.75 Nozzle on V3b

[innkeeper]

hi all, been a while...

i am mass printing Face Shields to help medical teams in my area.

in an attempt to increase speeds, I have acquired a .75 nozzle

I am looking for some info to help with a starting point on speeds.
does anyone know the flow rate of a V3b hotend?
I plan to try and push this as far as I can get away with, like .5 layer height and 1.0mm extrusion width..

if anyone has gone down his road before and can fill me in, that be great.

thanks

[airscapes]

I use the .75 nozzle a lot with V4 M2. .5 layer and .8 Width, you won't make it to 1.0 no way.. You are not going to go faster you will go slower, but the job will get done faster with the .5 layer height. Keep your perimeters to 1 where you can (they are fat no need for more than one most of the time) I know I tried printing something at 60mmS and it was not happening.. hot end could not keep up.. 50mmS was pushing it with PLA. I love this nozzle for larger items it really is nice.. made flower pots with it using vase mode and PETG really nice and heavy duty. I am sure you are aware you will need to alter your Z offset with .5 layer and may need to alter you retraction... it is kind of drippy with that big old hole.. Extrusion Multiplier with S3D seem to be .93 with most filaments.. and I do set filament average measured thinness in the slicer as well.
Sorry Ed, I should have said, ALWAYS verify extrusion multiplier while setting/checking Z offset..
And here is a cal square for .8 EW to set Z offset and spot check EM and a 2 layer square to verify EM. if the OP does not have them

[ednisley]

push this as far as I can get away with

The fundamental limit comes from the heater's ability to bring cold plastic up to extrusion temperature inside the 20 mm hot zone.

Using airscape's example, the extruded thread is 0.5 mm thick × 0.8 mm wide = 0.4 mm², so laying down that thread at 50 mm/s means the extruder is heating plastic at 20 mm³/s and is "pushing it with PLA".

In round numbers, normal printing speeds with a normal nozzle and normal plastics runs around 10 mm³/s, so a practical upper limit is probably around 15 mm³/s.

As far as thread size goes, the diameter of the flat area around the nozzle orifice sets the maximum thread width, because the nozzle must compress the thread against the previous layer. If the thread is wider than the nozzle, the gooey plastic curls up around the sides of the nozzle and doesn't bond well. The rule of thumb is to round up the orifice diameter to the next convenient number:

• 0.35 mm nozzle → 0.4 mm thread
• 0.75 mm nozzle → 0.8 mm thread

The maximum thread (= layer) thickness should be about 60% of the thread width, so a 0.8 mm wide thread calls for a 0.5 mm layer thickness.

Aaaaand, as always, calibrate the Extrusion Multiplier for whatever conditions you're using to ensure the slicer and the hardware agree on how much plastic is coming out of the nozzle.

[innkeeper]

Update,

So using a .75 nozzle with a 1.0 extrusion with worked fine, I just had to slow things down a bit and up the nozzle temps to prevent extender skipping. The print quality didn't suffer at the 1.0 extrusion width and it made perfectly functional face shield frames with equal quality to the printers running .8 and 1.0 nozzles ... which is all I needed it to do. I did upgrade the extruder stepper to a slightly higher current / torque one mid-project. now that this project need is done it goes back on the shelf. Though this time I am going to cover it so I don't have to clean up as much dust if I dig it out again.