Help with nGen (flow problems)

As I wrote yersterday, I’m trying to get good nGen prints. It seeems as my PLA experience doesn’t help here.
Below is a print as an example. There are “missing lines” in some places, infill is stringy especialy if the infill area is small (when it’s bigger, flow gets more stable) and on the first solid layer after infill a lot of lines break (=holes). But most of the print is OK :confused:
I’m printing at the recommended 230°C, this one was done with 0.15mm layer height and speeds between 20 (outer shell) and 50mm/s (infill), 1mm retract length. So nothing spectacular. It got a little bit better with tuned pressure control (my Marlin expansion code), but not too much. Fan runs at 20%, except first solid layer after infill, where it runs at bridging speed = 100%.

Every idea is welcome!

Edit: I did 4 cold pulls with PLA before starting my nGen tests today so I’m sure the nozzle is clean.

Hi Sebastian

I am a bit shy trying to give advice to somebody with tons more experience in 3D printing then I have.
My tests are done on a Mini in a AC controlled room. This means I have the luxury of pretty stable room temperature with low humidity.
Room Temperatur is 25°C

I had to reduce flow for nGen to 97%
I have found that 225°C to 227°C works a bit better. This might have a relation to room temperature.
Speed settings in Cura are still a bit confusing for me I have reduced the print speed in the first tab to 40mm/s

With this setting I did not see any missing lines. The stringing also improved but is not gone.
The first layer after infill does not look nice with mine but I don’t end up with holes there. Not sure if I was lucky or if I fixed it without knowing I have an issue.

I have the feeling that environment temperatures and humidity play a huge role in printing result. If you send me a STL I can do a test print here and send you Fotos.

Please excuse that I am not yet used to the correct terminology… will come over time I hope :wink:

All the Best

Experience is relative, every answer can add new important details :wink:
My room temperature is about 23°C. A print speed of 40 makes everything much more simple, but I don’t want to go back to such numbers :slight_smile: I will print an extrusion rate test (a single perimeter cylinder) to get a feeling where nGen starts to have problems at 230°C. Lower temps will help with stringing, thats true but up to now I only have problems with stable flow so I will keep 230° for the first step.

My assumption is that there are still small bits of PLA in some corners of the hot end - even with my cold pulls. PLA will burn over time at 230°C and every time a piece comes loose it may block the nozzle for a short time… This might be true because the error rate seems to get lower from print to print but I’m not changing any important variables during this.
I had also simmilar problems when switching between PLA and PETG, but not nearly as bad. One cold pull and max. 20cm of extruded filament did the job with PETG, maybe nGEN is much worse here. Of course that would be quite bad, as it prevents quick changes between PLA and nGen. And nGen is a little bit expensive for normal prints, compared to my ESun PLA…

Edit: Or this might be the final step for me to change to an e3d v6 Hot end…

The extrusion test was very intresting. With PLA, I got first problems at 11mm³/s, at 13mm³/s I had to abort it. I was testing in 2mm³/s steps so something between 9 and 11 was the limit for PLA.
With nGen, I wasn’t able to find the upper limit - Marlin isn’t fast enough in calculating the movement in my test at 13mm³/s even when I switch off my advance pressure control. I had to abort the print at 15mm³/s because the printer was jerking like crazy trying due to brake down because of the movement buffer underrun and accelerating again when it had new points :laughing:
But up to 13mm³/s there is no sign of flow problems. But it’s hard to tell due to the jerky movement at 13mm³/s, so I would set 11 as a upper limit for nGen.

That means my problems are cleary not due to flow problems like too high speed or too low temperature. I was using < 6mm³/s for the gecko print.

For nGen on my Mini, I run a nozzle temp of 230° C and bed at 70° C. I have flow set at 90%. I use 0 cooling until the 50th layer and then 25% from there up. Of course I had to reduce cooling a bit after I replaced the tiny squirrel cage filament fan with a 25mm fan and shroud. My print speed is 40 mm/s. Hopefully this info will be useful. Here is a small tank I printed at .15mm layer height.

The problem solved itself from alone. Most likely I had some debris from PLA inside my nozzle that were not comming out with the cold pulls. I printed a lot of test peaces since last evening and my first real part in the last hour without gaps in the perimeters.

Thanks for your input!

I’m printing the Elephant now at 0.15mm layer height, again small imperfections as in my first picture here in the perimeters :imp:
The only similarity between the occurrence of the errors I can see is that they always start on perimeters with a low radius like on the tusk of the elephant or the leg of the gecko above.
Maybe related to this, or not, is the second problem that drives me crazy with nGen: On rectilinear infill or bridging (with is nearly the same kind of thing…) nGen behaves realy strange: as soon as the nozzle comes from a solid ground to free air (bridging start) or it comes acros a infill line of the previous layer, the printed line is nearly braking of. It’s like the extruder stops to extrude for a very short time, but that’s not the case. The extruded line is still connected to the start of the bridge with a very fine hair and start to be a solid line about 1-3mm later. This is especialy true if the infill area is small, so the printer has to do some jumps and start a new line from a new place to complete the infill. If the infill can be printed in one long movement, only the first start is “hary”.
Print speed, acceleration, fan speed - nothing seems to influence this behavior.

The wired thing is, I’m used to see the opposite thing with PLA: Wenn PLA starts bridging, there is a small “blob” right after the solid part because the nozzle has no more backpressure in that moment.

If somebody can explain this behavior, he will be my hero. I’m starting to develop a very ambilvalent relationship to nGen :confused:

Moin Sebastian

One of the reasons I love nGen is that it prints pretty much in the same range as the other Materials I use.
In fact I have looked on printing temperatures when I selected different materials to prevent the “coking” effect.

the bridging issue is really weird.
I have not seen this on my prints.
Yes I agree with nGen the first layer after infill ist very much “waveform” but well connected.
Let me try to do a tesprint tonight to see if I just did not see it or if it really does not happen to me.

You are printing 0.15 height and 20% infill?
Let me try a test cube to see.

All the Best

The elephant was printed at 0.15mm, the gecko at 0.2mm. Other settings I used:
.) 0.4mm nozzle, all line widths at 0.48mm
.) 230°C nozzle, 80°C bed temp
.) 20% infill at 60mm/s
.) Perimeter speed 60mm/s, external perimeters 20mm/s
.) Solid infill 60mm/s, top solid infill 40mm/s.

After the elephant print, I checked the extruder gears - they are OK. I’m now printing it again with PLA for a comparison, but up to now this print looks perfect as usual for PLA.

Attached are two details pictures of failures in the elephant perimeters and two infill test pieces with marked errors and indicated print direction:

Tha elephant gets printed as one peace I guess?

Maybe I should try that one as well
But that will probably only be on Friday as my day job is asking until then :smiley:

All the Best

Yes, one pieace without support.
No need to hury, the nGen spool is now back in the storage until I need the special properties over PLA or somebody opens my eyes what’s wrong with my printer :slight_smile: