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Thread: Decent Espresso Machines (DE1) - Any thoughts?

  1. #251
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    Why not embed the scale in drip try a la https://home.lamarzoccousa.com/wp-co...o__AWA0015.png

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    New: lighter drip tray, flush diffuser, new mixing chambers

    Lots of interesting espresso-parts stuff arrived today (saturday), and so I thought I'd share...

    Yes, the pace of postings is picking up from me, because we're wrapping up so many different things up and can proceed to making these machines. It's mostly mechanical stuff at this point: the tablet software and firmware is looking good, another month or so of work to do.
    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    DRIP TRAY

    We're looking at alternatives to ceramic for the drip tray because:
    - it weighs 770g (1.7lbs) -- that's really heavy to air ship these to you.
    - it can break if you drop it
    - it is not easy to add plumbing to a ceramic dish
    - if we want to add "gravimetric" dosing by putting the scale under the drip tray, saving 500g will really help us get way under our 2000g scale limit.

    We're considering melamine for the drip tray (NOT for the water tank, have no fear), and today we received samples of a metaline container that is very similar in dimensions to our ceramic drip tray, but it comes in at 1/3rd the weight, and won't break (easily) if you drop it. Plus, you can mould a plumbing drain in it fairly easily (for the DE1PRO).

    ceranmela2b.JPG
    weightcerab.JPGweighmelab.JPG

    Melamine FAQ:
    https://www.fda.gov/Food/ResourcesFo.../ucm199525.htm

    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    We're still working on a "flush diffuser" (what slows down a flush so you don't get splashed) and we've decided that the best solution is to have a big enough container to hold the "waste water" and then let it splash around and drain out. We prototyped the idea below yesterday and it worked well. In order to weigh the drip tray, we need to have a few millimeters of "play" around it, so that the drip tray doesn't touch anything, so we think that moving the diffuser into the machine body itself, and not close to the drip tray, is a good idea.

    flushdiffuserb2.JPG

    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    Our new iterations of the manifolds (mixing chambers) came in today, made from high-tech Ultem. The big improvement here is that the water connectors are now all moulded directly into the Ultem, and everything is using "clips" to be held into place. This removes a lot of material needed (lower cost), removes lots of potential water leak sources (every water seal is a liability) and greatly simplifies assembly *and* repair.

    We also received a new iteration of temperature probes (with the threads, in the photo below) but we're hoping to move off of those, and have a "clip connector" design for our temperature probe, because threaded components that have a water seal on them are notorious to get right in production: if you screw them in too tightly you stress the seal out, and too loose and obviously you leak. The clip connectors don't have that problem. The parts for the new "clip connector" temperature probe design is in that upper plastic bag.

    We're also trialing a new kind of gold-tipped temperature sensor in the small manifold -- keen eyes will spot 3 little drill holes on the amber-colored component on the right. We'll decide in the next two weeks on which of these 3 temperature sensor options we want to go with.

    manifoldsb.JPG

  3. #253
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    Quote Originally Posted by thebookfreak58 View Post
    Why not embed the scale in drip try a la https://home.lamarzoccousa.com/wp-co...o__AWA0015.png
    Because:
    a) that design is a mess to clean up. Lots of crevasses for espresso to drip into and dry
    b) you can't get a usb cable in there to keep the scale charged
    c) you can only weigh a single cup. Double-spout portafilters won't work.

  4. #254
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    Quote Originally Posted by Melbroaster View Post
    Question: With the weight of the driptray water, drip tray and mug on the scale (ie 1.5kg- would you expect that the accuracy of the scale to reflect each extra gram added to the scale to be as consistent as each gram added to the scale starting from a zero load?
    You are absolutely right to point this out.

    Generally, with a load sensor, the more weight you put on it, the less accurate it is.

    With 1 kilo of ceramic and a full drip tray of water on it, our shot weighing would be accurate to 1g. That's still pretty good, considering that when you stop a shot, there are still a few grams that continue to come out, so that accuracy in weighing espresso shots isn't usually needed to be more than gram accurate. And what I'm describing is the worst case scenario (full drip tray of water, ceramic material)

    That's one reason why we're working on lowering the weight of the drip tray from 770g to 250g, by moving away from ceramic and having a melamine drip tray.

    Assuming your drip tray is mostly empty of water, a melamine drip tray should give us espresso-shot-weighing accuracy in the 0.3g to 0.5g range, probably more than is needed for this application.
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  5. #255
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    When will the decent espresso machine ship?

    I get asked "when are you planning on shipping this machine" as well as "I thought this machine was done? why are you still fiddling?".

    Those are very reasonable questions , and here's what I've got to say on this topic.

    - -

    THE SALES TOUR:

    Back in November, we had a working Beta machine. Not yet feature complete, but close, and making good espresso. I went on a two month sales tour, and received a lot more interest than I had expected, especially for the DE1+'s high end features. People wanted to place orders right now, give us money, to get in line to get one of the first machines. I thought we were just a few months from being able to make what I was demoing to the public.

    During the tour, my 3 Beta machines broke down several times due to shipping damage. Upon my return to Decent HQ in January, I decided to fire my mechanical engineer due to these problems, and a lack of progress while I had been gone. I hired a new one to redesign how everything was mounted inside the machine. As we went through all the internals, component by component, we found lots of areas that were "ok", but really could be improved, and rather than wait for a future version, I decided to do the improvements now.

    These improvements meant:

    - easier to repair (with more space inside, comes apart easily)
    - longer machine life (with better cooling, many fewer water seals, longer parts longevity)
    - lower energy consumption, faster startup
    - better espresso (better temperature stability, better pumps)

    Since it's Bugs and I funding this company and the R&D, I felt it was our decision to make: to spend more time and money making the DE1 machines better for even the earliest customers.

    - -

    SOME POTENTIAL FUTURE PROBLEMS FOUND

    In February I hired Jeremey and Matt from Blossom Coffee - two founders of a company who did something similar to us five years ago, but it didn't go that well. They're serious engineers and businessmen with direct experience in our field, and:

    a) their extensive review of our hardware uncovered new problems with our existing designs, especially in terms of longevity

    b) they had many performance improving suggestions that I thought were worth doing, and that I'd feel bad if our 1st customers didn't have.

    The big component I was avoiding touching was the heated group head, because it worked, but Jeremy's arguments for longevity and better & faster temperature control won me over, so I decided two weeks ago to bite the bullet and implement his suggestions.

    - -

    DESIGN FREEZE END OF APRIL, MANUFACTURING START IN JUNE

    We're making great espresso, just as we did back in November, and we're whittling down the list of mechanical decisions.

    Our deadline for hardware changes is the end of April, at which point the CAD model moves away from my "creative" mechanical engineer, over to my two "production" engineers, who will refine the drawings for each manufacturing partner, so that each gets made, and we'll start ordering final parts in May. Manufacturing of these "early access" machines then starts in June, and that's when we'll also be applying for final UL certification.

    And of course, the day-to-day discussion progress will continue to take place on this forum and on HomeBarista http://www.home-barista.com/marketpl...43925-730.html

    - John Buckman, co-founder.
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  6. #256
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    John, this is all sounding great! The extra time in testing is paying dividends in important areas that will help to deliver a better / more refined product that you and the team are happy with and that should lead to a greater experience for your customers. Sounds like a recipe for success there. All the best to you and the team. Might have a convert here.

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    Decent Knockbox now 50% larger

    Two weeks ago, I received a one-off (CNCed) version of our knockbox design. While it was nice looking, I found that its capacity was in the 6 to 8 pucks range, which was too little. To top it off, the knockbox looked teeny tiny next to our espresso machine, which itself is not that large either. I don't think there's that much of a market for ultra-compact knockboxes! Also, the small size meant that it was possible to bang the back of the knockbox when using it, and you can see a scratch in the photo below from my head barista Edison demonstrating this to me <sigh>.

    IMG_6123.JPG

    We've now tried 30%, 40% and 50% larger sizes, and I think I like the 50% size the most, because:
    - this gives us a capacity of about 22 coffee pucks
    - the relative size of the knockbox next to our espresso machine is better.

    Unfortunately, now I can't prototype this at a reasonable cost (it'd be cost to $1000 to make with CNC), so I'm going to to pay for a sheet metal stamping mould, and hopefully the size will be good and the mould can be used. :x

    The render below is the 50% larger version, with a portafilter in there for scale.

    preview-full-KNOCKBOX 50 + PF_0000.jpg

  8. #258
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    Looks like a better size. For reference it's a similarish shape to the Breville knock bin, which unlike some of their machines is built to last. I have one and I think it's pretty much the perfect size and shape for home use. I empty it once every week to week and a half, which would be 14-20 pucks and it's not quite full at 20. If you compare your size to the Breville one I reckon that's a good benchmark, though you wouldn't want to go any larger than it.
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    Revisited: getting an even water flow into the coffee bed.

    Occasionally, we've seen "cavities" in our spent coffee puck, after an espresso shot, that look like hot water came through harder than elsewhere. Ideally, we want water to come out of the group head shower in an even way, so this has been something to solve.

    We think that this problem is caused by how the holes on the group head shower are oriented. If you rotate the shower a bit, the holes can lie directly under where the water is coming out, and thus you'll have an uneven water distribution. We thought the problem was possible hole alignment between the shower and the shower screen, and that might contribute, but definitely getting the water to flow through the shower evenly is the first priority.

    By the way, this is what a shower looks like:

    IMG_6050b.JPG

    and this screen sits on it, right on top of the coffee bed.

    IMG_6049.JPG

    To test this theory, we loosened the screw, rotated the group head shower slightly, and voila! the holes-in-the-puck problem went away.

    However, I don't think that's not a great solution for you guys, because it means everyone then has to worry about how these holes align if they take this apart to clean it. We thought that it'd be better if the hot water entered the group head as close to the center as possible, so that it has a better chance of flowing out everywhere evenly, and in such a way that hole alignment didn't matter.

    Below is an annotated CAD drawing of our solution. The water path now has a little "cave" that redirects it very near the center, and in such a position that no shower screen holes will ever be below it.

    FYI that hole on the far left is for flushing the dirty water out at the end of the shot. We have a separate water path for that so that we don't soil the clean "making espresso" water path.

    And FYI #2, we're likely going to redesign that shower, rather than using an off-the-shelf part, to have more holes in it, so that water enters in a more distributed manner into the shower screen.

    grp.jpg

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    Quote Originally Posted by level3ninja View Post
    Looks like a better size. For reference it's a similarish shape to the Breville knock bin, which unlike some of their machines is built to last. I have one and I think it's pretty much the perfect size and shape for home use. I empty it once every week to week and a half, which would be 14-20 pucks and it's not quite full at 20. If you compare your size to the Breville one I reckon that's a good benchmark, though you wouldn't want to go any larger than it.
    Thanks for the tip. Could I trouble you to give me a height and width measurement on the Breville, for comparison?

    Of all the competitor's knockboxes out there, Breville's is the one I think is most elegant looking. Their design has class.

    Whoops, just found it on Amazon:
    • Measures 6-4/5 by 7 by 7-1/4 inches

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    Here's some more measurements just in case: Imgur: The most awesome images on the Internet

  12. #262
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    Regarding the knock box, this is where even a cheap 3D printer would make sense. For well under your $1K CNC'd price, you could purchase a 3D printer and print a full size sample. It might not be as strong as the production version but at least you would be able to hold it and check sizing etc.

    Cheers,

    Matt
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    Quote Originally Posted by MattyRay View Post
    Regarding the knock box, this is where even a cheap 3D printer would make sense. For well under your $1K CNC'd price, you could purchase a 3D printer and print a full size sample. It might not be as strong as the production version but at least you would be able to hold it and check sizing etc.
    I used to outsource my 3D printing to a people-with-3D-printers-at-home web service (I forget the name), and my first hire in Hong Kong was Alex Chau, who did great 3D prints and who I met this way. He would touch up the 3D prints w/o telling me, but I could see the filing marks. Great attitude toward quality!

    Unfortunately, our knockbox is now larger than most 3D printers (including Alex's makerbot) will print. He could make it in two pieces and glue it together, but it'd be a bit shabby looking.

    Besides, we really need to (literally) bang on it a while before I'm comfortable making 500 of them.

    We do use 3D printing a *lot* here, and we have a graveyard of previous designs that's pretty interesting.
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    I really do not understand why you are wasting your skills , time and resources on designing another knock box ?
    The returns have to be trivial
    surely the focus should be on final details and testing, testing, testing, to find the inevitable bugs in the Espresso machine.

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    Quote Originally Posted by blend52 View Post
    I really do not understand why you are wasting your skills , time and resources on designing another knock box ?
    The returns have to be trivial
    surely the focus should be on final details and testing, testing, testing, to find the inevitable bugs in the Espresso machine.
    +1. I have bought several Oz made Grindensteins for smaller cafes - I think they also make much larger ones. My personal oldest one is probably over 20 years old by now and it still looks new. A moderate pressure water jet keeps it pristine over the years, and the centre "knock piece" is still unmarked - although these days I use VST baskets and knocking pucks out is a distant memory (they flick out now). Short of running over it with a large truck or feeding it into the intake of a jet engine I cannot see how you would destroy it.

    Oh, the home one costs about $A30 with a wide choice of colours. If the aforementioned Breville is half as good, the whole global market for a knockbox must be worth, oh, let me see, a few peanuts.

    John (DE), it reminds me of an old screensaver "Shouldn't you be doing something more productive?" - like getting the espresso machine manufactured so I can buy one?

    TampIt

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    Quote Originally Posted by TampIt View Post
    John (DE), it reminds me of an old screensaver "Shouldn't you be doing something more productive?" - like getting the espresso machine manufactured so I can buy one?
    I understand that your interest is in our espresso machine, and that's great, but we currently have a full line of coffee accessories (12 different kinds of products) at https://decentespresso.com/ and we sell a lot of them. Our most popular accessory is the "competition milk jugs" https://decentespresso.com/milk_jug but our digital milk thermometer is a close second https://decentespresso.com/milk_thermometer

    I have 3 full time employees dedicated to our accessories business, and it's helping pay the bills for two years of espresso machine R&D. These accessories bring cash in the door, every day, and boxes go out.

    Having a functioning accessories business has meant that we've had to fully build out our logistics, supply chain, manufacturing relationships, fulfilment, order handling, tracking, tech support and accounting systems. Most of these systems were primitive and bug-ridden when we were first launched them, but they're now fairly mature.

    These are all things we'd need to have a well run espresso machine business, and it means that when we ship our espresso machine, the rest of the company will be totally ready for it. If we had no product except for a not-yet-shipping espresso machine, none of this would have been built out. I'm working off the assumption that our espresso machine will be a success, and I don't want to be a victim of its success.
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  17. #267
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    Quote Originally Posted by decentespresso View Post
    I understand that your interest is in our espresso machine, and that's great, but we currently have a full line of coffee accessories (12 different kinds of products) at https://decentespresso.com/ and we sell a lot of them. Our most popular accessory is the "competition milk jugs" https://decentespresso.com/milk_jug but our digital milk thermometer is a close second https://decentespresso.com/milk_thermometer

    I have 3 full time employees dedicated to our accessories business, and it's helping pay the bills for two years of espresso machine R&D. These accessories bring cash in the door, every day, and boxes go out.

    Having a functioning accessories business has meant that we've had to fully build out our logistics, supply chain, manufacturing relationships, fulfilment, order handling, tracking, tech support and accounting systems. Most of these systems were primitive and bug-ridden when we were first launched them, but they're now fairly mature.

    These are all things we'd need to have a well run espresso machine business, and it means that when we ship our espresso machine, the rest of the company will be totally ready for it. If we had no product except for a not-yet-shipping espresso machine, none of this would have been built out. I'm working off the assumption that our espresso machine will be a success, and I don't want to be a victim of its success.
    Good to see this. While there has been great concentration on this forum to whatever issue you serve up and the clear interest of everyone in a high quality long lasting machine, perhaps an even bigger factor in longevity of the machines we buy is how good and sustainable your business plan/team is. So the above comments at least allude to cash flow and the development of a distribution system that works - at least for small, low tech items. Naturally, I'm full of optimism in the hope of having a great machine but my friend the financial analyst was sadly, a lot more pessimistic

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    Finalizing the water tank design.

    This week, we're finalizing the water tank design, so we can send it out for manufacturing. For at least the first 500 machines, we'll be using porcelain (ceramic). While it is heavier than other options, it's totally food safe, even in quite hot water, and totally dishwasher safe : lots of other material aren't.

    We've previously allowed the water tank to slide out the front and the back. However, I'm blocking the back-fill because I've now had two employees think they're being helpful and unplug the 220V power plug as another person fills the water tank. That has them holding an open electrical wire inches from pouring water. Not good.

    Banning filling from the back gains us 100ml of capacity because I can get rid of the little 1cm rim on the back. It also avoids the problem of the tank sliding out when you lift the DE1.

    From the front, we've always had a little rim

    IMG_6134.jpg

    that you squeeze with your fingers to pull the tank out.

    IMG_6133.jpg

    However, ceramics are glazed and very rounded, and it's not been very easy to grab this. If we make the rim bigger, it becomes easier, but at a significant cost in water tank capacity (100ml for 1cm). There's also a ceramic deformation problem that if we have a rim on the front, we need to have a symmetrical rim on the back or the tray will deform when drying.

    So, I've decided to remove all rims from the drip tray, which gains us 200ml of water capacity (bringing us up to 2000ml) but now we need a dependable way to get the water tank out.

    My favorite idea is to put the tank on runners, so you push it in, hear a click, and it stays put. Then, push it again to have it pop out. Here's a video of what I mean:



    However, that's going to take some R&D to get right, and I want to kill all the R&D that I can so that we can move to shipping.

    Jeffrey's low-tech-but-just-works idea is to have a metal "pull tab" like so:

    IMG_6135.jpg

    placed to the left of the water tank:

    IMG_6136.jpg

    a little tug of the finger:

    IMG_6137.jpg

    tugs the water tank out.

    We've also considered button a metal "collar" around the entire water tank, so you pull that, or a strap, but this pull tab seems the most simple.

    I'm soliciting ideas now, so let me know what you think of this, and if you have any other (simple) suggestions!

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    I like the pull tab idea, hopefully the way it's attached to the tank is solid and it's not in danger of coming apart during transport or use.

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    Now building beta 7

    David in Seattle is building our beta 7 machine now. It's crazy how much cleaner the design has become with a few months of iterations!

    david.jpg

    And we have new iterations of the group head and main mixing chamber (the amber colored part) made now and ready to slot in.
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    New group head water path

    We' re-engineered our group head water path, because we wanted to make sure that water hit the coffee evenly and with minimum force.

    On our earlier machines and on most other machines, water enters via one hole, and then needs to be distributed evenly by the group head shower. The shower screen doesn't always manage to do this, which can result in uneven water flow into the puck. Some people buy expensive shower screens (the last part, touching the espresso puck) to try to even the water flow out there.

    In this new design, water is entering in via one hole, flowing around a temperature probe, and then being channeled out in a 6-pointed star pattern. Water no longer will exit with any force. This makes the group head shower's job much easier, so it will be much more likely to evenly flow water into the puck, and with even force out of every hole.

    newgroup.jpg
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    Will that make brew water pressure equal on all 6 exits points of the shower disc? If not, is the shower screen good enough to even things out across the coffee puck's surface?

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    Quote Originally Posted by JojoS View Post
    Will that make brew water pressure equal on all 6 exits points of the shower disc? If not, is the shower screen good enough to even things out across the coffee puck's surface?
    The goal is indeed for there to be enough space in that chamber so that the water flows out all 6 exits at an equal flow rate per hole, and at low velocity. Ideally, that would be 1ml/second per hole.

    Now that i think about it, we can actually measure that to see if that's happening, by using some tubes to direct the six outputs to different vessels, and weighing the accumulated water in each. Ideally, they should weigh the same after a 30s "shot" with no coffee.

    Last week, we also decided to design our own brass group head shower, because we can make one that has a lot less mass (for faster warmup and better temperature profiling ability during the shot) and a better hole distribution pattern that mates with our new 6-pointed-star design. That'll get drawn up next week.

    hmm... I just realized that you asked a different question, about "equal brew pressure" and the answer is "probably" but when the pressure is 9 bar, I'm not sure it will matter if the pressure is equal there, as long as the flow is, because after this hunk of brass there's a chamber, a shower and a screen, and that's where pressure needs to be equal. At least that's what I think your question is...

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    Yes I did ask about brew water pressure being equal on all 6 holes. I can imagine unwanted channeling during the shot if it is not. Pressure release after the shot can also cause uneven disruption on the puck that might lead to misdiagnosis of coffee prep procedures. Will the shower screen require tweaking in terms of position and how tight it is screwed on to get even flow?

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    Quote Originally Posted by JojoS View Post
    Yes I did ask about brew water pressure being equal on all 6 holes. I can imagine unwanted channeling during the shot if it is not. Pressure release after the shot can also cause uneven disruption on the puck that might lead to misdiagnosis of coffee prep procedures. Will the shower screen require tweaking in terms of position and how tight it is screwed on to get even flow?
    The shower screen needs to be on tight enough that the gasket in the center is water tight, but otherwise, no positioning required. We're designing our shower so that the rotation of the shower should not have an effect.

    As to your pressure question, since the pattern is symmetrical, I would expect pressure to be evenly distributed, but we'll keep an eye on that.

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    Quote Originally Posted by decentespresso View Post
    This week, we're finalizing the water tank design, so we can send it out for manufacturing. For at least the first 500 machines, we'll be using porcelain (ceramic). While it is heavier than other options, it's totally food safe, even in quite hot water, and totally dishwasher safe : lots of other material aren't.

    We've previously allowed the water tank to slide out the front and the back. However, I'm blocking the back-fill because I've now had two employees think they're being helpful and unplug the 220V power plug as another person fills the water tank. That has them holding an open electrical wire inches from pouring water. Not good.

    Banning filling from the back gains us 100ml of capacity because I can get rid of the little 1cm rim on the back. It also avoids the problem of the tank sliding out when you lift the DE1.
    G'day John

    Great - filling from the back is always a pain unless you can access both sides of a bench. I can't here, and most homes would be similar I suspect. In fact, refilling my 3 litre "wide, shallow" tank is a PITA, made worse by the low water indicator triggering when 1 litre is left in the tank. My other machine has a 2.2 lire tall deep tank and the low water warning is when 200ml is left. In other words the extra capacity of the larger tank is useless in a practical sense due to the shallow design - and it often sloshes over if I fill it "up to the mark".

    It is probably too late now for "run 1" but why do a lot of makers (including this one) persist in a wide, shallow tank? They tend to splash, be more difficult to fill without spillage and essentially create a whole pile of problems that a tall, deep tank just does not have (i.e. the La Cimbali I learnt on in 1970 had a full height tank). In my current setup I have a low hanging set of kitchen cupboards above the machine which precludes filling from the top (my preferred option) and because it fills from the back it means I have to pull the whole machine out (or at least turn it around and juggle it on the edge of the bench) when I refill it. If I overfill it, water invariably splashes out of the machine somewhere. Your idea of filling it from the front is an improvement, however the tank shape is still an unnecessary pain. Just my 2 cents.

    Quote Originally Posted by decentespresso View Post

    From the front, we've always had a little rim that you squeeze with your fingers to pull the tank out.

    My favorite idea is to put the tank on runners, so you push it in, hear a click, and it stays put.

    However, that's going to take some R&D to get right, and I want to kill all the R&D that I can so that we can move to shipping.

    Jeffrey's low-tech-but-just-works idea is to have a metal "pull tab" like so: (that) tugs the water tank out.

    I'm soliciting ideas now, so let me know what you think of this, and if you have any other (simple) suggestions!
    How about adding a foldout tab with a filling spout / funnel at the side so the tank only needs to come out for cleaning & maintenance? I use filtered rainwater, and there is no residue for months at a time - so no need to remove the tank very often anyway. I guess I am presuming it has a gauge? If not, why not a basic tall glass tank with a viewing slot on the front or the side for level (it always impressed me as a better idea to have no moving parts)?


    Quote Originally Posted by decentespresso View Post
    The goal is indeed for there to be enough space in that chamber so that the water flows out all 6 exits at an equal flow rate per hole, and at low velocity. Ideally, that would be 1ml/second per hole.

    Now that i think about it, we can actually measure that to see if that's happening, by using some tubes to direct the six outputs to different vessels, and weighing the accumulated water in each. Ideally, they should weigh the same after a 30s "shot" with no coffee.

    Last week, we also decided to design our own brass group head shower, because we can make one that has a lot less mass (for faster warmup and better temperature profiling ability during the shot) and a better hole distribution pattern that mates with our new 6-pointed-star design. That'll get drawn up next week.

    hmm... I just realized that you asked a different question, about "equal brew pressure" and the answer is "probably" but when the pressure is 9 bar, I'm not sure it will matter if the pressure is equal there, as long as the flow is, because after this hunk of brass there's a chamber, a shower and a screen, and that's where pressure needs to be equal. At least that's what I think your question is...
    This distributor / rotor looks good and should work well under 9 bar - mind you, my understanding of fluid dynamics is mediocre.

    A lot of more exotic (and also lower end - see a Sunbeam 6910/ 7000) machines use two showerscreens to give a better spread. If you still have some uneven flow issues I suggest you try a second screen with different sized holes. The only issue is the need to allow a little bit of low pressure water through after the shot to keep it cleaner.

    TampIt
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    Quote Originally Posted by TampIt View Post
    It is probably too late now for "run 1" but why do a lot of makers (including this one) persist in a wide, shallow tank? They tend to splash, be more difficult to fill without spillage and essentially create a whole pile of problems that a tall, deep tank just does not have (i.e. the La Cimbali I learnt on in 1970 had a full height tank). In my current setup I have a low hanging set of kitchen cupboards above the machine which precludes filling from the top (my preferred option) and because it fills from the back it means I have to pull the whole machine out (or at least turn it around and juggle it on the edge of the bench) when I refill it. If I overfill it, water invariably splashes out of the machine somewhere. Your idea of filling it from the front is an improvement, however the tank shape is still an unnecessary pain. Just my 2 cents.
    I can't speak for other manufacturers, but the shape of our tank is dictated by the shape of the espresso machine. We all want as large a tank as possible, so that means it takes up the entire width and depth of the machine. At the same time, the machine has to fit under a kitchen cabinet, so we can't make it too tall.

    Another major issue is UL safety compliance. UL does not like it if water can overflow into the electronics. One of the UL tests has them overflowing the tank on purpose. That's a big reason why our water tank is under the machine.

    Two years ago, the design we wanted to make did in fact have a tall vertically oriented tank, and I tried really hard to make that work. Ultimately, though, I had to kill that idea because no glass maker would agree to make this sort of vessel out of borosilicate. We could have made it from soda-lime glass but it would have been extraordinarily heavy (2kg) and brittle.

    We could have done this side-tank design if I'd been willing to use plastic for the water tank, but I wasn't willing. So, about a year ago, I made the executive decision to drop the side tank and move the tank under the machine.

    I agree that sloshing is an issue with all these tank designs (ours and others). There are real world mechanical constraints, such as the need to have "draft" along the vertical walls, so that the form can be removed from a mould. We designed a baffle made from stainless steel - it's 6 pieces of metal that make a kind of "waffle" in the tank (it's visible in one of the "spilling the beans" videos). Boats use these for this same problem. I don't know yet if that will really be necessary, though. If we keep the friction down between the enameled tank and the metal rails, sloshing is minimized.

    And thanks for all your suggestions, I've got them in my head now as ideas.

    For history's sake, here is a render of the DE1 about a year ago, with the vertical tank on the side. It sadly was not practical to manufacture this idea. I put about 6 months of heavy searching and paying for moulds and samples, ultimately fruitless.

    de1_pic1.jpg

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    Quote Originally Posted by JojoS View Post
    Will that make brew water pressure equal on all 6 exits points of the shower disc? If not, is the shower screen good enough to even things out across the coffee puck's surface?
    The backpressure is driven by the downstream resistance to flow; at such a low flowrate it should be almost the same everywhere above the puck.

    Shower screens are about the flow velocity and distribution, not pressure.

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    Quote Originally Posted by MrJack View Post
    The backpressure is driven by the downstream resistance to flow; at such a low flowrate it should be almost the same everywhere above the puck.

    Shower screens are about the flow velocity and distribution, not pressure.
    Thanks for the clarification MrJack. Does that mean that we can expect flow to be even from all 6 exits points for the duration of the shot and any channeling will be due to improper coffee prep? Do you see this 6 point dispersion disc + shower screen system as forgiving to coffee prep faults and inconsistencies?

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    Quote Originally Posted by decentespresso View Post
    I can't speak for other manufacturers, but the shape of our tank is dictated by the shape of the espresso machine. We all want as large a tank as possible, so that means it takes up the entire width and depth of the machine. At the same time, the machine has to fit under a kitchen cabinet, so we can't make it too tall.

    Another major issue is UL safety compliance. UL does not like it if water can overflow into the electronics. One of the UL tests has them overflowing the tank on purpose. That's a big reason why our water tank is under the machine.

    Two years ago, the design we wanted to make did in fact have a tall vertically oriented tank, and I tried really hard to make that work. Ultimately, though, I had to kill that idea because no glass maker would agree to make this sort of vessel out of borosilicate. We could have made it from soda-lime glass but it would have been extraordinarily heavy (2kg) and brittle.

    We could have done this side-tank design if I'd been willing to use plastic for the water tank, but I wasn't willing. So, about a year ago, I made the executive decision to drop the side tank and move the tank under the machine.

    I agree that sloshing is an issue with all these tank designs (ours and others). There are real world mechanical constraints, such as the need to have "draft" along the vertical walls, so that the form can be removed from a mould. We designed a baffle made from stainless steel - it's 6 pieces of metal that make a kind of "waffle" in the tank (it's visible in one of the "spilling the beans" videos). Boats use these for this same problem. I don't know yet if that will really be necessary, though. If we keep the friction down between the enameled tank and the metal rails, sloshing is minimized.

    And thanks for all your suggestions, I've got them in my head now as ideas.

    For history's sake, here is a render of the DE1 about a year ago, with the vertical tank on the side. It sadly was not practical to manufacture this idea. I put about 6 months of heavy searching and paying for moulds and samples, ultimately fruitless.
    G'day John

    I stand corrected. Just when I thought regulations could not get more out of touch with basic sound engineering practice some other idiot proves me wrong - in this case UL "standard".

    I guess all I can suggest is the same setup as two machines I know with vertical removable tanks (one stainless / right hand front, one plastic / right hand rear) - both of them are in a "top filling, fully sealed at the sides, drainholes in the bottom leading to the outside world" setup, and both of them have to use a door to access the tank - and now I suspect UL is the rationale behind why they did that. FWIW, it may be a cheaper long term approach given the need for baffles in shallow wide tank designs - less material cost.

    Good luck with what must seem like an unending series of technical decisions in developing a new tech espresso machine. FWIW, my take is if I buy version one of anything I expect a few teething troubles anyway, and by contacting the maker they usually get sorted in the medium term.

    TampIt
    PS: I had no idea your accessories business was already firing. Sorting out logistics before "the big one" is a really, really good idea. if you reckon another knockbox in the marketplace will help - go for it.

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    I realise this particular horse has bolted, and i hate to lower the tone of the discussion, or use language that is unbearable to many on this forum, but, as a working example of a effective, spill proof, removable external water tank,..... several of the " Nespresso" ( sorry for the language) m/cs have very neat design solutions......which i must assume meet all relavent regulations.!

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    Can anyone tell me how long blend52 has been banned from the forum for?

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    Quote Originally Posted by trentski View Post
    Can anyone tell me how long blend52 has been banned from the forum for?
    He isn't.


    Java "Look again" phile
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    Quote Originally Posted by Javaphile View Post
    He isn't.


    Java "Look again" phile
    Whoosh....
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    Quote Originally Posted by readeral View Post
    Whoosh....
    Yup, too busy with everything else to see the obvious.


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    Quote Originally Posted by blend52 View Post
    I realise this particular horse has bolted, and i hate to lower the tone of the discussion, or use language that is unbearable to many on this forum, but, as a working example of a effective, spill proof, removable external water tank,..... several of the " Nespresso" ( sorry for the language) m/cs have very neat design solutions......which i must assume meet all relavent regulations.!
    We've actually bought a fair number of different nespresso models on the used market in order to take them apart. On the whole, we find the internals' engineering to be exemplary, and we've learned a lot from them. Generally, because the sale-price of those machines is so low, they put a ton of work into inexpensive-to-make-and-reliable design solutions. Lots and lots of custom moulded parts, but very nice water seals and vibration isolation and dampening.

    But as far as water tanks go, all the Nespresso machines use plastic as their tank material, and they have a drain-down design which:
    - only works for unheated water (we preheat ours to as high as 70C)
    - calcification makes them rather ugly.
    - they are not dishwasher safe
    - once they get "cloudy" there is no way to fix that.
    - the rubber gasket where the water travels tends to fail due to calcification.

    So we haven't been able to follow Nespresso's water tank designs, but we really like their shipping-worthiness (resistance to shock) and their pump mountings have inspired ours.

    u-range-1-272x300.jpg81hKDhgpfuL._SL1500_.jpg

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    our CAD files will be freely available online

    We've been mulling this over, and
    - to give people greater confidence in investing their money into buying our espresso machines,
    - to foster a greater community of espresso-hardware-hackers
    we've decided that...

    CAD FILES FOR ALL DECENT ESPRESSO PARTS WILL BE FREELY AVAILABLE ONLINE

    That's right, we're going to publish CAD files for all our espresso machine parts.

    That way, should anything ever happen to our company, and you have one of our machines, you'll always be able to get the part. Except for the two circuit boards, everything in our machine can be either purchased on the open market (pumps, heaters, Android tablets) or manufactured (CNCed) as a one-off part. That's how we've built our machines during prototyping.

    We're going to be using Onshape https://www.onshape.com/ to publish and share these files, because it imports/exports well with Solidworks, exports to most other formats and it's free for non-private use.

    Besides giving you (the potential customer) a huge safeguard, I'm personally hoping that this will encourage DYIers to take our parts, modify them, republish their improvements via onshape, so that we and other DYIers can try the ideas out.

    For example, if you have an idea for a different water path into the coffee puck--perhaps something that preferentially puts water into the center that is typically denser--you can modify our CAD, have that new part made (it costs us about USD$100 to make a one-off) and test it out. If the idea "has legs" then other people can download your idea and have them printed as well.

    Rights-wise, we'll retain the copyright to our parts, but give you rights to make use (copy) and make derivative works from it. I have to give it more thought, but I might use a Creative Commons by-nc-sa v3.0 license https://creativecommons.org/licenses/by-nc-sa/3.0/hk/

    As a start, here is the flush diffuser (so you don't get splashed when the shot ends into the drip tray):
    https://cad.onshape.com/documents/6727c54dafbd47f2c6485d18/w/afd08d2bee2ec6efc551dff8/e/55a9442f4efca099eea362bf

    You'll need to create a free onshape.com account first to be able to view the objects.

    cadprev.jpg


  38. #288
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    Quote Originally Posted by decentespresso View Post

    But as far as water tanks go, all the Nespresso machines use plastic as their tank material, and they have a drain-down design which:
    - only works for unheated water (we preheat ours to as high as 70C)
    - calcification makes them rather ugly.
    - they are not dishwasher safe
    - once they get "cloudy" there is no way to fix that.
    - the rubber gasket where the water travels tends to fail due to calcification.

    So we haven't been able to follow Nespresso's water tank designs,........
    No, i understand you could not replicate their designs. ( though different material choices might well eliminate most of your problem points ?)....but i was simply suggesting that there are well engineered examples of spill proof external external water tanks that comply with consumer regs etc.
    There are many "plastic" materials that could be chosen to substitute for the current ceramic which would function happily at 70+C whilst being more durable and likely cheaper.
    PS..i do find it hard to understand why you pre heat the entire water reseviour when a small inline heater could suffice
    PPS.. Does anyone actually put their water tank in the dishwasher ?
    PPPS...All above is just discussion as your design is beyond any major redesign at this stage !

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    Quote Originally Posted by decentespresso View Post
    We've been mulling this over, and
    - to give people greater confidence in investing their money into buying our espresso machines,
    - to foster a greater community of espresso-hardware-hackers
    we've decided that...

    CAD FILES FOR ALL DECENT ESPRESSO PARTS WILL BE FREELY AVAILABLE ONLINE


    That is an inspired decision. I hope it evolves exactly as you plan with a community providing different and novel solutions or better more durable versions (if required)

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    Thanks to Ben for running a fluid simulation of our old group head design. Besides looking cool, it proves to us that this old design wasn't giving us even flow, and so moving to a new design is a very good idea. Next week we'll have a flow simulation of our new design.

    I would theorize that other espresso machines that have single holes into the group head chamber have similarly uneven water flow. It's then up to the group head shower and screen to even it out.

    Last edited by decentespresso; 1st April 2017 at 06:15 PM.

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    Quote Originally Posted by blend52 View Post
    There are many "plastic" materials that could be chosen to substitute for the current ceramic which would function happily at 70+C whilst being more durable and likely cheaper.
    Mention the word "plastic" and "hot water" on Amazon.com and watch the mob march toward you with lit torches in hand.

    Just as an example, not 10 minutes ago I received this email:
    My highest priority is the purity of the water contact surfaces. I would be interested in following water from the reservoir through the portafilter and identifying each material that the water comes in contact with. I have to admit that the special plastic for the mixing chamber and the Teflon tubing does give me pause,
    and that was written by someone with a technical education. I will leave to your imagination what less schooled people might write.

    Bottom line: lots of people would not only not buy our machine if we had a plastic tank, but they would agitate to tell others they shouldn't buy it either. That's why the only plastics we use are things like medical-grade Ultem and solid teflon.

    Quote Originally Posted by blend52 View Post
    PS..i do find it hard to understand why you pre heat the entire water reservour when a small inline heater could suffice
    Two reasons:
    1) it's much easier to accurately heater water from 50<x<70 to 90 than from 16 to 90
    2) at 110V/13A (yes, that part of the world) you're right at the electrical edge of possibility going from 16 to 90 with on demand heating, at espresso flow rates of 6 ml/s.

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    Quote Originally Posted by decentespresso View Post
    Now that i think about it, we can actually measure that to see if that's happening, by using some tubes to direct the six outputs to different vessels, and weighing the accumulated water in each. Ideally, they should weigh the same after a 30s "shot" with no coffee.
    I was actually thinking about exactly this yesterday. Have you tried it out?

  43. #293
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    Quote Originally Posted by decentespresso View Post
    Mention the word "plastic" and "hot water" on Amazon.com and watch the mob march toward you with lit torches in hand.

    Bottom line: lots of people would not only not buy our machine if we had a plastic tank, but they would agitate to tell others they shouldn't buy it either. .......
    .....sounds like irrational paranoia there.


    Quote Originally Posted by decentespresso View Post
    ......Two reasons:
    1) it's much easier to accurately heater water from 50<x<70 to 90 than from 16 to 90
    2) at 110V/13A (yes, that part of the world) you're right at the electrical edge of possibility going from 16 to 90 with on demand heating, at espresso flow rates of 6 ml/s.
    ..Couldnt you "pre heat" to 16 - 50 degC with an in line heater before it goes to the group ?
    " Espresso flow rates of 6ml/s"......seems a bit excessive ??
    Last edited by blend52; 2nd April 2017 at 09:29 AM.

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    Quote Originally Posted by blend52 View Post
    Couldnt you "pre heat" to 16 - 50 degC with an in line heater before it goes to the group ?
    An inline heater likely won't work, given the limitation is power...

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    Quote Originally Posted by MrJack View Post
    I was actually thinking about exactly this yesterday. Have you tried it out?
    Not yet: still designing the group head and shower, and next weekend we'll see if it is even when using a fluid simulation. If it is, then we'll have it made (in brass) and use "real" water and weigh the output from each hole.
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    Quote Originally Posted by MrJack View Post
    An inline heater likely won't work, given the limitation is power...
    That's right, we couldn't do this on 110V. I realize this isn't an issue at 220V, but we didn't want to delay the 220V launch.

    But separately, the point still remains that the less C you need to quickly climb, the more accurate you can be. 16->90 is going to be less accurate "on demand" than 50C/70C to 90C. We're currently hitting less than 1C error *in the puck*, and since my focus is on drink quality, I'd rather the compromise be a preheating step, and be able to deliver good temperature accuracy.

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    Fluid simulation of our new group head design.

    We're rethinking the water output into the group head so that instead of the standard single hole (most machines) we use a calibrated maze to output water out of six holes. At 6 millileters/second, each hole should output 1 ml/second.

    This design is a lot better than the single-hole version we previously had, with each hole now averaging: 99.70%, 107.80%, 107.40%, 99.30%, 103.90%, 103.90% (total =6.22ml/second). We can still do better, though!




    preview-full-pasted-file-2-1.png
    Attached Images Attached Images
    Last edited by decentespresso; 2nd April 2017 at 04:40 PM.
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    Nice design. I hope it rinses well. Coffee residue produced after the shot tends to accumulate in hard to reach areas even with plain water back flushing.
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    Quote Originally Posted by JojoS View Post
    Nice design. I hope it rinses well. Coffee residue produced after the shot tends to accumulate in hard to reach areas even with plain water back flushing.
    Definitely a valid concern. I think we're OK, though, because all these channels should only ever have clean (water tank) water in them.

    We built a separate water path for flushing water out for this very reason you have brought up.

    When we started this two years ago, I had my two lead engineers intern at two coffee repair shops in Seattle. They found coffee oils in the water tube leading into the group heads of other espresso machines due to backflushing. That's why we created a "forward flush" water path out of the group head. It is used only for dirty water, and the water-for-espresso water path is always kept clean.

    In the drawing below, I point an arrow at the water flush hole. Pressure is held constant on the water intake path (on the left), and pressure is released via the flush hole. There's a cover plate on top of this, keeping the water in the channels, but it's not shown in this drawing.

    preview-lightbox-pasted-file-2.png

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    Recap with new info: even water flow in the Decent Espresso group head

    We were worried that water going into our espresso group head was not being distributed evenly.

    On most espresso machines (ours too, until recently), water comes into the group head (above the shower) via one hole. We used a computer based fluid simulation to show how the water is distributed on top of the shower with this way of doing things:



    You can see that water is not all all evenly distributed. It's likely that other espresso machines, that have one hole to bring water into the group head chamber, have similarly uneven water distribution. It is then up to the shower to even this out. We thought it'd be better if both parts (the top and the bottom of this chamber) tried their best to even the water flow out, and also that they be designed to work in tandem.

    So....

    We've now redesigned the water output into our group head so that instead of the standard single hole (most machines) we use a calibrated maze to output water out of six areas of two holes each.

    At 6 millileters/second, each two-hole group should output 1 ml/second. This design is a lot better than the single-hole version we previously had, with each hole now averaging (in our simulation): 0.997, 1.078, 1.074, 0.993, 1.039, ml/second (a worst case error of 7%)



    We then designed a new shower screen, so that when water is going onto the coffee slowly (such as during a slower preinfusion) the holes are calibrated to put water evenly around the entire puck. We used different heights in our shower screen to evenly output water across the entire puck at different water flow rates, with higher flow rates moving water further inwards. Our theory is that at slower water flow rates you want water circulating evenly around the entire center of the puck, so that through capillary action the entire puck is most likely to receive the water.

    Our flow simulations show that this design is achieving a worst case error of 3% unevenness at flow rates varying between 1ml/second to 6ml/second.

    shower1.jpgshower2.jpg

    and finally, in the photo below you can see that we aligned the 12 holes on the cover plate on the top of the group head so that they each feed to a different area of the shower. There is a rotational-lock feature on these parts so that they always fit together the right way.

    shower3.jpg

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