From a201385008de76c5e52ec40fc63e6b292863e71c Mon Sep 17 00:00:00 2001
From: Kevin O'Connor <kevin@koconnor.net>
Date: Fri, 4 Nov 2016 19:28:07 -0400
Subject: [PATCH] extruder: Consistently use extrude distance in calculations

Avoid mixing the travel distance of the head (and its associated
velocity and acceleration) with the distance the filament moves.
Instead, use the filament travel distance.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
---
 klippy/extruder.py | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/klippy/extruder.py b/klippy/extruder.py
index 198a89ed..ad439421 100644
--- a/klippy/extruder.py
+++ b/klippy/extruder.py
@@ -28,20 +28,23 @@ class PrinterExtruder:
             # Extrude only move - limit accel and velocity
             move.limit_speed(self.stepper.max_velocity, self.stepper.max_accel)
     def move(self, move_time, move):
-        move_d = move.move_d
-        inv_accel = 1. / move.accel
+        axis_d = move.axes_d[3]
+        extrude_r = axis_d / move.move_d
+        inv_accel = 1. / (move.accel * extrude_r)
 
-        start_v, cruise_v, end_v = move.start_v, move.cruise_v, move.end_v
+        start_v = move.start_v * extrude_r
+        cruise_v = move.cruise_v * extrude_r
+        end_v = move.end_v * extrude_r
         accel_t, cruise_t, decel_t = move.accel_t, move.cruise_t, move.decel_t
-        accel_d = move.accel_r * move_d
-        cruise_d = move.cruise_r * move_d
-        decel_d = move.decel_r * move_d
+        accel_d = move.accel_r * axis_d
+        cruise_d = move.cruise_r * axis_d
+        decel_d = move.decel_r * axis_d
 
         retract_t = retract_d = retract_v = 0.
         decel_v = cruise_v
 
         # Update for pressure advance
-        if (move.axes_d[3] >= 0. and (move.axes_d[0] or move.axes_d[1])
+        if (axis_d >= 0. and (move.axes_d[0] or move.axes_d[1])
             and self.pressure_advance):
             # Increase accel_d and start_v when accelerating
             extra_accel_d = (cruise_v - start_v) * self.pressure_advance
@@ -71,14 +74,13 @@ class PrinterExtruder:
                     decel_d -= extra_decel_d
 
         # Determine regular steps
-        extrude_r = move.axes_d[3] / move_d
         forward_d = accel_d + cruise_d + decel_d
         start_pos = self.extrude_pos
-        end_pos = start_pos + forward_d * extrude_r
+        end_pos = start_pos + forward_d
         inv_step_dist = self.stepper.inv_step_dist
         new_step_pos = int(end_pos*inv_step_dist + 0.5)
         if new_step_pos != self.stepper_pos:
-            steps = forward_d * extrude_r * inv_step_dist
+            steps = forward_d * inv_step_dist
             step_offset = self.stepper_pos - start_pos * inv_step_dist + 0.5
             self.stepper_pos = new_step_pos
             sdir = 0
@@ -119,10 +121,10 @@ class PrinterExtruder:
 
         # Determine retract steps
         start_pos = end_pos
-        end_pos -= retract_d * extrude_r
+        end_pos -= retract_d
         new_step_pos = int(end_pos*inv_step_dist + 0.5)
         if new_step_pos != self.stepper_pos:
-            steps = retract_d * extrude_r * inv_step_dist
+            steps = retract_d * inv_step_dist
             step_offset = start_pos * inv_step_dist - self.stepper_pos + 0.5
             self.stepper_pos = new_step_pos
             mcu_time, so = self.stepper.prep_move(