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Purging Volume Clarification Needed  

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Asraff Amzani
(@asraff-amzani)
Estimable Member
Purging Volume Clarification Needed

Hi, I've been wondering about the purging volume for example in the handbook page 20 https://www.prusa3d.com/downloads/manual/prusa3d_manual_mmu2_eng_1_01.pdf the table for purging each colour chart, I am confused for the "unloaded" and "loaded" part for example in the table of black it is 100 and 60, does that mean that, when preparing to change filament, the printer will extrude 100mm of black before changing to the next filament?

Does this mean
1. "unloaded" is how much to purge before changing to the next filament?
2. "loaded" is how much to purge after that filament has been switched?

P.S
This is a repost at the correct topic section

Posted : 19/11/2018 8:39 am
PJR
 PJR
(@pjr)
Antient Member Moderator
Re: Purging Volume Clarification Needed

No, not quite. Both figures are used to calculate the purge after a tool change.

If you have 2 filaments, say Black and White, when changing from black to white, you will need high purge values on both, but when changing from white to black, you need both low purge values., so (as an example), black should be 80/30 and white should be 20/70. so this would purge 150 (80 + 70) when changing from Black to White and only 50 (20 + 30) when changing from White to Black.

Hope this helps.

Peter

Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…

Posted : 19/11/2018 3:33 pm
Peter L
(@peter-l)
Honorable Member
Re: Purging Volume Clarification Needed

For what it's worth, I always use the "advanced" settings. It looks more intimidating but it gives a lot more control, and there's a lot of situations where the simplistic "purge out + purge in" model doesn't really cut it.

I also just find it easier to think in terms of "When changing from A to B, purge X".

Posted : 21/11/2018 4:09 pm
Asraff Amzani
(@asraff-amzani)
Estimable Member
Topic starter answered:
Re: Purging Volume Clarification Needed


No, not quite. Both figures are used to calculate the purge after a tool change.

If you have 2 filaments, say Black and White, when changing from black to white, you will need high purge values on both, but when changing from white to black, you need both low purge values., so (as an example), black should be 80/30 and white should be 20/70. so this would purge 150 (80 + 70) when changing from Black to White and only 50 (20 + 30) when changing from White to Black.

Hope this helps.

Peter

I am still confused on the unload/load figures during the filament swapping. Lets say black was 80/30 on e1, white is 20/70 at e2, when transitioning to e1 from e2, would it be using e1 values?


For what it's worth, I always use the "advanced" settings. It looks more intimidating but it gives a lot more control, and there's a lot of situations where the simplistic "purge out + purge in" model doesn't really cut it.

I also just find it easier to think in terms of "When changing from A to B, purge X".

This i strongly agree as well, I tried to print cleo the kitten between black at e1 and gold at e2. My setting was (under advanced purging volume)

e1>e2 160 (gold)
e1>e3 160 (This is white)
e2>e1 60
e3>e1 60
Rest are 140

From what I understand, those values are somewhat identical to the simplified unload/load length = total advanced purge value. I noticed that, on the gold printed parts, the colour are still darker because of the black colour bleeds into the gold. 1 multi colour cleo with wipe into infill, another cleo as sacrifice.

Also, I'm not fond of mm^3, is it the normal mm length?

The purging information, should have better explanation in the handbook and inside slic3rpe instead of explaining; unload/load needs x/x length to purge which is confusing.

Posted : 21/11/2018 5:26 pm
Peter L
(@peter-l)
Honorable Member
Re: Purging Volume Clarification Needed



Also, I'm not fond of mm^3, is it the normal mm length?

I'm with you on that. Cubic millimeters is an unconventional choice, since almost nothing else in 3D printing is measured by the volume of plastic. I can understand the technical reasons for the choice, but it would have been better to use linear mm extruded.

That said, at the end of the day it's just a number. There's roughly 2.4 mm^3 per linear mm (using 1.75mm filament), and one mm^3 is very approximately one microgram of material, depending on exactly which material you're using. So purging 100mm^3 is approximately 40mm of filament and 0.1g of plastic.

Posted : 21/11/2018 5:42 pm
Asraff Amzani
(@asraff-amzani)
Estimable Member
Topic starter answered:
Re: Purging Volume Clarification Needed




Also, I'm not fond of mm^3, is it the normal mm length?

I'm with you on that. Cubic millimeters is an unconventional choice, since almost nothing else in 3D printing is measured by the volume of plastic. I can understand the technical reasons for the choice, but it would have been better to use linear mm extruded.

That said, at the end of the day it's just a number. There's roughly 2.4 mm^3 per linear mm (using 1.75mm filament), and one mm^3 is very approximately one microgram of material, depending on exactly which material you're using. So purging 100mm^3 is approximately 40mm of filament and 0.1g of plastic.

For my colour bleeds, can check the picture here https://shop.prusa3d.com/forum/how-do-i-print-this-printing-help--f55/missing-layers-t26015.html

Is there any open issues on github right now regarding cubic mm should be linear mm/length mm instead in the github?

How do I calculate that linear mm when you said 100mm3 =~40mm of filament length?

Posted : 21/11/2018 6:06 pm
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