Advice for Volcano 1.2 mm nozzle

[paboman]

hi,
I am trying to create a base profile for printing PLA with my new volcano setup and 1.2mm nozzle.
In vase mode it print beautifully 220°C at 40mm/s but the problem begins when retraction are involved.

No matter what I set in the retraction box the new perimeter start extruding too late leaving a gap.

Ho do I tell S3D to unretract more than the retraction value?
Lets say i have a retraction of 2mm and want to unretract 3mm before the beginning of the new perimeter
thx!

[dkightley]

The setting you need is Extra restart distance.

[paboman]

thank you for reply.
I have tried negative and non negative value but its just not un retracting

Now I have tried with Extrusion distance set to 1 and Extra restart distance set to 10 but it only perform the 1mm of retraction

[dkightley]

Lifted from the "Tip of the DAY" thread on extruder settings:

Retraction Distance: How much filament will be retracted when the software does a retract. For standard Direct Drive, usually .5 to 2.5 mm will work well. For Bowden extruders, 5 to 8.5 mm seems to work well.

Extra Restart Distance: When the software does a prime (after retracting), it will prime the same amount as retracted. However, you can modify this by placing an Extra Restart Distance, if you notice that your prints have minor blobs at the starting points, you may find that placing a small negative Extra Restart Distance can help, such as -.2 mm.

I think you're a bit off on your values.

[paboman]

That settings was only an example, it allowed me to catch the extruder not turning.
In the end was the acceleration of the extruder set too high.

Now i have hard time figuring out what the value of should be of extra restart distance.
My retraction is 2mm which seems to be ok, if I unretract 2mm then it create a blob at the start point while less unretraction will leave a void in the start of the layer.

Has anyone experience with big nozzle not printing in vase mode ?

[WhiteHare]

If you're too close to the volumetric extrusion limit, you might have problems. Try reducing your speed by 10% and see what happens. I have a volcano with a 0.8mm nozzle, and I print at 91% of the theoretical speed limit for volumetric extrusion without problem. I haven't tried a 1.2mm nozzle, but I presume the principle is the same.

[jgwinner]

Pardon me for jumping on, but I was intrigued by:

I have a volcano with a 0.8mm nozzle, and I print at 91% of the theoretical speed limit for volumetric extrusion without problem.

How do you calculate that? What settings did you change (I realize this could be printer specific) to use the .8mm nozzle?

Thank you,

== John ==