenu/ExportToFolderProcess.cs
+++ b/PrintQueue/OptionsMenu/ExportToFolderProcess.cs
@@ -177,11 +177,6 @@ namespace MatterHackers.MatterControl.PrintQueue
                                     }
                                 }
                             }
-                            if (!foundAmountInGCode)
-                            {
-                                GCodeFile gcodeFile = new GCodeFile(gcodeFileName);
-                                total += gcodeFile.GetFilamentCubicMm(ActiveSliceSettings.Instance.FilamentDiameter) / 1000;
-                            }
                         }
                     }
 
@@ -195,7 +190,7 @@ namespace MatterHackers.MatterControl.PrintQueue
 
                         if (ActivePrinterProfile.Instance.DoPrintLeveling)
                         {
-                            GCodeFile unleveledGCode = new GCodeFile(savedGcodeFileName);
+							GCodeFileLoaded unleveledGCode = new GCodeFileLoaded(savedGcodeFileName);
                             PrintLevelingPlane.Instance.ApplyLeveling(unleveledGCode);
                             unleveledGCode.Save(outputPathAndName);
                         }
diff --git a/PrinterCommunication/Io/PrinterIoGCodeFile.cs b/PrinterCommunication/Io/PrinterIoGCodeFile.cs
index bf5613148..4d54b84b7 100644
--- a/PrinterCommunication/Io/PrinterIoGCodeFile.cs
+++ b/PrinterCommunication/Io/PrinterIoGCodeFile.cs
@@ -37,7 +37,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication.Io
 {
     public class PrinterIoGCodeFile : PrinterIoBase
     {
-        GCodeFile loadedGCode = new GCodeFile();
+        GCodeFile loadedGCode;
         int printerCommandQueueIndex;
         public PrinterIoGCodeFile(GCodeFile loadedGCode)
         {
@@ -68,7 +68,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication.Io
                 {
                     for (int zIndex = 0; zIndex < loadedGCode.NumChangesInZ; zIndex++)
                     {
-                        if (currentIndex < loadedGCode.IndexOfChangeInZ[zIndex])
+                        if (currentIndex < loadedGCode.GetInstructionIndexAtLayer(zIndex))
                         {
                             return zIndex - 1;
                         }
@@ -106,11 +106,11 @@ namespace MatterHackers.MatterControl.PrinterCommunication.Io
                     && currentIndex < loadedGCode.Count)
                 {
                     int currentLayer = CurrentlyPrintingLayer;
-                    int startIndex = loadedGCode.IndexOfChangeInZ[currentLayer];
+                    int startIndex = loadedGCode.GetInstructionIndexAtLayer(currentLayer);
                     int endIndex = loadedGCode.Count - 1;
                     if (currentLayer < loadedGCode.NumChangesInZ - 2)
                     {
-                        endIndex = loadedGCode.IndexOfChangeInZ[currentLayer + 1] - 1;
+                        endIndex = loadedGCode.GetInstructionIndexAtLayer(currentLayer + 1) - 1;
                     }
 
                     int deltaFromStart = Math.Max(0, currentIndex - startIndex);
diff --git a/PrinterCommunication/PrinterConnectionAndCommunication.cs b/PrinterCommunication/PrinterConnectionAndCommunication.cs
index f7d8ffe92..fcdc22399 100644
--- a/PrinterCommunication/PrinterConnectionAndCommunication.cs
+++ b/PrinterCommunication/PrinterConnectionAndCommunication.cs
@@ -296,7 +296,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication
         double actualBedTemperature;
         double targetBedTemperature;
         string printJobDisplayName = null;
-        GCodeFile loadedGCode = new GCodeFile();
+        GCodeFile loadedGCode = new GCodeFileLoaded(); // we start out by setting it to a nothing file
         IFrostedSerialPort serialPort;
         Thread readFromPrinterThread;
         Thread connectThread;
@@ -2450,7 +2450,7 @@ namespace MatterHackers.MatterControl.PrinterCommunication
 
             LinesToWriteQueue.Clear();
             ClearQueuedGCode();
-			loadedGCode = new GCodeFile(gcodeFilename);
+			loadedGCode = GCodeFile.Load(gcodeFilename);
 
             switch (communicationState)
             {