Dab of filament at each start causing bulges in the model

[DennisM]

Hi, I'm not sure how best to explain this, but for some reason my newly built Voron extrudes just a little bit too much filament at the start of a path, and sometimes at the corners of a model. Basically it bulges the corners of the model enough to make it appear like the model is warping upwards (because there's more filament at those places than on the rest of the model).

I will gather some photos but I wanted to start with asking if there are specific slicer settings (Prusa for me) that I should be looking at? I have not run into this issue before with my other printers.

[DennisM]

 

This happens to be PLA but it also happens with ABS and PETG.

[DennisM]

Wow when looking at these up close it looks terrible, in my opinion. Not just the corners but the layers don't seem very clean.

[DennisM]

I'm exploring "pressure advance" to see if that's the culprit:

https://github.com/AndrewEllis93/Print-Tuning-Guide/blob/main/articles/pressure_advance.md

[mvdveer]

7 hours ago, DennisM said:

pressure advance

May be your answer. Also see Andrew Ellis discussion on this. He has two methods in his tuning guide. I ended up using both to ge the results I wanted.

[DennisM]

 

It seems like that was it (pressure advance). Had not known about this before and was already going through Andrew's guide since it is a new build.

I did notice that it only works for me when I add this to the printer.cfg:

pressure_advance: 0.04

I wanted to try setting it per-filament, in PrusaSlicer with:

SET_PRESSURE_ADVANCE ADVANCE=<value>

But that failed miserably. Of course when trying this method I commented out the line in the printer.cfg and it didn't work. The prints were horrible - missed filament at the start of each layer, corners missing filament, infills fell short of the edges, etc.

Also, interesting enough, when I discovered that I accidentally tried to print a file with the above line in the gcode file, I removed it, but then tried to print again and the value persisted in klipper because it still was messed up even though the value wasn't in a new gcode file, so I restarted klipper to clear it and things worked after that.

So at this point I'm just leaving it as 0.40 in the printer.cfg and that's working out for me.

 

[claudermilk]

So putting SET_PRESSURE_ADVANCE in your filament Custom G-Code Start G-Code isn't working?  I have that in for most of my filament definitions; I use SuperSlicer, but it should be the same in PrusaSlicer.

[DennisM]

Can you confirm the actual line in your gcode looks something like this (with maybe a different value of course):

SET_PRESSURE_ADVANCE ADVANCE=0.40