Not understanding Max Volumetric Speed
 

Not understanding Max Volumetric Speed  

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paul.c42
(@paul-c42)
Active Member

I tend to use Simplify3D and am trying to wean myself off it and on to PrusaSlicer, but I keep having failures with it, so keep running back to S3D.

Here is my latest issue:

I have a simple model that prints in TPU without issue on S3D, even with a decent amount of retraction, which seems to be frowned on when using TPU.

I decided to slice this very same model in PrucaSlicer and it jams when printing every time.  I reload the the S3D model with no adjustments to tension or temperatures and normal service is resumed.

On the PrusaSlicer I use the Generic Flex as a base and don't bother playing with the speeds as the way I understand it the Max Volumetric Speed value (MVS) will cap them at safe values.  Is that not right?

Even if it is, I do not understand the attached dialogue.  The way I am reading this is that even though the MVS is a very safe 1.2mm3/s it will still be set to a staggering 16.28mm3/s when printing infill and other rates that exceed the MVS set for perimeters and bridging.

This may well explain me jamming issues, but I feel that I must me misinterpreting what is being suggested by this text.

Would someone explain how this actually works please?

Thank you.

Posted : 14/08/2020 10:47 pm
3Delight
(@3delight)
Moderator Moderator
paul.c42
(@paul-c42)
Active Member

Thank you for the links.  I'd had found and read all three of those, but they didn't seem to cover my question.

Hoping one of the authors of those posts may be along soon.

Cheers.

Posted : 15/08/2020 6:59 pm
3Delight
(@3delight)
Moderator Moderator

Sorry they didn't help, fingers crossed for you!

Posted : 15/08/2020 7:01 pm
3Delight
(@3delight)
Moderator Moderator

One of those articles: http://projects.ttlexceeded.com/3dprinting_prusaslicer_max_volumetric_speed.html

Was written by a user on here " bobstro": https://forum.prusaprinters.org/forum/profile/bobstro /

Why not send him a message and see if he can help you out.  He seems a very helpful chap.

Posted : 15/08/2020 7:11 pm
paul.c42
(@paul-c42)
Active Member

@3delight

I did notice bobstro had some activity here, but wasn't sure of the etiquette on PMing folks.  I'll reach out to him and see how I get on.

Cheers

Posted : 15/08/2020 7:41 pm
3Delight
(@3delight)
Moderator Moderator

Most people don't mind as long as your polite. I hope he's able to help you. 👍 

Posted : 15/08/2020 7:51 pm
malcmcm
(@malcmcm)
Trusted Member

Sorry I can't help you with volumetric flow but there is a popular profile for flex that people seem to have success with: https://www.prusaprinters.org/prints/12586-ninjaflex-profile-zero-stringing-flawless-print-be

 

Looking at the profile the changes are mostly with the retraction speed and length (actually has a large length of 5mm) and also slows all the speeds way down to 15mm/s but there is a massive change made to the E jerk limit found in machine limits, down to 1.5mm/s. That seems to be the change made to help combat extruder jams. Maybe try messing around what that variable or try the profile

Posted : 16/08/2020 4:36 am
bobstro
(@bobstro)
Illustrious Member
Posted by: @paul-c42

[...] On the PrusaSlicer I use the Generic Flex as a base and don't bother playing with the speeds as the way I understand it the Max Volumetric Speed value (MVS) will cap them at safe values.  Is that not right?

The slicer will use the most restrictive of calculated MVS based on Extrusion Width X Layer Height X Speed or the MVS setting in the Filament Settings profile or the MVS setting in the Print Settings profile. You should be able to view the speeds used in preview mode in PrusaSlicer after slicing and see this effect.

Even if it is, I do not understand the attached dialogue.  The way I am reading this is that even though the MVS is a very safe 1.2mm3/s it will still be set to a staggering 16.28mm3/s when printing infill and other rates that exceed the MVS set for perimeters and bridging.

I see that in your screen capture. Can you save your part & settings in a 3MF project file, zip it and upload it here? MVS should cap all feature speeds, so I'm not sure why you're seeing that jump for infill.

Edit: I see what you mean about the tool tip message under Max volumetric speed in Filament Settings. Those speeds seem very high. After slicing, I verified my print speeds and actual volumetric rates, and everything was capped at my restricted MVS value. I'm not sure what the text is trying to suggest... so I've ignored it.

This post was modified 2 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 : 16/08/2020 7:03 pm
paul.c42
(@paul-c42)
Active Member
Posted by: @malcmcm

Sorry I can't help you with volumetric flow but there is a popular profile for flex that people seem to have success with: https://www.prusaprinters.org/prints/12586-ninjaflex-profile-zero-stringing-flawless-print-be

That is great link, thank you.  The info in the E jerk setting is particularly interesting, as I the effects of that would not be noticeable when simply viewing the speeds or volumetric flow rates on the sliced model display.

This could explain the jamming, even with the speeds and flow rates seeming so reasonable.

I'll be giving that a play.

Cheers

Posted : 16/08/2020 7:31 pm
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