3D printing doesn’t always work perfectly.
I hate to say it, but, you know, when even
commodity inkjet printers still need a bit
of help every now and then, I think 3D printers
are actually pretty good on that front today.
But, still, there are things that can go wrong
due to user error, the manufacturer not doing
their homework or because of bad materials.
We’re going to look at some of the most
common hiccups you can run into and where
to start when fixing them.
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I gotta tell you, it’s one thing when you’re
trying to get a printer to work better, but
trying to get it to produce sub-par prints
with just the right issues so that I can show
you what they look like… well, that’s
one that only some people will enjoy doing.
I’m sorry Mini that I had to do this to
you.
But before we start going through what bad
prints look like, I think we should start
with what an actual good print looks like,
because I pretty often see people asking about
how they can fix things they think are wrong
with their setup, but are actually just inherent
properties of the filament printing process.
And by the way, you can actually hide or emphasize
these just by changing the lighting and the
angle you photograph your parts from.
One of the things you might see that are actually
normal are a bit of texture on the layers,
again if photographed from the right angle,
small detail isn’t always going to print
well, especially when a part ends up in a
pointy spot where the nozzle doesn’t have
a chance to move away and give that area a
chance to cool, the underside of parts might
have a few loose loops where the geometry
just wasn’t all that great and you will
always see the layer start point, you can
hide them on the model, but there will always
be at least a little dot visible.
There might also be a bit of ringing visible
on edges and some gaps in top layers, but
you know, with the current tech we have, some
things are just not worth optimizing away
because you’re going to have to make some
big compromises to get rid of that one artifact
that you may end up introducing other issues
in the process.
And the fact that these prints aren’t perfect
is one of the reasons why for example glittery
filament has become so popular.
It distracts your eye.
Since we’re usually printing at layer heights
of 150µ or so, the layers themselves often
visually disappear, that’s why prints done
with big nozzles and at large layer heights,
like with the Volcano, tend to look more appealing
or more consistent than ones where you try
to get everything perfect, but you can never
quite make it and anything that is still wrong
then sticks out like a sore thumb.
Anyway, that’s just to say, 3D prints, especially
with filament printers, are never perfect,
it’s often just an art of hiding the flaws
that are still there well enough so that you
stop noticing them.
But there are still a few “real” issues
that can be fixed and need addressing.
I’ll go over what they look like and where
to start looking for fixes for them, and I’ll
have guides linked in the description below
to where you can find more details, but obviously
I can’t go through all the possible fixes
and permutations of them in this video.
Let’s start with extrusion problems.
Obviously, those are going to be the most
common ones since the rest of the printer,
mechanically, isn’t much more than a light
motion system and those aren’t that complex
of a beast to tame.
But we’ll get to that in a second.
First, what I’d group into “too little”
or “too much filament”.
If your filament toolhead is consistently
extruding, but is laying down the wrong amount
of material, you are going to get what’s
known as underextrusion or overextrusion.
Underextrusion manifests as poor performance
on overhangs, on top solid layers with gaps
in there, or on sloping top surfaces where,
again, you might start seeing gaps.
Parts will also be much weaker than necessary.
Now, most printers are actually set up to
underextrude by about 5% out of the box - that
makes for prettier prints than overextruding
by 5%, and most people are not going to notice
prints that don’t look perfect much more
than they’ll notice parts that break a bit
more easily, so they just veer on the safe
side.
But when there is too much underextrusion,
it starts becoming a real issue.
You can experiment directly on your printer’s
LCD and then, the easiest way to make that
permanent is to save it in your slicer.
Overextrusion is a lot more easily noticeable
- worst case, prints end up with blobs and
literally overflowing walls, but it’s actually
most noticeable on top surfaces where the
material can’t escape out to the side, but
end up piling up on top so that the nozzle
ends up dragging through the material.
Same idea as with underextrusion, you can
live play around with the multiplier directly
on the printer and then save it in the slicer.
So over- and underextrusion are both things
that are continuous, so they’re present
from the very first layer all the way to the
last.
But there are a bunch of hiccups that can
happen at any time during a layer.
So what’s actually somewhat common is that
your print will start out fine, but at some
point you’ll notice that you’re not getting
enough filament anymore.
That can be a whole bunch of things.
1) Some particle clogging your hotend.
2) The PTFE liner in your hotend kinking.
For both of those, see episode 4 of this series
on how to do a cold pull and how to repair
the PTFE.
3) The hotend overheats.
That’s down to either a poorly assembled
hotend, issues with the cooling fan or just
using a poorly-made all-metal hotend.
4) Overheating in the extruder due to motor
heat.
Add cooling or reduce the stepper current
for that motor.
5) Bad filament with, for example an inconsistent
diameter that gets stuck or even just simply
rubs somewhere along the extrusion path.
Next, what if you get blobs on your prints?
For that, we should distinguish between tiny
blobs that you get from moisture pops and
bigger blobs you get where the printer starts
and stops a line.
So, for that first one, use dryer filament,
or dry the filament you have.
For the second one, your retract settings
are not quite perfect.
Now, there is not one perfect set of settings
here, yet, but generally, if your retract
settings are too aggressive, you’ll end
up with blobs, if they are not aggressive
enough, you’ll get stringing on your prints.
And some hotends just aren’t great for filament
flow control, so in those cases where you
can’t seem to find a good compromise for
retract settings, I’d personally rather
have a bit of stringing, since that’s easy
to either tear off or quickly melt off with
a hot air gun.
Other extrusion issues can stem from temperature
problems - either printing at usually too
low of a temperature, remember, hotends even
in the same model of printer can vary by quite
a lot in whether they report a temperature
that is too high or too low, or from an inconsistent
temperature in the hotend itself.
A good way to track how stable the temperatures
are is to use the graph in Octoprint or even
just the one in Pronterface.
Just connect your printer via USB and you
can keep track of what’s happening during
a print.
If the temperature is wandering around, it’s
time to check if everything on the hotend
is correctly assembled and if it is, but temperature
is still inconsistent, a PID tune might be
in order.
Again, I’ve linked those more advanced tutorials
below.
Again, covering every fix in full detail would
have made this a two-hour-long unwatchable
mess, so I’m trying to keep it relatively
short here.
Alright, let’s move on to bed adhesion and
warping.
Five things to check if your parts come loose
during printing or you’re seeing the corners
start to lift up: 1) Compatibility between
the filament you’re using and the bed surface
on your printer, for example the textured
PEI sheets are best for prints with large
contact areas or for typically high-adhesion
PETG filament, while smooth PEI gives you
maximum adhesion even with small PLA prints
2) Sufficient ambient temperature, 3) Correct
bed and nozzle temperature for your filament
4) Correct nozzle distance for the first layer
and 5) a level, square, trammed bed, however
you want to call it.
Let’s go over bed leveling real quick: The
goal is to get an even, well-enough squeezed-down
first layer.
If you look at it, it should be smooshed down
enough to eliminate gaps, but no so much that
the nozzle is digging through material.
And of course, it needs to be even throughout
the entire are you’re printing on.
If you’ve got a printer with sensor-based
autoleveling, you just need to set the nozzle
distance, on the Prusas, there’s a specific
test print feature for that, but on other
printers you can just watch the first layer
and make adjustments as you go.
For leveling, the most common way to get it
done is to use a piece of paper, preheating
your printer, and, with the nozzle at the
“zero” height, checking above each leveling
spot and adjusting until the nozzle just barely
brushes against the paper.
That should give you a good starting point
for absolute height as well.
And as a tip so you don’t have to get it
absolutely perfect, you can also increase
the first layer height and extrusion width
to make that make that layer more robust against
small imperfections in the leveling.
Staying with temperature-related issues, if
you’re seeing curling, molten down fine
details and gaps in your top solid layers,
chances are you are printing too hot, too
fast or with not enough cooling.
All settings you can adjust in the “Filament”
tab in your slicer - try one at a time and
see which one helps the most.
If you’re printing too cold or with too
much cooling for your filament, you’ll get
brittle and dull-looking parts instead.
If adjusting temperatures doesn’t help with
top layers, you might simply need to increase
the amount of top solid layers and the infill
percentage.
Now, lastly, mechanical issues.
There’s three distinct ones that I want
to go over.
The first one is kind of hard to spot if you’re
not exactly sure what to look for.
If bearings, motors or other functional parts
are loose or worn down, you might end up seeing
inconsistent vertical surfaces.
If you grab your printer’s moving axes,
it’s ok if you can slightly flex them, but
if there is actual play in them, you should
probably investigate further into you printer’s
bearing and structural setup.
If you’re seeing ripples on sharp corners,
that’s commonly known as ghosting or ringing
and it’s a result of excessive flex along
the X or Y axes of a machine.
A common suggestion would be “tighten the
belts”, but that can only get you so far
if the setup is just built with too much flex.
For example cheap belts will often be way
more springy than quality ones or if the forces
from acceleration and deceleration of the
toolhead and bed have to be transferred through
flimsy bits of material.
You can work around that by reducing the “Jerk”
and “Acceleration” settings on your printer,
but don’t just slam those as low as you
can because you’ll be introducing other
issues on your prints with that and they will
take significantly longer to complete.
If you’re seeing a small gap on the top
solid infill of your parts where it looks
like there’s something wrong with only every
second gap, somewhere on the machine you have
backlash from either a loose pulley on a motor
or for example excessive friction on one of
the linear axes.
So as always, you want to have things tight,
but not too tight.
If in doubt, I would go with “less tight
than you might think”.
And lastly, the dreaded shifts.
These can be a bit unpredictable as to when
and where they happen, but the base cause
is always the same: The stepper motor on that
axis is asked to produce more torque than
it can deliver.
That can be down to, again, a sticky axis,
dirt on your linear guide surface that a wheel
or bearing gets caught on, or even resonances
where the printer is doing many small, repeated
moves that just hit one of the resonant frequencies
that excites the combination of for example
bed, belt and motor combination.
A simple, but inelegant solution would be
to just increase the current going to the
stepper motor, but drivers have a limit to
how much current they can provide and if they
overheat, might in turn also cause skipped
steps when they shut themselves down for safety.
If you can touch the driver chips without
getting burnt, they usually still have some
headroom left.
How exactly to adjust them depends on your
exact printer model, but again, adjusting
stepper driver currents is usually not something
that needs to be done by you, the user.
At least if you have a decent printer to start
with.
You can also, again, decrease acceleration
and jerk here, which helps a lot with issues
from resonances.
So of course, this is not a full list of every
single thing that can go wrong, but it also
doesn’t mean that everything that I just
listed will go wrong.
And as with any of the tweaks that I’ve
shared on my videos, if you overdo them, chances
are you’re still going to fix your original
issue, but end up making other things worse
that you’re only going to notice down the
road.
So if you’ve made a bunch of changes to
your print settings etc, maybe try going back
to stock and using what you’ve learned along
the way to go for a less intrusive fix next
time.
And of course, if you’re having problems
with a specific printer, it’s always advisable
to get in touch with the manufacturer first
since they are the ones who should know their
machines the best.
I hope this video helped you at the very least
to start looking in the right direction for
fixes - if it did, get subscribed - but again,
not every machine is the same and the exact
procedures might be different on different
machines.
So that’s it for this one, in the next and
last video of this series, we’ll look at
where you can go from here, now that you have
a working, reliable printer.
Until then, thank you for watching, keep on
making, and I’ll see you later.
