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| -rw-r--r-- | docs/Pressure_Advance.md | 26 |
1 files changed, 19 insertions, 7 deletions
diff --git a/docs/Pressure_Advance.md b/docs/Pressure_Advance.md index 7bb694e1..f4cc4b8e 100644 --- a/docs/Pressure_Advance.md +++ b/docs/Pressure_Advance.md @@ -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 |