Hmmm…. Well, I admit it – I enjoy coffee and 3D
printing! So why not combine both and make 3D printing
filament with coffee! That’s why I made my own Bio-Composite material
for 3D printing by mixing Spent Coffee Grounds with PLA. We’ll talk about why such a material might
be useful, what I had to do to make it printable on a regular 3D printer, how the mechanical
properties are, and most importantly, how it smells during printing. Let’s find out more! Guten Tag everybody, I’m Stefan and welcome
to CNC Kitchen. Squarespace sponsored part of this video. Try out how easy it is to create your own
beautiful-looking website by browsing Squarespace.com/cnckitchen to get a free trial! Coffee is one of the most popular beverages
on the planet, with around 4 billion cups consumed every day. This results in a giant amount of spent coffee
grounds. Even though some of these leftovers get composted,
used as fuel or fertilizer, a huge amount ends up in the landfill. I really enjoy my morning cappuccino, so I
thought, why not use the leftover spent coffee grounds and add them to 3D printing filament. But why add coffee to a polymer? Polymer additives can be separated into three
groups: reinforcing additives like glass or carbon fibers that improve mechanical properties,
functional additives like plasticizer or impact modifiers which act more on a micro or molecular
level and the third category which are fillers. Fillers are usually cheap materials to add
volume and reduce the price of the final product. Spent coffee grounds are a filler and maybe
actually pretty good ones, ecologically and economically speaking. Economically because, it’s a waste product
that is widely available. Ecologically because it reduces the use of
polymers and pigments and as an organic filler might even improve compostability when added
to something like PLA. The coffee particles increase the surface
area, absorb more moisture, and act as fertilizer during composting. I’m currently even running a composting-at-home
experiment to determine what happens to biopolymers in a non-industrial compost. I’m quite curious how coffee PLA will do
there. If you don’t want to miss the results, make
sure to subscribe and select the notification bell! Now quickly some trivial knowledge, but still
pretty interesting! In preparation for this video and researching
coffee and spent coffee grounds, I wondered how much mass of the coffee that we put into
the portafilter ends up in the cup and how much is disposed of as our spent coffee grounds
that could be used as a filler. To quickly test this, I brewed a bunch of
coffees for which I meticulously weight the ground coffee before the brewing process and
then after drying the pucks for 18h at 100°C in an oven. The extraction yield, so the amount of coffee
substances that were transferred to the cup during brewing was an astonishing 22% on average,
also taking the initial moisture of the coffee into consideration, which really impressed
me because I thought it was way less. To make my coffee filament, I collected even
more pucks from my coffee maker that contain the remaining 78% of the beans and then dried
them overnight in a food dehydrator. Since we usually drink espresso, the coffee
grounds were already quite fine. I still thought it was good to use the most
favorite kitchen tool of Germans, the Thermomix, to blend it even more. After a bit on the highest speed, I ended
up with a nice and fine powder that, so I thought, was ready to make some filament. I went down into my basement and started preheating
my 3DEVO Desktop Filament Extruder that I currently still have at my disposal. Once the heating zones were at the temperatures
for extruding PLA, which is around 180°C, I added some plain PLA pellets first to purge
out the leftover material that was still in the barrel from its last use. Once clean PLA came out of the nozzle, I extruded
around 200g of clear PLA that we’ll use for our reference prints when we later test
the strength of our coffee grounds composite PLA. While the spool was slowly filling, I premixed
250g of virgin PLA pellets with 5% of our spent coffee grounds and shook everything
well to distribute the filler evenly. Why 5%? Because this was a starting ratio that was
recommended to me, and we can later always try more. The coffee stuck nicely to the pellets, which
should help us with even mixing of the polymer and the particles during the extrusion process. Once the roll of plain PLA was ready, I stopped
spooling and added the pellet-coffee-mix to the hopper. The material is then fed into the heating
zone via an extrusion screw, where it melts and gets homogenized. At the end, the liquid mass comes out of a
nozzle, get cooled, measured and then pulled to the proper diameter. It took around 10 minutes until the rest of
the clear PLA was purged out, and I was able to see a change in color and material with
tiny pieces of coffee in it. I noticed that the property of the melt changed
as soon as I added the coffee grounds to the mix. The material came faster and more liquid out
of the nozzle without changing any other parameters. The reason might be a higher melt flow index
because the polymer either hydrolyzed due to moisture residue in the powder or the oils
contained in the coffee grounds that act as a plasticizer. When the color and diameter stabilized, I
started the spooling process and wound up a nice roll of golden-brownish filament with
dark speckles in it. Before continuing with any other tests, I
took the roll for a spin. I loaded it into my Prusa Mk3 and started
a first print, which worked great….until after a bunch of layers, the nozzle clogged. So, I cleaned it out and restarted it, only
to again end up with the same problem. What happened? My Prusa has a standard 0.4mm nozzle installed. If we’re adding the coffee grounds to the
filament and there is only a single grain larger than this diameter, the printer will
clog. For this reason, I switched to a 0.6mm nozzle
and was able to continue printing without an issue. The material seemed a bit stringy, which I
also experienced with other wood fills in the past. Otherwise, the parts turned out really nice! Unfortunately, only using this material with
a larger nozzle wasn’t an option for me. Who knows if there is another particle in
the filament that might even clog a 0.6mm nozzle. This is why I ordered a 60-mesh sieve which
has a hole size of around 0.25mm. Since this is smaller than our 0.4mm nozzle
size, it should make sure that there are no particles in the coffee grounds that can block
the nozzle. Due to the stringing I got with my first batch
of coffee PLA, I re-dried the leftover coffee grounds for 4 hours at 100°C in my oven and
then sieved them. Interestingly, a substantial amount of particles
didn’t make it through the sieve, which shows how many potentially dangerous particles
were still in the mix. I tried further grinding the leftovers in
a mortar but only had little success. A ball mill might be really beneficial for
such an application. Using the sieved, spent coffee grounds, I
extruded two more rolls of material, one with 5% coffee content, the other one with even
10%. The first one where I again only used 5% of
additives turned out beautiful with an awesome color! Unfortunately, the 10% spool caused me quite
some trouble. Even with the mixing screw of the extruder,
there were regular lumps of coffee in the filament, which made it brittle at that location
and could potentially cause problems during printing. My 3DEVO Composer uses a mixing screw where
the tip has a specific structure that should improve mixing but it seems that even this
wasn’t enough. In industrial applications usually a twin-screw
extruder is used for something like that where the material really gets thoroughly mixed. Even though I don’t have something like
that, I still have some tricks up my sleeves like mixing the coffee grounds with ground
up pellets to increase the surface area so that the materials can better stick to each
other, but that has to wait a little more. If you have any experience with that, please
let me know! Printing the spool with 5% coffee PLA on the
Prusa Mk3 with a 0.4mm nozzle worked great, and I didn’t have a single clog anymore. Parts turned out well, with beautiful color
and texture. Unfortunately, the 10% coffee content material
was not printable, even using a 0.6mm nozzle because the small orifice constantly clogged
every time a lump of coffee grounds tried to pass it. Let’s now talk about the smell during printing. There was definitely an odor in the air after
the parts were printed. Unfortunately, the smell wasn’t as nice
as when entering a coffee house, though there was a roasted, though almost burnt sweetness
in the air. This is kind of understandable because for
once, coffee aroma is quite volatile. Since the coffee grounds in the filament were
brewed and dried for a substantial amount of time, there isn’t that much of the initial
fragrance left. This doesn’t mean that 3D printing coffee
filament smells bad; quite the contrary, similar to wood-filled materials, it’s actually
quite pleasant, just maybe a bit underwhelming if you’re expecting freshly brewed coffee. Let’s finally also look at the strength
of our coffee PLA and if it could still be used for more than decorative purposes. For this, I printed tensile samples and a
test hook in the clear PLA that we extruded in the beginning and our second batch of 5%
coffee PLA. Then I mounted them one after the other in
my DIY universal test machine and loaded them until failure. First, the samples that were printed horizontally. Plain PLA was able to bear 58 MPa on average,
whereas the material filled with coffee grounds was 10% weaker and failed at 53 MPa. The samples that were printed standing behaved
similarly with 35 MPa failure stress for plain PLA and 27 MPa for the coffee PLA. The test hooks showed very similar results. The one printed in plain PLA failed at 69
kg and the one printed in coffee PLA at 61 kg. So, we see a degradation of properties but
not by a lot. This bio-composite still seems to be able
to take some beating. I’d be really interested to know how the
properties further degrade with higher coffee contents, but that needs to wait until I figure
out proper mixing. So, let me tell you a secret. Probably 90% of my videos aren’t done until
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first website or domain purchase. So this was my experience with 3D printing
filament made with spent coffee grounds. I learned a lot about the process and really
look forward to further experiments. But what’s your opinion? Let me know if you would buy such a filament
and for which reason? Is it the ecological aspect, the texture and
the color, or is it even the smell? Thanks for watching, everyone! I hope you found this project interesting! If you want to support my work, consider becoming
a Patron or YouTube member and check out the other videos in my library! I hope to see you in the next one! Auf wiedersehen and goodbye!
