Hacking the DF64 exit chute - Page 16

Grinders are one of the keys to exceptional espresso. Discuss them here.

#151: Post by ltanzil »

iyayy wrote:perhaps i may suggest printing a replacement for the whole front chute cover instead?
then u have more option to go wild.
the portafiler holder still screws to the body, no issue there i think. issue is if you want a knocker, will 3dprint material works instead of metal?
otherwise maybe you can design extended nozzle that goes further out than the front chute cover, and knock on that instead? and maybe spring load it from bottom side / body.
im not sure however how flexible a 3dprint is to multiple flexing and knock stress tho.
Great idea knocking the extended nozzle. 3d print the whole front cover is out of my league (bit of old school :D ) and the portafilter holder is threaded to the chute cover not the body.
but i like the idea of knocking the extended nozzle, that quite simple. the hard part is just choosing the right type of spring and where to put it so it look nice.

GDM528 (original poster)

#152: Post by GDM528 (original poster) »

In case anybody out there is still using the DF64, and thinking about replacing the exit chute...

I've updated the design of the detachable downspout component, with thicker walls on the section that captures the expansion chamber. Mine was starting to develop some cracks, and this thicker version should forestall that.

I've also updated the expansion chamber, eliminating the internal ribs that were meant to mix up the flow of grinds. Turns out the difference with the ribs isn't very significant, and more importantly those ribs were catching the grind and triggering clogs. I observed that when a clog starts in the downspout it propagates up the chute crazy-fast, so by the time I notice it's too late.

The path from the grind chamber to the dosing cup is now smooth and free of any possible constrictions in the path. The updated files are dated November 25th: "Expansion chamber" and "35 degree downspout - no base tilt".
https://grabcad.com/library/df64-exit-c ... ownspout-1

I've been grinding pretty fine lately, under 5 ticks above burr-chirp. The near flour-like texture of the grind has taught me a couple new behaviors to cut down on clogging events:
1) I grind into the factory dosing cup, and just before starting the grind I use my breath to fog the inside of the cup so the fines stick and stay contained as the cup fills up, and when I perform step #2...
2) I lightly tap on the bellows during the grind to puff out any grind accumulation before it gets out of control. Emphasis on "light" and "tap". The springs holding the burrs apart are really stiff, so IMHO the effect of me tapping occasionally on the bellows has a trivial effect compared to all the mayhem going on in the burr teeth. Gravity doesn't have much of an effect on very fine grind, so I have to do something to keep them moving along.


#153: Post by gaudenzio »

Hello coffee lovers, this is my very first message in this forum. :D
First of all, thank you Gary for your wonderful work!

I own a DF64 and of course I'm fine-tuning, trying to get the best of it.

I got into this rabbit hole of choosing the most suitable material for my 3d print. I'm planning to print the exit chute only.

On one hand, the cheap option is the classic resin with SLA print. (I found a place here in Spain where I can get it for about 15$).
But someone in this thread mentioned that it would be great to print it in some anti-static or conductive material, in order to reduce the static issue.
I've done some research about anti-static materials (ESD), there's ESD-ABS and ESD-PLA, but both, afaik, are only compatible with FDM printing and not SLA printing, which will give a more rugged finish. I also have some concerns about how food safe these materials are. EBS materials are usually designed for electronics, not for food use, ant the anti-static properties are usually achieved by adding some metallic nano-particles in the mix (carbon, nickel, etc..).

I almost decided to go for the classic resin, but I saw that I could get for about 50-60$ a stainless steel chute, delivered from China. The technology is SLM (Selective Laser Melting), which will give a slightly rough finish, but I guess I could easily polish the inside.

Delivery time is not an issue, I can wait the extra time for the metal chute if it's the best option.

Any suggestions? Are the anti-static properties of the chute really important? Do you see anything relevant that I didn't take into account?

Thanks in advance and cheers from the rabbit hole.

GDM528 (original poster)

#154: Post by GDM528 (original poster) »

Welcome to HB, gaudenzio!

Technically speaking, the term 'anti-static' is only for the material itself - not the surrounding area. So even a well-grounded metal chute won't dissipate the static charge of the grounds that don't contact the surface of the chute. It will help, but many of the grounds exiting the grinder just fly through without touching anything. The metal versions I built still had enough charged grounds to keep me looking for alternatives, not to mention the cost and/or skills required to create a metal chute.

I gather that most people are skipping the downspout and expansion chamber, but that's where much of the static management happens. Eliminating the clump crusher significantly reduces the time the grounds spend in the grinder, but the process of dissipating static charge is generally kinda slow. So, I settled on a scheme to contain the grounds long enough for the charge to dissipate in the catch cup.

As suggested early in this thread, I did try coating the interior of my SLA-printed chute with a food-grade epoxy. The coated surface is smoother, but grind will still accumulate over usage. There's no lower limit on grind particle size, so as smooth as the surface might be, there will eventually be a smaller particle (or oil droplet) that will take hold - which in turn will create an opportunity for yet another particle...

On a related note, I've found that small changes (as in, like, just a couple degrees C) in my home roasting profile can cause huge changes in the static behavior of the grind. I've stopped thinking that static is just a grinder issue - some roasts are just gonna misbehave.

All that said, a mirror-polished stainless steel exit chute would look freaking awesome ;)


#155: Post by mmartins »

Would an ABS chute be too dangerous due to not be food safe?

GDM528 (original poster)

#156: Post by GDM528 (original poster) »

There's quite a bit of online information regarding the food safety of 3D printing materials. It's a 'do your own research' scenario, which, alas, can land you on either side of the safe/not-safe fence. For me personally, most of the food I eat is not universally considered 'safe' ;)

I observe the coffee grinds interacting with the exit chute (and the grinder overall) in two ways:
1) The grind particle 'flies' through the chute in a matter of milliseconds, never touching chute in any sort of significant way.
2) Some grind particles will adhere to the walls of the chute and accumulate over time.

I consider #2 above to be the most worrisome. If the accumulated coffee grind can stay in place long enough, it could start to mold - yuck. So, I place a high priority minimizing long-term grind accumulation. The original DF64 clump crusher and exit chute has some pretty significant nooks and crannies that can hold the grind in place indefinitely, and cleaning it out is a PITA.

As for what material to print with, I suggest a key thing to consider is the resulting surface finish. A rough surface will accumulate grind faster. I've never tried it, but I understand there are some post-print surface treatments that smooth out the print lines of ABS parts - however I wonder if any of that solvent stays in the ABS...

I use a chute printed with an SLA resin that isn't rated as food safe, but I've coated the interior with a food safe epoxy. I consider the most important aspect of that epoxy is that it produces a hard, glossy surface finish. Grind still accumulates, but I've found it easier to knock it loose with a few good whacks on the bellows.


#157: Post by Jonk »

GDM528 wrote:If the accumulated coffee grind can stay in place long enough, it could start to mold - yuck.
I think that's highly unlikely. Roasted coffee has extremely low moisture content. What usually happens is that the oil hardens into rancid cakes, reminiscent of liquorice candy :wink: so uh, a different kind of gross that many cafés and shops unfortunately doesn't consider.


#158: Post by philadendron »

Thanks for your hard work in creating these parts. I'm thinking of having the chute printed and then coating with the food safe epoxy you mentioned. Can you advise what epoxy you used and how it's working for you? Thanks.

GDM528 (original poster)

#159: Post by GDM528 (original poster) replying to philadendron »

I searched for keywords "food safe", "clear", and "hard". Then picked the smallest quantity possible - which was still way more than needed.
https://www.amazon.com/dp/B087PKBYLX?re ... tails&th=1

The epoxy is pretty thick, like honey, so I used a foam-tipped swab to smear it inside the chute. One layer seemed like it was just enough to coat and smooth the surface, but a second layer wouldn't have hurt. After letting it fully cure, clean thoroughly with alcohol and polish with a paper towel. Resulting surface was smooth and glossy (just like they said). Definitely not anti-stick for oily dark roast beans, but pumping the bellows clears it nearly every time.


#160: Post by victor_rf »

Hi guys!

I'm planning to print a modified exit chute for my DF64 to replace my current declumper.

I have a doubt that may sound ridiculous, but I never work with these type of products: how do you trate the inner part of the exit chute with epoxy resine and make the coatting smooth and regular?

Thank you very much!