flow rate

Thoughts about Raise3D, 3D printing and making in general.
Targo
Posts: 4
Joined: Fri Aug 25, 2017 9:09 am

flow rate

Postby Targo » Fri Sep 01, 2017 3:33 pm

Hi,
I have a basic question about the surface at the Raise printer.
If I increase the feed rate under the page "Tune" proportionally also
increases the flow rate or do I have to additionally increase manually?

Thanks for an answer

greeting
Frank

EldRick
Posts: 92
Joined: Thu Jun 22, 2017 5:55 am

Re: flow rate

Postby EldRick » Fri Sep 01, 2017 4:23 pm

Feed rate = flow rate. It's terminology from lathes and other CNC machinery.

Jetguy
Posts: 1599
Joined: Tue Mar 22, 2016 1:40 am

Re: flow rate

Postby Jetguy » Fri Sep 01, 2017 4:44 pm

No, it does not not.

Feed rate is how fast the TOTAL GLOBAL system moves to include coordinated moves that include extrusion.
Flow Rate is a SPECIFIC modifier that changes the distance multiplier for the extruder feeder ONLY.
Last edited by Jetguy on Fri Sep 01, 2017 11:44 pm, edited 1 time in total.

Jetguy
Posts: 1599
Joined: Tue Mar 22, 2016 1:40 am

Re: flow rate

Postby Jetguy » Fri Sep 01, 2017 5:03 pm

It's all about understanding a line of gcode and how the values affect it.
G1 coordinated move means ALL actions complete the same TIME.
So, you might have G1 X100 Y200 E2.34 F1200
The distances beside the axis names are in mm. The feed rate is in mm per minute so divide by 60 for mm/second
Assuming we started at XYZE coordinate 0 for all axis, then X moves 100mm, y 200mm, and E2.34mm and the gobal speed limit and desired speed is F1200. Since the longest distance wins here- it determines the total time for the entire move. Example, the speed limit is F1200/60= 20mm/s so 200mm takes 10 seconds. Well the 100mm move in X and the 2.3mm move of the extruder feeder pushing the filament into the nozzle are also going to take 10 seconds. They are going slower than 20mm/s but again, this is because a G1 is a coordinated move.
Also note, the extruder is generally the smallest distance by a huge factor in any line of gcode so changing the speed of the typical gcode segment- even doubling speed is still relatively slow for how far the extruder feeder is going to push in distance of filament.
This is why generally, you do not need to modify flowrate just because you adjusted feed rate.

If you have feed rate on the LCD or per gcode command set to 100%= no change to the "F" value.
If you adjust it greater than 100% then it's higher than the "F" value- but note the gcode distances are the same.
You push the same amount of plastic into the nozzle and thus out of the nozzle because the physical geometry and thus volume is the same regardless of how fast you go.

Flowrate is a modifier that specifically modifies the commanded the E value distances VS the gcode.
Say 110% percent flowrate multiplies that distance by increasing it 10% Back to the example of 2.3mm original line of gcode, that is .23mm more filament than the line of gcode originally said.

Jetguy
Posts: 1599
Joined: Tue Mar 22, 2016 1:40 am

Re: flow rate

Postby Jetguy » Fri Sep 01, 2017 5:31 pm

Also, this goes back to understanding HOW a slicer works in the first place.
You give a slicer the following values (yes, you set a lot more than just these values, but for this discussion, the parts the affect extrusion):
STL file
layer height
Nozzle diameter
Filament diameter

When the slicer cuts the STL into layers and then tries to figure out how to draw the 2D layer with the nozzle, it creates the straight line segments or lines (remember, current 3D printers do not support arc or curves- all lines are straight lines making up polygons). Each line represents a cylinder and has a length (whatever it took to make that line of the 2D drawing), the width (derived from the nozzle diameter), and the height (layer height). That means there is a logical volume of plastic to make that cylinder. Since you also give the slicer the input filament diameter, then it uses that diameter as a cylinder of infinite length to represent the spool of filament. So the math is if we have a volume of a segment and we know the diameter of the raw filament, then we can determine the length of the filament to push in to the nozzle to extrude a hot noodle of filament that exact shape and volume of the logical segment of gcode.

And this is where the multipliers kick in.
Most slicers besides ideamaker takes this logical gcode and modifies it before writing the final print file. So in Simplify 3D or Cura, or any dozen other slicers but not ideamaker, the Flow rate multiplier (or whatever specific name they call this adjustment value) modifies the values in the file.
Ideamaker is unique in that it simply adds a command to the gcode to tell the printer controller when reading the gcode to make an "on the fly" adjustment of the final value sent to the steppers.

The reason why I'm trying to highlight this for you.
If you use the tuning on the LCD screen and change either feed rate or flow rate multipliers, then when the gcode files contains a flowrate multiplier command- it will then reset it to follow the gcode. Hint, Ideamaker puts in flowrate multiplier commands into gcode. Other slicers may not do this.

So, where this can go wrong.
If you change the screen and then print another file or the same file- it can and may revert back to the flowrate set in the gcode. Worse, if you print a gcode file made by another slicer and manually set anything other than 100% on the screen, you are now having the firmware multiply the intended values in your gcode. This could result in unintended over or under extrusion and then if you were to reboot the printer- suddenly the same file prints with totally different extrusion multiplier.

Feed rate changes on the other hand- potentially every line of gcode could have a different "F" value so this global value is never set by the slicer and added to gcode. In other words, just know that if you tune feedrate- then it's always multiplying the value in a given line of gcode.
For example a perimeter speed of 15mm/s with a 120% multiplier then moves up to 18mm/s (15+3) but a 120mm/s travel move is now 144mm/s (120+24)

EldRick
Posts: 92
Joined: Thu Jun 22, 2017 5:55 am

Re: flow rate

Postby EldRick » Fri Sep 01, 2017 8:55 pm

Sorry - I should have said flow rate = speed multiplier. I do know better...
:oops:
However, the CNC source of the terminology is correct as stated.

Jetguy
Posts: 1599
Joined: Tue Mar 22, 2016 1:40 am

Re: flow rate

Postby Jetguy » Fri Sep 01, 2017 11:52 pm

Yes but 3D printing throws radically different functions for some of the commands. I caution folks to avoid direct comparison because if you then go read a CNC gcode guide you will make mistakes that do not work on a 3D printer- especially Marlin. Best to look at the source https://github.com/Raise3D/Marlin-Raise ... n_main.cpp
// M220 S<factor in percent>- set speed factor override percentage
// M221 S<factor in percent>- set extrude factor override percentage

Understanding the 2 control board system, all interactions, the front panel LCD function- these are things not well explained in the manual- let alone the unique 3D printing gcode commands that are completely different from the CNC world.

Again, sorry, I'm not trying to point fingers or blame, just want to point users to the best information I know specific to the printer and cover topics that are not covered anywhere in documentation or the manual. If you want to master this printer and use it to your maximum advantage these are things and underlying facts that need to be understood- and again- nowhere in the manual, wiki, or guides.

Targo
Posts: 4
Joined: Fri Aug 25, 2017 9:09 am

Re: flow rate

Postby Targo » Sat Sep 02, 2017 9:52 am

Hello,
Thanks for the very detailed explanation. Now much has become clearer to me.
The connections between axis feed and extrusion can not be so simple, otherwise the result
would be too much dependent on the settings.


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