SOLVED Best way determining correct pressure advance?

  • Hi again.. 🙂

    I was wondering, what is correct way of determining the correct value of pressure advance?

    With 0 pressure advance I get corners so bad, I haven't ever seen them that bad on a 3D printer, so I figured I will need to use Pressure Advance.

    This is a simple test cube I printed:

    2019-12-12 20.47.19.jpg

    first 5mm is 0 pressure advance, later 5mm are 0.0825 pressure advance. It looks MUCH better, but how would one determine correct value? I used modified marlin code and one python script I found here, but don't know much about it.

    I have a converted Prusa MK2.5 bear running a Bear extruder (bondtech).

    Is it per filament?

    Maybe somebody has better expertise and can explain it better? 🙂

  • @Veti

    I tried this, seemed to be very unintuitive.. 😕 This is where "around 0.0825" comes from..

  • also other factor like jerk and acceleration play into this. (also for the extruder)

    why does looking at the test print to determine the best value seem unintuitive to you?

  • @Veti

    I'm almost blind.. 😅

    I feel around my prints with my nails most of the time.. 🙂

  • IMO, the best way is to look at, from the top, the outer perimeters of a sharp corner.

    Without PA, or too low of PA, the extrusion width will grow on the side of the corner that the nozzle is coming from, and the side of the corner that the nozzle accelerates away from will display thinner extrusion width than normal.

    With too much PA, the opposite will happen: the side of the corner that the nozzle is coming from will now be too little, and the side of the corner that the nozzle accelerates away from will be too thick.

    You have found a good value when you can not tell the difference between the two sides of the corner.

  • @bot

    Is this value filament specific?

  • @Murloc992 I would assume so. Probably, at least, for different types of plastic. Similar PLA might use the same value, though. TBH, I've only tested PA with PLA and only in certain circumstances.

  • the blob at the top left could also be an indicator for 2 things.

    -you are printing at a temperature that is to hot, causing the extruder to leak.

    -your extrusion factor is to high, which results results in more material in some areas because of pressure buildup.

  • @Veti

    This is just PETG. It always does this blob at the end of the print for me..

  • I think I might have found the value that fits. 0.07 to 0.08, does this look like a normal value? I just printed a 50mm tall two perimeter cube without any auto-cooling slow downs and tracked how the corner bulges shrinked. At 0.07 they just seemed to disappear instantly. Weird.. After 0.08 the corners started shrinking very much.

  • @Murloc992 said in Best way determining correct pressure advance?:

    does this look like a normal value?

    it really depends on your individual setup. there is no general value that works on every printer.
    if you are happy with the quality, then thats the right value for your printer.

    quote from dr cox:

    It’s regular-strength Tylenol! Here’s what’cha do: Get her to open her mouth, take a handful, and throw it at her. Whatever sticks, that’s the correct dosage.

Log in to reply