Does your printer sometimes get a certain distance up a print and it fails like this?

Or it prints but it looks like this? I'm about to show you why this normally happens,

and how to fix it.

As always with 3d printing issues there's multiple reasons why you might get a single

symptom - in fact I have an upcoming video on how important a proper diagnostic process

is when it comes to 3d printing issues.

But this particular issue is such a telltale sign of a single common problem that I thought

it's worth sharing as its own special video.

What normally happens is that the first few layers or so will print perfectly, then a

couple of centimeters up, or maybe more, trouble starts.

This, in case you didn't know, is underextrusion. Too little material coming out of the nozzle.

It's officially caused by a blocked nozzle but when it happens like this, BUT it's just

the symptom you see, part of a chain of events is happening that leads to the blocked nozzle.

I'm not here to waste your time so Here's why. Stay watching though if you can, to see

some cool demonstrations of what's going on.

Usually what's going on here is that you're printing on the fast side, you might not be

but either way you will have a fair bit of filament flowing out of the nozzle.

This of course is removing the thermal energy from the nozzle.

Down low, you are getting thermal energy from the heated bed so you get away with it,

But the further you get away from the heated bed, the less that extra heat is helping,

So eventually, you reach a tipping po int - where the temperature of the PLA in the

hotend is dipping down just too much...and you're in partial blockage territory.

And it might even resolve itself and carry on, maybe spontaneously or maybe when it gets

to a different shaped layer. Some really weird things can happen when you're just on the

boundary of a blocked nozzle

You might or might not get clicking from the extruder, it depends on the extent and length

of the blockage and also how good a grip your extruder has on the filament. My mini deltas

rarely click when underextruding, but the noise is the first sign of a problem on the

ender 3 v2, but it does depend on the filament too.

Through the magic of colour changing PLA I can show you how far the heat propagates up

from the bed, this bed is at 50C.

Looking at the part under the microscope you can see that there's really almost no layer

to layer adhesion at all, this is fairly disastrous in terms of part strength especially if you

were printing vase mode where it's likely the piece will just fall apart.

So as you might have gathered by now the solution is pretty simple once you have identified

the cause. I actually suggest making special profiles

for fast printing, set the temperature to 5 or 10 degrees hotter than usual when you're

in a draft or fast mode. Do this in cura by just changing print temperature

and saving a profile, in prusaslicer you have to have a separate filament profile but it's

essentially the same, just another thing to remember to set when you change profile

Bear in mind also that in my experience as PLA ages and is left out, it seems like it

needs to be printed at a higher temperature. So a reel that might have printed fine at

200C a month ago might now need 210C.

And of course you can be printing so low that you have these recognisable signs even from

the start of the print. If you want to know what temperature I use

for PLA, I used to print at 195C, but I now recommend printing at a minimum of 200C, and

for printing fast, for example 60mm/s on a larger part, I recommend around 215C.

Well - I hope that helps a bit to avoid this particularly frustrating print ruining phenomenon.

If you found this useful I have way more of this kind of stuff, it's kind of what I do,

so please subscribe. Otherwise, thank you for watching!