diff --git a/klippy/chelper/__init__.py b/klippy/chelper/__init__.py
index 7366cc81..51f59e59 100644
--- a/klippy/chelper/__init__.py
+++ b/klippy/chelper/__init__.py
@@ -16,7 +16,7 @@ COMPILE_CMD = ("gcc -Wall -g -O2 -shared -fPIC"
                " -o %s %s")
 SOURCE_FILES = [
     'pyhelper.c', 'serialqueue.c', 'stepcompress.c', 'itersolve.c',
-    'kin_cartesian.c', 'kin_corexy.c', 'kin_delta.c',
+    'kin_cartesian.c', 'kin_corexy.c', 'kin_delta.c', 'kin_extruder.c'
 ]
 DEST_LIB = "c_helper.so"
 OTHER_FILES = [
@@ -71,6 +71,14 @@ defs_kin_delta = """
         , double tower_x, double tower_y);
 """
 
+defs_kin_extruder = """
+    struct stepper_kinematics *extruder_stepper_alloc(void);
+    void extruder_move_fill(struct move *m, double print_time
+        , double accel_t, double cruise_t, double decel_t, double start_pos
+        , double start_v, double cruise_v, double accel
+        , double extra_accel_v, double extra_decel_v);
+"""
+
 defs_serialqueue = """
     #define MESSAGE_MAX 64
     struct pull_queue_message {
@@ -109,7 +117,7 @@ defs_std = """
 
 defs_all = [
     defs_pyhelper, defs_serialqueue, defs_std, defs_stepcompress, defs_itersolve,
-    defs_kin_cartesian, defs_kin_corexy, defs_kin_delta
+    defs_kin_cartesian, defs_kin_corexy, defs_kin_delta, defs_kin_extruder
 ]
 
 # Return the list of file modification times
diff --git a/klippy/chelper/itersolve.c b/klippy/chelper/itersolve.c
index e79d5f5f..72e6ad89 100644
--- a/klippy/chelper/itersolve.c
+++ b/klippy/chelper/itersolve.c
@@ -17,19 +17,6 @@
  * Kinematic moves
  ****************************************************************/
 
-struct move_accel {
-    double c1, c2;
-};
-
-struct move {
-    double print_time, move_t;
-    double accel_t, cruise_t;
-    double cruise_start_d, decel_start_d;
-    double cruise_v;
-    struct move_accel accel, decel;
-    struct coord start_pos, axes_r;
-};
-
 struct move * __visible
 move_alloc(void)
 {
@@ -80,7 +67,7 @@ move_eval_accel(struct move_accel *ma, double move_time)
 }
 
 // Return the distance moved given a time in a move
-static double
+inline double
 move_get_distance(struct move *m, double move_time)
 {
     if (unlikely(move_time < m->accel_t))
diff --git a/klippy/chelper/itersolve.h b/klippy/chelper/itersolve.h
index bd8fba0e..23b3201d 100644
--- a/klippy/chelper/itersolve.h
+++ b/klippy/chelper/itersolve.h
@@ -7,12 +7,26 @@ struct coord {
     double x, y, z;
 };
 
+struct move_accel {
+    double c1, c2;
+};
+
+struct move {
+    double print_time, move_t;
+    double accel_t, cruise_t;
+    double cruise_start_d, decel_start_d;
+    double cruise_v;
+    struct move_accel accel, decel;
+    struct coord start_pos, axes_r;
+};
+
 struct move *move_alloc(void);
 void move_fill(struct move *m, double print_time
                , double accel_t, double cruise_t, double decel_t
                , double start_pos_x, double start_pos_y, double start_pos_z
                , double axes_d_x, double axes_d_y, double axes_d_z
                , double start_v, double cruise_v, double accel);
+double move_get_distance(struct move *m, double move_time);
 struct coord move_get_coord(struct move *m, double move_time);
 
 struct stepper_kinematics;
diff --git a/klippy/chelper/kin_extruder.c b/klippy/chelper/kin_extruder.c
new file mode 100644
index 00000000..6b34980f
--- /dev/null
+++ b/klippy/chelper/kin_extruder.c
@@ -0,0 +1,54 @@
+// Extruder stepper pulse time generation
+//
+// Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <stdlib.h> // malloc
+#include <string.h> // memset
+#include "compiler.h" // __visible
+#include "itersolve.h" // struct stepper_kinematics
+#include "pyhelper.h" // errorf
+
+static double
+extruder_calc_position(struct stepper_kinematics *sk, struct move *m
+                       , double move_time)
+{
+    return m->start_pos.x + move_get_distance(m, move_time);
+}
+
+struct stepper_kinematics * __visible
+extruder_stepper_alloc(void)
+{
+    struct stepper_kinematics *sk = malloc(sizeof(*sk));
+    memset(sk, 0, sizeof(*sk));
+    sk->calc_position = extruder_calc_position;
+    return sk;
+}
+
+// Populate a 'struct move' with an extruder velocity trapezoid
+void __visible
+extruder_move_fill(struct move *m, double print_time
+                   , double accel_t, double cruise_t, double decel_t
+                   , double start_pos
+                   , double start_v, double cruise_v, double accel
+                   , double extra_accel_v, double extra_decel_v)
+{
+    // Setup velocity trapezoid
+    m->print_time = print_time;
+    m->move_t = accel_t + cruise_t + decel_t;
+    m->accel_t = accel_t;
+    m->cruise_t = cruise_t;
+    m->cruise_start_d = accel_t * (.5 * (cruise_v + start_v) + extra_accel_v);
+    m->decel_start_d = m->cruise_start_d + cruise_t * cruise_v;
+
+    // Setup for accel/cruise/decel phases
+    m->cruise_v = cruise_v;
+    m->accel.c1 = start_v + extra_accel_v;
+    m->accel.c2 = .5 * accel;
+    m->decel.c1 = cruise_v + extra_decel_v;
+    m->decel.c2 = -m->accel.c2;
+
+    // Setup start distance
+    m->start_pos.x = start_pos;
+}
diff --git a/klippy/extruder.py b/klippy/extruder.py
index 35a1140c..c6c351e7 100644
--- a/klippy/extruder.py
+++ b/klippy/extruder.py
@@ -4,7 +4,7 @@
 #
 # This file may be distributed under the terms of the GNU GPLv3 license.
 import math, logging
-import stepper, homing
+import stepper, homing, chelper
 
 EXTRUDE_DIFF_IGNORE = 1.02
 
@@ -47,6 +47,13 @@ class PrinterExtruder:
             'pressure_advance_lookahead_time', 0.010, minval=0.)
         self.need_motor_enable = True
         self.extrude_pos = 0.
+        # Setup iterative solver
+        ffi_main, ffi_lib = chelper.get_ffi()
+        self.cmove = ffi_main.gc(ffi_lib.move_alloc(), ffi_lib.free)
+        self.extruder_move_fill = ffi_lib.extruder_move_fill
+        sk = ffi_main.gc(ffi_lib.extruder_stepper_alloc(), ffi_lib.free)
+        self.stepper.setup_itersolve(sk)
+        # Setup SET_PRESSURE_ADVANCE command
         gcode = self.printer.lookup_object('gcode')
         if self.name in ('extruder', 'extruder0'):
             gcode.register_mux_command("SET_PRESSURE_ADVANCE", "EXTRUDER", None,
@@ -154,82 +161,42 @@ class PrinterExtruder:
             self.stepper.motor_enable(print_time, 1)
             self.need_motor_enable = False
         axis_d = move.axes_d[3]
-        axis_r = abs(axis_d) / move.move_d
+        axis_r = axis_d / move.move_d
         accel = move.accel * axis_r
         start_v = move.start_v * axis_r
         cruise_v = move.cruise_v * axis_r
-        end_v = move.end_v * axis_r
         accel_t, cruise_t, decel_t = move.accel_t, move.cruise_t, move.decel_t
-        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
+        extra_accel_v = extra_decel_v = 0.
         start_pos = self.extrude_pos
         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
+            # Calculate extra_accel_v
             pressure_advance = self.pressure_advance * move.extrude_r
             prev_pressure_d = start_pos - move.start_pos[3]
-            if accel_d:
+            if accel_t:
                 npd = move.cruise_v * pressure_advance
                 extra_accel_d = npd - prev_pressure_d
                 if extra_accel_d > 0.:
-                    accel_d += extra_accel_d
-                    start_v += extra_accel_d / accel_t
+                    extra_accel_v = extra_accel_d / accel_t
+                    axis_d += extra_accel_d
                     prev_pressure_d += extra_accel_d
-            # Update decel and retract parameters when decelerating
+            # Calculate extra_decel_v
             emcv = move.extrude_max_corner_v
-            if decel_d and emcv < move.cruise_v:
+            if decel_t and emcv < move.cruise_v:
                 npd = max(emcv, move.end_v) * pressure_advance
-                extra_decel_d = prev_pressure_d - npd
-                if extra_decel_d > 0.:
+                extra_decel_d = npd - prev_pressure_d
+                if extra_decel_d < 0.:
+                    axis_d += extra_decel_d
                     extra_decel_v = extra_decel_d / decel_t
-                    decel_v -= extra_decel_v
-                    end_v -= extra_decel_v
-                    if decel_v <= 0.:
-                        # The entire decel phase is replaced with retraction
-                        retract_t = decel_t
-                        retract_d = -(end_v + decel_v) * 0.5 * decel_t
-                        retract_v = -decel_v
-                        decel_t = decel_d = 0.
-                    elif end_v < 0.:
-                        # Split decel phase into decel and retraction
-                        retract_t = -end_v / accel
-                        retract_d = -end_v * 0.5 * retract_t
-                        decel_t -= retract_t
-                        decel_d = decel_v * 0.5 * decel_t
-                    else:
-                        # There is still only a decel phase (no retraction)
-                        decel_d -= extra_decel_d
 
-        # Prepare for steps
-        step_const = self.stepper.step_const
-        move_time = print_time
-
-        # Acceleration steps
-        if accel_d:
-            step_const(move_time, start_pos, accel_d, start_v, accel)
-            start_pos += accel_d
-            move_time += accel_t
-        # Cruising steps
-        if cruise_d:
-            step_const(move_time, start_pos, cruise_d, cruise_v, 0.)
-            start_pos += cruise_d
-            move_time += cruise_t
-        # Deceleration steps
-        if decel_d:
-            step_const(move_time, start_pos, decel_d, decel_v, -accel)
-            start_pos += decel_d
-            move_time += decel_t
-        # Retraction steps
-        if retract_d:
-            step_const(move_time, start_pos, -retract_d, retract_v, accel)
-            start_pos -= retract_d
-        self.extrude_pos = start_pos
+        # Generate steps
+        self.extruder_move_fill(
+            self.cmove, print_time, accel_t, cruise_t, decel_t, start_pos,
+            start_v, cruise_v, accel, extra_accel_v, extra_decel_v)
+        self.stepper.step_itersolve(self.cmove)
+        self.extrude_pos = start_pos + axis_d
     cmd_SET_PRESSURE_ADVANCE_help = "Set pressure advance parameters"
     def cmd_default_SET_PRESSURE_ADVANCE(self, params):
         extruder = self.printer.lookup_object('toolhead').get_extruder()