Posts made by Threepwood

@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.

@deckingman I have printed another benchy in this yellow/green filament and it has come out the same, but without the blobbing on the chimney. The settings for both were identical.

@deckingman The hole is only 3mm. I think the misshapenness is just where the seam is. I have set the steps/mm as perfectly as I can with calipers measuring 100mm. My magnetic filament monitor which has been previously carefully calibrated also confirms my min/max extrusion is 98% to 102%. The extrusion factor I'm using in slicer is 98%, which for me has always given my a good compromise between quality and strength.

I ran a test with 3 test parts at 90%, 80% and 70% extrusion rate.

Despite underextruding a lot, the corner bulges are still there unfortunately.

The temperature sensor is a PT1000 and it is configured as a PT1000 in my config. My old sensor was also a PT1000, so I didn't have to change that in my config. The filament always behaves as I would expect it to at given temperatures, and when I start up from cold, the 3 temperature sensors in the printer all show the same temperature within 1-2 degrees (the other 2 are thermistors).

This is a benchy I printed in 20-25 minutes a few days ago on this setup.

It looks pretty much flawless to me apart from the chimney having blobs on it, which was a problem I had with 3.5.0rc-1, (I've now gone back to 3.4.6) and the hull line. Which is just due to not having enough control in SuperSlicer or Orca to stop the fan from cooling as much on that layer, when the deck starts printing, without causing problems with cooling elsewhere. But there is no sign of overextrusion or high temperatures.

So I don't think there are any problems with my slicer settings or my config. Everything is now dialed in very well and the only problem I'm getting is the bulges on sharp corners. The benchy doesn't show up this issue because all corners are rounded.

@deckingman I have tried printing at 240°C and the result is the same. I previously tried a print where the PA value was increased as the print got taller, by the end the value was far too high, causing the top infill to have gaps in it, but the bulging was consistent all the way from the bottom to the top.

Left is PA test. Right is 240°C test.

The new hotend does ooze a little more due to the longer melt zone, but I have it tuned in well enough that I don't get any stringing.

@deckingman said in Unable to stop severe bulging in corners with new print head:

bulging corners could be due to the rate of filament flow not slowing down at the end of a move at the same rate of change of the head speed, thus giving over extrusion at that point.

This is why I also tried running tests with height modifiers on extruder jerk and XY jerk, starting from far too low at 200, all the way up to far too high at 4800. These were independant tests, so the XY and E jerk values would cross over. I did a similar set of tests with acceleration on XY and E. All with no change at all in the bulging.

I pulled the belts tight by hand before I secured them using the method in the picture below and found before I adjusted the belt tensioners, that they were already tighter than I expected. Unfortunately, this was after I had trimmed off the excess. However, I don't think they are overly tight. They are a tiny bit tighter than before I changed the belts and print head. According to Gates, new belts should be installed at a higher tension anyway, so I imagine they will loosen up a little over time.

@fcwilt Thanks for your input. I hadn't thought about using coasting. I might have to run a test with it. I was under the impression that it was only used on retractions though.

@deckingman It's a core xy Voron 2.4 with a VZbot extruder and hotend. I've checked the rigidity quite a few times since I rebuilt it, by holding the nozzle with the steppers energised. It has always been very rigid. If I hold the whole print head, I can get a little flex from the Gates belts with enough force applied, but not much, belt tension is good, if anything possibly a little tighter than I would like. If I apply a force to the print head in the Y direction, I can only get a tiny amount of flex from the torsion of the 20mm carbon tube. I've been using the same carbon tube for over a year, and it seems to hold up well to higher temperature. Overall, it's more rigid than the old setup due to changing printed parts to aluminium parts and it's half the weight. I checked and re-lubed the linear rails before I reinstalled and I before I put the belts on, I checked the movement and it was smooth and low friction. I'm printing ABS at 255. I'll try going lower, but I like the layer adhesion I get with 255, but 245 looks nicer. I haven't tried 245 with this setup yet. I'll give it a go.

I've only had this problem since changing from the standard Voron print head to the VZbot extruder and hotend. The old setup needed a PA of 0.032, the new one only 0.02-0.025. The new setup has a longer melt zone. The old one was a standard V6 type heat block. The nozzle is a 0.5mm CHT, but that hasn't changed.

Hi all,

I have been tuning my new setup for two weeks, and thought I was just about finished until I printed a bracket I needed, only to find I'm getting severe bulging in corners which I'm unable to improve.

I have tried changing/disabling pressure advance, jerk, acceleration, speed, input shaping, extruder jerk. All of the tests look as bad as the first print I noticed it on.

I think this problem is what is also causing ripples on low poly curves as I and others mentioned in this thread.
https://forum.duet3d.com/topic/33692/input-shaper-causing-stutters-and-blobs-on-curves-rrf3-5-0-rc-1

I think it may be what is being discussed towards the end of this thread. https://forum.duet3d.com/topic/28981/issues-with-pressure-advance-since-rrf-3-4/ One user in that thread also said they were getting bulging in every segment of a low poly curve, which is what I am getting. Reading through that thread, it seems that a PA smoothing factor may be able to fix this issue, as has been found on Klipper, but it is not available on RRF.

Can anyone suggest anything else I can try? I'm completely at a dead end.

Sorry for bumping such an old thread, but I think I am having similar issues. No matter what my PA setting is, I am getting buldging corners. Also @gnydick said "Right now, with even just a low poly curved surface, each segment is ~1.5mm long, I get a bulge at every direction change." This is something I, and some others have found to be a problem in this thread.https://forum.duet3d.com/topic/33692/input-shaper-causing-stutters-and-blobs-on-curves-rrf3-5-0-rc-1

Is PA smoothing something that may be impelmented any time soon? Is there any other fix for this?

I'm considering moving over to Klipper to see if I can solve some of the issues I'm having, but I really wish I didn't have to since I'm generally really happy with RRF on my Duet 3 Mini.

@gloomyandy I hadn't noticed he was printing at 0.1mm layer height. I suppose that will help a bit with getting consistent extrusion since he's only having to get to 30mm³/s rather than 60mm³/s (I'm asuming 0.5mm width). But still he seems able to print each of the holes very cleanly even though he's going from retration to 30mm³/s with an acceleration of 35,000mm/s² and a jerk of 30 (or 1800 in RRF language).

My point was just that it does seem he is able to get the extruder to keep up with incredible acceleration and that, in my opinion, it's not pointless to reduce X carriage and printhead weight.

I'm still on a 24v system and 2 motors, whereas Vez is using 4 motors and 48v, so I won't be hitting the speeds he's getting. I seem to be able to get decent results with 200mm/s outer walls, 250mm/s inner walls at 4000mm/s² acceleration and 300mm/s, 10,000mm/s² acceleration for infill. All at 1200 jerk and 0.2mm layer height. Weirdly 600 jerk was causing the ringing in low poly curves to be much worse.

I did try going back over to 3.5.0-rc.1 just to test if the input shaping changes would improve the low poly curve banding, but the result was identical.

@deckingman Then how do you explain this? Printing at 600MM/s 35K

@deckingman You are correct that flow cannot be increased as suddenly as an X/Y acceleration on a well tuned printer. But pressure advance will counter this. As long as the printer knows the hotend is about to slow down for a corner, then speed up again, it can reduce and then increase filament pressure ahead of the X/Y moves by a set time in M572. In my case this is around 0.025 of a second.

@deckingman It's not maximum speed that we are trying to achieve with a lightweight gantry, but higher accelerations and jerk. I do like the printers you have built, but comparing them to something like the VZbot is like comparing a TGV train to an F1 car, at least in terms of linear acceleration.

@Arminas I don't think the M593 L parameter will change the minimum length move that input shaper will be applied to. It will only stop input shaping being applied if it slows down the overall acceleration of the move too much.