Just what is going on with the extrusion rate?

I’m beginning to think that there is some real merit to this thread:

I print at 100% with Inland PLA and nGen, and get the same issues as before in my last thread - strings, oozing and lack of detail. On the second layer, the nozzle plows through the first layer because it is so thick.

I print with both at 85% flow rate and the strings and oozing almost disappear. I even started ramping up the temperature on the PLA and have discovered that the temperature might have been only a small part of my previous problems. The 15% reduction in the extrusion rate has made the single biggest improvement to my prints’ quality.

I’m beginning to wonder how much the environment that the printer is used in impacts the print quality. I’m almost sure ambient temperature may play a significant role in print quality, but to what extent? What other environmental factors may be at work here? I know that some cooking recipes must be altered to account for differences in air pressure at different altitudes. Could this also affect 3D printers as well? And if that is the case, why is it the extrusion rate and not the temperature change that improves the quality the most?

Settings I have changed from the stock nGen profile:
Layer Height: 0.2 (formerly 2.5)
Flow %: 85 (formerly 100)
Initial Layer Thickness: 0.4 (formerly 0.425)

Have you measured your filament diameter and applied that to your settings?

The extrusion rate makes a huge difference in my prints. Per the previous post, if your Cura (assuming) settings specify that you’re using 2.85mm filament the printer will extrude the material at a rate that would produce the specified layer height & width based on that diameter. But if in fact the filament is wider that your setting, i.e. 3.00mm, there is more material being pushed through the nozzle that the printer thinks. Lowering the flow rate slows it down. I see changing the filament diameter and adjusting the flow rate as achieving the same goal. By your lowering the flow rate to 85% you told the printer to slow down the rate at which it pushes the material through the heated nozzle.

So having a correctly measured filament at 100% flow rate is ideal, but if your filament diameter setting is lower than the true diameter, lowering the flow rate achieves a similar result.

I’m relatively new to all of this but above is my understanding of how the settings affect each other. Hopefully what I’ve said helps. But if I got something wrong someone will correct my information.

Check the e-steps.

Then use the flow rate / multiplier to adjust for filament… different filament brands and color can affect the extrusion finish.

Have you measured your filament diameter and applied that to your settings?

- Rhoderman

Yes, the nGen is within .01 of the standard 2.85, of course I would expect that level of precision from something I paid over $55/kg for… ($42 for 3/4kg)

Check the e-steps.

- kcchen_00

I was wondering if that might be the root of my problems. Both Inland PLA and Colorfabb nGen seem to print the best at 85% flow rate. I didn’t think the two materials could be so similar that I would basically just change the hot end and bed temperatures and hit print, but that seems very much the case.


some adjust meant in flow between different filaments I have to do as well.
going down to 85% sounds a lot to me. I would support kcchen_00 that you should verify e-steps. As soon as you have those right it is much easier to find the rest of the settings.

My feeling is that ambient temperature has quite some impact. My A/C is keeping my room around 25°C. “around” is the right word there :wink: actually the temperature fluctuates between 24°C and 26°C. This effect I can see in my prints even though the temperatures of Bed and Hotend are stable.

To see real impact by ambient pressure changes, i believe it has to change a lot in short time. Probably you would have more of a storm damage on your house in that case :wink:

I mainly use nGen and can not say anything about PLA. For nGen it is that the viscosity change between 225°C and 235°C is not very much. Saying that I guess that a temperature change on the Hotend will not change a lot on layer dimensions. On the other hand is has an impact on the cooling behavior of the filament. So stringing, bridging, layer adhesion and these things are pretty much temperature related. The trouble is that the cooling settings are depending on the layer dimensions as well… Thus you are back to the e-step question :wink:

All the Best

My mini was overextruding out of the box as well. I started by adjusting the flow, but then later adjusted the e-steps so I could keep flow at about 100%. I say about, as I find for different filaments I need to adjust it about 5% for the best results.

My logic is that since Lulzbot is based in Colorado, and I’m in Ohio, that there might be some kind of altitude related air pressure thing going on that impacted the factory set calibration. The fact that multiple people have had the same issue seems to support this claim. Either that, or that the Mini is calibrated for HIPS and it is wildly different from anything else.

I’m in Utah, at a similar altitude. I don’t see how reasonable pressures could change the printer calibration. I think they just set it a bit high as it’s easier to get decent prints with overextrusion than with underextrusion. Steppers don’t use atmospheric pressure to regulate anything that I’m aware of, so it seems unlikely that it would be an issue. I think it’s set a little high to make the first prints easier for the user and even with it a bit high, you still get good quality prints on all but the more demanding jobs. By the time it becomes an issue, the user is more likely to have learned about tuning the printer and they will adjust as needed. Even if it were dead on, filament diameter varies a little even on the best rolls, some filaments want a little more or less extrusion, some designs work better a little higher or lower, etc… There’s no such thing as one size fits all with 3D printing.

Apparently, I’m finding this out the hard way. I have noticed that large flat things, like a Raspberry Pi case, do best with higher temps for better layer adhesion, small detailed things do best with lower temps for minimal stringing and everything does better with less extrusion to prevent blobs and get sharper edges and details.

I don’t see how reasonable pressures could change the printer calibration.

Like I mentioned above, some recipes must alter the cooking temperatures and ingredient measurements (especially yeast, flour and leavening) to account for air pressure differences at different altitudes. Aside from the extrusion rate, I noticed some stringing with the nGen (usually temperature related) while using Lulzbot’s nGen profile (which was likely created in Colorado) and thought that maybe something similar to the cooking recipes was going on.

So I did the flow rate test where I make a mark on the filament at a measured distance, extrude some filament (at 100% flow rate), and measure again. It turned out to be within a tenth of a millimeter, which could easily be due to me being off a little on the measurement. The printer appears to be correctly calibrated. I don’t know why 85% gives me better results, it just does.

Unless my math is all wrong, 1.85 vs. 1.95 diameter is 11% more volume per unit of length.

1.85 & 1.95?

2.85/3.00 = 95%

According to my measurements of nGen, it varies from 2.83 to 2.85, 2/100 of one millimeter. I leave the diameter set at 2.85 and drop the flow rate to 85%. 0.85 x 2.85 = 2.4225

Hi Neamerjell

having the e-steps sorted please allow me to ask:
The nozzle diameter is set to your actual nozzle?

Can you print a few single lines and measure hight and width of those.

All the Best

Okay, to do this, I opened OpenSCAD and made a “cube([10,10,1],0);” and exported it as an STL. This should be a 10mm x 10mm x 1mm shape. I set the initial layer height to be the same as the rest of the layers, the layer height is 0.2, temp 230, flow rate 85%, 0% infill, and in expert settings set the black magic to “spiralize the outer contour”, and yes, the nozzle is set to 0.5mm.

As best as I can tell, depending on how hard I push my calipers together, it measures 9.82 x 9.83 x 0.99.

Just to see what the difference would be, I printed a second one at 100% flow rate: 10.24 x 10.25 x 1.07.

So now I have a matching set of Barbie doll scale coffee coasters… :unamused:

So! It looks like you need to calibrate your steppers(X/Y) if your ‘cubes’ are the wrong size. :nerd: Then start your flow tests again after you fix that.

You never now what you need them for :laughing:

With a similar test I am adjusting my flow rate per Filament:
Starting from

I reduced the Flow rate until it fits the measurements.
Just to be safe that I have not used to high printing speeds I have verified the setting with different speeds.
Last I have reduced the Hot end Temperature slowly to see when this starts having an impact.

Ok admitted you will have even more micro coffee coasters at the end, but you also will have much more insights how each filament behaves in your Mini :wink:

All the Best

Thanks, this sounds like some good advice. Someone else said that the slicer settings are not only specific to the filament used, but also to the model being printed. I’m finding this out the hard way. I finally dialed in the settings for the Inland PLA, and I am almost there with the Colorfabb nGen - the adjustable wrench turned out well at 95% flow rate. I still think there may be some environmental influence at work that could account for the default profiles off a bit. Its really too bad that Cura can’t run the equivalent of a shell script or batch file that prints several test pieces and change settings on the fly for each one… wait, can that actually be done???

That sound much more in the ball park than the 85% before. Good to see you are getting closer :sunglasses:

If it can be done I believe it has to go via a plugin. I have to admit that I am to much a beginner to have looked into scripting.
Right now I am playing around with Simplify3D and Cura to compare which one works best for me on which Part.

All the Best

Last thing to consider is the shrinkage of plastics… ABS is about 2%. Measure that calibration cube in a day or two.

Everyone’s printing environment is different. Which is why there is no silver bullet when it comes to advice… and also why an enclosure (which can help control consistency of the print environment) almost always improves prints.

Learn your printer (and environment), understand why a setting or adjustment helps and apply to your print environment.