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mrehorst

Cura Settings for Volcano with 0.8 mm nozzle

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I've been struggling with print quality using a newly installed volcano with a 0.8 mm nozzle. The extrusion stops a couple mm before the end of a layer and leaves gaps in the prints. It's as if coasting were turned on and set too long. I tried turning on coasting and setting a negative value, but Cura won't slice when I do that.

How do I get it to extrude right to the end of the line? There is also a small gap that occurs during printing (marked "?") that I'll tackle after I get the bigger problem solved.

end%20of%20layer%20gaps.jpg

I had a similar gap at the start of each layer, after a relatively long travel move. The infill is supposed to start at the perimeter, but there's about a 5 mm long gap between the perimeter and the start of the infill. I solved that by turning on retraction at 0.1 mm, and setting the retraction extra prime amount to 4 mm.

layer%20start%20gap.jpg

I'm wondering if the surface tension of the molten filament is pulling the filament back up into the heater block with this large nozzle. I don't need to use retraction at all, and I have this problem with the plastic not starting exactly when it should, and stopping a little too soon.

I did not see this behavior with a standard v6 heater block and a 0.4 mm nozzle. I did see similar behavior with the standard heater block and a 0.6 mm nozzle.

I'm printing ABS, extruder temp is 270C, printing at a modest 50mm/sec, 150mm/sec travel.

I would appreciate insight from the experts. Thanks!

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I was having this same issue with the 1.2mm volcano nozzle.

 

By configuring the line width to be a bit larger than the nozzle it helps to minimize these gaps.

(im using 1.4mm line width)

 

also, there is a setting in slic3r under retraction settings called "extra length on restart"

I've found that setting retraction length to 0.1 and extra length to 0.5 helps.

 

i suspect that the volumetric pressure settings might help with this as well but i havent tried that yet.

 

i also recommend using at least the 1.3.0 version of slic3r.

 

 

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On 12/9/2017 at 7:44 PM, mrehorst said:

wondering if the surface tension of the molten filament is pulling the filament back

I think this.  I think you are printing too hot - the filament needs to cool very fast as it touches the layer below so it stays in place.

 

When PLA comes out of the nozzle it cools very rapidly (milliseconds) and shrinks and comes out like snot - like mucus.  It sticks to itself very well (not sure if it's surface tension or just likes to stick to itself like snot).

 

So it's like a liquid rubber band.  when you go around those corners it gets pulled inside the part sometimes.  to get it to stay in place like mortar on a brick wall you need to either slow down and/or lower the temp.

 

With a volcano it heats the PLA extra well and you can print much cooler.  What temp are you printing at?  I would lower 10C or 20C down to maybe 190C or even 180C.  You might also have to print slower so the filament has a few milliseconds to cool before the nozzle moves away and starts tugging on the filament.

 

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