Difference between M592 and M572?



  • Could someone explain the difference between M572 and M592?
    Both seems to be for handle back pressure in the tube.

    Testing the effect from M572 is simple, i got benefits from it.
    But i might could have benefits from M592 too.
    But how does this work?

    Thx in advance!



  • Maybe like this?

    M572 pressure advance: is for manipulate flowrate at start and end from loop.

    M592: compansate the flow at corners for example.

    Could this match in approximately?



  • @peterfrosta Not quite. M572 pressure advance might be better described as pressure compensation. So what can happen at the start of a print move is that the head moves quickly but it takes time to melt and extrude the filament so the rate of flow out of the nozzle does not accelerate as fast as the print head, leading to under extrusion at the start of a move. Then at the end of a move, the print head decelerates but because pressure has built up within the nozzle, this continues to force filament out, even though the extruder is slowing down, leading to over extrusion at the end of a move. M572 compensates by speeding up the extruder at the start of a move and slowing it down before the end of a move.

    M592 is primarily to compensate for extruder slippage. So although the extruder might be turning at the correct speed, if it doesn't grip the filament properly, it can slip. It works by speeding up the extruder in the middle of a move. My advice is to use this with caution because if you don't have extruder slippage, applying M592 will simply lead to even more of a build up of pressure, which will require even more pressure compensation.

    To some extent, the two are mutually exclusive, especially when printing at high speed. On the one hand, the extruder might slip requiring M592. On the other hand, if the extruder does not slip, then you'll get a build up of pressure requiring M572.



  • @deckingman said in Difference between M592 and M572?:

    @peterfrosta Not quite. M572 pressure advance might be better described as pressure compensation. So what can happen at the start of a print move is that the head moves quickly but it takes time to melt and extrude the filament so the rate of flow out of the nozzle does not accelerate as fast as the print head, leading to under extrusion at the start of a move. Then at the end of a move, the print head decelerates but because pressure has built up within the nozzle, this continues to force filament out, even though the extruder is slowing down, leading to over extrusion at the end of a move. M572 compensates by speeding up the extruder at the start of a move and slowing it down before the end of a move.

    M592 is primarily to compensate for extruder slippage. So although the extruder might be turning at the correct speed, if it doesn't grip the filament properly, it can slip. It works by speeding up the extruder in the middle of a move. My advice is to use this with caution because if you don't have extruder slippage, applying M592 will simply lead to even more of a build up of pressure, which will require even more pressure compensation.

    To some extent, the two are mutually exclusive, especially when printing at high speed. On the one hand, the extruder might slip requiring M592. On the other hand, if the extruder does not slip, then you'll get a build up of pressure requiring M572.

    thx for your fast and good explanation.
    M572 is likly i thought. Now, with your words i think i understand M592 too.
    Thanks a lot!

    I never noticed slipping Filament and M572 eleminate in first tests my blobs pre and post from perimeter at higher speed.
    I was fighting against long time. played so much with retraction, E-acc and E-Jerk.
    So i'm very happy 🙂



  • @peterfrosta My personal opinion is that you have to be very careful indeed before concluding that filament slippage may be an issue. The only reports I've seen as evidence of it are where people have extruded 100mm or so of filament, and measured the filament itself. The problem with that is this is not reprentative of what happens in "real life" because a 100mm filament move would need an XY move of many metres, which will never happen unless you have a really large printer. Also, it is highly likely that if slippage occurs, it would be due to back pressure which will build up during the course of a long move. Therefore that slippage might only happen after say 50 mm of filament has been extruded and there may be no slippage on the first 50 mm, or so which is the band within which most "normal" print moves occur. So using non linear extrusion may be compensating for something that does not happen under normal circumstances. Hence you need to be very careful before deciding that a print issue is due to filament slippage.
    That's just my opinion - others will likely disagree.


Log in to reply