The problem with grinders

A small part of the coffee industry moans quite a lot about coffee grinders, especially espresso grinders.  I confess I am one of those people, and I thought I’d post a little bit about what makes us so grumpy but also look at why nothing has happened.

These are coffee grinders from the 50s (photo by yellow_speedster):

This is a coffee grinder available in 2009:

I went with a Faema grinder here because I think the ones above are Faema too.

So – in 50+ years what has changed?  The cheeky answer would likely be that coffee grinders have gotten less beautiful, but that is besides the point.  There has been virtually no evolution.  A bean hopper above horiztonal burrs, feeding the ground coffee sideways into a dosing chamber.

Why haven’t coffee grinders evolved?  Because they don’t need to.  For a long time there was very little innovation in espresso machines too 1. I’ve probably mentioned before (ad nauseum) how Italy is pretty happy with espresso, and for a long time had little drive to improve it – I say this as a good thing in many ways, espresso in Italy is a lot better (on average) than anywhere else.

Just about everywhere espresso spread, Italian technique spread too: 6-7g doses, delivered from a dosing chamber with a goodly amount of coffee in it, ground that day.  Coffee grinders haven’t evolved because the vast, vast majority of technique hasn’t needed them too.

As well as being a moaner I hope I am a realist.  The size of the speciality coffee community, in terms of % of grinders bought annually, is very small. Just think of the ratio of good cafes to bad in your local area.  What we want would demand a healthy spend on R&D that would likely take a long time for the manufacturers to recoup due to limited sales of high end grinders.

With espresso machines I think there have been a few key differences that sped up evolution – one of which is the home user community, brought together by the internet.  There were probably more PIDs on home espresso machines globally than commercial ones for a little while – though someone from the days could probably give a more accurate timeline.  The R&D work, the beta-testing, to some extent was already done.  People were measuring and reporting the effects on shot temp stability and in only a very few years this technology has become a part of at least one of every manufacturers range of espresso machines.

Perhaps the home enthusiasts will create the breakthrough in grinders.  It really wouldn’t surprise me, going to be conversation already going on online.  So what do people want?  Interestingly a lot of what commercial operations want from a grinder, home baristas want from a grinder – despite the very different applications.

Grinding to order – without clumps

Grinding to order has two advantages:  firstly the coffee is fresh, secondly there is minimal waste.  To achieve this we are mostly using standard doser or doserless grinders with digital timers – either factory fitted, or hacked in afterwards.  No one really wants to use a dosing chamber – there is something quite silly about the extraordinary number of dosing pulls that a busy day requires, but we don’t want clumps.  Most grind on demand grinders produce clumps of grounds that don’t really help the even extraction of coffee.  The Mazzer Robur is better than most, but still not perfect.  The doser at least breaks up these clumps.

Annoyingly most of these clumps are created because even doserless grinders are based on doser grinders, and therefore have horizontal burrsets.  To get the coffee from the burrs to the portafilter it passes through a little tunnel and in that journey gets somewhat compacted causing clumps.  Not all grinders have horizontal burrs – a number of shop grinders have vertical burrsets.  The Simonelli Mythos grinder was interesting to me because it has angled burrs, fed by an auger.  However, the coffee still travels through a little tunnel on the way to the portafilter so clumping remained an issue.

The only espresso grinder that I’ve seen that doesn’t do the little tunnel thing is the Disco Volante grinder, made by La Marzocco some years ago, that has a dosing chamber all around the burrset.  A wonderful idea (photo by Mark Prince):

Cool running

A big problem with grinders in high volume locations was the build up of heat.  Adding fans to the casings of grinders has been going on a while, though in my opinion it doesn’t really address the source of heat.  Most fans remove heat generated by the motors, and no doubt the do generate some heat.  The most damaging heat is in the burr chamber.  Espresso brewed from grounds that were heated dramatically as they were ground doesn’t taste as good as coffee that was ground at a lower temperature. 2

The biggest problem, when it comes to heat build up in the burrs, is coffee itself – specifically ground coffee.  Ground coffee does a superb job of insulating the burrs, meaning they get hotter quicker.  In an ideal world the burrs would grind until completely clear of coffee on each usage, which would significantly decrease the rate at which the grinder gets hot.  This is a problem – because that would mean measurement of the coffee before it is ground, something a timer could not do.  This is one problem that I hope someone comes up with an elegant solution for.  We could actively cool the burr chamber, but it would be tricky to cool the burrs themselves.

Just about every advancement in coffee grinders has been about trying to improve that basic model of grinder that we saw from the 50s. What if we just started again, what if we wrote a simple list of things we want a machine to be able to do and created a machine designed to only do that.  On my list would be the following:

– To finely grind a controlled portion of coffee quickly and repeatedly

– To retain no ground coffee

– To give accurate control over the size of the portion and the size of the grinds

– To prevent build up of heat around the coffee

I like a simple list, it feels more achievable.  Do we need it to do any more than that?  I’d love to hear your thoughts in the comments.

Should any manufacturers be reading this – I will happily donate a good number of hours of my time to work in any way helpful if you want to build something like this.  Just drop me a line.

  1. beyond inventive ways to stop customers cheating on coffee agreements with free-loan machines!  ↩︎
  2. This is an observational opinion – I would welcome argument, clarification and more discussion  ↩︎

56 thoughts on “The problem with grinders

  1. Great post James, and I wholeheartedly concur.

    I haven’t had any clumping issues with my Robur though, but it still heats up, is a pain in the a.. to fine-adjust and until we’d run about 50 kgs of coffee through it was also giving very uneven doses. The fan in the back is also starting to get noisy. So although this is my (for the time being) preferred grinder, it’s still so far away from perfect. And who oh why can’t Mazzer make their 380V/3-phase version doserless?!?

    A few things has happened since the 50’s, but very few companies have tried to re-do the whole thing. Mahlkönig is trying new roads. The K-30 is a grinder meant for the whole market – not specifically for the specialty shops – and for that purpose they’ve succeeded in making a doserless grinder, that apparently is selling well. But it just doesn’t deliver as well in taste as it should.

    Other companies have been working on stuff that for one reason or the other still hasn’t seen the light of day outside labs and a few trade show. It’s a pity. I’ve never tried the Versalab grinders but would love to, since they at least have tried to think outside the box on addressing some of the issues you mention.

    I do think there is a market for the type of grinder you are after. Even though the specialty coffee shops are small percentage-wise, there is an increasing number. And they are *all* looking for a better grinder solution. I’ve talked with several grinder producers in the past about the need for a new grinder that address these issues, but so far no luck. I hope someone will take up your offer of helping them and we will see something come out of it.

  2. I don’t think making the Robur-E 3 phase would make a lot of difference. Most of the motor heat, that 3 phase would reduce, is already reduced by the fan. Could be wrong on this though.

    I get the K-30, it is a great solution for a lot of places that brings quality up quite a long way quite easily. Easy to train on, hard to misuse (relative to most grinders). Just runs a little hot because the wider market values speed over cup quality.

    The Versalab is interesting, but I’m a little wary after the internet chatter about it.

    I doubt very much anyone will get in touch, as excited as I would be, because in a recession I don’t think anyone has the budget for a project like this. Sadly.

  3. I too am quick to complain about the lack of innovation in the field of grinders. However, reading your blog post I thought surely that you’d bring up the Versalab M3. Just in the last few weeks I’ve gotten to fiddle around with one a bit and while it is far from perfect, it is at least a step away from trying to fix something with more, or less, or a different shape of the same. It is belt driven to prevent heat from the motor transferring to the burrs and coffee, it volumetrically doses whole beans (this could use some fine tuning, doses were not as consistent as timed grinders I’ve used), and it grinds through an entire dose, emptying the burrs of coffee between each use. I only got about a half hour with it, and it was clear to me that it was a long way from functional in a busy shop setting, but I like the unorthodox approach. Curious if you’ve heard about it or played with one and what you think. Their website:

  4. With the 3-phase Robur you can grind at a slower rpm > less heat during grinding.
    From what I’ve heard motor hear is not the main problem. It’s actually very little that transfers. Most is from the contact between beans and burrs while grinding. The larger burrs on a Robur have more mass to take up this heat, but consequently once it’s hot also more to retain it. Belt drive is a small improvement, but an improvement nonetheless. And I see 3-phase the same way. What I really want is 3-phase and the ability to chose rpm :-) I’ve heard people talk about liquid cooling in stead of just a fan (like high-tech gaming computers) but that the problem then can be condensation.

    I like your list because it’s not concrete – it’s about the issues, not about the specific solutions.

  5. I had a chance to use the versalab about a year ago, and while I see great potential, it was a bit slow for a high-volume application. It took a full 30 seconds to grind one dose, and the lack of a chute actually caused the coffee to donut around the portafilter, leading to channeling in the center.

    I’ve been thinking quite a bit about grinders lately, actually. I’ve been working on a design with a conical burr, set directly over the portafilter, with an auger to aid distribution. I’d also like to work out how to add a really big heatsink to the burrs. I haven’t had an opportunity to build one yet. Maybe this year sometime.

  6. I don’t know whether or not you realise it, but you are on the path to a ‘systems engineering’ process to designing a new grinder: not relying on what has existed in the past but analysing the ‘need’ and constructing a set of ‘requirements’. The next step is to analyse those requirements and design and construct a ‘system’ that addresses all those requirements and therefore meets the need.

    Because you laid out the problem so well as a systems engineering case study, it made me wonder: Have you considered approaching the mechanical engineering departments of any universities? The nature of the project (“Design a better coffee grinder”) I think would really appeal to an honours year student based on its
    -size (could be completed as an honours year project),
    -technical complexity (it’s a reasonably simple problem, but it has many quantifiable performance parameters),
    -marketability (if anyone gets this right there could be some good money in it!)
    -geek value (c’mon – we all know what I mean here)
    -subject matter (what uni-student doesn’t want to work with coffee..??)

    Bottom line – more brain-power on the problem; minimal R&D spend; Caffinated Uni Students; everyone happy… food for thought.

  7. I too have experience lots of problems with the new coffee grinders these days. Some even costs me a couple of hundred bucks and all I get is a grind that is not uniform. I am more happy using my hand powered grinder, the old school type as I have read in For it is better and gives me the quality grind I have always wanted.

  8. Back to the old grinder quandary, my new grinder is a Eureka MDL and whilst it produces a very uniform grind from relatively large conical burrs, the doser is clumsy and leaves a trail of grounds around the outer edge.
    The exit chute is actually beneficial in this instance, as without a coffee clogged chute to control the drop of grounds, this particular grinder sprays coffee absolutely everywhere.
    Regarding the belt drive, Mazzer once produced the M100 which employed this system but it seems to have all but dissapeared, its quite funny to see them used as props in New Zealand’s long running TV soaps such as Shortland Street. There’s very little info about the M100’s online, but they still come up second-hand infrequently on NZ auction sites, I often wonder why they were abandoned.

  9. I think I’d be interested in doing something like this if I felt I could devote a decent about of time to it to really push it through. I don’t mind admitting that I would have absolutely no idea where to begin.

  10. Jim,

    I think your list of requirements is a little basic, but…

    “- To finely grind a controlled portion of coffee quickly and repeatedly” … how much, how quickly.
    “- To retain no ground coffee
    – To give accurate control over the size of the portion and the size of the grinds
    – To prevent build up of heat around the coffee”

    I would also add,
    -To deliver said portion, cleanly and evenly into a portafilter.

    I think that the makers of the Mythos should be the people to contact. The Eureka Mythos already is “different” in that it has angled burrs. I have replaced my Cimbalis with Eureka Mignons, expressly because the coffee retained is the least I have ever seen.

    I weigh the coffee per dose… a bit extreme I know. But it has become clear to me that the throat of this grinder holds 7-8g below the metal door. It should be simple enough to modify the trapdoor and hopper chute, to use these to set a specific amount of coffee. It would be at least as accurate as a timer IMO.

  11. What if you could do a grinder like the mahlkönig VTA 6 or the guatamala, but with some sort of built in scale, like the überboiler?

  12. Well I’m up for it James, if you’re interested, I’m 60% through the design process anyway. I’ve already talked to a friend who has access to various CNC machines and it shouldn’t be too hard to put something together. It wouldn’t of course be a production model, more like a beta version, probably something that wouldn’t ever be released to be honest.

    There’s a thread on HB about a DIY grinder and some interesting ideas there:

    I know you mentioned vertical burrs as a solution to coffee retention, but this also creates some problems, coffee will stick to elements surrounding the burrs and I’m not sure it will work as well with a conical burr set as it would with a flat burr set.

    Anyways I think it would be an interesting project and I’m open to suggestions/discussion.


  13. Liquid cooling was the first thing that came to mind for me as well – however, I don’t see the issue with condensation. Having had some experience with it in building systems myself, I can assure you no condensation was ever involved. Any hint of external moisture would make it absolutely unthinkable in that environment.
    I can’t really see liquid cooling as being financially viable for home or low-end commercial grinders though, as the cost of the liquid cooling system would add far more to the manufacturing cost than either fans or passive cooling.

  14. Lots of the comments here have been about heat problems.

    If we are really looking at this anew, heat should not be a problem. A small portion with no grounds retained, would IMO mean very little heat. Heat comes from grinding large quantiites of coffee. If nothing is retained then there is no mass of coffee to warm up.

    The biggest problem I see is clumping, and I reckon I could solve that if I had an engineer who could work on it!

  15. As I’ve said before, if you get rid of grinds retention (grinds build up around the burrs) you will get rid of most heat problems. You will of course still have heat build up through friction if grinding loads of coffee continuously, but with an open design it shouldn’t be too bad. I think all modern grinders have burr chambers which are quite small, there’s a lot of metal around and quite a lot of coffee grinds build up around the burrs as well which means low heat loss and quite a lot of insulating material (grinds).

    As for clumping, has anyone actually checked how bad it is? do a blind test comparing clumped and unclumped shots? I believe clumping is mostly caused by the horizontal path between the burr chamber – the doser/funnel, and compression of coffee on that path. Which again brings us back to the dreaded ‘motor below burrs / burr chamber side exit’ design, the cause of all that’s bad in the grinder world.


  16. I notice almost no clumbs with an Anfim Super Caimano and lots with an Anfim (regular) Caimano.
    The first one has more power and bigger burrs and I thought this always was the reason.

    For heating up I don’t see a big problem. I just use more than one grinder if needed. Costs some money, but the results are just fine.
    With 1 Mahlkonig K 30 I can not grind more than 2 kilograms in one afternoon without over heating.
    With 1 Super Caimano I can grind up to 5 kilograms an afternoon. I have 2 of those baby’s now for our main blend, and that’s enough. :-)

    Happy new year James and Anette and see you at the WBC.

  17. Rob,

    you demonstrate perfectly how difficult the problem is. For you 5 kilos per afternoon is needed. For that the Anfim Super Caimano or the Eureka Mythos are probably fine.

    But for me 250 grams is probably busy. But I do NEED to have a machine that will grind 17g no old grinds left behind and ideally no clumps. We are clearly looking for different things from a grinder.

  18. “The Versalab is interesting, but I’m a little wary after the internet chatter about it.”

    Whether or not there’s great potential with such a grinder, failing to empirically investigate it leaves us with nothing valuable to say about it. Citing “chatter” as a reason for not investigating something doesn’t seem consistent with the rest of your work. You’re an inspiration to many, and I’ll be so bold as to suggest that it’s due to your love of the scientific method. You help to challenge age-old assumptions, dispel myths and troubleshoot pervasive issues. All of your readers benefit, which is why they come back again and again.

    That’s the last time I’ll mention “Versalab” until I’ve had a chance to use it myself, and I hope that someone familiar with it on an intimate level could elaborate, suggest improvements to the design, or trash it altogether if it fails to perform. (Flattery will also be rationed)

    An empirical assessment:

  19. I might be wrong and feel free to correct me, but I doubt the Versalab is a good commercial grinder. It has a tiny ‘hopper’ and was designed for per-shot bean dosing. I know there’s a solution which uses a hopper, but it looks bizzare and imho it looks like trying to fix something that wasn’t properly designed in the first place (or was designed for something else).


  20. As of October 2009, Mahlkoenig is working on slowing down motor speed. Brian, their US Rep., told me a bit about it, though I’m still working on my comprehension of Hz in relation to motor speed.

    I’ve been impressed by their level of interest in the USBC/WBC and feedback they’ve sought from baristas. The accuracy on the K-30 is pretty impressive, too. I really think the K-30 could be a great transition piece that is in the budget of quite a few stores. The footprint of the twin is pretty sweet, too.

  21. Slowing down the engine of the K30 is a good idea.
    Maybe this helps them to become more accurate. I don’t see how you think that the accuracy of the K30 is impressive.
    There are worse grinders on the market, like the new LM one, but we notice an average weight difference of 0,75 grams per shot! That’s not very accurate I think.

    But they still need bigger burrs. Maybe this helps them to become more accurate as well.

    I want to end with a positive note on the K30’s. In Belgium and Holland we make a lot of café crèmes on the espresso machines (15 cl lungo coffee’s). For this purpose I didn’t see a more interesting machine then the K30 yet. Most Italian manufacturers are not into this type of grind. The Mahlkonigs do handle this way better and a better tasting cup is the result.

  22. I don’t know loads about grinders, but I like engineering projects. The grinder I use at the cafe I run has a built in grinder which I have just realised is probably the reason for the taste not being right. One the burrs are heated from the machine and also the beans in the hopper as I have noticed go off much quicker because they heat up. Anyways I will correct that by just filling up less.

    Anyways I have some ideas for a grinder. What you say above is you want a grinder that produces a clump free grinder, that is able to quickly deliver coffee to a portafilter when required without a doser.

    Solution remove the doser and the small channel that coffee would normally go down. Design a burr that grinds coffee into the center rather than grinding to the outside, this way the coffee could be ground right into a portafilter. This would obviously give a new problem, How do you make the burr spin if a portafilter is going to be where the motor used to be? Use a brushless motor, with the windings of the motor surrounding the burr chamber. heat sink fins could be mounter directly onto this burr to cool it down when in operation, although you would still have the problem of the stationary burr heating up. The last thing is the burr will need to be large enough with in reason so that the coffee can be ground at a faster rate without the need of the doser.

    Thats my contribtion, its funny how everyone into coffee is an engineer of some kind, ha.

  23. I just had another thought, Considering the cost involved with R&D, why don’t we design the grinder. The open grinder project were by we all contribute ideas, we then review all the ideas, try to combine them. We then work on a proto-type mock-up. keep tweaking things. We would obviously need to get a grinder manufacture to back us. We do the R&D they create a proto-type, someone tests it and so on we will evaluate the design. But we take the large cost out of them. They would just have to make a few proto-types. They then sell the product we wanted and designed for them.

  24. Hi Will,

    that topic is an interesting one, it died a bit though, probably because people don’t have time/money and personally I’ve found that my Mazzer Major works pretty well, so I’ve lost a bit of motiviation to build anything. Still I’m up for it and would probably be able to produce a working model, the problem is that there’s hardly anyone interested in talking about it. Most baristas moan about grinders, but if you ask them what they would like or how they see a properly designed grinder they don’t know what to say.

    Sketchup is not bad, but painful to use sometimes which I’ve discovered on my own when doing the mockup drawings. Still probably enough to show how the finished grinder would look like.


  25. absolutely correct. Those grinders never changed except for the price. My previos grinder has been very faithful for 7 years already and im very satisfied with it.

  26. thanks very much for this excellent post jim!

    wrt the la marzocco disco volante: there have been other macinadosatori which employed this arrangement. one was made by the firm f.a.b.e.r. of italy. i saved some photos of an example only to lose them in a computer disaster. the f.a.b.e.r. had a rectangular painted body but essentially operated the same as the disco volante.

    btw – i don’t believe either of the fifties era units shown in the photo awere made by faema. cannot see close enough detail to hazard a guess as to the mfr.

  27. yeah I’m on the market for a coffee grinder and having some problems – can’t find one which consumers seem to excell in. I spent a long time digging through the reviews here …. and also wading through the ones on amazon. This article is right how they don’t appear to have changed much in 50 years ! Please recommend one (if anyone can), that you’ve used from experience – i would appreciate that alot. thank you .

  28. The only one that I could reccommend is the Eureka Mignon. It’s not perfect, what is? but it is compact, reasonably priced and solid simple grinder. I have been using it as the main grinder in my small cafe for nearly a year with no problems.

  29. Don’t know if anyone has mentioned this before but. I am thinking there could be a lot to gain with a grinder that would take care of the partical size. And then I am talking about producing fines particulary.
    Fines, because of their size have the tendency to overextract very rapidly. This goes for espresso as well as even more for the various filter coffee’s. I wonder is it just me worrying about this. Or??

  30. Very nice post and discussion here !
    I’m coming late, and as a non professional but as a coffee lover !

    If you can add to the list of requirements the one I mention below, and if someone makes it into a real product, I would certainly buy from you one of those !
    My requirements:
    * Can have two or more than two containers for beans to allow use of different beans, and why not “make your own instant blend” (the Versalab allow this is a way, but not perfectly)
    * Direct to the portafilter with no grind left over anywhere.
    * Portafilter holder that works
    * A way to mark / memorize your adjustement of the grinder: I often change beans and go back to beans I know. Different beans requires different adjustment of the grind. I always have to fight to find the perfect adjustementr, even if I know the beans … would love to have this simply stored by a marker.

    Thanks for the very interesting and educating discussion in any case !

  31. True, you forgot about design changes. A new model every year, so the marketing guys have some new fodder and can invent new fancy feature names, but at the end it boils down to the same old thing.

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