FiloAlfa PETG

[Ducati87 0]

Hello, this is my first time that I'm printing with filoalfa PETG, but I noticed an underextusion with 100% of flow. The width and height settings are the Cura default. How can I improve or solve this kind of problem?
Thank you.

[GregValiant 1,246]

The best way to check is to adjust the flow during a print using the LCD control.  Once you get it dialed in to an acceptable percentage then you can change all the flow settings in Cura to that number, and save it as your PETG profile.

II don't know if it's a slightly different diameter of filament, different coefficient of expansion, or what it is but there is an effect there that makes it different than PLA.

[Ducati87 0]

8 hours ago, GregValiant said:

The best way to check is to adjust the flow during a print using the LCD control.  Once you get it dialed in to an acceptable percentage then you can change all the flow settings in Cura to that number, and save it as your PETG profile.

II don't know if it's a slightly different diameter of filament, different coefficient of expansion, or what it is but there is an effect there that makes it different than PLA.

thank you for the reply. I read on the Cura settings support that "modifying the flow in order to solve the underextrusion, is not a definitely a solution". In any case, I would to print a single wall cube in order to understand if the flow is ok or not.

[GregValiant 1,246]

I read that.  I'm not talking about a 30% change as a permanent fix.  Going from 100% to 105% when changing a material is acceptable to me.  If you were to print a lot of PETG then it might be worth re-calibrating.  For a few prints, and if the percentage is low, then rather than re-calibrating every time I changed spools (necessary if they spend time sitting on a shelf absorbing moisture) I would just tweak the flow rate.  Some folks will no doubt consider that quick-and-dirty.

 

There are arguments both ways regarding calibrating with a "single wall cube" versus a "double wall cube".  Good luck.

 

[Ducati87 0]

59 minutes ago, GregValiant said:

I read that.  I'm not talking about a 30% change as a permanent fix.  Going from 100% to 105% when changing a material is acceptable to me.  If you were to print a lot of PETG then it might be worth re-calibrating.  For a few prints, and if the percentage is low, then rather than re-calibrating every time I changed spools (necessary if they spend time sitting on a shelf absorbing moisture) I would just tweak the flow rate.  Some folks will no doubt consider that quick-and-dirty.

 

There are arguments both ways regarding calibrating with a "single wall cube" versus a "double wall cube".  Good luck.

 

thank you for the support. Do you suggest to use a single o double wall cube? Thank you.

[GregValiant 1,246]

I make no recommendation.  It is my sincere belief that when I tell the printer to extrude 100mm of filament, and 100mm of filament gets extruded, that my flow calibration is both complete and sufficient.  If filament diameter varies (and I do check it) then I might revisit the calibration or adjust the material diameter setting in Cura.

 

Consider that if 1 filament is 1.75mm diameter and the second is 1.73mm diameter and I don't re-calibrate (or make the adjustment to the Material Setting) for the second, I will under-extrude by 2.25%.  For me, that is easily adjusted (using my finely calibrated Mark I eyeball) by kicking the flow up during the print.  In my End-Gcode in Cura, I have M221 S100 to re-set the global flow rate.  There is also an M220 S100 to adjust the feed rate just in case I made a change during the print.

 

Consider a single line of extrusion.  It isn't trapped on either side and is free to flow where it wants.  Is that the usual real world scenario?  Is the resultant width of a single-line wall a number I want to calibrate too?  In vase mode (always single wall) I usually push the .4 nozzle at .6 line width.  The resultant print is stronger because the flow is higher and the wall is thicker.  It's a personal preference for that single scenario.

 

A dual wall cube has 1 index move (the line width) of the nozzle.  The outside edges are free to flow and the measured  width is a function of not just E-steps, but also the line width.  I have to ask myself again, do I need to calibrate the Flow volume to the wall width?  Should I consider a shrinkage factor?  Should I re-calibrate every time I change filament spools?  I voted no to all of that.

 

I got into this to print things.

 

Sorry about the rant.  I shouldn't have had the third cup of coffee.