Flow rate is ignored from prusa  

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Feday
(@feday)
Active Member

It seems that the flow rate is not working at all when slicing with cura for my MK3s, I was wondering if anyone else can double check on their end so I can tell "if it's just me".  Or some combination of my software.

Cura 4.9.1.

Rambo 3.9.2 (release notes for newer versions mention nothing about flow rate)

Posted : 10/06/2021 8:08 am
Diem
 Diem
(@diem)
Honorable Member

Er, you are getting no extrusion at all?

Cheerio,

Posted : 10/06/2021 5:11 pm
bobstro
(@bobstro)
Illustrious Member

Are you referring to the Material->Flow setting in Cura? What have you set it to and what results are you getting?

For Cura support, you'll probably get better help over on the Ultimaker Cura forums.

 

My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 10/06/2021 5:46 pm
Feday
(@feday)
Active Member

My prints are just fine in general. I'm experimenting with printing PCTG at the moment, which seems to shrink a little when cooling. To try to combat this I'm playing with extrusion and fan speeds. That's going well overall, results are getting better...

The issue I see is that when I set flow to 110% in cura and I check during printing in the "tune" menu on the printer it's at whatever I set it to previously, also after swapping filaments.

Posted : 10/06/2021 9:59 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @feday

[...] The issue I see is that when I set flow to 110% in cura and I check during printing in the "tune" menu on the printer it's at whatever I set it to previously, also after swapping filaments.

Ah, OK. That makes sense. When you view the flow value in the Tune printer menu, you are looking at the internal flow value. This can be changed in several ways:

  • By setting a value in the firmware configuration (where only 100% makes sense of course).
  • By using the M221 Sxx gcode command. 
  • By adjusting flow from the Tune menu during a print.

These all have the same effect and the results are visible in the printer menu.

If you change the flow setting in your slicer, you are affecting the slicer calculations used to generate extrusion commands. This has roughly the same effect, but the results are not visible in the tune menu on the printer. The printer, being a rather dumb device, has no awareness of the settings used to slice the gcode.

If you change the flow setting on the printer, that rate is applied against the rates generated by the slicer. 

I hope this makes sense. As an example, if you generate your gcode with your slicer setting (in PrusaSlicer, it would be Filament Settings->Filament->Filament->Extrusion multiplier) to 90% and used the Tune menu option to dial in 110%, you'll be printing at roughly 100% (well, 99%) normal flow rate but the printer menu will show 110%.

I've written up some notes on this topic as it related to PrusaSlicer here that you might find useful.

This post was modified 6 days ago 3 times by bobstro
My notes and disclaimers on 3D printing and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan...
Posted : 10/06/2021 10:33 pm
Feday
(@feday)
Active Member

That totally makes sense, thanks! I suppose got confused by things like fan speeds an temps translating into the tune menu.

Posted : 11/06/2021 7:50 am
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