So this is what the iTopie i3 looks like now
- you’ll notice that Luke decided to go
with a modern penta-color paint job with the
classic white and black main elements, metallic
silver and gold on the feet to match brass
and steel details on the printer’s mechanics,
and they all nicely complement the bright
red printed parts. So as you can tell, it’s
going to be a very classy printer once he
actually gets around to finishing it. Today
though, i want to specifically focus on one
element, which isn’t even in here yet: The
hotend.
Hi everyone, Tom here, and picking a hotend
that is right for your idea of the printer
you want to build can be somewhat daunting
with so many choices out there. But once you
start breaking them down, there really are
only a few factors that define what type of
hotend you’re dealing with and what sort
of performance you should expect from it.
Now, the biggest factor and the one you’re
going to see right away because it’s going
to be shoved in your face is “all metal”
or PTFE-based. Let’s start with the very
first hotend i used, this thing, not an all-metal
design, obviously, it’s got a mount made
from PEEK, which is a super-strong plastic
that doesn't melt until, like 300°C, so way
beyond what you’d typically use with 3D
printing filaments. And the PEEK provides
both the insulation between the heater block
and the mount as well as the mechanical strength,
after all, there is an extruder pushing filament
into this thing. You can see that the heater
block down here, where the filament melts,
has pretty much a direct thermal path up to
the PEEK part. But because PEEK isn’t really
slippery, the hotend would constantly jam
if it didn’t have a PTFE aka Teflon insert
in here, and while you often still see PTFE
inserts with newer all-metal hotends, this
one reaches down all the way into the heater
block. All-metal hotends, like the E3D v6,
the recently reviewed DyzeEND-X or many other
hotends, either have the PTFE liner stop somewhere
in their heatsink or don’t use a liner at
all. Now, the consequences from using a PTFE
liner are diverse, the most obvious one being
that you can use all-metal, or, more precisely
PTFE-free hotends up to a higher maximum temperature.
Reason being, PTFE starts to really soften
beyond 250, 260°C and somewhere in that range,
also start releasing gaseous neurotoxins - which
is the same reason why you shouldn’t leave
Teflon-coated pans on the stove for too long
without anything in them. So while all all-metal
hotends easily go up to 300°C and some even
further, the safe usable temperature range
for hotends that use a PTFE-liner or insulator
for anything that’s touching the heater
block ends at those 260°C max. As far as
robustness and reliability goes, you could
argue both ways - all-metal hotends use a
heat break that is machined to have a very
thin stainless steel tube section as an insulator,
and naturally, that section is fairly easy
to bend and break and at the same time, is
pretty tricky to manufacture with a smooth
inside bore to prevent filaments like PLA
from sticking to the hot metal sides. On the
other hand, the PTFE liner can leak if assembled
with too little pressure and, worst case,
kink and block the filament path if assembled
with too much pressure and used with too high
of a temperature, but they tend to provide
an easier filament pushing experience for
the extruder, which can be particularly helpful
with flexible filaments. You can also get
hybrid types, like the E3D lite6, Printrbot
Ubis 13s or the soon-to-be-reviewed Flexion
hotend, those still have a PTFE liner all
the way into the melt zone but also use stainless
steel as a structural and insulating element,
cutting out the cost for a large chunk of
PEEK as an insulator or for a precisely machined
heat break.
Both PTFE-based and all-metal hotends can
work extremely reliably with PLA, PET and
many other not-so demanding plastics, but
for regular use with ABS or even more extreme
plastics, you should definitely go with an
all-metal hotend.
Ok, so that’s been a lot of talk on one
subject, let’s look into what else i’d
look for in a hotend. And let’s start out
with the overall geometry - how big is it,
will it fit your particular printer and extruder?
Is it too short or too long? All very simple
things, but easily overlooked. So the de facto
standard for hotend mounting, is this 16mm
groovemount. While many hotends might look
similar or compatible, there are minor differences
between them that keep them from being universally
cross compatible - not even the E3D v5 and
v6 use the exact same mounting geometry. And
really, for that, there’s not much else
to say than “in case of doubt, check with
the manufacturer”, there are simply too
many different extruder mounts and hotends
out there. Next up, length and girth. Now,
a long hotend is usually not going to hurt
anything, at worst, you might lose a few millimeters
of vertical build space, but a hotend that
is too short can cause issues in two spots,
other than self-confidence - one, you might
end up bottoming out your Z-drive, and two,
at the actual carriage that, well, carries,
the hotend, there’s typically going to be
bearings and sensors and what not sticking
out the bottom there, so make sure the hotend
is actually the lowest part out of those.
Then, the circumference of the entire hotend
assembly. This is the size of a classic PEEK-based
hotend like the original Ubis or the Jhead
or whatever, and this is what a modern all-metal
one looks like, so, obviously, if the printer
you want to build only has space for a super
slim one, then obviously, buying one that
is this big isn’t really the smartest thing
to do. And keep in mind you might need to
fit things like a bed sensor and part cooling
fan around the hotend as well. Though, i’ve
got to say, newer printer designs typically
have the space to fit even the larger hotend
types.
Ok, so one more thing about geometry, there’s
basically three zones in any hotend, and ones
that have these zones clearly separated tend
to have the most predictable performance.
There’s the cold end, the transition zone
and the melt zone, and the mistake some manufacturers
have made with all-metal types was to not
properly define the transition zone, so depending
on what print settings you used, the filament
would start to soften at an arbitrary point
somewhere above the melt zone, and cause some
whacky behaviour. This isn’t as crucial
in PTFE-lined hotends, as the liner will insulate
the filament and compensate a lot for this
sort of wonky behavior, but for all-metal
types, having a sharp transition from the
cold zone to the transition zone to the hot
zone is pretty crucial. So the cold end will
typically not be much warmer than ambient
if you have a fan blowing over it, as most
hotends do these days. It’s not really crucial
how exactly the cold end looks as long as
it’s doing its job of cooling well enough,
so let’s move on to the transition zone,
which is the weakest, but also the most important
part of any all-metal hotend. Essentially,
a longer transition zone leaves more plastic
in a semi-molten sticky gooey state, so ideally
you want that zone to be as short as possible.
Most hotends get this about right, but be
careful with ones that seem to have a particularly
long transition zone. On hotends with a PTFE
liner, there often isn’t a dedicated transition
zone per se, which is ok for them. And lastly,
the melt zone, this one will be at a consistent
temperature throughout, and, basically, the
longer it is, the faster you’ll be able
to print with a given set temperature. Which
is why the E3D Volcano is so ridiculously
long. But with a longer melt zone you do lose
some precision and increase stringing and
blobbing, while a shorter than usual melt
zone will need higher temperatures to print
since the plastic has less time to heat up
in there.
One more very important point is serviceability-
sooner or later, you’re going to have a
jam or break something on the hotend. Now,
if you’ve got one that has like a one-piece
nozzle heat break connector thing, there’s
no way you’ll clean that in any decent amount
of time, and if you have to replace it for
example should you bend it, you’ll obviously
have to replace the entire thing. And while
we’re at nozzles and the likes, the standard
nozzle size today is 0.4mm, which works for
a lot of different applications, if you want
slightly faster build speeds and are ok with
slightly thicker layers, for example for a
larger printer, 0.5mm or 0.6mm are still very
flexible sizes, and if you want to go the
opposite way and get maximum precision and
detail resolution out of your printer, 0.3mm
would still be an acceptable choice. I wouldn’t
recommend 0.2mm unless you really want to
live on the bleeding edge, since you’ll
need to use insanely low layer heights and
speeds to even profit from that kind of nozzle
size and you’ll be at constant risk of jamming
your nozzle with even the tiniest particles.
But if you get a hotend that you can disassemble,
you can always just swap in and try out a
different size if you want to.
And one last note, especially with the hotend,
please do yourself a favor and buy genuine
parts if you’re building your first printer
or don’t have the engineering or machining
knowledge or simply not the time to figure
out how to make a clone work. I mean, they
all look great in the pictures, but there
are so many things a Chinese manufacturer
will be able to mess up when he’s only machining
these by some incomplete drawings and pictures
he found online, some of the sellers even
claim to have improved the original designs,
but it’s more like “well downright cloning
didn’t work, so here’s something we huddled
up to make it somewhat functional” when
clearly, the ones manufacturing these don’t
even know how the parts should properly fit
together. Look at this, this is completely
unusable. Yes, i only paid 4$ for this, but
then again, you get what you pay for, and
this sort of stuff isn’t what i would want
to deal with when getting a printer up and
running.
So in general, the big names when it comes
to hotends like E3D, the UBIS used in the
Printrbots, the Hexagon as used in Lulzbot’s
printers, those are good all-round choices.
But if you want to go for something completely
different you should now have a some guidelines
of what to look for.
Anyways, thanks for watching, leave me a thumbs
up if you learned something, get subscribed
if you want to learn even more in the future
or maybe even consider directly supporting
this channel on Patreon. And that’s about
it for today, see you in the next one!
