
Fast desktop-scale extrusion 3D printing - lainon
http://news.mit.edu/2017/new-3-d-printer-10-times-faster-commercial-counterparts-1129
======
Animats
Pushing filament with a gear was never a good design; it was just something
that hobbyists could build easily. Injection molding machines use a screw
drive to push molten plastic. This new machine uses a scaled-down version of
the injector screw of an injection molding machine.

Design and manufacture of injection molding screws is complicated but well
understood.[1] They're not easy to machine, but that's what CNC mills and
four-slide machines are for. It's like making a drill bit, something that's
done industrially millions of times a day but is very tough for hobbyists.

I'd wanted to use a laser for heating in a 3D printer, but not to heat the
plastic being deposited. The fundamental problem with filament-type 3D
printers is that you're welding a hot thing to a cold thing. That never works
very well. That's what causes cold solder joints and weak welds in metal. In
3D printing, it's why the bonds between layers are much weaker than the
plastic's inherent tensile strength. I wanted to have a small laser (about
10W) aimed ahead of where the filament is being deposited, to heat up the
material already placed. That way, both sides are hot as the weld occurs,
which should yield a much better weld. This is what the heated build plate and
heated build chamber designs are trying to accomplish, but they're not putting
the heat the one place it's really needed.

As lasers in the 10W range become more affordable, this looks like a better
idea. A few years ago, it was an insanely expensive idea, but now, you can get
10W for about $300.

[1]
[https://www.plasticsportalasia.net/wa/plasticsAP~zh_CN/funct...](https://www.plasticsportalasia.net/wa/plasticsAP~zh_CN/function/conversions:/publish/common/upload/technical_brochures/TI_Screwdesigns.pdf)

~~~
cptskippy
Heated build plates and enclosures are primarily to prevent the part from
warping and pulling itself off the build plate.

The problem with trying to bond two hot layers together is that they distort.
Typically the previous layer has not solidified enough and so most printer
employ a cooling fan to lower the temperature of the previous layer, not raise
it.

It's very hard to find the right balance of extrusion temperature, fan speed,
feed rate, and a myriad of other factors that affect print quality.

Honestly your comment makes me think you've never actually used an FDM
printer.

~~~
jstanley
Actually the fan is to cool the _current_ layer, immediately after depositing,
to solidify it as quickly as possible. That it also cools the previous layer
is just an accident.

I think Animats is right. It would be better to locally heat the previous
layer right before depositing, and then cool the joint right after.

Unfortunately that requires highly precise heating and (even harder) cooling,
so is probably still a few years away.

~~~
Animats
Localized cooling isn't hard. Laser cutters do it; they have a tiny nozzle
spraying compressed air (in some machines, an inert gas) on the cutting site.

For temperature feedback, a non-contact IR sensor would work. Operate the IR
sensor only during the off time of the laser (presumably pulse-width
modulated) and you can read the temperature while heating.

------
jaclaz
"Finally, they devised a high-speed gantry mechanism — an H-shaped frame
powered by two motors, connected to a motion stage that holds the printhead."

It seems a CoreXY or H-bot design, I always believed that the issue with this
design (like _any_ cartesian design) is with the limits of acceleration and
"drag" of (relatively) massive parts, particularly because the X and Y axis
have not the same weight/mass when changing orientation of the movement (the Z
is less of a problem, at least with "large" surface prints, the issue here is
only around precision), and that was the reason why Delta's are usually
faster.

Maybe a Delta with that head/printing gear can move even faster ...

~~~
coredog64
My wife has several Delta and XY printers. The deltas are much faster, but
they're also much more "fiddly".

~~~
virtualritz
Could you define "fiddly" in this context, please?

~~~
hexane360
Harder to calibrate, mostly.

In a CoreXY printer you can calibrate the X and Y axes more or less
independently. In a delta you have to take several points to get exact values
for arm lengths and therefore a solution to the mechanism.

------
QAPereo
Very cool, but big caveats as usual from a uni press piece.

 _However, they ran up against a small glitch in their speedier design: The
extruded plastic is fed through the nozzle at such high forces and
temperatures that a printed layer can still be slightly molten by the time the
printer is extruding a second layer. “We found that when you finish one layer
and go back to begin the next layer, the previous layer is still a little too
hot. So we have to cool the part actively as it prints, to retain the shape of
the part so it doesn’t get distorted or soften,” Hart says. That’s a design
challenge that the researchers are currently taking on, in combination with
the mathematics by which the path of the printhead can be optimized. They will
also explore new materials to feed through the printer._

~~~
valine
That’s a problem with most 3D printers I think. I usually get around it by
printing multiple copies of the object at the same time. By the time the
printer gets around to the first copy it’s cool enough not to cause issues.
Obviously it’s a much harder problem to solve the faster you print.

~~~
alanfalcon
Doesn't work as well when you just want to pop out a quick small prototype so
you can test it, iterate, and do it again, but definitely that works for some
applications. And as they mention, path optimization can also help here. As a
contrived example, if you're building an upside down extruded "T" shape, maybe
you could work on building up the stem as high as possible as quickly as
possible, and spending the "cooldown" time working on extending and building
up the base. I'm not aware of any 3D printers that move beyond the simple
"build from the bottom up" approach[1], but it seems possible to take into
account the bulk/size/shape of the printhead and do some advanced things -- if
the payoff is there.

[1] I also know approximately nothing about this space, I'm not speaking from
an area of expertise, just novice theory. Maybe this is already being done or
maybe it's simply impossible because the printhead is just far too bulky.

~~~
valine
There are some experimental 3D printers that deviate from the “build from the
bottom up approach.” Here is a pretty cool 5 axis 3D printer:
[https://m.youtube.com/watch?v=w8Fl8L4yk8M](https://m.youtube.com/watch?v=w8Fl8L4yk8M)

~~~
SAI_Peregrinus
Or production devices. DMG Mori makes a ($250,000) 5-axis CNC that can do 3D
printing (selective laser sintering). Example:
[https://www.youtube.com/watch?v=1TwVkAuvGwM](https://www.youtube.com/watch?v=1TwVkAuvGwM)

------
Ccecil
The main benefit to the speed will be realized when they scale the build area
of the machine. As I suspect they realized it is difficult to get past the
physics of the plastic cooling without causing other issues (delamination,
warping, etc). The gain will be largely noticed when they are printing with
this extruder using a build area larger than 1m cubed. The issue on large
printers is being able to get the newly deposited material down while the
previous layer has not cooled too much (delamination), although, this can be
can be partially controlled with things like heated build chambers and
such...they are patented.

This idea was tossed around in #reprap for a few years (I know I have heard
the idea thrown out there) and I am glad to see someone working on it.
Although, I disagree that a screw drive is needed. I use hobbed gearwheel
drive on my extruders and rarely is the issue the hobb slipping. Typically, it
is the motor stalling instead. This isn't so much a product of the drive
wheel/extruder as it is the hotend not being able to keep up with the
commanded extrude volume...since this hotend doesn't have that issue (or so it
seems) I suspect the conventional extruder could be used with just a
modification to hotend/heater design.

Once the commercial 3d printing market moves up to things like servos, encoder
feedback, etc. I suspect the speeds of things will start ramping up greatly.
The issue isn't so much the tech but the cost...people are cheap.

edit: After reading the linked arxiv page. I see they are using closed loop
servo motors/drivers and a RAMBO controller. They could go faster if they used
a 32 bit controller like a smoothieboard or duet instead of the 8bit "arduino
based" controllers. {Not saying RAMBO is a bad board, they are known to be
very reliable for OEMs}

Not to mention that Smoothieware has the control modules for lasers and cnc
built in as well as the 3d printer so it requires probably no firmware
modification to get this running...just config and maybe a custom bin.
(Disclaimer: I work directly with the Smoothie project so I may be biased)

~~~
lylecheatham
> Although, I disagree that a screw drive is needed. I use hobbed gearwheel
> drive on my extruders and rarely is the issue the hobb slipping. Typically,
> it is the motor stalling instead.

Although that may be the problem on your printer, it's simple to fix because
one can always add a larger motor. The problem that they solved is that
eventually, a stronger motor won't cut it because the hobbed gear will slip,
and that's what this paper is all about. Optimizing the motor is done by just
upscaling it, but optimizing the drive is what made them to move away from the
existing hobbed gear setup.

> They could go faster if they used a 32 bit controller like a smoothieboard
> or duet instead of the 8bit "arduino based" controllers. {Not saying RAMBO
> is a bad board, they are known to be very reliable for OEMs}

I would actually predict a minimal increase in speed. 32-bit controllers don't
make for inherently fast printers, they allow for it if utilized properly.
What you'll find though is that Marlin and Smoothie both use the GRBL planner
under the hood, and generate very similar output. The only major difference I
noticed in the output between the two is that Smoothie generates smoother
(hence the name) step waveforms.

I guess you can also generate steps at a higher frequency with smoothie, but
you should be careful equating higher step frequencies with higher speeds,
when most of the time people are running with microstepping settings. Higher
frequency allows you to get more dynamic range between speed and precision,
but that's not really what the paper was about.

------
marcosscriven
I’d like to see some close ups of the prints. In the video you can see the
print bed vibrating like crazy, and each layer can’t be anywhere near solid if
there’s a tenth of the time to cool, even with a fan.

I wonder if you could have a something that squirts a fine jet of liquid
nitrogen, just behind the print head? Expensive though I suppose.

~~~
jaclaz
>I wonder if you could have a something that squirts a fine jet of liquid
nitrogen, just behind the print head? Expensive though I suppose.

Maybe - just a semi-random idea, mind you - a Ranque-Hirsch (or Vortex) tube
(and a source of compressed air) would be enough and possiby be more
practical:

[https://en.wikipedia.org/wiki/Vortex_tube](https://en.wikipedia.org/wiki/Vortex_tube)

~~~
louithethrid
Add Peletier elements to that, cooling the air to cool, heating the filament
to print.

------
schpaencoder
In the mid 1980 there was a similar craze related to dot-matrix printers and
their cps (chars per second, or how fast they were). Then laser printers
became cheap and everyone forgot about the dot-matrix. I guess this is the
same thing. Fast forward 15 years.

~~~
gh02t
Probably the next revolution in 3D printing speed will be something that
prints an entire object at once, maybe via some sort of science fiction style
hologram illuminating a resin. There are technologies that kinda resemble this
on the cutting edge (like continuous liquid interface production), but we are
still really far away from that ideal. For the foreseeable future we are
probably doomed to incremental improvements.

~~~
vbuwivbiu
It's probably possible to create a "matter hologram": we already know we can
put molecules as large as C60 in quantum superposition. If we could create a
coherent source of such molecules and pass them through a beamsplitter and
suitable modulator (to shift their phase), combining the two beams, we could
create an interference pattern in free space which would reify the object,
like the replicator in star-trek.

~~~
gh02t
The nicest thing about our mythical hologram printer is that supports would be
unnecessary for stuff like overhangs and you could maybe even print complex
internal structure, depending on just how capable your 3D hologram was. One
can dream...

~~~
vbuwivbiu
I think we should rename our mythical printer from "hologram" (which implies
replay) to "quantum interference printer"

~~~
scoot
Are you serious, or was that just a quip?

~~~
simcop2387
Pun intended? QuIP would be as nice name.

------
The_Double
Link to the paper for those interested:
[http://www.sciencedirect.com/science/article/pii/S2214860416...](http://www.sciencedirect.com/science/article/pii/S2214860416303220)

edit: Arxiv link:
[https://arxiv.org/abs/1709.05918](https://arxiv.org/abs/1709.05918)

------
unlimitedbacon
"The team identified three factors limiting a printer’s speed: how fast a
printer can move its printhead, how much force a printhead can apply to a
material to push it through the nozzle, and how quickly the printhead can
transfer heat to melt a material and make it flow."

None of these are the actual limiting factor on print speed. Many 3D printers
are capable of traveling at 300 mm/s, and extruding at more than 100 mm/s, yet
in practice the fastest parts of a print are usually done at 60 - 80 mm/s.
This is because the faster you try to go, the worse the print quality is. The
outer shells of a print, where quality is most important, are usually done at
30 mm/s.

Quality 3D printing is all about maintaining a delicate thermal balance. You
want the plastic to cool to below it's melting point (if it has one) as soon
as it leaves the nozzle so that it hardens and maintains it's shape. However
you also want to keep it warmer than it's glass transition temperature in
order to combat the effects of thermal contraction.

As you try to go faster the soft plastic will get dragged around harder and
will have less time to cool. The layer below will be softer when the layer
above is being deposited on top of it. This causes sharp corners to get
rounded off and overhangs to curl upwards.

The article does not have any close up shots of the objects printed on this
machine, but I expect that they are pretty rough. As QAPereo pointed out, the
article mentions that they ran into this problem. This does not mean that this
is a bad idea, though. Products like E3D Volcano and the Lulzbot Moarstruder
have proven that there is a niche in the 3D printing marked for fast sloppy
printing.

Another thing that they don't talk about is how this extruder deals with
retraction. One nice thing about gear driven extruders is they give you very
precise control over how much plastic is being put out. You can also quickly
retract the filament a bit to drop the chamber pressure and minimize plastic
leaking from the nozzle as it travels from one part of the print to another.
I'd like to know how well the auger is able to do this.

~~~
lylecheatham
Checkout the second to last page for pictures:
[https://arxiv.org/abs/1709.05918](https://arxiv.org/abs/1709.05918)

I think you bring up a good point about the lack of precision at high speed. I
think the next big thing in this industry is going to be diving into the
factors behind the 'sloppyness' you mention.

> I'd like to know how well the auger is able to do this.

I can answer this one! it's actually more like a nut on a bolt, instead of an
auger, meaning it can reverse just fine.

------
wheresmyusern
this is absolutely brilliant. i have no idea how nobody thought of this
before. it was so obvious, just melt the plastic faster. so blindingly
obvious. i have personally spent many hours trying to design a faster printer.
its encouraging to know that there was a very elegant solution right under my
nose the whole time. maybe there are a few more?

~~~
tfolbrecht
If you think that's a great idea, how about this one: Melt the plastic even
faster than that. I'll be expecting my check in the mail.

~~~
richk449
No! No, no, not 6! I said 7. Nobody's comin' up with 6. Who makes prints in 6
minutes?

~~~
ralusek
Actually most printers can make it all the way up to 10. The one I've got at
home heats at 11; one hotter.

------
blincoln
If it incorporates a gantry design and a laser powerful enough to melt
plastic, how hard would it be to make it a multipurpose 3D printer/2D (+depth)
laser cutter? Getting two useful tools for the price (and space) of one would
make this an easy sell to me, at least.

~~~
lucaspiller
Take a look at machines like the HyperCube which are attempts at a generic CNC
machine with swappable tools/print heads.

[https://www.thingiverse.com/thing:1752766](https://www.thingiverse.com/thing:1752766)

------
wheresmyusern
what are the problems with printers today? for hobbyist extrusion printers?

\- they are slow (fixed). but even 10x leaves something to be desired.

\- they cant print all shapes elegantly. for many shapes you need scaffolding.
its a nuisance.

\- they are course. print layers, even at the thinnest settings, are still
rather thick. also, there is a lot of inconsistency, stringing and surface
imperfections.

find a way to solve these problems in a relatively cheap printer and we might
actually see the revolution that was talked about when 3d printing first
arrived.

~~~
bunderbunder
Two others: They are big, and they are expensive. That makes owning a 3D
printer something that still doesn't make a lot of economic sense for me. I'm
not certain it ever will.

I'm waiting for the equivalent of a Kinko's for 3D printing. That will make 3D
printing much more accessible to me, and I assume it would also get me access
to 3D printers that can do much higher quality work than the at-home models
are capable of.

~~~
gh02t
> I'm waiting for the equivalent of a Kinko's for 3D printing

A lot of universities offer this to their students already. Commercially, off
the top of my head, Staples and the UPS store have some 3D printing services
available at a limited number of stores but I don't think it has been terribly
successful. Problem is, 3D printing is IMO not much more than a novelty unless
you are designing your own parts, but then iterating on a custom design is
painful and expensive with a commercial service.

I use my 3D printer a ton, both for work and for hobby stuff, and it usually
takes a few tries to get a design right. That's hard to do sitting in a store
or by mail and typical markup for those services is like 10-20x actual cost.
It quickly gets expensive enough that buying your own printer starts to make
sense, especially when quality printers can be had for <$500 nowadays and
quite serviceable printers for <$200.

There's really not a huge difference in quality between the higher end
printers and the good examples of the affordable ones (at least, comparing FDM
printers to their kin, SLA/DLP is a different beast entirely). Most of the
difference is in convenience and secondary features like dual extrusion or
self-leveling.

------
jseip
The first person to put this (or equivalent) on Kickstarter is going to raise
a lot of money.

------
mwrouse
There is absolutely no way that video is in real time. What kind of servos are
they using?

~~~
jstanley
This kind of 3d printer generally uses stepper motors, not servos.

From what I can see, this printer appears to use stepper motors too. I'd
believe it's real-time.

The X axis is held in place vertically by the 2 shiny metal rods you can see,
and is dragged back and forth by the black rubber belt, which is controlled by
a stepper motor.

~~~
mwrouse
I know, I have several printers mtself. They are using only servos. Which is
why it's faster probably. EMJ-04 series.

The rate at which it jumps around is just ridiculous though.

------
tfolbrecht
And if reliability is an issue, just stick another print head on to print a
backup print in tandem. Can I be accepted into MIT now?

------
janoc
[deleted as completely wrong - don't write posts before having coffee! Mea
culpa!]

~~~
lexicality
That article describes a completely different university and a different
acceleration technique

------
cdancette
It moves fast, but it still has to melt and apply the plastic, and it seems
harder to make this part go 10x faster

~~~
JamesUtah07
> The key to the team’s nimble design lies in the printer’s compact printhead,
> which incorporates two new, speed-enhancing components: a screw mechanism
> that feeds polymer material through a nozzle at high force; and a laser,
> built into the printhead, that rapidly heats and melts the material,
> enabling it to flow faster through the nozzle.

That's the exactly what is making this new 3D printer 10x faster

~~~
LeifCarrotson
> a screw mechanism that feeds polymer material through a nozzle at high force

Practically all existing 3D printers have this.

The laser does seem novel - most use an electrically heated head nozzle to
melt the plastic like a hot glue gun - but I remain skeptical when they list
screw feed as an innovative ceature.

~~~
jaclaz
>Practically all existing 3D printers have this.

No, usually they have a rotary feeder, i.e. "pinch-wheel", it seems like what
they propose is a screw feeder, likely a screw with the axis roughly in the
same direction as the filament, with "higher grip" on the filament, but
probably it depends also on the specific filament material:

>"In most desktop 3-D printers, plastic is fed through a nozzle via a “pinch-
wheel” mechanism, in which two small wheels within the printhead rotate and
push the plastic, or filament, forward. This works well at relatively slow
speeds, but if more force were applied to speed up the process, at a certain
point the wheels would lose their grip on the material — a “mechanical
disadvantage,” as Hart puts it, that limits how fast the printhead can push
material through.

Hart and Go chose to do away with the pinchwheel design, replacing it with a
screw mechanism that turns within the printhead. The team fed a textured
plastic filament onto the screw, and as the screw turned, it gripped onto the
filament’s textured surface and was able to feed the filament through the
nozzle at higher forces and speeds. "

------
Peter-W
I'm impressed by the speed in the video, I thought it was sped up at first.

