Warn when adding big parts to the queue

SlicerConfiguration/Slicing/SliceLayers.cs

@@ -83,10 +83,16 @@ namespace MatterHackers.MatterControl.Slicing
 				{
 					SliceLayer layer = allLayers[layerIndex];
 					double zHeight = layer.ZHeight;
-					if (zHeight < minZ || zHeight > maxZ)
+					if (zHeight < minZ)
 					{
+						// not up to the start of the face yet
 						continue;
 					}
+					if (zHeight > maxZ)
+					{
+						// done with this face
+						break;
+					}
 					Plane cutPlane = new Plane(Vector3.UnitZ, zHeight);
 
 					Vector3 start;