fix: Cincinnati post processor arc feedrate, G89 spacing, pallet exchange, and preamble

- Add radius-based arc feedrate calculation (Variables/Percentages modes)
  with configurable radius ranges (#123/#124/#125 or inline expressions)
- Fix arc distance in SpeedClassifier using actual arc length instead of
  chord length (full circles previously computed as zero)
- Fix G89 P spacing: P now adjacent to filename per CL-707 manual syntax
- Add lead-out feedrate support (#129) and arc lead-in feedrate (#127)
- Fix pallet exchange: StartAndEnd emits M50 in preamble + last sheet only
- Add G121 Smart Rapids emission when UseSmartRapids is enabled
- Add G90 absolute mode to main program preamble alongside G20/G21

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Core/Geometry/ArcFit.cs

@@ -56,6 +56,60 @@ namespace OpenNest.Geometry
             return (new Vector(cx, cy), radius, MaxRadialDeviation(points, cx, cy, radius));
         }
 
+        /// <summary>
+        /// Fits a circular arc constrained to be tangent to the given directions at both
+        /// the first and last points. The center lies at the intersection of the normals
+        /// at P1 and Pn, guaranteeing the arc departs P1 in the start direction and arrives
+        /// at Pn in the end direction. Uses the radius from P1 (exact start tangent);
+        /// deviation includes any endpoint gap at Pn.
+        /// </summary>
+        internal static (Vector center, double radius, double deviation) FitWithDualTangent(
+            List<Vector> points, Vector startTangent, Vector endTangent)
+        {
+            if (points.Count < 3)
+                return (Vector.Invalid, 0, double.MaxValue);
+
+            var p1 = points[0];
+            var pn = points[^1];
+
+            var stLen = System.Math.Sqrt(startTangent.X * startTangent.X + startTangent.Y * startTangent.Y);
+            var etLen = System.Math.Sqrt(endTangent.X * endTangent.X + endTangent.Y * endTangent.Y);
+            if (stLen < 1e-10 || etLen < 1e-10)
+                return (Vector.Invalid, 0, double.MaxValue);
+
+            // Normal to start tangent at P1 (perpendicular)
+            var n1x = -startTangent.Y / stLen;
+            var n1y = startTangent.X / stLen;
+
+            // Normal to end tangent at Pn
+            var n2x = -endTangent.Y / etLen;
+            var n2y = endTangent.X / etLen;
+
+            // Solve: P1 + t1*N1 = Pn + t2*N2
+            var det = n1x * (-n2y) - (-n2x) * n1y;
+            if (System.Math.Abs(det) < 1e-10)
+                return (Vector.Invalid, 0, double.MaxValue);
+
+            var dx = pn.X - p1.X;
+            var dy = pn.Y - p1.Y;
+            var t1 = (dx * (-n2y) - (-n2x) * dy) / det;
+
+            var cx = p1.X + t1 * n1x;
+            var cy = p1.Y + t1 * n1y;
+
+            // Use radius from P1 (guarantees exact start tangent and passes through P1)
+            var r1 = System.Math.Sqrt((cx - p1.X) * (cx - p1.X) + (cy - p1.Y) * (cy - p1.Y));
+            if (r1 < 1e-10)
+                return (Vector.Invalid, 0, double.MaxValue);
+
+            // Measure endpoint gap at Pn
+            var r2 = System.Math.Sqrt((cx - pn.X) * (cx - pn.X) + (cy - pn.Y) * (cy - pn.Y));
+            var endpointDev = System.Math.Abs(r2 - r1);
+
+            var interiorDev = MaxRadialDeviation(points, cx, cy, r1);
+            return (new Vector(cx, cy), r1, System.Math.Max(endpointDev, interiorDev));
+        }
+
         /// <summary>
         /// Computes the maximum radial deviation of interior points from a circle.
         /// </summary>

OpenNest.Core/Geometry/GeometrySimplifier.cs

@@ -134,13 +134,11 @@ public class GeometrySimplifier
 
         if (midpoints.Count < 4) return MirrorAxisResult.None;
 
-        // Centroid
+        var centroid = new Vector(
-        var cx = 0.0;
+            midpoints.Average(p => p.X),
-        var cy = 0.0;
+            midpoints.Average(p => p.Y));
-        foreach (var p in midpoints) { cx += p.X; cy += p.Y; }
+        var cx = centroid.X;
-        cx /= midpoints.Count;
+        var cy = centroid.Y;
-        cy /= midpoints.Count;
-        var centroid = new Vector(cx, cy);
 
         // Covariance matrix for PCA
         var cxx = 0.0;
@@ -192,12 +190,25 @@ public class GeometrySimplifier
         return bestResult.Score >= 0.8 ? bestResult : MirrorAxisResult.None;
     }
 
+    private static double NormalizeAngle(double angle) =>
+        angle < 0 ? angle + Angle.TwoPI : angle;
+
     private static Vector Normalize(Vector v)
     {
         var len = System.Math.Sqrt(v.X * v.X + v.Y * v.Y);
         return len < 1e-10 ? new Vector(1, 0) : new Vector(v.X / len, v.Y / len);
     }
 
+    private static double PerpendicularDistance(Vector point, Vector axisPoint, Vector axisDir)
+    {
+        var dx = point.X - axisPoint.X;
+        var dy = point.Y - axisPoint.Y;
+        var dot = dx * axisDir.X + dy * axisDir.Y;
+        var px = dx - dot * axisDir.X;
+        var py = dy - dot * axisDir.Y;
+        return System.Math.Sqrt(px * px + py * py);
+    }
+
     private static double MirrorMatchScore(List<Vector> points, Vector axisPoint, Vector axisDir)
     {
         var matchTol = 0.1;
@@ -206,14 +217,7 @@ public class GeometrySimplifier
         for (var i = 0; i < points.Count; i++)
         {
             var p = points[i];
-
+            var dist = PerpendicularDistance(p, axisPoint, axisDir);
-            // Distance from point to axis
-            var dx = p.X - axisPoint.X;
-            var dy = p.Y - axisPoint.Y;
-            var dot = dx * axisDir.X + dy * axisDir.Y;
-            var perpX = dx - dot * axisDir.X;
-            var perpY = dy - dot * axisDir.Y;
-            var dist = System.Math.Sqrt(perpX * perpX + perpY * perpY);
 
             // Points on the axis count as matched
             if (dist < matchTol)
@@ -223,14 +227,12 @@ public class GeometrySimplifier
             }
 
             // Reflect across axis and look for partner
-            var mx = p.X - 2 * perpX;
+            var reflected = new MirrorAxisResult(axisPoint, axisDir, 0).Reflect(p);
-            var my = p.Y - 2 * perpY;
 
             for (var j = 0; j < points.Count; j++)
             {
                 if (i == j) continue;
-                var d = System.Math.Sqrt((points[j].X - mx) * (points[j].X - mx) +
+                var d = reflected.DistanceTo(points[j]);
-                                         (points[j].Y - my) * (points[j].Y - my));
                 if (d < matchTol)
                 {
                     matched++;
@@ -259,14 +261,7 @@ public class GeometrySimplifier
 
             var ci = candidates[i];
             var ciCenter = ci.BoundingBox.Center;
-
+            if (PerpendicularDistance(ciCenter, axis.Point, axis.Direction) < 0.1) continue; // on the axis
-            // Distance from candidate center to axis
-            var dx = ciCenter.X - axis.Point.X;
-            var dy = ciCenter.Y - axis.Point.Y;
-            var dot = dx * axis.Direction.X + dy * axis.Direction.Y;
-            var perpDist = System.Math.Sqrt((dx - dot * axis.Direction.X) * (dx - dot * axis.Direction.X) +
-                                            (dy - dot * axis.Direction.Y) * (dy - dot * axis.Direction.Y));
-            if (perpDist < 0.1) continue; // on the axis
 
             var mirrorCenter = axis.Reflect(ciCenter);
 
@@ -328,12 +323,8 @@ public class GeometrySimplifier
         var mirrorEp = axis.Reflect(ep);
 
         // Mirroring reverses winding — swap start/end to preserve arc direction
-        var mirrorStart = System.Math.Atan2(mirrorEp.Y - mirrorCenter.Y, mirrorEp.X - mirrorCenter.X);
+        var mirrorStart = NormalizeAngle(System.Math.Atan2(mirrorEp.Y - mirrorCenter.Y, mirrorEp.X - mirrorCenter.X));
-        var mirrorEnd = System.Math.Atan2(mirrorSp.Y - mirrorCenter.Y, mirrorSp.X - mirrorCenter.X);
+        var mirrorEnd = NormalizeAngle(System.Math.Atan2(mirrorSp.Y - mirrorCenter.Y, mirrorSp.X - mirrorCenter.X));
-
-        // Normalize to [0, 2pi)
-        if (mirrorStart < 0) mirrorStart += Angle.TwoPI;
-        if (mirrorEnd < 0) mirrorEnd += Angle.TwoPI;
 
         var result = new Arc(mirrorCenter, arc.Radius, mirrorStart, mirrorEnd, arc.IsReversed);
         result.Layer = arc.Layer;
@@ -357,15 +348,16 @@ public class GeometrySimplifier
             }
 
             chainedTangent = ComputeEndTangent(result.Center, result.Points);
+            var arc = CreateArc(result.Center, result.Radius, result.Points, entities[j]);
             candidates.Add(new ArcCandidate
             {
                 StartIndex = j,
                 EndIndex = result.EndIndex,
-                FittedArc = CreateArc(result.Center, result.Radius, result.Points, entities[j]),
+                FittedArc = arc,
                 MaxDeviation = result.Deviation,
                 BoundingBox = result.Points.GetBoundingBox(),
-                FirstPoint = result.Points[0],
+                FirstPoint = arc.StartPoint(),
-                LastPoint = result.Points[^1],
+                LastPoint = arc.EndPoint(),
             });
 
             j = result.EndIndex + 1;
@@ -386,14 +378,16 @@ public class GeometrySimplifier
             ? chainedTangent
             : new Vector(points[1].X - points[0].X, points[1].Y - points[0].Y);
 
-        var (center, radius, dev) = TryFit(points, startTangent);
+        var endTangent = GetExitDirection(entities[k]);
+        var (center, radius, dev) = TryFit(points, startTangent, endTangent);
         if (!center.IsValid()) return null;
 
         // Extend the arc as far as possible
         while (k + 1 <= runEnd)
         {
             var extPoints = CollectPoints(entities, start, k + 1);
-            var (nc, nr, nd) = extPoints.Count >= 3 ? TryFit(extPoints, startTangent) : (Vector.Invalid, 0, 0d);
+            var extEndTangent = GetExitDirection(entities[k + 1]);
+            var (nc, nr, nd) = extPoints.Count >= 3 ? TryFit(extPoints, startTangent, extEndTangent) : (Vector.Invalid, 0, 0d);
             if (!nc.IsValid()) break;
 
             k++;
@@ -413,9 +407,23 @@ public class GeometrySimplifier
         return new ArcFitResult(center, radius, dev, points, k);
     }
 
-    private (Vector center, double radius, double deviation) TryFit(List<Vector> points, Vector startTangent)
+    private (Vector center, double radius, double deviation) TryFit(List<Vector> points, Vector startTangent, Vector endTangent)
     {
-        var (center, radius, dev) = FitWithStartTangent(points, startTangent);
+        // Try dual-tangent fit first (matches direction at both endpoints)
+        if (endTangent.IsValid())
+        {
+            var (dc, dr, dd) = ArcFit.FitWithDualTangent(points, startTangent, endTangent);
+            if (dc.IsValid() && dd <= Tolerance)
+            {
+                var isRev = SumSignedAngles(dc, points) < 0;
+                var aDev = MaxArcToSegmentDeviation(points, dc, dr, isRev);
+                if (aDev <= Tolerance)
+                    return (dc, dr, System.Math.Max(dd, aDev));
+            }
+        }
+
+        // Fall back to start-tangent-only, then mirror axis
+        var (center, radius, dev) = ArcFit.FitWithStartTangent(points, startTangent);
         if (!center.IsValid() || dev > Tolerance)
             (center, radius, dev) = FitMirrorAxis(points);
         if (!center.IsValid() || dev > Tolerance)
@@ -430,16 +438,6 @@ public class GeometrySimplifier
         return (center, radius, System.Math.Max(dev, arcDev));
     }
 
-    /// <summary>
-    /// Fits a circular arc constrained to be tangent to the given direction at the
-    /// first point. The center lies at the intersection of the normal at P1 (perpendicular
-    /// to the tangent) and the perpendicular bisector of the chord P1->Pn, guaranteeing
-    /// the arc passes through both endpoints and departs P1 in the given direction.
-    /// </summary>
-    private static (Vector center, double radius, double deviation) FitWithStartTangent(
-        List<Vector> points, Vector tangent) =>
-        ArcFit.FitWithStartTangent(points, tangent);
-
     /// <summary>
     /// Computes the tangent direction at the last point of a fitted arc,
     /// used to chain tangent continuity to the next arc.
@@ -447,15 +445,10 @@ public class GeometrySimplifier
     private static Vector ComputeEndTangent(Vector center, List<Vector> points)
     {
         var lastPt = points[^1];
-        var totalAngle = SumSignedAngles(center, points);
-
         var rx = lastPt.X - center.X;
         var ry = lastPt.Y - center.Y;
-
+        var sign = SumSignedAngles(center, points) >= 0 ? 1 : -1;
-        if (totalAngle >= 0)
+        return new Vector(-sign * ry, sign * rx);
-            return new Vector(-ry, rx);
-        else
-            return new Vector(ry, -rx);
     }
 
     /// <summary>
@@ -496,12 +489,12 @@ public class GeometrySimplifier
         var range = System.Math.Max(System.Math.Abs(dInit) * 2, halfChord);
 
         var dOpt = GoldenSectionMin(dInit - range, dInit + range,
-            d => MaxRadialDeviation(points, mx + d * nx, my + d * ny,
+            d => ArcFit.MaxRadialDeviation(points, mx + d * nx, my + d * ny,
                 System.Math.Sqrt(halfChord * halfChord + d * d)));
 
         var center = new Vector(mx + dOpt * nx, my + dOpt * ny);
         var radius = System.Math.Sqrt(halfChord * halfChord + dOpt * dOpt);
-        return (center, radius, MaxRadialDeviation(points, center.X, center.Y, radius));
+        return (center, radius, ArcFit.MaxRadialDeviation(points, center.X, center.Y, radius));
     }
 
     private static double GoldenSectionMin(double low, double high, Func<double, double> eval)
@@ -554,20 +547,28 @@ public class GeometrySimplifier
         var firstPoint = points[0];
         var lastPoint = points[^1];
 
-        var startAngle = System.Math.Atan2(firstPoint.Y - center.Y, firstPoint.X - center.X);
+        var startAngle = NormalizeAngle(System.Math.Atan2(firstPoint.Y - center.Y, firstPoint.X - center.X));
-        var endAngle = System.Math.Atan2(lastPoint.Y - center.Y, lastPoint.X - center.X);
+        var endAngle = NormalizeAngle(System.Math.Atan2(lastPoint.Y - center.Y, lastPoint.X - center.X));
         var isReversed = SumSignedAngles(center, points) < 0;
 
-        // Normalize to [0, 2pi)
-        if (startAngle < 0) startAngle += Angle.TwoPI;
-        if (endAngle < 0) endAngle += Angle.TwoPI;
-
         var arc = new Arc(center, radius, startAngle, endAngle, isReversed);
         arc.Layer = sourceEntity.Layer;
         arc.Color = sourceEntity.Color;
         return arc;
     }
 
+    /// <summary>
+    /// Returns the exit direction (tangent at endpoint) of an entity.
+    /// </summary>
+    private static Vector GetExitDirection(Entity entity) => entity switch
+    {
+        Line line => new Vector(line.EndPoint.X - line.StartPoint.X, line.EndPoint.Y - line.StartPoint.Y),
+        Arc arc => arc.IsReversed
+            ? new Vector(System.Math.Sin(arc.EndAngle), -System.Math.Cos(arc.EndAngle))
+            : new Vector(-System.Math.Sin(arc.EndAngle), System.Math.Cos(arc.EndAngle)),
+        _ => Vector.Invalid,
+    };
+
     /// <summary>
     /// Sums signed angular change traversing consecutive points around a center.
     /// Positive = CCW, negative = CW.
@@ -587,12 +588,6 @@ public class GeometrySimplifier
         return total;
     }
 
-    /// <summary>
-    /// Max deviation of intermediate points (excluding endpoints) from a circle.
-    /// </summary>
-    private static double MaxRadialDeviation(List<Vector> points, double cx, double cy, double radius) =>
-        ArcFit.MaxRadialDeviation(points, cx, cy, radius);
-
     /// <summary>
     /// Measures the maximum distance from sampled points along the fitted arc
     /// back to the original line segments. This catches cases where points lie

OpenNest.Posts.Cincinnati/CincinnatiFeatureWriter.cs

@@ -70,7 +70,7 @@ public sealed class CincinnatiFeatureWriter
             {
                 var speedClass = _speedClassifier.Classify(ctx.CutDistance, ctx.SheetDiagonal);
                 var cutDist = _speedClassifier.FormatCutDist(ctx.CutDistance, ctx.SheetDiagonal);
-                writer.WriteLine($"G89 P {lib} ({speedClass} {cutDist})");
+                writer.WriteLine($"G89 P{lib} ({speedClass} {cutDist})");
             }
             else
             {
@@ -108,7 +108,7 @@ public sealed class CincinnatiFeatureWriter
                 sb.Append($"G1 X{_fmt.FormatCoord(linear.EndPoint.X)} Y{_fmt.FormatCoord(linear.EndPoint.Y)}");
 
                 // Feedrate — etch always uses process feedrate
-                var feedVar = ctx.IsEtch ? "#148" : GetFeedVariable(linear.Layer);
+                var feedVar = ctx.IsEtch ? "#148" : GetLinearFeedVariable(linear.Layer);
                 if (feedVar != lastFeedVar)
                 {
                     sb.Append($" F{feedVar}");
@@ -138,11 +138,11 @@ public sealed class CincinnatiFeatureWriter
                 var j = arc.CenterPoint.Y - currentPos.Y;
                 sb.Append($" I{_fmt.FormatCoord(i)} J{_fmt.FormatCoord(j)}");
 
-                // Feedrate — etch always uses process feedrate, cut uses layer-based
+                // Feedrate — etch always uses process feedrate, cut uses layer/radius-based
+                var radius = currentPos.DistanceTo(arc.CenterPoint);
                 var isFullCircle = IsFullCircle(currentPos, arc.EndPoint);
                 var feedVar = ctx.IsEtch ? "#148"
-                    : isFullCircle ? "[#148*#128]"
+                    : GetArcFeedrate(arc.Layer, radius, isFullCircle);
-                    : GetFeedVariable(arc.Layer);
                 if (feedVar != lastFeedVar)
                 {
                     sb.Append($" F{feedVar}");
@@ -223,16 +223,45 @@ public sealed class CincinnatiFeatureWriter
         }
     }
 
-    private static string GetFeedVariable(LayerType layer)
+    private static string GetLinearFeedVariable(LayerType layer)
     {
         return layer switch
         {
             LayerType.Leadin => "#126",
-            LayerType.Cut => "#148",
+            LayerType.Leadout => "#129",
             _ => "#148"
         };
     }
 
+    private string GetArcFeedrate(LayerType layer, double radius, bool isFullCircle)
+    {
+        if (layer == LayerType.Leadin) return "#127";
+        if (layer == LayerType.Leadout) return "#129";
+        if (isFullCircle) return "[#148*#128]";
+        return GetArcCutFeedrate(radius);
+    }
+
+    private string GetArcCutFeedrate(double radius)
+    {
+        if (_config.ArcFeedrate == ArcFeedrateMode.None)
+            return "#148";
+
+        // Find the smallest range that contains this radius
+        ArcFeedrateRange best = null;
+        foreach (var range in _config.ArcFeedrateRanges)
+        {
+            if (radius <= range.MaxRadius && (best == null || range.MaxRadius < best.MaxRadius))
+                best = range;
+        }
+
+        if (best == null)
+            return "#148";
+
+        return _config.ArcFeedrate == ArcFeedrateMode.Variables
+            ? $"#{best.VariableNumber}"
+            : $"[#148*{best.FeedratePercent.ToString("0.##", System.Globalization.CultureInfo.InvariantCulture)}]";
+    }
+
     private static bool IsFullCircle(Vector start, Vector end)
     {
         return Tolerance.IsEqualTo(start.X, end.X) && Tolerance.IsEqualTo(start.Y, end.Y);

OpenNest.Posts.Cincinnati/CincinnatiPostConfig.cs

@@ -269,12 +269,35 @@ namespace OpenNest.Posts.Cincinnati
         /// </summary>
         public double LeadInArcLine2FeedratePercent { get; set; } = 0.5;
 
+        /// <summary>
+        /// Gets or sets the feedrate percentage for lead-out moves.
+        /// Default: 0.5 (50%)
+        /// </summary>
+        public double LeadOutFeedratePercent { get; set; } = 0.5;
+
         /// <summary>
         /// Gets or sets the feedrate multiplier for circular cuts.
         /// Default: 0.8 (80%)
         /// </summary>
         public double CircleFeedrateMultiplier { get; set; } = 0.8;
 
+        /// <summary>
+        /// Gets or sets the arc feedrate calculation mode.
+        /// Default: ArcFeedrateMode.None
+        /// </summary>
+        public ArcFeedrateMode ArcFeedrate { get; set; } = ArcFeedrateMode.None;
+
+        /// <summary>
+        /// Gets or sets the radius-based arc feedrate ranges.
+        /// Ranges are matched from smallest MaxRadius to largest.
+        /// </summary>
+        public List<ArcFeedrateRange> ArcFeedrateRanges { get; set; } = new()
+        {
+            new() { MaxRadius = 0.125, FeedratePercent = 0.25, VariableNumber = 123 },
+            new() { MaxRadius = 0.750, FeedratePercent = 0.50, VariableNumber = 124 },
+            new() { MaxRadius = 4.500, FeedratePercent = 0.80, VariableNumber = 125 }
+        };
+
         /// <summary>
         /// Gets or sets the variable number for sheet width.
         /// Default: 110
@@ -301,4 +324,34 @@ namespace OpenNest.Posts.Cincinnati
         public string Gas { get; set; } = "";
         public string Library { get; set; } = "";
     }
+
+    /// <summary>
+    /// Specifies how arc feedrates are calculated based on radius.
+    /// </summary>
+    public enum ArcFeedrateMode
+    {
+        /// <summary>No radius-based arc feedrate adjustment (only full circles use multiplier).</summary>
+        None,
+
+        /// <summary>Inline percentage expressions: F [#148*pct] based on radius range.</summary>
+        Percentages,
+
+        /// <summary>Radius-range-based variables: F #varNum based on radius range.</summary>
+        Variables
+    }
+
+    /// <summary>
+    /// Defines a radius range and its associated feedrate for arc moves.
+    /// </summary>
+    public class ArcFeedrateRange
+    {
+        /// <summary>Maximum radius for this range (inclusive).</summary>
+        public double MaxRadius { get; set; }
+
+        /// <summary>Feedrate as a fraction of process feedrate (e.g. 0.25 = 25%).</summary>
+        public double FeedratePercent { get; set; }
+
+        /// <summary>Variable number for Variables mode (e.g. 123).</summary>
+        public int VariableNumber { get; set; }
+    }
 }

OpenNest.Posts.Cincinnati/CincinnatiPostProcessor.cs

@@ -112,8 +112,9 @@ namespace OpenNest.Posts.Cincinnati
                 var sheetIndex = i + 1;
                 var subNumber = Config.SheetSubprogramStart + i;
                 var cutLibrary = resolver.ResolveCutLibrary(plate.Material?.Name ?? "", plate.Thickness, gas);
+                var isLastSheet = i == plates.Count - 1;
                 sheetWriter.Write(writer, plate, nest.Name ?? "NEST", sheetIndex, subNumber,
-                    cutLibrary, etchLibrary, partSubprograms);
+                    cutLibrary, etchLibrary, partSubprograms, isLastSheet);
             }
 
             // Part sub-programs (if enabled)
@@ -148,6 +149,18 @@ namespace OpenNest.Posts.Cincinnati
             vars.GetOrCreate("LeadInFeedrate", 126, $"[#148*{Config.LeadInFeedratePercent}]");
             vars.GetOrCreate("LeadInArcLine2Feedrate", 127, $"[#148*{Config.LeadInArcLine2FeedratePercent}]");
             vars.GetOrCreate("CircleFeedrate", 128, Config.CircleFeedrateMultiplier.ToString("0.#"));
+            vars.GetOrCreate("LeadOutFeedrate", 129, $"[#148*{Config.LeadOutFeedratePercent}]");
+
+            if (Config.ArcFeedrate == ArcFeedrateMode.Variables)
+            {
+                foreach (var range in Config.ArcFeedrateRanges)
+                {
+                    var name = $"ArcFeedR{range.MaxRadius.ToString("0.###", System.Globalization.CultureInfo.InvariantCulture)}";
+                    vars.GetOrCreate(name, range.VariableNumber,
+                        $"[#148*{range.FeedratePercent.ToString("0.##", System.Globalization.CultureInfo.InvariantCulture)}]");
+                }
+            }
+
             return vars;
         }
     }

OpenNest.Posts.Cincinnati/CincinnatiPreambleWriter.cs

@@ -37,15 +37,21 @@ public sealed class CincinnatiPreambleWriter
 
         w.WriteLine(CoordinateFormatter.Comment("MAIN PROGRAM"));
 
-        w.WriteLine(_config.PostedUnits == Units.Millimeters ? "G21" : "G20");
+        w.WriteLine(_config.PostedUnits == Units.Millimeters ? "G21 G90" : "G20 G90");
+
+        if (_config.UseSmartRapids)
+            w.WriteLine("G121 (SMART RAPIDS)");
 
         w.WriteLine("M42");
 
         if (_config.ProcessParameterMode == G89Mode.LibraryFile && !string.IsNullOrEmpty(initialLibrary))
-            w.WriteLine($"G89 P {initialLibrary}");
+            w.WriteLine($"G89 P{initialLibrary}");
 
         w.WriteLine($"M98 P{_config.VariableDeclarationSubprogram} (Variable Declaration)");
 
+        if (_config.PalletExchange == PalletMode.StartAndEnd)
+            w.WriteLine("M50");
+
         w.WriteLine("GOTO1 (GOTO SHEET NUMBER)");
 
         for (var i = 1; i <= sheetCount; i++)

OpenNest.Posts.Cincinnati/CincinnatiSheetWriter.cs

@@ -37,7 +37,8 @@ public sealed class CincinnatiSheetWriter
     /// </param>
     public void Write(TextWriter w, Plate plate, string nestName, int sheetIndex, int subNumber,
         string cutLibrary, string etchLibrary,
-        Dictionary<(int, long), int> partSubprograms = null)
+        Dictionary<(int, long), int> partSubprograms = null,
+        bool isLastSheet = false)
     {
         if (plate.Parts.Count == 0)
             return;
@@ -64,12 +65,12 @@ public sealed class CincinnatiSheetWriter
         w.WriteLine("N10000");
         w.WriteLine("G92 X#5021 Y#5022");
         if (!string.IsNullOrEmpty(cutLibrary))
-            w.WriteLine($"G89 P {cutLibrary}");
+            w.WriteLine($"G89 P{cutLibrary}");
         w.WriteLine($"M98 P{varDeclSub} (Variable Declaration)");
         w.WriteLine("G90");
         w.WriteLine("M47");
         if (!string.IsNullOrEmpty(cutLibrary))
-            w.WriteLine($"G89 P {cutLibrary}");
+            w.WriteLine($"G89 P{cutLibrary}");
         w.WriteLine("GOTO1( Goto Feature )");
 
         // 3. Order parts: non-cutoff sorted by Bottom then Left, cutoffs last
@@ -94,7 +95,9 @@ public sealed class CincinnatiSheetWriter
         // 5. Footer
         w.WriteLine("M42");
         w.WriteLine("G0 X0 Y0");
-        if (_config.PalletExchange != PalletMode.None)
+        var emitM50 = _config.PalletExchange == PalletMode.EndOfSheet
+            || (_config.PalletExchange == PalletMode.StartAndEnd && isLastSheet);
+        if (emitM50)
             w.WriteLine($"N{sheetIndex + 1} M50");
         w.WriteLine($"M99 (END OF {nestName}.{sheetIndex:D3})");
     }

OpenNest.Posts.Cincinnati/FeatureUtils.cs

@@ -1,6 +1,7 @@
 using System.Collections.Generic;
 using OpenNest.CNC;
 using OpenNest.Geometry;
+using OpenNest.Math;
 
 namespace OpenNest.Posts.Cincinnati;
 
@@ -105,11 +106,48 @@ public static class FeatureUtils
             }
             else if (code is ArcMove arc)
             {
-                distance += currentPos.DistanceTo(arc.EndPoint);
+                distance += ComputeArcLength(currentPos, arc);
                 currentPos = arc.EndPoint;
             }
         }
 
         return distance;
     }
+
+    /// <summary>
+    /// Computes the arc length from the current position through an arc move.
+    /// Uses radius * sweep angle instead of chord length.
+    /// </summary>
+    public static double ComputeArcLength(Vector startPos, ArcMove arc)
+    {
+        var radius = startPos.DistanceTo(arc.CenterPoint);
+        if (radius < Tolerance.Epsilon)
+            return 0.0;
+
+        // Full circle: start ≈ end
+        if (Tolerance.IsEqualTo(startPos.X, arc.EndPoint.X)
+            && Tolerance.IsEqualTo(startPos.Y, arc.EndPoint.Y))
+            return 2.0 * System.Math.PI * radius;
+
+        var startAngle = System.Math.Atan2(
+            startPos.Y - arc.CenterPoint.Y,
+            startPos.X - arc.CenterPoint.X);
+        var endAngle = System.Math.Atan2(
+            arc.EndPoint.Y - arc.CenterPoint.Y,
+            arc.EndPoint.X - arc.CenterPoint.X);
+
+        double sweep;
+        if (arc.Rotation == RotationType.CW)
+        {
+            sweep = startAngle - endAngle;
+            if (sweep <= 0) sweep += 2.0 * System.Math.PI;
+        }
+        else
+        {
+            sweep = endAngle - startAngle;
+            if (sweep <= 0) sweep += 2.0 * System.Math.PI;
+        }
+
+        return radius * sweep;
+    }
 }

OpenNest.Tests/Cincinnati/CincinnatiFeatureWriterTests.cs

@@ -297,7 +297,7 @@ public class CincinnatiFeatureWriterTests
         ctx.SheetDiagonal = 30.0;
         var output = WriteFeature(config, ctx);
 
-        Assert.Contains("G89 P MILD10", output);
+        Assert.Contains("G89 PMILD10", output);
     }
 
     [Fact]
@@ -470,6 +470,123 @@ public class CincinnatiFeatureWriterTests
         Assert.True(m131Idx < m47Idx, "M131 should come before M47");
     }
 
+    [Fact]
+    public void LeadoutFeedrate_UsesVariable129()
+    {
+        var config = DefaultConfig();
+        config.KerfCompensation = KerfMode.PreApplied;
+        var codes = new List<ICode>
+        {
+            new RapidMove(1.0, 1.0),
+            new LinearMove(2.0, 1.0) { Layer = LayerType.Leadout }
+        };
+        var ctx = SimpleContext(codes);
+        var output = WriteFeature(config, ctx);
+
+        Assert.Contains("F#129", output);
+    }
+
+    [Fact]
+    public void ArcLeadin_UsesVariable127()
+    {
+        var config = DefaultConfig();
+        config.KerfCompensation = KerfMode.PreApplied;
+        var codes = new List<ICode>
+        {
+            new RapidMove(10.0, 20.0),
+            new ArcMove(new Vector(12.0, 20.0), new Vector(11.0, 20.0), RotationType.CCW) { Layer = LayerType.Leadin }
+        };
+        var ctx = SimpleContext(codes);
+        var output = WriteFeature(config, ctx);
+
+        Assert.Contains("F#127", output);
+    }
+
+    [Fact]
+    public void ArcFeedrate_VariablesMode_UsesRadiusRangeVariable()
+    {
+        var config = DefaultConfig();
+        config.KerfCompensation = KerfMode.PreApplied;
+        config.ArcFeedrate = ArcFeedrateMode.Variables;
+        // Arc with radius 0.5 (center at 10.5, 20; start at 10, 20) → R=0.5 → #124 (R ≤ 0.750)
+        var codes = new List<ICode>
+        {
+            new RapidMove(10.0, 20.0),
+            new ArcMove(new Vector(11.0, 20.0), new Vector(10.5, 20.0), RotationType.CW) { Layer = LayerType.Cut }
+        };
+        var ctx = SimpleContext(codes);
+        var output = WriteFeature(config, ctx);
+
+        Assert.Contains("F#124", output);
+    }
+
+    [Fact]
+    public void ArcFeedrate_PercentagesMode_UsesInlineExpression()
+    {
+        var config = DefaultConfig();
+        config.KerfCompensation = KerfMode.PreApplied;
+        config.ArcFeedrate = ArcFeedrateMode.Percentages;
+        // Arc with radius 0.1 (≤ 0.125) → 25%
+        var codes = new List<ICode>
+        {
+            new RapidMove(10.0, 20.0),
+            new ArcMove(new Vector(10.2, 20.0), new Vector(10.1, 20.0), RotationType.CW) { Layer = LayerType.Cut }
+        };
+        var ctx = SimpleContext(codes);
+        var output = WriteFeature(config, ctx);
+
+        Assert.Contains("F[#148*0.25]", output);
+    }
+
+    [Fact]
+    public void ArcFeedrate_LargeRadius_UsesProcessFeedrate()
+    {
+        var config = DefaultConfig();
+        config.KerfCompensation = KerfMode.PreApplied;
+        config.ArcFeedrate = ArcFeedrateMode.Variables;
+        // Arc with radius 10 (> 4.500) → falls through to #148
+        var codes = new List<ICode>
+        {
+            new RapidMove(0.0, 0.0),
+            new ArcMove(new Vector(20.0, 0.0), new Vector(10.0, 0.0), RotationType.CCW) { Layer = LayerType.Cut }
+        };
+        var ctx = SimpleContext(codes);
+        var output = WriteFeature(config, ctx);
+
+        Assert.Contains("F#148", output);
+    }
+
+    [Fact]
+    public void ArcFeedrate_NoneMode_UsesProcessFeedrateForNonCircle()
+    {
+        var config = DefaultConfig();
+        config.KerfCompensation = KerfMode.PreApplied;
+        config.ArcFeedrate = ArcFeedrateMode.None;
+        // Small radius arc but mode is None → process feedrate
+        var codes = new List<ICode>
+        {
+            new RapidMove(10.0, 20.0),
+            new ArcMove(new Vector(10.2, 20.0), new Vector(10.1, 20.0), RotationType.CW) { Layer = LayerType.Cut }
+        };
+        var ctx = SimpleContext(codes);
+        var output = WriteFeature(config, ctx);
+
+        Assert.Contains("F#148", output);
+    }
+
+    [Fact]
+    public void G89_PAdjacentToFilename()
+    {
+        var config = DefaultConfig();
+        var ctx = SimpleContext();
+        ctx.LibraryFile = "MS135N2.lib";
+        var output = WriteFeature(config, ctx);
+
+        // P must be directly adjacent to filename, no space
+        Assert.Contains("G89 PMS135N2.lib", output);
+        Assert.DoesNotContain("G89 P MS135N2.lib", output);
+    }
+
     private static int CountOccurrences(string text, string pattern)
     {
         var count = 0;

OpenNest.Tests/Cincinnati/CincinnatiPostProcessorTests.cs

@@ -43,6 +43,74 @@ public class CincinnatiPostProcessorTests
         Assert.Contains("M99", output);
     }
 
+    [Fact]
+    public void Post_EmitsLeadOutVariable()
+    {
+        var nest = CreateTestNest();
+        var config = new CincinnatiPostConfig { PostedAccuracy = 4 };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+        Assert.Contains("#129=", output);
+    }
+
+    [Fact]
+    public void Post_WithArcFeedrateVariables_EmitsRangeVariables()
+    {
+        var nest = CreateTestNest();
+        var config = new CincinnatiPostConfig
+        {
+            PostedAccuracy = 4,
+            ArcFeedrate = ArcFeedrateMode.Variables
+        };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+        Assert.Contains("#123=", output);
+        Assert.Contains("#124=", output);
+        Assert.Contains("#125=", output);
+    }
+
+    [Fact]
+    public void Post_WithArcFeedrateNone_OmitsRangeVariables()
+    {
+        var nest = CreateTestNest();
+        var config = new CincinnatiPostConfig
+        {
+            PostedAccuracy = 4,
+            ArcFeedrate = ArcFeedrateMode.None
+        };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+        Assert.DoesNotContain("#123=", output);
+        Assert.DoesNotContain("#124=", output);
+        Assert.DoesNotContain("#125=", output);
+    }
+
+    [Fact]
+    public void Post_EmitsG90InPreamble()
+    {
+        var nest = CreateTestNest();
+        var config = new CincinnatiPostConfig { PostedAccuracy = 4 };
+        var post = new CincinnatiPostProcessor(config);
+
+        using var ms = new MemoryStream();
+        post.Post(nest, ms);
+
+        var output = Encoding.UTF8.GetString(ms.ToArray());
+        Assert.Contains("G20 G90", output);
+    }
+
     [Fact]
     public void Post_ImplementsIPostProcessor()
     {

OpenNest.Tests/Cincinnati/CincinnatiPreambleWriterTests.cs

@@ -24,9 +24,9 @@ public class CincinnatiPreambleWriterTests
         var output = sb.ToString();
         Assert.Contains("( NEST TestNest )", output);
         Assert.Contains("( CONFIGURATION - CL940 )", output);
-        Assert.Contains("G20", output);
+        Assert.Contains("G20 G90", output);
         Assert.Contains("M42", output);
-        Assert.Contains("G89 P MS135N2PANEL.lib", output);
+        Assert.Contains("G89 PMS135N2PANEL.lib", output);
         Assert.Contains("M98 P100 (Variable Declaration)", output);
         Assert.Contains("GOTO1 (GOTO SHEET NUMBER)", output);
         Assert.Contains("N1 M98 P101 (SHEET 1)", output);
@@ -44,7 +44,72 @@ public class CincinnatiPreambleWriterTests
 
         writer.WriteMainProgram(sw, "Test", "", 1, "");
 
-        Assert.Contains("G21", sb.ToString());
+        Assert.Contains("G21 G90", sb.ToString());
+    }
+
+    [Fact]
+    public void WriteMainProgram_EmitsG90WithUnits()
+    {
+        var config = new CincinnatiPostConfig { PostedUnits = Units.Inches };
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var writer = new CincinnatiPreambleWriter(config);
+
+        writer.WriteMainProgram(sw, "Test", "", 1, "");
+
+        Assert.Contains("G20 G90", sb.ToString());
+    }
+
+    [Fact]
+    public void WriteMainProgram_EmitsG121_WhenSmartRapidsEnabled()
+    {
+        var config = new CincinnatiPostConfig { UseSmartRapids = true };
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var writer = new CincinnatiPreambleWriter(config);
+
+        writer.WriteMainProgram(sw, "Test", "", 1, "");
+
+        Assert.Contains("G121 (SMART RAPIDS)", sb.ToString());
+    }
+
+    [Fact]
+    public void WriteMainProgram_OmitsG121_WhenSmartRapidsDisabled()
+    {
+        var config = new CincinnatiPostConfig { UseSmartRapids = false };
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var writer = new CincinnatiPreambleWriter(config);
+
+        writer.WriteMainProgram(sw, "Test", "", 1, "");
+
+        Assert.DoesNotContain("G121", sb.ToString());
+    }
+
+    [Fact]
+    public void WriteMainProgram_EmitsM50_WhenStartAndEnd()
+    {
+        var config = new CincinnatiPostConfig { PalletExchange = PalletMode.StartAndEnd };
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var writer = new CincinnatiPreambleWriter(config);
+
+        writer.WriteMainProgram(sw, "Test", "", 1, "");
+
+        Assert.Contains("M50", sb.ToString());
+    }
+
+    [Fact]
+    public void WriteMainProgram_OmitsM50_WhenEndOfSheet()
+    {
+        var config = new CincinnatiPostConfig { PalletExchange = PalletMode.EndOfSheet };
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var writer = new CincinnatiPreambleWriter(config);
+
+        writer.WriteMainProgram(sw, "Test", "", 1, "");
+
+        Assert.DoesNotContain("M50", sb.ToString());
     }
 
     [Fact]

OpenNest.Tests/Cincinnati/CincinnatiSheetWriterTests.cs

@@ -32,7 +32,7 @@ public class CincinnatiSheetWriterTests
         Assert.Contains("#110=", output);
         Assert.Contains("#111=", output);
         Assert.Contains("G92 X#5021 Y#5022", output);
-        Assert.Contains("G89 P MS135N2PANEL.lib", output);
+        Assert.Contains("G89 PMS135N2PANEL.lib", output);
         Assert.Contains("M99", output);
     }
 
@@ -137,9 +137,110 @@ public class CincinnatiSheetWriterTests
         Assert.True(g85Idx < g84Idx, "G85 (etch) should come before G84 (cut)");
 
         // Etch uses etch library
-        Assert.Contains("G89 P EtchN2.lib", output);
+        Assert.Contains("G89 PEtchN2.lib", output);
         // Cut uses cut library
-        Assert.Contains("G89 P MS250O2.lib", output);
+        Assert.Contains("G89 PMS250O2.lib", output);
+    }
+
+    [Fact]
+    public void WriteSheet_StartAndEnd_NoM50OnNonLastSheet()
+    {
+        var config = new CincinnatiPostConfig
+        {
+            PalletExchange = PalletMode.StartAndEnd,
+            PostedAccuracy = 4
+        };
+        var plate = new Plate(48.0, 96.0);
+        plate.Parts.Add(new Part(new Drawing("TestPart", CreateSimpleProgram())));
+
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
+
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "", isLastSheet: false);
+
+        var output = sb.ToString();
+        Assert.DoesNotContain("M50", output);
+    }
+
+    [Fact]
+    public void WriteSheet_StartAndEnd_M50OnLastSheet()
+    {
+        var config = new CincinnatiPostConfig
+        {
+            PalletExchange = PalletMode.StartAndEnd,
+            PostedAccuracy = 4
+        };
+        var plate = new Plate(48.0, 96.0);
+        plate.Parts.Add(new Part(new Drawing("TestPart", CreateSimpleProgram())));
+
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
+
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "", isLastSheet: true);
+
+        var output = sb.ToString();
+        Assert.Contains("M50", output);
+    }
+
+    [Fact]
+    public void WriteSheet_EndOfSheet_AlwaysEmitsM50()
+    {
+        var config = new CincinnatiPostConfig
+        {
+            PalletExchange = PalletMode.EndOfSheet,
+            PostedAccuracy = 4
+        };
+        var plate = new Plate(48.0, 96.0);
+        plate.Parts.Add(new Part(new Drawing("TestPart", CreateSimpleProgram())));
+
+        var sb = new StringBuilder();
+        using var sw = new StringWriter(sb);
+        var sheetWriter = new CincinnatiSheetWriter(config, new ProgramVariableManager());
+
+        sheetWriter.Write(sw, plate, "TestNest", 1, 101, "", "", isLastSheet: false);
+
+        var output = sb.ToString();
+        Assert.Contains("M50", output);
+    }
+
+    [Fact]
+    public void ComputeArcLength_FullCircle_Returns2PiR()
+    {
+        var start = new Vector(10.0, 20.0);
+        var arc = new ArcMove(new Vector(10.0, 20.0), new Vector(15.0, 20.0), RotationType.CW);
+        var length = FeatureUtils.ComputeArcLength(start, arc);
+
+        // Radius = 5, full circle = 2 * PI * 5 ≈ 31.416
+        Assert.Equal(2.0 * System.Math.PI * 5.0, length, 4);
+    }
+
+    [Fact]
+    public void ComputeArcLength_Semicircle_ReturnsPiR()
+    {
+        // Semicircle from (0,0) to (10,0) with center at (5,0), CCW → goes through (5,5)
+        var start = new Vector(0.0, 0.0);
+        var arc = new ArcMove(new Vector(10.0, 0.0), new Vector(5.0, 0.0), RotationType.CCW);
+        var length = FeatureUtils.ComputeArcLength(start, arc);
+
+        // Radius = 5, semicircle = PI * 5 ≈ 15.708
+        Assert.Equal(System.Math.PI * 5.0, length, 4);
+    }
+
+    [Fact]
+    public void ComputeCutDistance_WithArcs_UsesArcLengthNotChord()
+    {
+        // Full circle: chord = 0 but arc length = 2πr
+        var codes = new List<ICode>
+        {
+            new RapidMove(10.0, 20.0),
+            new ArcMove(new Vector(10.0, 20.0), new Vector(15.0, 20.0), RotationType.CW) { Layer = LayerType.Cut }
+        };
+        var distance = FeatureUtils.ComputeCutDistance(codes);
+
+        // Full circle with R=5 → 2πr ≈ 31.416
+        Assert.True(distance > 30.0, $"Expected arc length > 30 but got {distance}");
     }
 
     [Fact]

OpenNest.Tests/GeometrySimplifierTests.cs

@@ -1,4 +1,7 @@
 using OpenNest.Geometry;
+using OpenNest.IO;
+using System.IO;
+using System.Linq;
 using Xunit;
 
 namespace OpenNest.Tests;
@@ -127,4 +130,52 @@ public class GeometrySimplifierTests
         // Index 6 is the fitted arc replacing the second run
         Assert.IsType<Arc>(result.Entities[6]);
     }
+
+    [Fact]
+    public void Apply_DynaPanDxf_NoGapsAfterSimplification()
+    {
+        var path = @"C:\Users\aisaacs\Desktop\Sullys Q29 DXFs\SULLYS-031 Dyna Pan.dxf";
+        if (!File.Exists(path))
+            return; // skip if file not available
+
+        var importer = new DxfImporter();
+        var result = importer.Import(path);
+        var shapes = ShapeBuilder.GetShapes(result.Entities);
+
+        var simplifier = new GeometrySimplifier { Tolerance = 0.004 };
+
+        foreach (var shape in shapes)
+        {
+            var candidates = simplifier.Analyze(shape);
+            if (candidates.Count == 0) continue;
+
+            var simplified = simplifier.Apply(shape, candidates);
+
+            // Check for gaps between consecutive entities
+            for (var i = 0; i < simplified.Entities.Count - 1; i++)
+            {
+                var current = simplified.Entities[i];
+                var next = simplified.Entities[i + 1];
+
+                var currentEnd = current switch
+                {
+                    Line l => l.EndPoint,
+                    Arc a => a.EndPoint(),
+                    _ => Vector.Invalid
+                };
+                var nextStart = next switch
+                {
+                    Line l => l.StartPoint,
+                    Arc a => a.StartPoint(),
+                    _ => Vector.Invalid
+                };
+
+                if (!currentEnd.IsValid() || !nextStart.IsValid()) continue;
+
+                var gap = currentEnd.DistanceTo(nextStart);
+                Assert.True(gap < 0.005,
+                    $"Gap of {gap:F4} between entities {i} ({current.GetType().Name}) and {i + 1} ({next.GetType().Name})");
+            }
+        }
+    }
 }

OpenNest/Forms/CadConverterForm.cs

@@ -494,13 +494,30 @@ namespace OpenNest.Forms
 
             using var dlg = new SaveFileDialog
             {
-                Filter = "DXF Files|*.dxf",
+                Filter = "DXF 2018 (*.dxf)|*.dxf|" +
+                         "DXF 2013 (*.dxf)|*.dxf|" +
+                         "DXF 2010 (*.dxf)|*.dxf|" +
+                         "DXF 2007 (*.dxf)|*.dxf|" +
+                         "DXF 2004 (*.dxf)|*.dxf|" +
+                         "DXF 2000 (*.dxf)|*.dxf|" +
+                         "DXF R14 (*.dxf)|*.dxf",
                 FileName = Path.ChangeExtension(item.Name, ".dxf"),
             };
 
             if (dlg.ShowDialog() != DialogResult.OK) return;
 
-            var doc = new ACadSharp.CadDocument();
+            var version = dlg.FilterIndex switch
+            {
+                2 => ACadSharp.ACadVersion.AC1027,
+                3 => ACadSharp.ACadVersion.AC1024,
+                4 => ACadSharp.ACadVersion.AC1021,
+                5 => ACadSharp.ACadVersion.AC1018,
+                6 => ACadSharp.ACadVersion.AC1015,
+                7 => ACadSharp.ACadVersion.AC1014,
+                _ => ACadSharp.ACadVersion.AC1032,
+            };
+
+            var doc = new ACadSharp.CadDocument(version);
             foreach (var entity in item.Entities)
             {
                 switch (entity)