Hacking the DF64 exit chute - Page 3

Grinders are one of the keys to exceptional espresso. Discuss them here.
GDM528 (original poster)

#21: Post by GDM528 (original poster) »

999mor wrote:Awesome! Looking forward to it. So the printing on hold for now.

So, do you think that the epoxy resin is not needed?
Okay, posted downspout for 10-degree base tilt on GrabCAD: https://grabcad.com/library/df64-exit-c ... ownspout-1

This render shows the proper orientation for direct on-platform printing, hence the anti-cupping notch at the base.




The opening might flare a bit on the build platform, which can be trimmed with a sharp knife or sandpapered. Note the expansion chamber upper tube is oversized by 0.1mm for a snug fit - based specifically on my printer's characteristics, so that have to iterate a few times to get the perfect fit.

As for coating with epoxy resin, I'm presuming it's food safe? If it goes on thin, hard, and smooth, it might actually help any grounds from sticking on the walls of the chute. Can you link the epoxy you're looking at using?

999mor

#22: Post by 999mor »


GDM528 (original poster)

#23: Post by GDM528 (original poster) » replying to 999mor »

Thanks! You've introduced me to a world of food-safe resins I didn't know existed. Shame it costs so much, and 99.99% of it will be left over. However, It looks like you should be able to achieve a really nice glossy finish that would further reduce retention/exchange.

Speaking of retention and exchange, here's my exit chute another dozen grinds since the previous photo:



Just a teensy bit more accumulation at the start of the chute, and downstream looks basically the same. Every time I check for retention it comes up zero. I'm not aware of how to test for exchange, but it doesn't look like it would come from the chute.

I'd like to think the light patina from the grounds and oils flying past is a sorta-protective coating. Plus, only a fraction of the grounds will come in direct contact with the walls of the chute, and are in the chute for maybe 20 milliseconds. It's a personal decision: I'm OK with it for me, but I'd use biocompatible resin for a commercial version to eliminate any concern.

RoyCroppa

#24: Post by RoyCroppa »

Hey Gary, thanks so much for putting the time and effort in to doing this! Absolutely awesome. I've got a DF64 arriving tomorrow and I'm very excited to dive into mods. I just wanted to ask a quick question - I downloaded your exit chute from Grab Cad and imported it into Autodesk Fusion 360, as I wanted to remove the attachment from the end (the square block enabling to connect to the downspout), so that it would sit more flush - I am only planning on using the exit chute, as I have ordered a 'dosing collar' to prevent mess. First and foremost, I was going to ask if this would affect the functionality of the exit chute? My guess is no, but seeing as you've put so much time and thought into the design I thought I had better check! And also, as you can see from my screen grab, the screw holes and the chute itself, seem to be slightly off centre/asymmetrical. Is that how it is supposed to be? Or has my file opened strangely? I'm going to have to pay for someone else to 3d print it on etsy, so I just wanted to be 100% sure!! Thanks so much again for all the time you've put into this. It's much appreciated!

RoyCroppa

#25: Post by RoyCroppa »


Oops! Forgot to attach screen grab

User avatar
Jeff
Team HB

#26: Post by Jeff »

I'll admit these days that I'm no longer the one that assumes that what 90°C water doesn't kill, the alcohol in my beer will. I did find a reference that didn't seem to be selling coating products or loaded with affiliate links. https://formlabs.com/blog/guide-to-food ... -printing/

GDM528 (original poster)

#27: Post by GDM528 (original poster) »

RoyCroppa wrote:image
Oops! Forgot to attach screen grab
Yeah, the plug end looks weird because the DF64's exit port is offset a bit clockwise from dead-center. Dunno why they did that, but It was an annoyance in the CAD design process 'cause everything else in the design is centered. To save on plastic I chamfered the corners, since they weren't really contributing to the structural integrity. I was lazy and applied the same chamfer to opposing corners, which further exaggerates the asymmetry.

You should be fine trimming back the exit end to make it flush with the OEM cover plate. If I go back at some point to iterate on the design, I too may switch to a flush design so it's easier to install. But there are some points to consider as you proceed:

I think the 'secret sauce' of the exit chute design is the plug portion that fits into the opening from the grind chamber. It's a snug fit that calls out for the best possible print fidelity - which for my printer (Form 2) means it's the last feature printed, and at an angle that optimizes print quality. To that end, the exit portion of the chute is supposed to placed directly on the build surface, with enough surface area to hold firm throughout the printing process. So it'd be prudent to retain enough of that flange at the exit end of the chute, but note that it may be good to thicken the remaining flange to at least a couple millimeters.

There's a notch cut on the exit end of the chute, so when it's mounted on the build platform there will be a pressure relief to prevent 'cupping' issues. If you trim the notched portion off, you'll need to replace the notch.

You've piqued my curiosity about the 'dosing collar' you mentioned. Can you elaborate or post a picture of it?

RoyCroppa

#28: Post by RoyCroppa »

Ah ok, thank you for the explanation. Once again, that's very helpful.

And thanks for the heads up - I'll be sure to replace the notch! If I have a lot of success with it, I'm tempted to look into getting it machined out of aluminium / stainless steel, just to make it 100% food safe.

Would you mind elaborating on what your experience has been like with retention, specifically regarding the bellows? In other words, how much do you have to use the bellows with the new exit chute?

It would be a 'form over function' mod, but I love the idea of removing the bellows entirely and replacing with a Lagom P64 style top (with a similar antipopcorn piece to prevent beans from spraying out). But I'd only want to do this if I could achieve adequately low retention without the bellows.

Here's the link to the dosing collar - https://www.etsy.com/uk/listing/1101177 ... -listing-1 The reviews are all singing its praises, so I'm hoping I have a similar experience.

GDM528 (original poster)

#29: Post by GDM528 (original poster) »

RoyCroppa wrote:Ah ok, thank you for the explanation. Once again, that's very helpful.

And thanks for the heads up - I'll be sure to replace the notch! If I have a lot of success with it, I'm tempted to look into getting it machined out of aluminium / stainless steel, just to make it 100% food safe.

Would you mind elaborating on what your experience has been like with retention, specifically regarding the bellows? In other words, how much do you have to use the bellows with the new exit chute?

Here's the link to the dosing collar - https://www.etsy.com/uk/listing/1101177 ... -listing-1 The reviews are all singing its praises, so I'm hoping I have a similar experience.
Heads-up: as a fan of 3D printing, I have a predilection to designing objects such that they can't be fabricated any other way ;) The arc of the exit chute might have to be tweaked a bit to allow access for the CNC bit. Aluminum is on-again/off-again linked to Alzheimer's, so I imagine stainle$$ steel would be the bad-ass choice. Copper is also noteworthy for its antimicrobial properties.

I use a scale that reads to the nearest tenth of a gram, and every time I check retention, it's 0.0g. There's likely still some exchange happening from the grind chamber, but I'm not aware of a method to measure it. I get zero retention if I tap the bellows a few times to dislodge any grounds still in the grind chamber and stuck on the walls of the exit chute. Just light taps on the bellows so I don't disturb the grinds in the catch cup. I'll try measuring what sort of difference tapping the bellows makes - I'd bet it's pretty low. Sometimes I'll fist-pound the bellows to 'deep-purge' the grinder (into an empty catch-cup) - but almost nothing comes out if I've already tapped prior.

Thing is, it's no big deal to use the bellows nor is it an admission of failure on the design of the machine - just tap/tap/tap and I have peace of mind knowing I won't be tasting those grounds the next day. The bellows may end up being the only maintenance I need to perform on the grinder, ever again.

That's a really nice-looking dosing collar you found. The grind will still have an 'escape path' however, and you may observe grinds accumulating around the exit chute. I was going for 100% containment of the grinds, hence the downspout and expansion chamber. You might be able to design a cover for your dosing collar that would completely enclose the grinds.

basiecally

#30: Post by basiecally »

GDM528 wrote: Even though my resin isn't rated as biocompatible, I still consider it safer than my barrel-aged bottle of rum. Or bacon. Or pizza. The most common metal in contact with the coffee I drink is aluminum - which is linked to early onset Alzheimer's... I'm just gonna enjoy my coffee in the meantime ;)
I could have sworn that the relationship between Alzheimers and aluminium had been debunked but looking at it now it appears that there is still a possible link being looked into. https://www.sciencedirect.com/science/a ... 4015302512
Guess it's a question of causality though, as with most research into AD this far. There are meta analyses pointing towards a relation and especially a higher concentration of metals in the brains of patients with AD. As well as a chronic, high intake of Al making AD progress quicker. Then again, the British Alzheimers society lists the correlation as uncertain and has a few good points about dietary uptake. Look under the headline "Aluminium". https://www.alzheimers.org.uk/about-dem ... d-dementia

I think this goes for a lot of metals used in coffee making. Many brass fittings in espresso machines contain lead. A company here in Sweden had to do a large drive to replace certain parts in commercial, automatic espresso machines in office settings as a nation wide control revealed their machines to output significantly higher levels of lead in the beverages. But then again: the dose makes the poison. And other background exposure from different food stuffs will likely make up a larger daily intake. I don't know about you guys, but coffe is not my main dietary intake by volume :).

Alright, enough toxicology!
I don't have an SLA printer but I do have a Prusa Mini. I did a print with 0,07mm layer height in some Prusament PLA. Came out nice! Some visible layer lines but I decided to try and smooth it on the inside. Started with a small needle file and then followed up with 800 grit wet/dry sandpaper. I then burnished all places I could reach with a smooth brass burnisher. It installed very nicely but I've yet to make any coffee with it. I tried it out on some old, stale beans yesterday though and the grounds came out nice and fluffy. I've used it too little to be able to say anything about retention but I got out what I put in at least. And using the bellows yielded less, just a little bit of fines that dusted out. With my previous mod with the home made Mythos clump crusher copy I would get at least a little bit of actual grounds out. The last image is of the old exit chute used with the Mythos CC clone after a couple of months use without disassembled cleaning. I've cleaned what I could reach within the grind chamber more frequently.