Automated method from CNC Kitchen to evalute the maximum volumetric speed.
 

Automated method from CNC Kitchen to evalute the maximum volumetric speed.  

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ron
 ron
(@ron)
Estimable Member

Hello,

Stefan from CNC Kitchen posted there (   https://www.cnckitchen.com/blog/flow-rate-benchmarking-of-a-hotend   ) a method to evaluate the maximum volumetric speed of the hotend.

I just wanted to do the same. And then I decided to put some automation in it as the gcode posted is kind of manual:

G-Code for the flow test (the speed is given in mm/min ==> here 450mm/min = 7.5mm/s):

M83     ;relative extrusions 
G1 F450 ;450mm/min speed 
G1 E20  ;prime with 20mm 
G1 F3   ;slow extrude for pause 
G1 E0.1 ;0.1mm extrusion 
G1 F450 ;450mm/min speed 
G1 E250 ;250mm extrusion x2 to 
G1 E250 ;trick max extrusion limit

I join some gcodes to test different volumetric speed at different temperature like on the photo:

ColorFabb XT @ 270°C. The different volumetric speeds:

Back

12mm3/s    14mm3/s    16mm3/s

    10mm3/s    8mm3/s

3mm3/s    4mm3/s    6mm3/s

Front

There is sounds between each sequence of extrusion. The first is a prime (20mm of extrusion). You need to remove the prime after the sequence of 6 tones. You have 15s to do so. After the sequences are of 4 tones and a 15s pause. Then you can see if all is going well between sequences. With the two materials I tested, intervention wasn't necessary.

My results for the moment. My extruder is the standard one for a MK3S.

I will try to publish soon the raw values. And test more materials.

You are welcome to test the gcodes too and publish the data that will make a reference.

...
Posted : 10/06/2020 3:21 am
ron
 ron
(@ron)
Estimable Member

It's a shame I can't edit my own post. Then i add here more information on my printer:

  • MK3S with standard E3Dv6.
  • Silicon socket.
  • E3D Plated Copper Nozzle - V6 - 0.4mm (I think it is that one)

There are gcodes from 190°c to 280°C.

I hope I don't forget any interessting information.

...
Posted : 10/06/2020 3:41 am
bobstro
(@bobstro)
Illustrious Member

I've got an (IMO) simpler procedure and results here. The linked google docs spreadsheet includes my results, including using the 3D Solex nozzles that Stefan refers to.

I'm a little baffled by Stefan's comment about a slicer using maximum volumetric flowrate being a neat idea. PrusaSlicer and Slic3r have done this for years, and it's the main reason I prefer PrusaSlicer over the competition.

This post was modified 4 months ago 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 : 10/06/2020 6:24 am
ron
 ron
(@ron)
Estimable Member

I'm wondering how you can reach those values with a 0.4mm nozzle on E3D v6. Then I have few question. What are your tricks? What is OG R2 extruder setup? What are is your underextrusion rate at those speeds?

I prefer my method to chose upon consolidated measures.

Here two new materials. I'm surprised by how ABS behavior differ from other materials.

...
Posted : 10/06/2020 10:06 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @ron

I'm wondering how you can reach those values with a 0.4mm nozzle on E3D v6.

The filament and the nozzle matter most. PETG flows much more easily than PLA, especially at higher temperatures. A larger nozzle reduces back flow. The 3D Solex Matchless nozzles increase throughput considerably.

Then I have few question. What are your tricks?

I don't use those results directly, but they give me a maximum to be used. For example, when doing COVID printing in bulk, I was using a combination of filament and PETG that would flow at 40mm^3/s+ but limited my Max volumetric speed to 32mm^3/s in actual printing. So long as I stayed within reasonable limits, there weren't any surprises.

What is OG R2 extruder setup?

Original R2 (pre R3/Mk3s) extruder setup.

What are is your underextrusion rate at those speeds?

None. Again, I stay well below the indicated upper limits. Depending on the filament, that may still be well above Prusa's default settings. Per someone at Prusa that I corresponded with, the limits for PETG that Prusa provides are for good infill. Since I wasn't using infill, I was able to safely ignore those considerations. You have to choose reasonable settings for what you're printing.

I prefer my method to chose upon consolidated measures.

Use what you prefer of course. I'm just showing a ready way of identifying appropriate values for the Max volumetric speed setting in PrusaSlicer.

 

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 : 10/06/2020 10:36 pm
sw3De
(@sw3de)
Trusted Member

@ron

I liked those graphs a lot, thanks for sharing and please add more if you have.

Posted : 11/06/2020 4:21 am
ron
 ron
(@ron)
Estimable Member

Next: weight samples @2mm3/s too and consider that the reference sample. Later I will consider the underextrusion rate to those reference samples. 2mm3/s will be considered 100% for each temperature. 2mm3/s is about 25mm/s for the standard 0.2mm layer height profile.

Make an extrusion multiplier calibration @2mm3/s. Here I try to have the perfect extrusion @2mm3/s. I do extrusion multiplier calibration with a 2 perimeter wall. Each perimeter have a spacing of 0.4mm to target 0.8mm wall width. The calculated perimeter width should be then 0.421mm.

After that I will choose what would be the maximum underextrusion rate I accept (3%, 5%,..). That will give me the maximum volumetric speed for a given temperature. For infill I may accept bigger underextrusion than for the perimeters.

I'm still wondering what will be the best way to share my raw data.

In a mean time, I will probably do nGen. After that it depends on what kind of project I will work on.

 

This post was modified 4 months ago 4 times by ron
...
Posted : 11/06/2020 1:39 pm
bobstro
(@bobstro)
Illustrious Member
Posted by: @ron

[...] After that I will choose what would be the maximum underextrusion rate I accept (3%, 5%,..). That will give me the maximum volumetric speed for a given temperature. For infill I may accept bigger underextrusion than for the perimeters.

If I'm understanding you correctly, you intend to use final print weight as a measure of quality. I've seen surface quality and part strength used to gauge print quality, but have never seen Benchys weighed to determine print quality! It's an interesting approach, and use what criteria matter most to you. A few notes based on my experiences:

  • At best, you are measuring an average of the filament diameter and conditions that work best for the test spools. Filament does not remain static over time, absorbing moisture and suffering due to environmental conditions. Individual spools can vary even from the same manufacturer. Consider the impact of storage conditions.
  • The estimates are based on the slicer's expectations. Unless you've very closely calibrated the slicer settings with a specific filament and your specific printer, expect some variation. I'd baseline with a bunch of test prints, confirming that even the same part printed with the same settings from the same spool on the same printer are within your acceptable ranges, particularly over time.
  • If using print weight as a criteria, how critical is it relative to print finish and part strength? Better to have a strong part, good finish and/or an "accurate" weight?

I'm still wondering what will be the best way to share my raw data.

A google sheet allows others to filter and sort easily without a lot of work on your part. Just toss it out there. People will grab it and use it, then argue about it. 🙂 

In a mean time, I will probably do nGen. After that it depends on what kind of project I will work on.

IME, nGen prints very nicely and has essentially the same traits as PETG. It's similar to other co-polyesters such as MatterHackers Ryno. It's very good for getting good tolerances and fidelity. I've been able to print 0.15mm clearance tolerance tests using nGen, whereas with PLA I can only get to 0.2mm routinely. I like it a lot, although it is a bit pricey.

 

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 : 11/06/2020 2:51 pm
ron
 ron
(@ron)
Estimable Member

The new gcodes: VolumetricSpeed-r03

The prime is happening 3mm from the bed making it better to distinguish if we later forget to remove.

  • 6 tones when prime is finished.
  • 1 tone when the extrusion begin
  • 2 tones at the end of each extruded samples

Here the graph for nGen.

I decided to represent graph with underextrusion compared to 2mm3/s (except for PLA which is 3mm3/s because I didn't extrude for the moment samples at 2mm3/s) which is now my speed to calibrate the extrusion multiplier. For the different materials I tested:

We can see that if we want 5% maximum of underextrusion, for PET Prusa, we will go at 7mm3/s maximum @240°C and 4.5mm3/s maximum @220°C.

We may lack a bit of accuracy. Repeatability may be better. But for the time spent I think it is good information. Everyone may do its own test to confirm or infirm those figures.

External parameters that may affect the results:

  • variability of the filament section
  • ambiant temperature
  • filament humidity
  • extrusion wheel tension
  • thermistor accuracy
  • precision scale
  • ...

It is better to do all extrusions in a row.

Here my raw data (I'm sensible to de-Google-ifing):

https://lite.framacalc.org/9h70-7twccci83a

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Posted : 26/06/2020 5:51 pm
ron
 ron
(@ron)
Estimable Member

Here the results for TPU NinjaTek Armadillo. The under-extrusion comes quickly. For 5% maximum under-extrusion @240°C, it is 6mm3/s.

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Posted : 08/07/2020 3:41 am
ron
 ron
(@ron)
Estimable Member

Here the results for PP - FormFutura Centaur PP which is for the moment the more fluid at high extrusion speed. The temperature has not so much impact on the underextrusion.

I had to increase the extrusion length by 50% (750mm per samples) for that material as it is lighter (0.9 density). To get a better accuracy we could have done even more extrusion.

For 5% maximum under-extrusion @240°C, it is 12.5mm3/s.

...
Posted : 23/09/2020 3:21 pm
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