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I've noticed on my Ultimaker with an E3D I get an annoying amount of blobing on places where it retracts with Cura. I think its something with Cura, though I haven't been able to calibrate my extruder properly with it, the .5mm wall test doesn't work properly, it does 2 passes with Cura, and it ends up making it double thick, so I'm not sure if its supposed to be around .8mm or (trace widths are .4mm)?

Nylocke wrote:I've noticed on my Ultimaker with an E3D I get an annoying amount of blobing on places where it retracts with Cura. I think its something with Cura, though I haven't been able to calibrate my extruder properly with it, the .5mm wall test doesn't work properly, it does 2 passes with Cura, and it ends up making it double thick, so I'm not sure if its supposed to be around .8mm or (trace widths are .4mm)?

Daid's engine does not do single wall objects very well as it tries to fix thin wall issues as well as build supports for large overhangs. For the .5 wall test to work in Cura, you would have to reset your nozzle size to the .5 desired.

MSURunner wrote:

Nylocke wrote:I've noticed on my Ultimaker with an E3D I get an annoying amount of blobing on places where it retracts with Cura. I think its something with Cura, though I haven't been able to calibrate my extruder properly with it, the .5mm wall test doesn't work properly, it does 2 passes with Cura, and it ends up making it double thick, so I'm not sure if its supposed to be around .8mm or (trace widths are .4mm)?

Daid's engine does not do single wall objects very well as it tries to fix thin wall issues as well as build supports for large overhangs. For the .5 wall test to work in Cura, you would have to reset your nozzle size to the .5 desired.

So even though I have a .4mm nozzle I have to do what?

SHORT ANSWER: Extrusion width in Slic3r = Nozzle size in Cura. Set the nozzle size in Cura to be .5 mm.

The math associated with how the slicer works is that, especially in PLA, the material in must equal the material out (volumeterically). I figure you probably already know this, but it is a foreign concept for some so we'll hit it nonetheless. Characteristics like flow adjustment are there to adjust for that ratio that inevitably comes from the differences in how the filament was extruded from the industrial extruder to the extruder in the 3D printer. With that in mind, a slicer cares not what the nozzle diameter is. If you want x volume of plastic to come out, that's how much will come out. It's a lot like water. If I pour a gallon of water down a sink with a 1" opening verses a drain with a 3" opening, I haven't changed how much water is poured out. The difference, and reason for different nozzle sizes, is two-fold: controlling the size of stream of water as accurately as possible and controlling how quickly that water can escape. The 1" drain will drain more slowly and with a smaller, cleaner stream of water. The opposite is true for the 3" stream. Bringing that back to 3D printing, the smaller a nozzle is, the more controlled and cleanly one can extrude material. It also "drains" more slowly, which when dealing with PLA is known as ooze (again, I'm pretty sure you're on top of this, but just want to be CRYSTAL clear ). As such, with two identical hotends, heated to the same temp, with the same material but with only a difference in nozzle widths, we should see less material oozing out of smaller nozzle. Conversely, when we want to do a large print where there is less concern for accuracy, a larger nozzle allows more material to pass through, thus allowing thicker "controlled" extrusions and faster material delivery (print speeds). Now, to bring this towards what you need to do in Cura: simply change the nozzle size to .5 mm. Daid has tried to make the concept of 3D printing as simple as possible with Cura. The need for nozzle size and extrusion width in two separate variables is non-existent, AFAIC. Daid has apparently agreed since the time of initiating Cura. Cura originated as a cleaner front end of Skeinforge (think Repetier Host using SF and Slic3r). SF has the ability to declare extrusion widths and nozzle sizes, just like Slic3r, AFIK. As many users have noted, when you only declare nozzle size in Slic3r, it does not declare a set extrusion width and can attempt to "clean" things up with wider extrusions in certain areas, sometimes with BAD results. Since the most consistent and reliable extrusion a 3D printer can make is one of the same diameter as the nozzle, Daid uses this as the basis for his extrusion width. Since the material coming out of a .4 and .5 nozzle will be the same to fill a set volume, it won't care that you have a .5 nozzle or a .4 nozzle when the difference is that small. It will ask the extruder for the material to fill a .5 mm void, and assuming that you have sufficient heat in the hotend, it should extrude that much with approximately .05 mm of the "extra" material going around the .4 mm of the nozzle width. It is the desire to remove that "approximately," along with the factors above, that necessitates different nozzle sizes.

Ok wow thats quite interesting, I didnt know Cura did that shortcut, thanks man