Relationship between speed and temperature

[coffeecup 1]

My usual speed is 50mm/s on a UM1. When I speed up to 100mm/s, there is a significant under-extrusion. I need to increase the temperature of nozzle (I am using PLA) to improve the under-extrusion. When the temperature is increased to 245C, the under-extrusion is much better. But I dare not to further increase the temperature for safety sake. Is there anything I can do in order to print in high speed? Thank you.

 

[takei-naodar 0]

http://umforum.ultimaker.com/index.php?/topic/3976-almost-always-missing-layers-underextruding/

what layer thickness are you printing in?

 

[coffeecup 1]

I usually print in 0.2mm or 0.1mm layer thickness.

 

[IRobertI 454]

With 0.2mm layers and 100mm/s speed you are extruding at 8mm³/s which is just around the limit of what the printer is physically capable of. Instead of repeating information I'll just link you over to illuminarti's excellent blog post about it:

http://www.extrudable.me/2013/04/18/exploring-extrusion-variability-and-limits/

 

[gr5 1,365]

Scroll down to the photo of the purple cube (post #2) to see some data on speed versus temp.

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/

 

I usually print in 0.2mm or 0.1mm layer thickness.

 

Well that's a huge difference in volume (2X). You can of course print twice as fast at .1mm layers before you get underextrusion for a given temperature.

 

[coffeecup 1]

Thank you for the info. Will read them carefully.

 

[LePaul 297]

I guess I am missing the big lesson, slower print, lower temp?

 

[gr5 1,365]

The big lesson is pretty simple. The faster you print, the higher temp you will need to print with. Otherwise the extruder just can't deliver the needed pressure to get the desired filament out. The photos are useful because they recommend specific speeds and temps that are at the upper limit so you can stay well below those if you want prints without underextrusion.