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extruder: Don't assume start_v matches last end_v in pressure advance 

Due to minor differences in the extrude ratio, the last end velocity
of the filament may not exactly match the next move's start velocity
of the filament.  Implement more precise calculations for pressure
advance to take this into account.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2016-11-04 21:11:14 -04:00
parent a201385008
commit 93dd310add
1 changed files with 30 additions and 23 deletions
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15
klippy/extruder.py
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@ -44,16 +44,24 @@ class PrinterExtruder:
decel_v = cruise_v
# Update for pressure advance
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
extra_accel_d = (cruise_v - start_v) * self.pressure_advance
accel_d += extra_accel_d
move_extrude_r = move.extrude_r
prev_pressure_d = start_pos - move.start_pos[3]
if accel_t:
npd = move.cruise_v * move_extrude_r * self.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
prev_pressure_d += extra_accel_d
# Update decel and retract parameters when decelerating
if decel_t:
extra_decel_d = (cruise_v - end_v) * self.pressure_advance
npd = move.end_v * move_extrude_r * self.pressure_advance
extra_decel_d = prev_pressure_d - npd
if extra_decel_d > 0.:
extra_decel_v = extra_decel_d / decel_t
decel_v -= extra_decel_v
end_v -= extra_decel_v
@ -75,7 +83,6 @@ class PrinterExtruder:
# Determine regular steps
forward_d = accel_d + cruise_d + decel_d
start_pos = self.extrude_pos
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)