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So in matter control I'm trying to figure out how it knows the size of your nozzle? I have a .25,.5,.75and a stainless .25. What applications are best for those sizes?

MC doesn't know. You have to tell it in the settings.

Nozzles in the .4-.5mm range are generally considered good general-purpose nozzles. Smaller nozzles are used for parts with critical intricate details such as sharp corners or extremely thin walls. Larger ones are used to enable wider extrusion and taller layers for faster (but lower-quality) prints. Stainless is used to reduce contamination of the printed object or reduce nozzle wear when using abrasive filaments.

Do you know where in the settings? Thanks for all the other info?

Settings, printer, extruder, nozzle diameter. you may also have to go to filament, extrusion, extrusion width to adjust the support and first layer widths for good results.

is there a downside to using hardened/stainless nozzles on regular pla/abs?

Qdeathstar wrote:is there a downside to using hardened/stainless nozzles on regular pla/abs?

Just cost.
Technically they don't conduct heat as well as the Brass Nozzles, but I very much doubt that makes any measurable difference.
Be warned though, small nozzles can be very frustrating to print with especially if you don't have printing experience.

Polygonhell wrote:

Qdeathstar wrote:is there a downside to using hardened/stainless nozzles on regular pla/abs?

Just cost.
Technically they don't conduct heat as well as the Brass Nozzles, but I very much doubt that makes any measurable difference.
Be warned though, small nozzles can be very frustrating to print with especially if you don't have printing experience.

I've noticed it makes my prints want ~3C more heat for the same print speed, but beyond that, no real issues. I use a hardened steel .4 all the time, rather than deal with brass.

If I must be honest, .4mm for everything. I've a .25 and a .35 practically new. The need much slower speeds and very few times found need to use them.
HS nozzles... never tried them, I might buy a .4 one of these days. I think that over time, the tip of the brass one widens a bit. It happened with my first E3D hotend after using it constantly for more than 2 years. Never printed carbon filled filament or any abrasive filament though.
So, thanks for the tips, I was reluctant to buy a HS nozzle.

One day i'll try a .25 nozzle, but right now im switching from the stock hot end to the v6 w/ a hardened nozzle... Knowing what i know now, i probably would have gotten a prometheus, but i already got the V6... I do plan to some some iron fill/copper fill print

But, honestly, i find the activity of changing nozzles to be rather tedious. I think that the accerlation probe, if it works as advertized might make that easier.