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MileHigh3Der
(@milehigh3der)
Estimable Member
General Printer Capabilities Question

On a Prusa, 

-Is there a max volume of filament that will print?  Does it depend the material thermal absorption properties?  12V or 24V hotend? (Talking standard 0.4 nozzle, hotend and extruder).  Like how fast to print 100mm of filament.

-How much pressure can the extruder push the filament before it starts to slip? Assuming a rigid filament like PLA or PETG.  Is the torque of the motor or the grip of the extruder the limiting factor?). Can it be measured in how much force in kgs the filament is pushed with?

-What is the speed limit in x-y (is it different?) for the head to move, irrespective of the filament flow?

Just trying to figure out the theoretical max speed (volume and distance) that the printer could do.

I often hear printing speed, but often not with the layer thickness associated with it.  I was wondering what the printer is capable of doing if the limitations of the filament properties weren't an issue.  Looking specifically at the Mini, but I have a Mk3S also.  I would guess in real life the difference between Bowden and direct drive would make a difference, but assuming the filament is perfect, there shouldn't be a difference between the two, theoretically.

 

THANKS!

Posted : 18/09/2021 2:40 am
fuchsr
(@fuchsr)
Noble Member

You may want to check out Bob's notes on maximum volumetric speed:

https://projects.ttlexceeded.com/3dprinting_techniques_calibrating_volumetric_rate.html

Posted : 18/09/2021 5:01 pm
bobstro
(@bobstro)
Illustrious Member
Printer maximum throughput versus speeds and other considerations
Posted by: @milehigh3der

[...] Is there a max volume of filament that will print?  Does it depend the material thermal absorption properties?  12V or 24V hotend? (Talking standard 0.4 nozzle, hotend and extruder).  Like how fast to print 100mm of filament.

I believe you are referring to what is referred to as the "maximum volumetric speed" (MVS) in PrusaSlicer. This is the maximum volume of filament that the hotend -- the combination of the extruder, hotend, nozzle, and filament -- can melt and move. It is calculated as Layer Height X Extrusion Width X Speed. Depending on specifics, the range is somewhere in the range of 1 to 20mm^3/s. I've got a bunch of notes on this topic here that might be interesting.

-How much pressure can the extruder push the filament before it starts to slip? Assuming a rigid filament like PLA or PETG.  Is the torque of the motor or the grip of the extruder the limiting factor?). Can it be measured in how much force in kgs the filament is pushed with?

The extruder can generate enough torque to literally lift the printer if a suspended spool jams up. Pulling torque is not the limitation. If a jam occurs, the extruder generates sufficient torque to chew through the filament in short order. The real challenge is with flexible filaments, where you're literally pushing a springy noodle of filament a short (thanks to the direct drive extruder setup) length of very flexible material down into the hotend. Getting the extruder tension screws tight, but not too tight is a balancing act.

-What is the speed limit in x-y (is it different?) for the head to move, irrespective of the filament flow?

It is roughly the same on the Prusa Mk3 printer. You can get a bit more ringing in the Y axis thanks to the cartesian "bed slinger" design, but you're more likely to have filament issues at higher speeds. 70-80mm/s is generally not a problem for printing with appropriate filament and temperatures although "speed" is an illusion. To really print faster, you want a larger nozzle with a greater maximum MVS but will print with generally lower linear speeds.

Just trying to figure out the theoretical max speed (volume and distance) that the printer could do.

See the links above. The MVS testing procedure helps determine a "red line" maximum. In practice, you'll want to reduce those by close to 50% for print quality.

I often hear printing speed, but often not with the layer thickness associated with it.  I was wondering what the printer is capable of doing if the limitations of the filament properties weren't an issue. 

The biggest change I found (see above links) was printing PETG at higher temperatures compared to PLA with the same hardware. PETG can be moved at much greater rates provided you're prepared for a reduction in fine finish.

Looking specifically at the Mini, but I have a Mk3S also.  I would guess in real life the difference between Bowden and direct drive would make a difference, but assuming the filament is perfect, there shouldn't be a difference between the two, theoretically.

Theoretically. The Mk3 can handle a wider range of filaments without modification, and of course, has a larger bed that makes printing practical things with those exotic filaments more practical. But for most of what many of us print, the Mini is perfectly adequate.

 

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 : 19/09/2021 2:38 am
BogdanH
(@bogdanh)
Reputable Member

...But for most of what many of us print, the Mini is perfectly adequate.

Fully agree, but... here's my experience:
I only have Mini, which is my first printer. Being new to this, I tried to avoid beginner hassles, so I decided for Prusa. Being much cheaper than MK3S and good enough "for most of what I will print", I decided for Mini. But now I'm in doubt if I made the right decision.

Mini can be good choice for those who already have some bigger printer. But if it's meant to be the only printer, then Mini's print bed is just too small. I mostly print "useful stuff" and most of that fits on Mini's bed. However, it happens too many times, I wish Mini would have few centimeters bigger... MK3S sized bed. And so I'm now considering second printer, even I only need/wish one.

Mini+ with Bondtech upgrade & modified firmware...
Posted : 19/09/2021 8:13 am
MileHigh3Der
(@milehigh3der)
Estimable Member
Topic starter answered:
Thanks for the insights.

Thanks everyone for the insights.  This capabilities is one aspect of some stuff I’m looking at the other side is what on the filament side affects flow and properties.  So many variables!

With the mini, I can skip the extruded and just feed the filament to get an idea of resistance.  My idea is a more analytical approach to what is the best temp to print at for the max speed for a given nozzle size.

When i mentioned ‘head’ speed in the x-y, I was more wondering what is the mechanical speed limit- irrespective of laying down material and quality.

The comment about the force available for pushing the filament is interesting, and the comment about the extruded eating the filament is why I’m looking at driving the filament without an extruder- literally pushing the filament.  I find that extruder set-up (pressure, how clean, drive gears) is too variable - though I know that is the practical limit.

My main focus is the effect of pigment and additive effect on filament print and final properties, but I wanted to know where the edge of printability was and see if I could predict the best speed/temp for a filament based on a few print optimized ‘melt flow index’ data points.

Posted : 19/09/2021 12:29 pm
fuchsr
(@fuchsr)
Noble Member

 I find that extruder set-up (pressure, how clean, drive gears) is too variable

You specifically asked about the Mini so I should point out that as much as i love my Mini, the Mini's stock extruder is, IMHO, suboptimal, very sensitive. Works great with the Bondtech extruder though. 

Posted : 19/09/2021 2:08 pm
cwbullet
(@cwbullet)
Illustrious Member
support

 

Posted by: @fuchsr

 I find that extruder set-up (pressure, how clean, drive gears) is too variable

You specifically asked about the Mini so I should point out that as much as i love my Mini, the Mini's stock extruder is, IMHO, suboptimal, very sensitive. Works great with the Bondtech extruder though. 

That being said.  I strongly recommend you buy a mini or Mk3S and get use to the stock printer before any upgrades.  Upgrades hinder the ability to get support.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 19/09/2021 2:40 pm
bobstro
(@bobstro)
Illustrious Member
When maximums meet reality, expectations pay the price
Posted by: @milehigh3der

Thanks everyone for the insights.  This capabilities is one aspect of some stuff I’m looking at the other side is what on the filament side affects flow and properties.  So many variables!

There are a lot of filament varieties, and often more than one suited for any particular purpose. Definitely experiment. For example, I'd always understood PETG was more impact resistant than PLA, so was surprised when I took some larger (4inch/100mm) prints of each material and whacked them with a hammer. Both shattered into sharp shards. So much for my ideas of printing dog and kid toys! The same filament printed thinly will behave very differently than the same filament print as a solid block. Nothing beats first-hand testing results as you learn.

With the mini, I can skip the extruded and just feed the filament to get an idea of resistance.  My idea is a more analytical approach to what is the best temp to print at for the max speed for a given nozzle size.

That is pretty much what the MVS calibration procedure does. You take the slicer out of the picture and manually feed filament into a given hotend+nozzle combination and increase speeds until you experience failures (feed issues). You can get a higher MVS rate with increased temperature, but you can expect finish issues. You can get a much higher MVS rate with larger filaments, but details suffer. That upper limit is NOT your practical limit for quality prints.

When i mentioned ‘head’ speed in the x-y, I was more wondering what is the mechanical speed limit- irrespective of laying down material and quality.

I believe 200mm/s is the advertised maximum XY speed for the Prusa i3 Mk3. The printer gets very noisy if you try to push much past that and there's little benefit print-wise. I'm comfortable with 120-180mm/s move speeds. At higher speeds, the Y-axis weight will come into play. Hopefully, the bulk of your print time will be spent actually extruding filament, so move speeds shouldn't make a huge difference. Even on long moves, acceleration and jerk need to be taken into account. I recall 60mm/s being cited as the minimum distance to get up to full speed, so 120mm if you take deceleration into account. You're up to nearly half the Mk3 print bed before you hit anything near the maximum possible speeds. Many small or mid-sized prints are generated speeds far below the settings.

The comment about the force available for pushing the filament is interesting, and the comment about the extruded eating the filament is why I’m looking at driving the filament without an extruder- literally pushing the filament.  I find that extruder set-up (pressure, how clean, drive gears) is too variable - though I know that is the practical limit.

You can push the filament manually or by other means, but I assume you want to eventually feed equivalent settings into your slicer, no? That's why I go with manually entered gcode commands. I suppose a syringe/turkey baster filled with molten filament could work. InkJet 3D printer anyone?

My main focus is the effect of pigment and additive effect on filament print and final properties, but I wanted to know where the edge of printability was and see if I could predict the best speed/temp for a filament based on a few print optimized ‘melt flow index’ data points.

I liken the current state of hobbyist 3D printing to more like cooking than engineering. There's a lot of "flavor" that you master through experience, and it doesn't all translate well into hard black & white data that will work in every circumstance. At best, I've got a general set of parameters that I work within, but the ultimate variable is the print itself. What works for detailed miniatures will have little applicability to large functional prints. Your choice of test prints is going to bias your results, I'd think.

I just realized I didn't answer a couple of your original questions:

12V or 24V hotend?

The current Prusas are all 24V. It will be interesting to see if they move to an AC heated bed with the upcoming Max as even 24V only heats a large surface slowly.

(Talking standard 0.4 nozzle, hotend and extruder).  Like how fast to print 100mm of filament.

It's a 3D process, so my usual answer is "roughly 11.5mm^3/s". Meaning that the question can't be answered without also specifying extrusion width and layer height. Using general guidelines of 80% of nozzle size for layer height (0.32mm) and 120% of nozzle size as extrusion width (0.48mm), you can print at just under 75mm/s without exceeding 11.5mm^3/s. Use lower heights or widths and you can reliably print faster. Drop to a typical 0.20mm layer height and speeds can go up to just under 120mm/s reliably. YMMV with filament type, temperatures, print characteristics and other considerations. I've put together a spreadsheet to easily play around with these values that you're welcome to check out for examples.

 

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 : 19/09/2021 4:34 pm
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