Nozzle Size vs Print Speed

[timskloss]

After changing from a 0.5 to a 0.4 mm nozzle, PLA doesn't seem to flow as well at the same temperatures. I guess this would make sense because the hole is smaller, but the flow is not constant. I'm seeing a low-flow condition for about 2-4 seconds and then a high flow for about 1-2 seconds. This pattern repeats itself as I try to print at 40 mm/s. Increasing the nozzle temperature 10-15 degrees helps, but I still get the surging. If I cool down the nozzle the extruder cold end slips every 7 seconds or so. It would seem that pressure is building between the cold and hot ends and something somewhere needs to give.

Is surging a common problem when trying to print a filament at to high a speed with too small a nozzle?

[Xenocrates]

After changing from a 0.5 to a 0.4 mm nozzle, PLA doesn't seem to flow as well at the same temperatures. I guess this would make sense because the hole is smaller, but the flow is not constant. I'm seeing a low-flow condition for about 2-4 seconds and then a high flow for about 1-2 seconds. This pattern repeats itself as I try to print at 40 mm/s. Increasing the nozzle temperature 10-15 degrees helps, but I still get the surging. If I cool down the nozzle the extruder cold end slips every 7 seconds or so. It would seem that pressure is building between the cold and hot ends and something somewhere needs to give.

Is surging a common problem when trying to print a filament at to high a speed with too small a nozzle?

It's not a very common problem, but it is seen. Most of the time you get the filament driver skipping or ground away filament instead of surging, as it's a bit of a sweet spot symptom wise to get it, since it needs to be able to build enough pressure to overcome the low temp, without causing the filament driver to skip or strip.

[mhackney]

Here is the difference in area between a .4 and .5mm nozzle:

0.40mm: 0.12mm^2
0.50mm: 0.20mm^2

The ratio 0.12/0.20 = 0.60 shows that you have 60% of the area with a .4mm nozzle. Most people don't appreciate this, they think "it's only .1mm less diameter." but that seemingly small diametrical difference is a HUGE area difference.

Also, are you sure you changed ALL the parameters in your slicer to accommodate the .4mm nozzle? If you are trying to push more filament though a smaller hole you just might observe that type of flow surging. My money is that you didn't change slicer settings.

As you go to a smaller orifice with the HE280 I have discovered that it does require more heat to flow nicely. The E3D V6 hot end is much less sensitive to flow speed and diameter (within a reasonable range). I haven't done the experiments to plot the flow volume vs temperature for the HE280 yet but it is on my list.

[timskloss]

Also, are you sure you changed ALL the parameters in your slicer to accommodate the .4mm nozzle? If you are trying to push more filament though a smaller hole you just might observe that type of flow surging. My money is that you didn't change slicer settings.

I changed the nozzle size from 0.5 to 0.4 in printer extruder settings. What other settings are there? I'm using the new Matter Control for most slicing, and sometimes KISS.

[mhackney]

Most slicers allow you to set widths separately for infill extrusion and perimeter extrusion so you usually need to change at least 2. Are you using the MatterSlicer or Cura from Matter Control? Maybe post a screen shot of your slicer configuration page.

Also, how fast are you printing, that makes a difference too. You can only squeeze so much blood out of a turnip.

[timskloss]

Also, how fast are you printing, that makes a difference too. You can only squeeze so much blood out of a turnip.

I slowed down and am getting better results. Thanks for the help.

[mhackney]

I also meant to add, the limiting factor for print speed is almost always the extrusion flow rate (in mm^3/s). The 3D-Online V6 extruder can operate consistently at around 10mm^3/s tops. The Volcano was specifically designed to significantly improve flow rate to 30mm^3/s.

I don't know what the HE280 max rate is but it is on my list to measure. Based on my observations, it is lower than a V6. One way to compensate (sometimes) is to increase the hot end temperature to improve flow rate. I've found that I have to increase temp more than I'm used to with V6 extruders to print at 40mm/s or faster.

[geneb]

Are you referring to the hot end or the actual extruder (the bit with the stepper bolted on)?

g.

[mhackney]

Hot end where the filament melts and gets squeezed out.