Understanding Print Speed

[chrisw 70]

I'm only 2 months into 3D printing, so I'm still learning lots per day. One thing that seems confusing to me in Cura is print speed.

It's measured in mm of travel of the nozzle per second, if i understand that part correctly. However, the amount of filament getting pushed through the .4 mm nozzle seems like it would be better represented by a volume measurement. If I can print at 50 mm/s at .06 layer height, that doesn't mean I'll be able to do the same at .1 layer height.

I didn't realize that point when I first opened the UM2, read the manual, and started printing. In the Cura manual there's a statement explaining print speed, however I think it's leaving out some important data about the association of layer height to nozzle travel speed. The manual states:

"Basic Settings: Print Speed

Print speed sets the speed at which the print is put down. The default of 50mm per second is a bit low for an Ultimaker. But this is a safe starting point. People have printed up to speeds of 120mm per second. But this requires a well calibrated and tuned machine."

What was the layer height and the material used for the 120mm/s speed?

Maybe a useful feature in Cura could be to choose between using either a Print Speed setting, or a Material Volume per second speed. If I were to set the ideal flow rate for a particular material, and I kept using that material, then it seems I could adjust the layer height, and it would print just as well at all layer heights. The nozzle travel speed would be automatically adjusted inside Cura.

Or was that idea visited and tossed out long ago in the world of 3DP? Or am I completely off track and missing something about the speed calculations?

Chris

 

[gr5 2,172]

It would certainly be nice if Cura displayed the volume of filament your print will be printing for the given speed and also highlight in red if it is over maybe 7mm^3/sec and flash red if over 10mm^3/sec and be yellow if over 5mm^3/sec and green if under 5mm^3/sec. Then also you should be able to click on it and it should jump to 5mm^3/sec and lower your speed accordingly (or leave speed alone if already < 5mm^3/sec).

 

[illuminarti 18]

Volume per second is definitely the primary constraint on the extrusion system, but linear speed is also relevant for the mechanics of the system and effects like resonance and ringing. So you need to think about both; really.

Kisslicer has a nice feature that allows you to set a limit on volume per second, and will then adjust the gcode (linear speed) to keep everything below that limit. That can easily come into play on things like infill, if you try to print infill faster and in multiple layers at once.

 

[Daid 306]

Volume per second is definitely something that's in my head right now. As it's currently one of the most important parameters and not really shown anywhere in Cura.