Retraction Extra Prime Amount November 22, 2018 12:16PM Registered: 7 years ago Posts: 558
I've run across something on another forum concerning Retraction Extra Prime Amount. From what I've noticed, the Volcano 0.6 nozzle needs Extra Prime Amount after a retraction and was having some trouble figuring out what value should be used in Cura. Since I ran across this section of the Ultimaker forum, I figured I'd share my findings as other people might be interested or be a way to archive it for a later time.

To calculate the Extra Prime Amount after retraction necessary:

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

As for my testing with the Volcano 0.6, it appears the magic number is between 2.5mm and 5mm, with 5mm being way too much. At least this way I have some notion of how to apply this value against the nozzle size and extra prime amounts.
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