Any news on 0.6mm and 0.8mm high flow hotends?

Bambu Lab H2D
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I’ve done some testing and have been reasonably impressed with the max volumetric flow boosts that I’m getting from the 0.4mm high flow hotend. One example is hitting 53 mm^3/s for plain old Bambu ABS filament with all the default H2D settings before seeing any defects at all. That boost’s actual improvement in print times is minimal with the usual 0.4mm hotend’s line widths and layer heights, though. It’s mostly only with very high infill models.

Has anyone seen any news of when we might get 0.6mm and 0.8mm high flow hotends? That seems to be where the true value will be in paying $50 USD or more for a hotend. I’m hesitant to buy the standard 0.6mm and 0.8mm hotends for some of the CF/GF filaments, as that will effectively be money thrown away as soon as the high flow versions are available.

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Sorry I don’t have much value to add here, but for what it’s worth you can print cf/gf filaments with the HF 0.4 just fine. I’ve already printed a roll of siraya tech ppa-cf, a few rolls of tinmorry PETG-gf, a few more rolls of tinmorry PETG-cf, and some eSun PA-CF all on the HF 0.4. Not a single clog or anything.

I wasn’t really impressed with the quality I was getting with normal filaments though, so I wound up swapping the standard flows back in.

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What aspects of quality were impacted? Thanks for any info

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I didn’t have any print quality issues with the HF0.4 nozzles though. In fact it even made some issues less pronounced because of the increase fluidity of filaments.

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Aside from Maximum Flow Rate, which can obviously increase, what else, if anything, should one typically want to change in the print profiles when switching from a standard nozzle to a HF nozzle of the same diameter?

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If you’re not seeing much reduction in print-time if printing with a 0.4mm HF nozzle as compared to a 0.4 standard nozzle, I’m just wondering whether there’s reason to think the same might be true of 0.6 HF vs 0.6 standard as well, and likewise for 0.8mm. I don’t know the answer. I’m just wondering whether the same kind of pattern might apply. And if it does, maybe skip the HF nozzle? In which case your wait is over, since the 0.6 and 0.8 are already released (well, maybe not very often in stock in the US store, but released).

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It’s easier to hit the VFR wall on larger nozzles due to the hotend would be hard to keep up with the temperature, and you’re essentially getting 3.375 times more plastic (0.4->0.6 diameter, so 1.5x1.5x1.5 in xyz) to extrude. So yes, it’s much more challenging on large nozzles. But still, HF nozzles are beneficial even on 0.4mm, you get more than just speed changes: you get stronger parts, improved layer adhesions, better printability on low layerheights (like 0.08mm), less extrusion artefacts, lower nozzle backpressure…

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Hotellonely answered this, but let me try to make it a little clearer on the max volumetric flow rate for the larger diameter nozzles using numbers you may already be familiar with and can see in Bambu Studio.

The default line width for a 0.4mm nozzle is 0.42mm. The default layer height is 0.20mm. Many modern filaments that aren’t higher end technical filaments claim to print well up to 300 mm/sec speed. To calculate the volumetric flow you need for those settings, you just multiply them together (0.4 x 0.2 x 300) to get 24 mm^3/sec. It’s not difficult to hit that level of flow on a standard 0.4mm flow nozzle. That’s a contributing factor to the default max volumetric speed of both Bambu PLA Basic and PETG HF filament being set at 25 mm^3/s in Bambu Studio.

You can increase any or all of line width, layer height and speed to increase the necessary volumetric flow, of course. For most filaments, there’s still some headroom to allow that with the standard nozzles. The closer you get to the maximum that the nozzle can achieve, the more you risk all the issues that Hotellonely mentioned, but if you’re increasing those you likely know how to calibrate and tune filaments well enough to recognize defects when they start to happen.

Now let’s do the same math with the defaults for the 0.6mm nozzle, with 0.62mm line width, 0.3mm layer height, and the same 300 mm/s speed. Now we need 55.8 mm^3/s volumetric flow to keep up with only the default values. Bambu does adjust the default max volumetric flow for filaments when using the 0.6mm nozzle, but not a lot. For PLA Basic and PETG HF, they only move up from 25 to 30 mm^3/sec. That means that the fastest speed you’ll get when printing won’t be the 300mm/s default speed set in the model. You’ll only get a max of 161 mm/s because that’s the speed at which the default line width and layer height hits the max volumetric flow rate set on the filament. You just lost almost half your max speed (161 is <54% of 300) just because the nozzle can’t heat the filament quickly enough to keep up.

It gets even worse with the 0.8mm nozzle. The defaults of 0.82 line width, 0.4 layer height, and 300mm/s speed would demand a volumetric flow rate of 98.4mm^3/s to meet them. Bambu’s default max VFR for PLA Basic and PETG HF stay at 30mm^3/s for the 0.8mm nozzle like they are for the 0.6mm nozzle. That means that that max speed when printing those filaments will only be 91, not the 300 default speed set for the model, effectively a 70% loss in max printing speed.

Keep in mind that all those numbers are the default numbers and you can get somewhat higher max flow rate with good quality with the standard nozzles if you go to the trouble of running max VFR tests for each filament. You won’t get anywhere near what you’d get with a true high flow rate nozzle, though.

These numbers are why going to a larger nozzle doesn’t decrease overall print time very much for most models. High flow versions of the 0.6mm and 0.8mm hotends could make a huge difference, though, and that’s why I’m so eager to get them.

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This seems key. Thanks for your explanation! :clap: