extruder: Add support for instantaneous corner velocity

Add mechanism to perform look-ahead between moves with different
extrusion ratios.

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

2 files changed, 16 insertions, 22 deletions

diff --git a/config/example.cfg b/config/example.cfg
index ec648d77..fa293abc 100644
--- a/config/example.cfg
+++ b/config/example.cfg
@@ -111,6 +111,9 @@ filament_diameter: 3.500
 #   If a move requests an extrusion rate that would exceed this value
 #   it will cause an error to be returned. The default is: 4.0 *
 #   nozzle_diameter^2
+#instantaneous_corner_velocity: 1.000
+#   The maximum instantaneous velocity change (in mm/s) of the
+#   extruder during the junction of two moves. The default is 1mm/s.
 #max_extrude_only_distance: 50.0
 #   Maximum length (in mm of raw filament) that a retraction or
 #   extrude-only move may have. If a retraction or extrude-only move
diff --git a/klippy/kinematics/extruder.py b/klippy/kinematics/extruder.py
index faf90206..a5bef0db 100644
--- a/klippy/kinematics/extruder.py
+++ b/klippy/kinematics/extruder.py
@@ -6,8 +6,6 @@
 import math, logging
 import stepper, homing, chelper
 
-EXTRUDE_DIFF_IGNORE = 1.02
-
 class PrinterExtruder:
     def __init__(self, config, extruder_num):
         self.printer = config.get_printer()
@@ -41,6 +39,8 @@ class PrinterExtruder:
         self.stepper.set_max_jerk(9999999.9, 9999999.9)
         self.max_e_dist = config.getfloat(
             'max_extrude_only_distance', 50., minval=0.)
+        self.instant_corner_v = config.getfloat(
+            'instantaneous_corner_velocity', 1., minval=0.)
         gcode_macro = self.printer.try_load_module(config, 'gcode_macro')
         self.activate_gcode = gcode_macro.load_template(
             config, 'activate_gcode', '')
@@ -104,45 +104,36 @@ class PrinterExtruder:
     def stats(self, eventtime):
         return self.heater.stats(eventtime)
     def check_move(self, move):
-        move.extrude_r = move.axes_r[3]
+        axis_r = move.axes_r[3]
         if not self.heater.can_extrude:
             raise homing.EndstopError(
                 "Extrude below minimum temp\n"
                 "See the 'min_extrude_temp' config option for details")
-        if (not move.axes_d[0] and not move.axes_d[1]) or move.extrude_r < 0.:
+        if (not move.axes_d[0] and not move.axes_d[1]) or axis_r < 0.:
             # Extrude only move (or retraction move) - limit accel and velocity
             if abs(move.axes_d[3]) > self.max_e_dist:
                 raise homing.EndstopError(
                     "Extrude only move too long (%.3fmm vs %.3fmm)\n"
                     "See the 'max_extrude_only_distance' config"
                     " option for details" % (move.axes_d[3], self.max_e_dist))
-            inv_extrude_r = 1. / abs(move.extrude_r)
-            move.limit_speed(self.max_e_velocity * inv_extrude_r
-                             , self.max_e_accel * inv_extrude_r)
-        elif move.extrude_r > self.max_extrude_ratio:
+            inv_extrude_r = 1. / abs(axis_r)
+            move.limit_speed(self.max_e_velocity * inv_extrude_r,
+                             self.max_e_accel * inv_extrude_r)
+        elif axis_r > self.max_extrude_ratio:
             if move.axes_d[3] <= self.nozzle_diameter * self.max_extrude_ratio:
                 # Permit extrusion if amount extruded is tiny
                 return
-            area = move.axes_r[3] * self.filament_area
+            area = axis_r * self.filament_area
             logging.debug("Overextrude: %s vs %s (area=%.3f dist=%.3f)",
-                          move.extrude_r, self.max_extrude_ratio,
-                          area, move.move_d)
+                          axis_r, self.max_extrude_ratio, area, move.move_d)
             raise homing.EndstopError(
                 "Move exceeds maximum extrusion (%.3fmm^2 vs %.3fmm^2)\n"
                 "See the 'max_extrude_cross_section' config option for details"
                 % (area, self.max_extrude_ratio * self.filament_area))
     def calc_junction(self, prev_move, move):
-        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.
+        diff_r = move.axes_r[3] - prev_move.axes_r[3]
+        if diff_r:
+            return (self.instant_corner_v / abs(diff_r))**2
         return move.max_cruise_v2
     def lookahead(self, moves, flush_count, lazy):
         return flush_count