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docs: Update Pressure_Advance.md - don't set square_corner_velocity=0 

Setting the square corner velocity to zero would cause stuttering
during the test if a bed mesh is in effect.  It's possible to get the
desired effect by reducing the square corner velocity and setting the
pressure advance lookahead time instead.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
This commit is contained in:
Kevin O'Connor 2018-10-25 11:34:34 -04:00
parent 363bcfb233
commit ca7dd8bfd4
1 changed files with 19 additions and 7 deletions
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26
docs/Pressure_Advance.md
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@ -22,10 +22,11 @@ Use a slicer to generate g-code for the large hollow square found in
100mm/s) and a coarse layer height (the layer height should be around
75% of the nozzle diameter). It is fine to use a low infill (eg, 10%).
Use a low cornering speed during the test by issuing the following
G-Code command: `SET_VELOCITY_LIMIT SQUARE_CORNER_VELOCITY=0
ACCEL=500`. This will make the nozzle travel slower through corners
and thus emphasize the effects of extruder pressure.
Prepare for the test by issuing the following G-Code commands:
`SET_VELOCITY_LIMIT SQUARE_CORNER_VELOCITY=1 ACCEL=500` and
`SET_PRESSURE_ADVANCE ADVANCE_LOOKAHEAD_TIME=0`. These commands make
the nozzle travel slower through corners and they emphasize the
effects of extruder pressure.
For the first print use a pressure advance of zero by running
`SET_PRESSURE_ADVANCE ADVANCE=0.000`. Then print at least 10 layers of
@ -71,8 +72,8 @@ configuration also reduces ooze throughout the print.
At the completion of this test, update the extruder's pressure_advance
setting in the configuration file and issue a RESTART command. The
RESTART command will also return the acceleration and cornering speeds
to their normal values.
RESTART command will also return the acceleration, cornering speeds,
and look-ahead times to their normal values.
Important Notes
===============
@ -93,7 +94,7 @@ Important Notes
* It is not unusual for one corner of the test print to be
consistently different than the other three corners. This typically
occurs when the slicer arranges to always change Z height at that
corner. If this occurs, then ignore that corner and tune pressure
corner. If this occurs, then ignore that corner and tune pressure
advance using the other three corners.
* If a high pressure advance value (eg, over 0.200) is used then one
@ -105,6 +106,17 @@ Important Notes
enough torque to push the required filament. If this occurs, either
use a lower acceleration value or disable pressure advance.
* The pressure_advance_lookahead_time parameter controls how far in
advance to check if a head slow-down is immediately followed by a
speed-up - it reduces pointless pressure changes in the head. It is
recommended to follow the steps above so that it is set to zero
during tuning and to use the default (0.010) during normal prints.
It is possible to tune this setting - higher values will reduce the
amount of pressure change in the nozzle during cornering, but
setting it too high can cause blobbing during cornering. (Tuning
this value is unlikely to impact ooze.) The default of 10ms should
work well on most printers.
* Once pressure advance is tuned in Klipper, it may still be useful to
configure a small retract value in the slicer (eg, 0.75mm) and to
utilize the slicer's "wipe on retract option" if available. These