Slic3r Retractions

Hi

Can someone tell me why only between certain extrusion moves Slic3r does a retraction of material? I have been studying some of the G-Code but cannot seem to find a reason behind some of the "between extrusion" moves retracting before the "non-extrusion move".

Any thoughts?

Cheers

Adrian

Whether or not retraction occurs at a specific point is based on 1) the distance to be moved after retraction, and 2) whether or not you are crossing a perimeter. Both of these (along with several other parameters) can be set within slic3r's configuration. A good explanation of this can be found here.

Thanks a million

That explains it perfectly.

Do you think it is wisest to retract between all extrusion moves just to be sure?

Well, wise would be to retract only when needed
And the need depend on many things, but the main question is the same: do you mind if a bit of plastic will be out of the nozzle when it should not be, followed by a bit less plastic coming out when it should be at full extrusion?
It is also to bear in mind that retraction does not behave like an ideal mechanism. In practice it introduces some other effects that may generate issues.
The above are pretty generic, but imho is worthy thinking rather than applying a rule of thumb

I retract on any move over 2mm. And I have the "Only retract when crossing perimeters" unchecked. Retraction shouldn't cause issues because the slicer reverses the retraction when it reaches its destination. The slicer settings let you add a bit of extra filament to this reversal in case you are still experiencing oozing, but that is where you can have issues. Guessing at the amount to add back to offset any unexpected oozing is just asking for trouble.

The thing to remember is that retraction does not eliminate oozing. It just reduces the pressure a bit so that there is hopefully no oozing before you reach the move destination. It's just buying you some time. If your moves take too long, you might still experience some ooze, but in my experience, this is not an issue.

That's great

Thanks for the advice!

Adrian