Bug with shell calculation ?

[3dmakeme 0]

Hi Daid !

I was wondering if anyone has noticed the huge changes in printing times when changing the shell thickness. I was wondering if there was some kind of bug here. Let me explain.

I have a std 0,4mm nozzle (like most of us). So if i want to make a print with 2 perimeters i used to put 0,8mm for the shell thickness. And cura gives the printing time in my exemple : 7 hours.

https://www.evernote.com/shard/s24/sh/c7e69083-f24c-4819-a1d7-dda778a2b5df/53945d6dac5079c58b11a8f8e7708505/deep/0/Cura-14.09-0.8mm-shell.png

Now if i set the shell thickness to 1mm (wich is more than my 2 perimeters's nozzle size) i get a 6H print. Isn't that weird or is it just me misinterpreting things?

https://www.evernote.com/shard/s24/sh/5c0f6513-87fa-48c1-bd53-406762b38b90/7d165c772d431eed5308642480da7c8a/deep/0/Cura-14.09-1mm-shell.png

Thanks to all the cura team for this excellent software !

 

[pm_dude 27]

With a shell of 1mm only 2 perimeters are used just like with 0.8mm shell. My guess is that the change in time is because now there are less cases where top/bottom shell are inserted along the walls.

Try running the same exercise but uncheck the top fill and bottom fill in the expert menu.

[3dmakeme 0]

Hi pm_dude !

I've tried without top and bottom infill still 48 min time difference so my guess is top & bottom infill are not the problem... :(

 

[pm_dude 27]

Ok and with 0% infill what does it do?

Come to think of it, its kind of normal since the same amount of perimeter are used they are now more spaced out because each pass need to feed 0.5 mm wide instead of 0.4mm. If they are more spaced out they need to travel less and they reduce the infill needed.

[Daid 303]

With 1.0 shell you get 0.5mm width lines, which means less lines to fill the area, and thus less printing time.

 

[3dmakeme 0]

Ok Thanks a lot Daid !