extruder: Make sure EXTRUDE_DIFF_IGNORE doesn't trigger due to rounding

The code disables lookahead between two extruding moves with
significantly different extrude ratios.  Unfortunately, it was
possible for very tiny moves to show different extrude ratios just due
to how the slicer implements rounding when it produces the gcode.
Allow lookahead to be enabled between moves with extrude ratios that
are different if they don't noticeably produce more or less extrusion.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 9 insertions, 4 deletions

diff --git a/klippy/extruder.py b/klippy/extruder.py
index 98667b98..b62244e8 100644
--- a/klippy/extruder.py
+++ b/klippy/extruder.py
@@ -56,10 +56,15 @@ class PrinterExtruder:
             raise homing.EndstopMoveError(
                 move.end_pos, "Move exceeds maximum extrusion cross section")
     def calc_junction(self, prev_move, move):
-        if move.axes_d[3] or prev_move.axes_d[3]:
-            if (not move.axes_d[3] or not prev_move.axes_d[3]
-                or move.extrude_r > prev_move.extrude_r * EXTRUDE_DIFF_IGNORE
-                or prev_move.extrude_r > move.extrude_r * EXTRUDE_DIFF_IGNORE):
+        extrude = move.axes_d[3]
+        prev_extrude = prev_move.axes_d[3]
+        if extrude or prev_extrude:
+            if not extrude or not prev_extrude:
+                # Extrude move to non-extrude move - disable lookahead
+                return 0.
+            if ((move.extrude_r > prev_move.extrude_r * EXTRUDE_DIFF_IGNORE
+                 or prev_move.extrude_r > move.extrude_r * EXTRUDE_DIFF_IGNORE)
+                and abs(move.move_d * prev_move.extrude_r - extrude) >= .001):
                 # Extrude ratio between moves is too different
                 return 0.
             move.extrude_r = prev_move.extrude_r