
3D Printer Comparison: $200,000 vs. $2500 - hharnisch
http://additivepartdesign.com/3d/printers/2016/06/01/3d-printer-comparison.html
======
ChuckMcM
I enjoyed this article, but perhaps not for the reasons the author hoped. This
quote, _" With some tweaks to my G code and use of a nozzle that is more
suited for higher resolution prints I am confident that I could produce a part
that would be very close to the quality of the Stratasys produced part."_
really summed it up. It sums to "I can tweak my setup and get this part to be
good enough relative to the expensive machine." and that is great. What is
missing is it is _every friggin ' part_. Seriously, all of the $2,000 printers
have quirks that hit based on part geometry, especially in ABS. Part too long?
need to add hold down tabs to prevent warping. Too many overhangs? extra
supports. Too long a tool travel? Up the hotend temperature so that the
extruded material doesn't cool down to much.

You can make great parts but every machine is different, and every part you
make has a slightly different requirements. "Real" manufacturing tools are all
about the repeatability and setup. Pretty much any machining center can take a
gcode file, look at it, and adjust itself to make the best possible rendition,
or warn you if it can't do so and meet its advertised tolerances. A hobby
machine you print it, you tweak the parameters, you print it again, maybe you
tweak the gcode a bit, and finally you print a really nice part.

What gets you repeatability? measuring. There are so many things that you can
measure and hobby machines don't. Who puts glass slides (accurate to a tenth
of a micron) providing position feedback on the x, y, and z stages on a hobby
machine? Nobody, the slides and readers cost $1K just by themselves. There has
been some motion toward monitoring the feed of the filament to give a
"stripped filament" warning, but who measures the actual flow? the temperature
of the melt chamber and feed path?

I really enjoy my 3D printer, I'm printing out a damper for a meat smoker as I
write this, its going to be glorious, but its also the 3rd time I've printed
this particular part to tune it up. We'll see how it works on the smoker.

~~~
jacquesm
Welcome to the wonderful world of quality control :)

Making _something_ is easy, making something with a high repeat accuracy and
very low fail percentage is super hard.

I learned this the hard way myself with an IO expander for the Atari ST that I
designed. I needed it to drive the lathe/mill controller, the ST simply had
too little IO capacity so with a bunch of decoders and latches I was able to
drive a much larger number of motors and relays.

The first one worked like a charm. So did the second and the third. But the
fourth, we couldn't get it to work no matter what. Part variability led to
some signal arriving _just_ that much earlier causing the latches to remember
data that was still stale. The reason was - in retrospect - quite simple, the
design had assumed that the input to the latches had long stabilized before
the latch pulse was sent. But because on the ST the latch pulse took a
different route as well there could occur a tricky situation where the output
of the buffer driving the data bus on the far side would still be rising. To
make things worse, this would not happen repeatably, only with certain
patterns of 1's and 0's. In the end, a single buffer in line with the latch
pulse caused enough delay to stabilize the input to the latches and that
solved the problem.

(Of course not with _every_ board...).

Anyway, that was electronics, this is mechanics but the same principles apply.

Something funny is happening in youtube land, classical music.

There are a whole pile of 'youtube wonders' that can play an enormous variety
of material but that have never in their lives done a live concert. It took a
long time before one of those miracle people owed up to the recipe: record
hundreds, or even thousands of times. Pick the best.

That's the difference between an actual pianist and youtube miracle workers: a
pianist can do what they do repeatably, youtube miracle workers would end up
being booed out of actual performances.

Repeat accuracy is _very_ hard, mechanics, electronics, playing the piano, the
subject hardly matters.

I've been reading all kinds of books and articles about quality control last
year and I believe that in a mature market it is the only absolutely critical
element in any production process. If all your competitors are doing good QC
and you don't you're dead. Everything else can be fixed but without repeat
accuracy you'll be fighting a lost battle.

Another way to look at this is that for real world stuff where there is a
whole company dependent on the output of the 3D printer the cheap one is too
expensive, and the expensive one probably is cheap.

That's because if you were allowed to make a million parts with each and you
could take the best part from each set of parts they'd be very close. The
'best' part of those two might even be from the crappy machine. But if you
needed just 50000 parts that would simply work your cheap printer (or even a
small army of them) would wear out long before completing the order, and
that's what makes them expensive.

~~~
sbierwagen

      A pianist can do what they do repeatably, youtube miracle 
      workers would end up being booed out of actual 
      performances.
    

[http://grantland.com/features/anthony-gatto-juggling-
cirque-...](http://grantland.com/features/anthony-gatto-juggling-cirque-du-
soleil-jason-fagone/)

    
    
      Partly this was an illusion created by the combination of affordable 
      video equipment and the Internet; young jugglers now kept their 
      cameras running all the time, so if they hit a trick one time out of 
      100, they could upload the proof and make themselves look like gods, 
      even if they’d never be able to execute the trick onstage, like 
      Gatto could.

~~~
jacquesm
Exactly like that.

That's a lovely article by the way.

------
Certified
"The Stratasys printed part was printed with ABS material, 100% infill with a
standard layer height on normal detail settings. Not having direct access to
the machine I was not able to extract any real nitty gritty details on the
overall print set up. For the Lulzbot print that I created I used HIPS
material with a 0.5mm nozzle, 0.1mm layer height, 25% infill, 4 top and bottom
solid layers, 45 mm/s print speed with standard acceleration, 240C extrusion
temperature, 110C bed temperature, and an extrusion width of 0.6mm."

This is an apple to oranges comparison. I work with a Lulzbot 5, a Lulzbot
Mini, a Stratasys dimension elite, and two polyprinters on a daily basis and
have been working with 3D printers for over 10 years as part of my job. Why
was a material like HIPS ever used for comparison with ABS if both machines
can print with ABS? Why was the extrusion width 0.6mm on a 0.5mm nozzle? Why
is he comparing a 100% fill print with a 25% fill print? Why didn't he mention
that the Lulzbot Taz 5 he was using has a $500 print head upgrade to let it
print soluble support material as well? This whole article just reeks of
either someone who is either very new and inexperienced to Hobby 3D printers
or was intentionally trying to make the TAZ 5 look bad. I have done similar
comparison studies myself and have come to drastically different conclusions.
We sold the dimension elite a while ago.

~~~
avs733
I had some of the same questions...my suspicion is basically two fold

1) the infill change may have been intended to make the print times comparable
(he suggested both were about 18 hrs)

2) He may have been attempting to compare the default (or default-ish)
settings of each machine

~~~
MikeAPD
Hi, I wrote this article. To answer your suspicions.

1) Realistically they are within an hour of each other regardless of infill so
the total print time was negligible in this experiment. A few changes on both
machines could make either or print much faster. 2) Yes, it was my intention
to have the same layer heights and overall print settings as close to each
other as I could.

~~~
avs733
Thanks for the information

------
Animats
From the article: _" One defect I observed on the Lulzbot printed part was the
blade portion of the tool had a split in it from not bonding correctly. This
was most likely a cause of pushing the 0.5mm nozzle to its limits in terms of
layer height but a little glue and some pressure would fix this split no
problem."_

Er, that's called a "reject" in manufacturing.

This is the basic problem with low-end filament-type 3D printers - weak layer
bonding. You're welding a hot thing to a cold thing, which never works well.
And there's considerable thermal expansion, and thus shrinkage, in the
material, which produces internal stresses between layers. That's where things
crack.

~~~
patcheudor
"This is the basic problem with low-end filament-type 3D printers - weak layer
bonding. You're welding a hot thing to a cold thing, which never works well."

Bonding always works well for me and many others. The author of this story
choose to use a material (HIPS) which really should still be considered
experimental for most FDM printers. I've personally never had a lot of luck
with it and instead choose to use either PLA or ABS with a heated chamber &
with those two materials can build very strong parts with no boding problems
whatsoever. Here's an example of a violin I've recently printed:

[https://www.flickr.com/photos/patcheudor/26263996272/in/date...](https://www.flickr.com/photos/patcheudor/26263996272/in/dateposted-
public/)

Note that I've now printed five violins and in the 100's of hours it has taken
to do so not had a single failed print even when printing thin (typically .40
mm) shells.

~~~
Animats
Thin is the good case. It's thick parts that have problems. At TechShop,
things seem to crack around 2cm-3cm thickness.

~~~
patcheudor
I routinely do thick 100% fill parts in ABS with no issues.

------
aleon
This is an unfair comparison.. Having used a Stratasys Objet of around a
similar price point, the amount of detail you can get is incredible -- down to
fractions of a millimeter.

Sure, for the prints that were pictured in the comparison, either can do
relatively well, but the point of higher end printers is for higher resolution
prints, different materials, shapes of the print, etc. To ignore all of those
use cases and focus on a generic print that a hobbyist would make, of course a
hobbyist printer would suffice!

~~~
graeham
Exactly - this is a pretty simple part, without fine details that would
actually test an expensive printer.

Its like comparing how Facebook or Word works on a netbook vs a top-end
desktop.

And I'd say furthermore, although not knowing how the part is used - with such
flat features and 90-degree corners, probably the best way to make this would
be sheet metal, which with a waterjet cutter, press break, and spot welder
could be produced in 1/100th the time and cost.

------
tsomctl
No mention at all of the strength/rigidity/hardness of the jigs. The
professionally printed one was made from ABS, which is a harder plastic than
HIPS. It is also possible that the professional machine bonds the plastic
filament to the workpiece better. The best way to test this would be
destructively.

Of course, if the jig is just going to be used for a short period of time,
structural integrity doesn't matter. And the hobbyist machines are just going
to get better as technology improves.

~~~
saidajigumi
Also missing from the discussion are tolerances. If the Stratasys is able to
print meeting high significantly higher design tolerances, that alone could
justify the price tag. Certainly in other areas of manufacturing, adding zeros
to the accuracy/repeatability of a system often adds zeros directly to the
price tag.

If you can get a print hot off the printer and immediately say "LGTM" without
further ado, that may just mean your application isn't very demanding.

~~~
Domenic_S
Underrated comment here. The same exact part can cost $20 or $2,000 to produce
depending on tolerances!

------
MikeAPD
Hi, I wrote the article. I am really enjoying the comments everyone has
contributed. One major detail I left out was the amount of failed parts that
came out of the professional machine prior to getting a good one. I was
unaware of the reject rate at the time I wrote this. In addition, the
production tool ended up having resin added and then sanded to cover up some
of the imperfections on the "professional" print.

~~~
kragen
What was the reject rate? Also, some of us have asked some other questions
about tolerances and material properties in other comments on here; could you
answer them? I'm sorry about the somewhat intemperate comments of some of the
other commenters.

~~~
MikeAPD
I can't give you an exact reject rate but it went through at least 3
iterations before being acceptable. As for tolerances and material properties
(overall strength of the part) the Stratasys machine is superior in both
aspects. As I mentioned in the conclusion of the article, I would like to do
more experiments on the parts including dimensional analysis and possibly a
tensile or compression test. Having 1 data point (1 tool from each machine)
wouldn't be the best results for an accurate comparison but I would still be
interested in the results.

------
Merad
A few years ago in grad school I spent about a month designing a 3D printed
case for a Raspberry Pi + Camera [0]. We used a Makergear M2 (a $2000 printer
at the time).

The process had some frustrating moments, but overall it was an amazing
experience. 3D printers allow for a wonderful iterative design process. Come
in in the morning, pull parts off of the printer, measure, test fit, etc.
Tweak in CAD, or start working on the next part, and start printing your
changes/additions before lunch. By mid afternoon the print is done, and you
usually have time to do another round of changes that you can start printing
before you leave for the day.

Of course, this is all assuming that your printer is working continuously and
that you're ok tossing a lot of filament from those test prints. My experience
with the M2 was that typically I could get it dialed in and it would print
great for 2-3 weeks before it started misbehaving. Sometimes it was a simple
adjustment (re-level the bed, etc.), but most of the time there was no obvious
indication of the problem, and I'd spend several frustrating days leveling,
calibrating, cleaning, and generally tinkering until it started working
consistently once again.

There are also plenty of issues with the print quality and precision, but I've
already written more than I intended, so I'll skip them. Needless to say, it
was sufficient for our needs. IIRC, our final cost per case was $4 in material
(PLA) with a print time of about 6 hours.

It's a fascinating technology, and it's mind blowing how far it's come in the
last decade. I'm not sure that the FFF/FDM style printers will ever get to the
point where they're ready for use by the general public, but the overall
technology is here to stay. I wouldn't be surprised to see 3D printers become
as common as microwaves in my lifetime.

[0]: [http://i.imgur.com/JkF1WQ4.jpg](http://i.imgur.com/JkF1WQ4.jpg)

------
willvarfar
I have never seen a 3D printer, although I have seen a model (of a house plan)
made with a 3D printer. You folks who live near civilization and 'make'
communities are so lucky! :)

Are there any 3D printers that integrate a milling machine?

I imagine a machine that prints the model slightly oversize, milling and then
perhaps finally warming the surface to polish it, all as it goes...

I would love to have access to a hobby 3D printer as I have this idea that
won't die about making a cylindrical version of the Enigma
[http://wiki.franklinheath.co.uk/index.php/Enigma/Paper_Enigm...](http://wiki.franklinheath.co.uk/index.php/Enigma/Paper_Enigma)
with glowire or alternatively tracks for ball bearings, as a cheap present
people can buy at, say, Bletchley Park gift shop. Silly thing to get fixated
on.

~~~
jacquesm
> Are there any 3D printers that integrate a milling machine?

No, and there likely never will be. Why would you wait for hours to then
_still_ have to mill down your final product when all the advantages of 3D
printing are then lost _and_ all the advantages of milling are lost?

The advantages of 3D printing are that as an additive process it will work in
many environments where a subtractive process would not, the advantages of
milling are that - as a substractive process - it can make a final result that
is substantially stronger than most of the things you could do with a 3D
printer and that it most likely is much faster.

Re-working or finishing like that is typically reserved for casting and other
cheap mass production processes.

~~~
willvarfar
I was thinking of smooth curves.

Judging from the photos, even the expensive print has a voxelized appearance.
I've certainly seen that in the one 3D print I've handled too.

So my idea was to print slightly oversize, then mill and polish for perfect
curves.

~~~
blacksmith_tb
Don't people often just use acetone or another solvent to smooth the surface
of chunky prints (outdoors, I hope)? How effective that would be would vary
depending on the plastic, but it seems easier than milling (if not especially
precise).

~~~
jacquesm
Sandpaper? File?

------
huuu
If his conclusion were true companies like Shapeways would only use cheap
hobby printers. But ofcourse it is not.

Reliability, support, accuracy, all lacking with hobby printers.

~~~
onion2k
_If his conclusion were true companies like Shapeways would only use cheap
hobby printers. But ofcourse it is not._

It's far from a perfect analogy, but with servers Google demonstrated _really
well_ that the cost of high-end 'professional' equipment can be a waste of
money where cheap, commodity kit can be used at scale instead. It's not
completely unreasonable to think that a farm of cheap 3D printers could be
used in place of one high-end model eventually.

~~~
jib
People are freaking expensive. I think that is something that you miss easily.

200k sounds expensive for a printer, yet that is the cost of 1 guy for three
years (assuming western country).

The 200k machine just has to be a small bit better than the 2500 machine for
it to pay off so fast it is ridiculous. A commodity approach to printing
sounds like it would involve a lot of quality checks and other really pricy
manual things that would eat up that 200k in under a year.

If you can remove all human costs, then yes, commodity gear is likely better,
because you are paying for gear that knows that humans are expensive, so even
small savings in humans translate to a ton of cost, and so the professional
gear is priced accordingly.

~~~
onion2k
_The 200k machine just has to be a small bit better than the 2500 machine for
it to pay off so fast it is ridiculous. A commodity approach to printing
sounds like it would involve a lot of quality checks and other really pricy
manual things that would eat up that 200k in under a year._

Owning the 200k machine has to be better than owning _80_ of the cheaper
machines for it to be better. In a lot of scenarios that will be the case - if
you need the improved resolution, reliability, etc that the 200k machine
offers then the cheaper machines just aren't an option. In time though, as the
cheaper machines improve, the expensive machine may stop being a better
option.

~~~
lawless123
"In time though, as the cheaper machines improve, the expensive machine may
stop being a better option."

Or in time the expensive machine gets cheaper.

~~~
onion2k
That might also happen, but _in general_ cheap things get better faster than
expensive things get cheaper.

------
st3v3r
The professional printer printed out almost 4x the amount of material in the
same time (100% infill vs 25%). If it had the same settings for hollow infill,
it likely would have been much, much faster.

------
JabavuAdams
What a weird article!

The low-cost part is as good as the high-cost part ... except in all of these
ways that it's not, that I will outline here. Oh, and I basically just
eyeballed them, instead of measuring them. Oh, when pieces were missing due to
failure to print, I just kind of assume that they would have printed okay with
some tweaks.

What!? Amusing.

------
dbrgn
Here's another interesting comparison: $20,000 vs $600:
[http://www.hanselman.com/blog/3DPrinterShootout600PrintrbotV...](http://www.hanselman.com/blog/3DPrinterShootout600PrintrbotVs20000UPrintSEPlus.aspx)

------
kragen
I read this whole article hoping to find the part where he tests the tensile
strength, impact resistance, stiffness, and dimensional accuracy of the two
parts. It never came. Except for the part where he had a delamination
("split"), which I guess means zero strength for that part of the part.

I've been fairly disappointed with the strength of Prusa-Mendel-printed parts
I've made. Even if you don't have complete delaminations, it's easy to get
poor layer adhesion, which makes the parts fall apart under the least strain.
You can fight that by turning up the temperature and filament feed rate, at
the cost of dimensional accuracy (which you can compensate for in theory but I
haven't done so successfully, being just an amateur) but the higher heat also
weakens the PLA. Maybe this weakening is hydrolysis due to water absorption in
the filament; I don't have a way to measure that, except printing the same
thing a second time after dehydrating the filament, which I haven't done.

I was surprised to find that 100% infill is not always the strongest option,
even holding part geometry constant. Lower infill settings produce a more
compliant part, and it can consequently withstand higher impact energies.

I don't think you should hold part geometry constant when changing machines or
especially entire fabrication technologies. You should play to the strengths
of the machine you have. I know that's contrary to the outlook of 3D printing,
but it's true. Things like topology optimization can easily generate forms
that are impossible to injection-mold, relatively easy to FDM, and much
stronger. If you have the option of 25% infill, you can probably get a
stronger part by deploying the plastic you saved as ribs outside the main
body. And so on.

------
rebootthesystem
It would have been nicer to have seen a comparison using the same material as
well as a series of parts designed to test for specific issues in 3D printing.

Add to this printing 100 copies of each part and we might have ended up with a
useful set of data points.

------
GnarfGnarf
3D printing, especially hobbyist machines, is still in its infancy and
produces disappointing results. A large flat piece warps. The resolution is
coarse. It takes too long to produce even a simple piece. The machine needs
constant monitoring. It's at the equivalent of the DOS stage of personal
computing.

I wrote code to produce STL files. These files are accepted by hobbyist
printers. I sent it to a professional shop, they complained one of my
triangles wasn't closed, couldn't fix it or tell me which it was. Wonderful.

~~~
MrBuddyCasino
You probably knew this one, but still:
[http://runningahackerspace.tumblr.com/post/113272014704/sure...](http://runningahackerspace.tumblr.com/post/113272014704/sure-
we-have-a-3d-printer)

~~~
GnarfGnarf
That looks so sad :o(

------
3dprinted
Neat project comparing FDM.

Now, let's be a little more fair and start looking at what production
companies will be buying:

[http://www8.hp.com/us/en/printers/3d-printers.html](http://www8.hp.com/us/en/printers/3d-printers.html)

[http://www.stratasys.com/3d-printers/production-
series](http://www.stratasys.com/3d-printers/production-series)

No contest. Having multiple hundreds of thousands of colors, properties (like
heat-resistance, flexibility, different opacity), various different materials,
automated easily removable supports, decent precision, and serious speed beats
the shit out of your desktop model any day of the week. Sorry.

------
lawless123
The difference between food at a good restaurant and a great restaurant isn't
huge.

The price however usually is.

------
globuous
I'd like to see a similar post ten years from now, see how things have
evolved. I didn't realise how precise some of these industrial 3D printers
were! This gives me a lot of hope as to what I might have in my house in a
decade.

------
rnestler
What's also important when comparing 3D printers is maintenance cost and
effort. For example: The Ultimaker 2 we have in our Hackerspace needs regular
replacement (about every 600 printing hours) of the PTFE Coupler (hot end
part). Also sometimes you need to perform a cold pull
([https://ultimaker.com/en/resources/19510-how-to-apply-
atomic...](https://ultimaker.com/en/resources/19510-how-to-apply-atomic-
method)) if the nozzle is clogged.

------
taitems
Surely the high gloss finish on the black material is drawing attention to a
lot of the flaws as well? I'd really like to see a same colour comparison
between the two.

------
dekhn
I see cheap 3D printers like I saw linux in 1995: not quite the functional
equivalent of a $100K SGI workstation, but still a great way to get experience
in the area. You just have to understand that much of your time will be spent
tuning the printer, and fixing it, and upgrading it. I don't know that the
Statasys fails nearly as often as a cheap printer.

------
spriggan3
3D Printing is really great for industrial designers who want to prototype
products. My uncle is an industrial designer and I remember how costly it used
to be for him to come up with a simple prototype. Today a $2500 printer can
get one pretty far in a few hours, trully revolutionary. It gives a greater
margin for experimentation, trial and error.

------
dbrgn
Using different material and different infill is a bit of an unfair
comparison. Using 100% infill causes more problems with warping due to
shrinkage, thus increasing the difficulty. Using 25% avoids this, but
decreases stability a bit.

Regarding the print quality in general, I think an Ultimaker 2+ would give you
better results (also at a price of 2500$).

------
dekhn
Be aware that the high end printers include features that are patented, for
example soluble support, heated build chambers, etc, all have IP around them
that may prevent companies selling inexpensive printers from including those
features directly. This could translate to better results from the high end
printers.

------
crumpled
"The Stratasys machine uses a separate dissolvable support material that can
be washed away with a special salt water solution."

This can be achieved with dual extruder models Makerbot 2X or its FlashForge
clone, under $2500.

Use HIPS as the support material, print in ABS and dissolve HIPS in
d-limonene.

------
progman
3d printer testers should use a default model with complex geometry which
makes comparison much easier. For instance,

[http://www.thingiverse.com/thing:1019228](http://www.thingiverse.com/thing:1019228)

------
blahi
This seems like an interesting hobby. How much time is needed to achieve a
reasonably high understanding of this work? Not industrial grade expert, but a
knowledgeable layman. And where/how can I educate myself?

~~~
armamut
I'm not even an engineer, and I have made one. But, making a 3D printer by
yourself from ground up (or assembling one with the parts bought from china
etc.) takes a lot of time. I only paid attention at my spare times, so it took
my months. But I must say that, it is a very satisfying hobby. I strongly
recommend it :)

But if you want to buy one, you can find very nice 3D printers at $250 - $300
range from aliexpress etc. It may take hours, a day or a week for calibration
(depending on your printer model and printed part quality expectations), and
you are good to go.

But I must say that, 3D printers need maintenance and that can take your time
as well.

If you want to educate yourself, [http://reprap.org/](http://reprap.org/) is
the site you would want to visit. Not only for making your own printer, but
calibrating and maintaining a bought 3D printer as well...

~~~
blahi
No, I meant using a 3d printer to build cool stuff.

~~~
mlni
As a start you can just go to Thingiverse to search for a model that fills
your need and send it to the printer. That would take you all of a couple of
minutes. Per try, until it comes out ok.

If you want to try your hand at 3d modelling then you'll probably download
Sketchup as a start and noodle around while watching youtube tutorials on the
side. In about 8h you'll feel confident enough to actually model something
meaningful. After ~40h you'll be able to knock together a model quite
proficiently.

After you'll have gotten tired of Skethub producing broken STLs and not
allowing you to change your mind after modelling a thing, you'd move on to one
of the real CAD software package, like Solidworks or Fusion 360 (which is
great for beginners, btw). That rabbithole goes exactly as deep as you've got
time for :)

Fiddling with the printing itself will take a bit of setup time before each
print and then a lengthy wait (hours to days) to get the result, or see it
fail in some new and unfunny way. It's not really all that difficult, to be
honest, just takes some time to develop an intuition about what's likely to
fail.

------
lunchTime42
Additive manufacturing is bad from the getgo. Anything with errors, adding
upon with errors, is unsuitable for large scale precision manufacturing.

------
LELISOSKA
aren't resin printers increments better than normal 3d printers?

~~~
ZenoArrow
Yes, SLA printers like the Form 2 do offer better print resolutions than FDM
printers of a similar price.

[http://formlabs.com/products/3d-printers/form-2/](http://formlabs.com/products/3d-printers/form-2/)

The downside is they can't work with as wide a range of materials compared to
FDM printers, and the materials they can work with tend to be more expensive.

