Ironing Temps - PLA Crystallization In The Nozzle???

[inventabuild 5]

A few questions about ironing to make sure I'm not harming my nozzle:

 

1. If the Ironing feature in Cura is used to iron a large surface for a long period of time while the nozzle is held at printing temps, for example 1/2 hour or longer at 220C, is there a risk that the PLA will start to crystallize in the nozzle and affect its future performance?

 

2. Is the default ironing extrusion multiplier of 10% meant to help prevent PLA from crystallizing in the nozzle or to help smooth out the surface or both?

 

3. Would it be better to retract the filament out of the hot end while ironing to minimize the possibility of the PLA crystallizing in the hot end?

 

Thank you.

[nallath 1,065]

17 hours ago, inventabuild said:

If the Ironing feature in Cura is used to iron a large surface for a long period of time while the nozzle is held at printing temps, for example 1/2 hour or longer at 220C, is there a risk that the PLA will start to crystallize in the nozzle and affect its future performance?

I think you might have some terms mixed up. PLA crystalizes as it cools down. As long as it's hot, no crystaline structures will form. What can happen is that PLA that remains above a certain temp too long stards to degrade (and form a black nasty layer). I've not really seen this happen and if it does, it's really easy to remove when the nozzle is hot.
 

 

17 hours ago, inventabuild said:

Is the default ironing extrusion multiplier of 10% meant to help prevent PLA from crystallizing in the nozzle or to help smooth out the surface or both?

Mostly to fill it up. Keeping up the flow (especially on larger areas) also ensure that the pla inside the nozzle doesn't stay there too long. This could cause clogs (which doesn't damage the nozzle, but it does mess up your print)

 

17 hours ago, inventabuild said:

Would it be better to retract the filament out of the hot end while ironing to minimize the possibility of the PLA crystallizing in the hot end?

Not really. You also want that tiny bit of extra material when ironing.