@tim-0 I would use M106 and G4 "Wait" commands in the slicer end gcode.

M106 P2 S255         ; set bed fans to 100% to cool bed
G4 S180              ; wait 3 minutes
M106 P2 S0           ; turn off bed fans

G4 S180 will wait for 180 seconds before the next command.

As for your 3rd question. I'm not sure how to have an "if" command for temperature, hopefully someone else can help with that.

Out of curiousity, when would your print bed be under 30°C at the end of a print?

Another possibility if you have fans under the bed and a sealed chamber, you can use the fans to move heat around the chamber and increase chamber temperature! Importantly If you do this, run another PID tune for the bed before heating it!

@bluedust I'm using Super Slicer on my Duet 3 Mini. Also setting it to Rep Rap. I searched a recent gcode and found no line like that, despite the fact I'm using it for acceleration and jerk control.

Have you check to see if this command is in your start gcode in Super Slicer?

@phaedrux You make a good point. I was being lazy and keeping the whole line, and only changing the Z dive height, instead of finding out what values are optional in a M558 command.

@tim-0 There are Print_end.g and Print_start.g, which you could put the fan code in, but as I understand it, you will still need to edit the slicer start gcode to call the files. This will make it slightly easier to change between slicers.

I've not tried using meta commands, but it looks interesting.

Also, not sure if you are also using a Voron, I saw a mention of Voron in your .gcode file. I was having some overextrusion with Super Slicer and found this profile https://github.com/AndrewEllis93/Ellis-PIF-Profile

It's been giving me some really good prints, but make sure you change the build volume etc to your own because his is a Voron 2.4 350. And he's got it set up for Klipper, but I found all I had to do was change that to Rep Rap and input my own start gcode. He has a handy guide on there too https://github.com/AndrewEllis93/Print-Tuning-Guide

@jay_s_uk Here is the stl. I'm using a 0.5mm CHT nozzle.

Small bulge check.stl

@rex_sl I have added an L parameter to my M593.

M593 P"zvdd" F49 L800

As the gcode dictionary says "Lnnn (optional) Minimum acceleration allowed, default 10mm/sec^2. Input shaping will not be applied if it requires the average acceleration to be reduced below this value."

Hope that helps.

@dc42 I don't mean to be a nag, but is there any chance PA smoothing (or similar) will be added to RRF in the near future?

I've been trying to tune out corner bulging for days, changing just about everything I can and even buying a new nozzle, but I'm still not able to get a PA value that can remove the bulging without causing other extrusion problems in corners.

Now that I am actually back on 3.4.6. My problems seem to be gone again. Thanks @gloomyandy

Hopefully the next release of 3.5.0 will solve all these issues.

@Arminas It does fix the problem and I usually print STLs I have exported from CAD myself, but I'm not happy to leave it as it is. For one, there are some occasions that I want to print STLs from elsewhere, but also there may be times where features also trigger this vibration.

I've tried messing with input shaper, acceleration, jerk, speed and even pressure advance. Unfortunately, nothing really eliminates it at or above 100mm/s speed. I did find it became less obvious when I increased to 1200mm/min (20mm/s) jerk. I think this is because the printhead isn't slowing down as much for each section of the curve. Reducing acceleration to 4000 or lower also improved things. So I've set my slicer to print outer walls at 3000 acceleration and 100mm/s speed. I need to run more tests to check how slow I need to print inner perimeters.

I've reduced the weight of my print head and x carriage to half, and increased my max flow rate from 13mm³/s to 50mm³/s, but can't really utilise increased speeds due to unexpected artifacts.

@petriheino said in Issues with pressure advance since RRF 3.4:

@Threepwood could it be possible that your extruder is skipping steps during these high speed transitions?

No, it shouldn't be that. I'm able to extrude comfortably up to 30mm³/s with a 0.4mm CHT while printing and last night I even tried printing at 20mm/s XY speed (so 1.6mm³/s) for every print move with Ender 3 acceleration and jerk and I still got exactly the same corner bulging. This is using a VZbot hotend and extruder on a Voron 2.4.

@ctilley79 What makes you think that? I've been trying to fix this for days and I've checked everything I can think of multiple times. I'm really clutching at straws now. Open to trying other ideas.

@deckingman Fair enough if you don't want to talk about it anymore. Thank you for your guidence in my troubleshooting threads. It is your right to deny that it is possible to print well, above 4000 accelleration so I won't try to change your mind. What works for you, works for you.

I have tried printing much slower, down to 1000 acceleration with no improvement. At 10k I actually get LESS bulging.

In regards to the bulging in corners @dc42 said this is this thread: https://forum.duet3d.com/topic/28981/issues-with-pressure-advance-since-rrf-3-4

@dc42 said in Issues with pressure advance since RRF 3.4:

PA doesn't fully address the problem of over-extrusion in corners. I am looking to address this separately.

That thread shows that I'm not alone with this problem.

@dc42 I don't mean to be a nag, but is there any chance PA smoothing (or similar) will be added to RRF in the near future?

I've been trying to tune out corner bulging for days, changing just about everything I can and even buying a new nozzle, but I'm still not able to get a PA value that can remove the bulging without causing other extrusion problems in corners.

@deckingman When I first tested it with the 0.5mm nozzle, it wasn't too low. But perhaps I had a slight blockage, which increased back pressure. When I took the nozzle out, I could still see old black ABS at the entrance to the nozzle, with the last used white ABS in the middle. Another thing I found was that over time my extruder tension had loosened a little and filament was able to slip before the motor skipped.

With a VZbot build, I think it is assumed that a 0.5mm CHT/Bozzle nozzle is used with ABS. It's just a starting point and anyone going to the lengths of building a VZbot is likely to know that they should calibrate this value. My only point in mentioning it was that it certainly isn't an unreasonable value for PA.

Unfortunately after a lot more testing, and a new nozzle. I'm still getting obvious bulging in corners, which makes a lot of practical parts unusable due to fitment issues. I can start to counter it by using 10,000 accelleration for all print moves and at very, very high PA values like 0.12, but then I get huge underextruded areas before the corner and overextrusion after the corner.

I'm back at the idea that we need a "PA smoothing" value in RRF.

Small update. I've re-run my pressure advance tests and the results at both 255°C and 270°C are around 0.08 this time. When I ran the pattern and tower tests just after installing the new hotend and got 0.02 to 0.025.

Now importantly, I have just switched from a CHT 0.5mm to a CHT 0.4mm, so I would expect an increase, but the difference is huge. I suspect that before I moved to the 0.4mm nozzle, my ideal PA vaule was actually a lot higher than the 0.02 that I had originally set it to, due to the multiple tests I ran, which showed 0.02 to be a reasonable value. I later found that the offcial VZbot firmware has PA set to 0.02.

I have no idea why the PA value has increased so much. What kind of difference should we expect to see between a 0.5mm and 0.4mm nozzle? I wonder if there was some clogging in the old nozzle, but I'm not sure that the new 0.4mm should be so high.

@jay_s_uk Here is the stl. I'm using a 0.5mm CHT nozzle.

Small bulge check.stl

Hi guys,

Your questions got me thinking. I hadn't tried any other slicers. It didn't seem likely to me that a slicer setting could cause this.

This is the result of dropping the model into Orca and Cura.

I'm finally on to something! The Orca settings are pretty much a mirror of the SuperSlicer settings with speeds and accelerations and jerk. The corners are still not perfect, but what a difference! I can probably tune out the tiny bulge in Orca or Cura by slightly increasing PA value further.

I have now also tried using Vez3D's SuperSlicer config, which changes all settings in "Print settings" "Filament settings" and "Printer settings". But I still get bulging in SuperSlicer. So it seems as if the problem isn't a setting in SuperSlicer, but in how SuperSlicer is working with my printer and firmware. I ran a search for M572 to check it wasn't changing the PA value, and it returned no M572 found.

@deckingman The chamber isn't actively heated, it gets to around 50°C from the bed. For ABS I've been using 105°C on the bed for over a year. Any less and I have adhesion issues. The first time I noticed the bulging was on the bracket, which was quite a bit taller than a benchy.

I think this is some kind of issue within RRF that doesn't play well with this type of hotend. This hotend has the longest melt zone and with the lowest PA value that I've ever used, at least when the standard PA tests are used for calibration. As people with Klipper have found, changing the PA smoothing value has fixed this issue for them, but we don't have this option in RRF.

I was hoping there might be a workaround, but I'm not sure what else anyone can suggest, since we've changed everything I can think of except the hotend and the firmware.

Thank you for all your suggestions.

And here is the test piece in the black filament.