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DaHai8

Retraction Extra Prime Amount - Suggested Values?

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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 by Guest

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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 by Guest
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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.

  • Thanks 1

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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

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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

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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*

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