Retraction Extra Prime Amount - Suggested Values?

[DaHai8 74]

I'm getting holes in my prints where the print head is landing after a significant travel ( > ~40mm).

I'm pretty sure this is due to oozing after a long travel, along with Combing All enabled.

What would a good starting value for "Retraction Extra Prime Amount" be for a .4mm nozzle printing PLA?

P.S. Retraction Amount is 6mm and Speed is 60mm/s

Thanks!

Edited October 9, 2016 by Guest

[DaHai8 74]

Ok, let me put his this way:

Should I be trying values >1 mm3 or <1 mm3 ??

More than 1 cubic mm seems like a lot, yet less than 1 cubic mm seems really small. So I'm just looking for an idea where to begin with this setting and progress from there.

Thanks!

[DaHai8 74]

Many Days...

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And Hundreds of Prints...

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Thousands of Hours...

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Millions of Meters of Filament....

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I have my answers...(Drum Roll, Please....)

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Less than 1 !!!!

Thank you, thank you. Yes, I know I'm "Brilliant!!"

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Actually, I found a value equal to the cube of the nozzle size in mm works well.

In my case, .064 mm3

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Of course, I could just be fooling myself and .064 ~ .000

Who knows....(only the Shadow)

Edited October 15, 2016 by Guest

[conny_g 251]

A bit late to this thread, but I am just having the opposite issue:

Every time the nozzle retracted and starts at some other position I get a small blob there. Especially bad with small areas where there just needs to be 1-2mm of area extruded.

I used this setting to reduce this blob and I used -0.25mm^3, it seems to help.

0.25 is slightly more than the cube of nozzle diameter. 0.4 x 0.4 = 0.16.

[DaHai8 74]

There are three possibilities: one, some, or all may apply:

 

1. You're not retracting enough. Usually more than 2mm and less than 3mm is enough, but your mileage may vary.
   
2. You're traveling too slowly. As the head move from point A to point B, some filament will just naturally ooze out (its hot a gooey afterall). The quicker you get between point (travel speed), the less chance there is it will escape. But at really far distances, it may be unavoidable
   
3. You're printing too hot. The filament needs to be very soft to print and lamenate to the previous layer, but if its running like water (or hot honey), no amount of retraction or travel speed will be able to stop it.
   

 

This site helped me a lot in dialing in my retraction amount, travel speed and hot-end temperatures:

Retraction: Just say "No" to oozing

[FormFaktor 0]

There are three possibilities: one, some, or all may apply:

 

1. You're not retracting enough. Usually more than 2mm and less than 3mm is enough, but your mileage may vary.

2. You're traveling too slowly. As the head move from point A to point B, some filament will just naturally ooze out (its hot a gooey afterall). The quicker you get between point (travel speed), the less chance there is it will escape. But at really far distances, it may be unavoidable

3. You're printing too hot. The filament needs to be very soft to print and lamenate to the previous layer, but if its running like water (or hot honey), no amount of retraction or travel speed will be able to stop it.

 

This site helped me a lot in dialing in my retraction amount, travel speed and hot-end temperatures:

Retraction: Just say "No" to oozing

 

1. Well, as I've read and tested in printers using bowden to guide filament from extruder to printcore 4mm of retraction is a point when retraction starts to happen. This happens due to a tension in bowden tube, and retraction of 4mm just lower the tension. In UM machines retraction should have greater values.

2. I agree that travel move should be fast enough to break oozing material, but in some cases printers use Z-Hop, and travel happens after leaving a blob. If You guys use it, try to turn it off.

3. I agree as well, good way to set up temperature is to print an object few times while lowering temperature each time about 5 degrees. When underextrusion happens its to cold and you should slowly rise temp. Just when prints start looking good its the correct value (more or less)

Cheers

[yellowshark 153]

I use 5.5mm and 6.5mm.

[Psyonic 1]

bbbbbrrrrrrrrrrrrrrrmmmmmmmmmmmmmmmmmm

 

(that's my drum roll, and that's all I have to offer... sorry!)

[TheMystery 0]

To do it more mathematically:

*Math mode on*

For a nozzle size of 0.4 mm you need to calculate the area of the nozzle:

(Pi*d²)/4 = (3.141*0.4²)/4 = 0.126 mm²

After that you need to decide (or test) which amount of material is need to compensate the under-extrusion at the beginning. Therefore you have to multiply the length of extra prime.

So for DaHai8s 0.064 mm³ it means that you have an extra amount of approx. 0.5 mm

*Math mode off*

 

Hope that helps everyone who is finding this thread, like I do ;-)

*waiting for applause*

[vinnier 0]

clap clap clap clap 

[Night_Gryphon 0]

Can CURA be enhanced to do this calculations by itself like Simplify3D do? Where to ask this? Same thing for coasting settings...

[kulfuerst 6]

Shouldn't the extra prime amount roughly be equal to the coasting volume? To normalize the pressure again.

[Adam324 13]

I think so.  But that changes depending on how far (or how much time more specifically) is taken before it starts again.  If it only travels 10mm, there won't be much oozing.  If it were traveling 200mm, there would be a lot lost.

I used the scalable extra prime plugin in Cura which allows a variable amount depending on distance.  You set a minimum travel and and a maximum travel, and a then give it a length for the maximum distance.  It then scales that maximum length from the minimum and maximum travel.  It works well but I don't see it in the 4.0 beta and don't recall it in later 3.x versions either.

 

It would be great if you could give some kind of ooze number and then cura calculates all of it based on that one number.

 

Right now with newer Curas, you have to use a static amount with Retraction Extra Prime which is only optimal around one travel distance.  I hope the plugin author of scalable extra prime gets his plugins in Cura again.

Edited March 16, 2019 by Adam324

[burtoogle 513]

Very odd, I don't use extra prime at all and I don't get oozing and underextrusion following long travel moves.

 

Try using combing mode no skin and set max comb distance with no retract to something like 10.

[Adam324 13]

I am relatively new to 3d printing (only a year) so I don't claim to be an expert.  That is only what I have observed with my Duplicator 9.  I tested all of it with a print that does 4 - ~30mm cubes (whole thing only 1 layer thick) at each corner of the bed and with a line that goes along the outside edge of the bed connecting them and an X pattern connecting them to a 40mm cube in the center.  I would get some of the outside lines not connecting because it would start printing but nothing would come out until about 10mm or so.  Shorte travels around 30mm or so was fine.  I had to tweak the scalable extra prime to get the lines all connected.  Cura was doing long travels quite a few times.  I am trying to find that STL that I used.

EDIT: Thanks btw...I will check those settings and try them.

Edited March 16, 2019 by Adam324

[Adam324 13]

I probably shouldn't have posted this as I need to retest all of this again anyway.  I don't recall this being as big of an issue lately since going to newer versions.  I thought the scalable-extra prime was still working but I found out the plugin hasn't been installed when I looked earlier today after reading this thread.  Going to back to other versions showed that it wasn't installed there either.  Maybe I was having temp issues or something when I discovered this before.