PETG max volumetric flow rate
-
Hey all,
I put together a new machine and I'm trying to tune it. It has an e3d hemera on it with a supervolcano. I'm trying to get it to print petg reliably at a fast volumetric flowrate (60-80mm^3/s). I'm having issues with layer adhesion and general print quality at these speeds. I have a cpap part cooling fan, which should provide more than enough cooling. I can't seem to get decent prints at these speeds. I have a 0.8mm nozzle with a 1mm extrusion width. I get layer separation, poor layer adhesion, and just general sub par quality prints.
I can print PLA at 80mm^3/s with no real degradation of print quality. Is PETG really that resistant to fast print speeds? I'm currently printing a part at 30mm^3/s, and it's coming out pretty good, but print temp is at 275C with part cooling fan around 40% through the cpap blower.
My other machine has a CHT nozzle, and I print PETG at 20mm^3/s with no issue at all, so I just don't understand how I can only get an extra 10mm^3/s out of a supervolcano, vs a regular v6 block with a cht.
For what it's worth, I'm also using a copper nozzle and the standard copper block for the supervolcano, so I definitely should not be getting cold extrusion with the supervolcano.
Thanks.
-
@Surgikill You don't mention anything about under extrusion, just poor layer adhesion. In which case, we can probably rule out the hot end. Try less part cooling.
-
@Surgikill have you tested if it can even extrude it at 60-80 mm3 in free air. you could do a test and try and extrude 10 grams at 60mm3 and then weigh it at on a small jewellery scale to see how well it it does. is it actually underextruding?
Also I agree that less cooling might help
this might help too
https://www.youtube.com/watch?v=lBi0-NotcP0 -
@deckingman I'll try that. It seems to be a shit balance though. From before, I have reduced part cooling, and print quality suffers, or I increase part cooling and layer adhesion suffers. Bridges are also terrible, and certain infills will cause the petg to curl and break off like confetti.
-
@Surgikill Is the filament dry? I've had bad results in the past with PET-G that wasn't completely dry - and that was a brand new spool straight out of the vacuum packaging. I chased my tail for days before eventually tried another spool from a different manufacturer which immediately fixed all my issues.
-
@deckingman All of them go into dry boxes directly from the packaging, and every dry box has a humidity sensor. Like I said, I can take a spool and print it at 20mm^3/s with a v6 block with a CHT, and if I take that same spool and move it over to the supervolcan, I can't get more than 30mm^3/s.
-
Nozzle blockage?
-
@Surgikill one of the problems with big nozzle diameters is that there is actually less surface area in contact with the filament so it's harder to get the heat into the centre of the filament and heat it up the whole way through. I think petg might be worse for this than PLA because it tends to take more energy to melt (ie the energy of the state change rather than just the temperature)? The CHT nozzles are best for this because they split the filament and melt it in smaller chambers.
Other thought is how are you trying to increase volumetric flow? I have generally found PETG doesn't like to be extruded fast, but you can bump up the layer height or line width for a slower carriage speed? Wider lines and thicker layers is generally better for layer adhesion too. I've had success printing 1.5mm wide from a 0.8mm volcano (in pla mind) for some big vases.
-
@Phaedrux Not that I'm aware of. I can print PLA just fine at ridiculous flowrates.
@engikeneer I'm printing at 1mm line width and 0.2mm layer height. I'm using autospeed in prusaslicer, and just setting my max volumetric flowrate in there.
-
@Surgikill said in PETG max volumetric flow rate:
...................... I'm printing at 1mm line width and 0.2mm layer height. ....................
Have you tried a larger layer height - say 0.4mm? Just on the basis that PET-G is a lot more viscous than PLA, that layer height to width ratio might not be the best.
-
@deckingman Alright, I set up a spreadsheet and gcode to test volumetric flowrate. Here are the results. Sample size of 1, but it seems to be pretty accurate, and I don't want to nuke a roll of filament printing little poop pieces.
I was printing 50mm^3/s at 255, looks like that is already falling off the cliff for flowrate. I think I'm going to drop my flowrate to 35. Kind of disappointing, seeing as I can push 20 with the v6 and a CHT. I might just swap the super volcano out for a volcano with cht.
-
@Surgikill ........and did you try a larger layer height? As I said before, it might just be that 0.2mm thickness between layers is simply too restrictive with a viscous filament like PET-G. Your graph shows that it improves with temperature, which is likely a function of viscosity, so it's easier to squeeze the bead into shape. What I'm trying to say is that filament melt rate isn't the only thing that will affect volumetric flow rate. If it was me, I'd try other things like removing the restriction due to the proximity of the nozzle to the previous layer, before laying all the blame on the super-volcano.
-
@deckingman Yes, but that's still not going to fix my flowrate issues that can be seen in the graph. I used the same test that CNC kitchen did. I'm looking for rock solid stability, seeing as I need this printer for production. I don't want to be on a razor edge with my extrusion rate. I could probably bump the temp up to 275 and increase my flowrate to 50-60mm3, but I'm not sure if it's worth it due to the reduction in print quality.
Regardless, with my experience with a v6 and CHT, it seems that I should be able to get the same if not better flowrate with a volcano and cht vs a supervolcano, with a huge reduction in hotend weight so I can increase my print and travel speeds.
It's kind of annoying because you see it being touted that 'The supervolcano can extrude 11x faster than the v6', which seems to be only true for 1 very specific case, 1.4mm nozzle with abs.
-
@Surgikill said in PETG max volumetric flow rate:
@deckingman Yes, but that's still not going to fix my flowrate issues that can be seen in the graph.....................
It might - but if you don't try it, you'll never know. But you seem to have decided that it must be the super volcano so I can't help any further.
-
@deckingman I mean, I don't really know what to tell you. I just did volumetric flowrate tests like was suggested. Are you telling me that the graph I posted is wrong?? I can't go much higher than 265C with the filament, and ANY type of printing is going to create more backpressure than free air extrusion like in the tests. I fail to see the logic here.
Also I did try a larger layer height a week ago. Still had issues with it, and an unacceptable reduction in quality on curves.
-
Have you tested the resulting print for dimensional accuracy and layer adhesion? Going above the rated volumetric speed can cause all kind of issues, not all of them look like a failed print.
-
@Surgikill said in PETG max volumetric flow rate:
....................I fail to see the logic here.......................
I know you fail to see the logic - that's why I can't help you.
Let's down to some fundamentals. A hot end basically has one function to perform which is to melt plastic. In order to do that, heat must be transferred from a hot surface into that plastic. Basic physics dictates that the higher the contact area, the more plastic will be melted in a given time. We know that a super volcano has a larger melt chamber than a standard hot end so there is a larger surface area in contact with the plastic. If you don't like physics, let's try a cooking analogy. If you had a very small frying pan that could only accept one rasher of bacon, it would take X amount of time to cook that bacon. But if you had a bigger pan, and assuming the hob could heat that pan to the same temperature evenly, then you could cook 4, 6 or even more rashers of bacon in the same amount of time (because we have a larger surface area).
Now for sure PET-G is much more viscous than say PLA so the melt rate isn't the only factor involved when it comes to volumetric flow rate. But you can't blame the hot end for that (although that's what you seem to do). But take a look a look at this video https://www.youtube.com/watch?v=7tE-jNIZ7n0. In it you'll see that using a 1.5mm diameter nozzle with layer width of 1.65mm, layer height of 1.0mm first layer speed of 40mm/sec and the rest of the print at 47mm/sec, I got an average volumetric flow rate for the entire print of 44.75 mm^3 per sec without any under extrusion, skipped steps or other mishaps. I can't remember what temperature I used but it would have been close to my default for PET-G which is around 235 deg C.
Now for sure, my 6 input hot end isn't a super volcano but the total surface area of the melt chambers is similar. So how come I could attain a volumetric flow rate with PET-G which is much higher than you are able to? Maybe, just maybe, layer width and height has something to do with it? A low layer height will be much more restrictive to flow due to the proximity of the nozzle to the previous layer, than a higher layer height.
But having said all that, take a look at this video https://www.youtube.com/watch?v=gc8AciHjf4I. In it you'll see that using the same nozzle height and width, but with PLA, I achieved an average volumetric flow rate of 72.34 mm^3 per sec which is significantly higher than I was able to achieve with PET-G. So we can say for sure that filament type (likely viscosity) plays a significant part on all of this.
Now I'm no great fan of E3D but it seems to be unfair to blame their hot end (which appears to be doing it's job). Certainly filament type is a large factor in volumetric flow rate, but possibly layer height and width might also play a part. But you won't know unless you try which is something that you are unwilling to do.
-
@deckingman I think the volumetric flow test mechanism OP is using is independent of his print layer heights. It's basically creating blobs of set extrusion lengths as different rates, then measuring their masses to detect underextrusion.
So that method to determine comparable max flowrates before you get underextrusion for different hotend/nozzle combos is valid. What it might miss however is what the impact is on actual prints (e.g. do you get power layer bonding before you get underextrusion).
-
@engikeneer Yes, this is the point. @deckingman I do not understand how you think I can achieve more than 30-40mm3/s at elevated temperatures when the hotend is already failing to produce those flowrates in ideal conditions. Any flowrate for printing is going to be less than the calculated flowrates in the graph due to backpressure.
Question: Do you think extruding into free air produces more back pressure than extruding onto a previous layer? (yes/no)
I completely understand everything you said in your first and second paragraphs.
I think what you missed is that I'm more annoyed by the marketing materials saying it can produce '11x more flowrate than the v6', which is only true for a very specific combination of nozzle diameter and filament type.This is like buying a car that can do 500mph according to the marketing materials, but the manufacturer achieved that speed by dropping said car out of a cargo plane.
-
This is like buying a car that can do 500mph according to the marketing materials…
– You’d be instantly arrested if you tried this in the city of London –
…but the manufacturer achieved that speed by dropping said car out of a cargo plane.
– Don’t blame the car, better drop the marketing guys instead
I think what you missed is that I'm more annoyed by the marketing materials saying it can produce '11x more flowrate than the v6' …
@deckingman didn’t miss anything (except of some marketing blabla), he just explained the underlying physics.
…which is only true for a very specific combination of nozzle diameter and filament type.
Not to forget the melt rate and other factors. But in the end, it’s your choice: Either you hunt for speed, or you learn how to achieve good-quality prints with PETG. Believe me or not, but you can’t have both at the same time.
