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Revision to Pressure advance

Jason Znack

== Methods of finding the right amount of pressure advance ==
-The most simple method of tuning pressure advance is to slice a cylinder of 100mm diameter and at least 100mm tall, 1 bottom layer, 1 or 2 perimeters, and minimal or no infill. Ensure cooling is adequate for printing an object with very short layer times. Ensure the Z seam is aligned to a single point. Use a print speed close to your normal print speed. Ensure your extruder steps per mm has been calibrated. Ensure any wipe and coasting settings are disabled in the slicer.
+One option for finding your ideal PA value is to use a customizable python script developed by a forum user that generates a gcode file with varying amounts of PA which is described here: https://forum.duet3d.com/topic/6698/pressure-advance-calibration
+
+The most simple method of tuning pressure advance is to slice a 100mm cube, 1 bottom layer, 1 or 2 perimeters, and minimal or no infill. Ensure cooling is adequate for printing an object with very short layer times. Ensure the Z seam is aligned to a single point on the middle of a face. Use a print speed close to your normal print speed. Ensure your extruder steps per mm has been calibrated. Ensure any wipe and coasting settings are disabled in the slicer.
Now start the print with pressure advance disabled. After a few layers enable pressure advance by sending the M572 command with your desired starting amount in the gcode console. You may notice a brief pause in movement while the value changes. Continue the print for a few more layers. Try various amounts above or below the starting value and pay attention to the Z seam. Too little PA may result in a bulge at the end of the perimeter before the layer change. Too much PA may result in a gap at the seam.
-A more detailed test using a customizable scripted Gcode file is described here: https://forum.duet3d.com/topic/6698/pressure-advance-calibration
+If you use PrusaSlicer, you can use the before layer change gcode found in the Printer Tab > Custom Gcode, to automate the pressure advance value change.
+
+[code]
+; 0.2mm layer, 8 bands 5mm each, total height 40mm
+{if layer_num== 1}M572 D0 S0.0
+{elsif layer_num== 25}M572 D0 S0.05
+{elsif layer_num== 50}M572 D0 S0.10
+{elsif layer_num== 75}M572 D0 S0.15
+{elsif layer_num== 100}M572 D0 S0.20
+{elsif layer_num== 125}M572 D0 S0.25
+{elsif layer_num== 150}M572 D0 S0.30
+{elsif layer_num== 175}M572 D0 S0.35
+{endif}
+[/code]
+
+This script will insert a new M572 value every 25 layers. You can customize it by changing the S value at the end.
+
+== Interpreting the Results ==
+
+[image|2307]
+
+[image|2304]
+
+These images show the results of the various PA values. Choose the value where the seam is most even and the corners do not bulge. If there is a gap at the seam or corners, the PA value is too high.
+
+Once you choose a range that looks best, you can repeat the test and expand the values within the range. In this example case, the best value was 0.15. A repeat test could test all the values between 0.1 and 0.2, and so on. If you have a very long bowden tube, you may need to test a fairly wide range of values and may need to run multiple tests.
+
+Once you have a good value, do some other test prints of more detailed models, like a Benchy just to verify that there are no other odd issues.
== Side effects of enabling pressure advance ==

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