Splodgy printing with secondary nozzle

@hogster The small triangle is too small to be printed. The heat from the nozzle is melting the plastic and pushing it around. 

You have several choices: 

1. Print multiple parts so the small feature has time to cool

2. Change the material to something with a higher melting point

3. Change the design to give the white more time to cool

4. Make the white part larger

I suspect you will need at least two of the four and maybe all of them in order to get a good result.

Good advice from Ben. Also could be that the white filament is being overheated by the black filament.

http://cel-robox.com/materials

Eg The orange part of the materials matrix shows ABS and PLA are likely to have issues in combination.

Many thanks for the advice Ben, Pete!

I must admit I’m puzzled why the white is so much worse than the black, given how sharp and precise the black is … both are NGEN and both print fine on their own (unless I accidentally picked up some white PLA which is the only other type of filament material I have in my workshop — that might explain it if the melting point of the white was far lower than that of the black).

If that triangle were printed as part of the rest of the black part I imagine it would print perfectly — how come there is a difference when switching nozzle, assuming the same material was in both?

Many thanks for your help 😀

David 

@hogster Without seeing the models and setup it's really hard to offer additional advice. If you want to post screenshots of the setup in AutoMaker and maybe also your models I can look in more detail.

Ok thanks Ben, will try to find a moment to do some further investigation 😊 Thanks again, David

I think this is probably why I was surprised with the poor printing, as I’d made this item before where the secondary colour printing happened at a similar part in the print (right at the end), and here it worked perfectly … albeit it was black on white not white on black.

Judging by your recommendations above, this print shouldn’t have worked so well?

Thanks for your thoughts!

David 😀

A close-up view:

@hogster I would expect the part in the photos to work well because there is time for the black to cool between layers, when the print head is printing the rest of the white part that extends "above" the lettering. The print head and nozzle being away from the letters lets them cool and prevents the issue you had with the white on black print. With the white on black print the nozzle stays close to the white part the whole time and it doesn't get time to cool and stabilize, so it just gets mushed up. Same thing will happen if you print a single cone. The tip will not print well because the nozzle doesn't move away from the print long enough to cool between layers.

Ah I see that makes sense. So you think that small detail would have also ended up mushy if the whole part had been in black?

Thanks again 🙂

David

@hogster Yes, if the whole part would have been the same color the result would have been the same.

In my opinion, if you are using PLA and Ngen then I think its the difference between temps, IF PLA sits in a print head for a long time at temperature it becomes very runny so you are printing the model then when you go to print the letters in white this material has been at temperature for a long time then just comes running out. when you have printed the other way around the black ngen is much more stable when left at temperature and so is more controlled when it is finally used.

Thanks Ben 😊 

Lee - I haven’t used PLA for many years now, both nozzles have had NGEN in them all that time.

Many thanks,

David