Minimizing Waste and Static on Large Commercial Grinders

by **michaelbenis** on Wed Apr 22, 2009 11:23 am

How much of this tons of waste is there on the Roburs, compared to the Kony or the big flat Mazzers (Major) or SJ?

Are you talking about what gets left between the burrs Nicholas?

Cheers

Mike

Split from Conical grinder burr seasoning by moderator...

by **shadowfax** on Wed Apr 22, 2009 12:09 pm

Michael, the Robur E has a huge grind path due to the addition of the augur atop the burr set. If it spun at low RPMs, I imagine it might feed the burrs whole beans, but as it is it seems to cut them into smaller pieces before they load into the burrs. As near as I can tell, that adds to the Robur's already large path of smashed-up beans, although at least those particles between the augur and the burrs aren't fully ground. Add that problem to a covered chute that basically ensures that the grinding chamber and the chute are always full and a bit of a pain to clear out, and you have a difficult-to clean grind path that retains a lot of ground coffee when the hopper is charged and you've pulled a shot or two; 30-40g is probably a reasonable guess.

Then there's another problem that I've been thinking about lately, considering modding my own Robur to doserless. The chute is so large, and the grind chamber as well, that I don't know that the the path of the ground coffee into the funnel/hopper is even remotely a FIFO (First In First Out) queue. It looks like, under many circumstances, only a portion of the chute has moving coffee, meaning that, even though you might only have a small amount of stale coffee in the system, purging it by simply grinding more fresh coffee is potentially not going to work or require you to waste much more coffee than just the stale coffee that you're trying to get rid of. So, I've been thinking about shrinking my Robur's chute somehow to see if that will make it waste less coffee and create less static. My fear, of course, is that it will slow it down a lot and retain a lot more coffee.

by **michaelbenis** on Wed Apr 22, 2009 12:41 pm

Many thanks for that detailed reply. I've never seen a Robur.

Can you not uncover the chute, or is not a simple matter of removing a guard as on the SJ?

Plumbing pipe inserted in the grind chamber might reduce the inside diameter without introducing non-food grade materials. Or - if you find a glass jar the of the right diameter, you could cut off the bottom and leave the top as a small screw-on hopper lid. I'm just thinking aloud here. Absolutely no experience with either of these ideas.

Cheers

Mike

by **Theodore** on Wed Apr 22, 2009 12:46 pm

shadowfax wrote:Michael, the Robur E has a huge grind path due to the addition of the augur atop the burr set. If it spun at low RPMs, I imagine it might feed the burrs whole beans, but as it is it seems to cut them into smaller pieces before they load into the burrs. As near as I can tell, that adds to the Robur's already large path of smashed-up beans, although at least those particles between the augur and the burrs aren't fully ground. Add that problem to a covered chute that basically ensures that the grinding chamber and the chute are always full and a bit of a pain to clear out, and you have a difficult-to clean grind path that retains a lot of ground coffee when the hopper is charged and you've pulled a shot or two; 30-40g is probably a reasonable guess.

Then there's another problem that I've been thinking about lately, considering modding my own Robur to doserless. The chute is so large, and the grind chamber as well, that I don't know that the the path of the ground coffee into the funnel/hopper is even remotely a FIFO (First In First Out) queue. It looks like, under many circumstances, only a portion of the chute has moving coffee, meaning that, even though you might only have a small amount of stale coffee in the system, purging it by simply grinding more fresh coffee is potentially not going to work or require you to waste much more coffee than just the stale coffee that you're trying to get rid of. So, I've been thinking about shrinking my Robur's chute somehow to see if that will make it waste less coffee and create less static. My fear, of course, is that it will slow it down a lot and retain a lot more coffee.

It is for having less stale coffee,that I have bought Nino,as they insist,that it has very small amount of remaining coffee.

by **shadowfax** on Wed Apr 22, 2009 1:38 pm

michaelbenis wrote:Many thanks for that detailed reply. I've never seen a Robur.

Can you not uncover the chute, or is not a simple matter of removing a guard as on the SJ?

Plumbing pipe inserted in the grind chamber might reduce the inside diameter without introducing non-food grade materials. Or - if you find a glass jar the of the right diameter, you could cut off the bottom and leave the top as a small screw-on hopper lid. I'm just thinking aloud here. Absolutely no experience with either of these ideas.

The Robur looks just like a Super Jolly, except the hopper is a couple of inches taller, and the chute is much wider (as is, obviously, the grind chamber). The chute is also positioned somewhat to the right of the grind chamber, making the coffee exit tangentially rather than radially:

The Robur's huge grind chamber (via my Flickr) - Note where the chute is.

Detail of the exit chute (via my Flickr) - It actually widens somewhat toward the exit side (where it opens into the doser chamber).

Anyway, my "doserless" conversion would involve a Robur E funnel which has just become available at some expense ($230 IIRC), and then something to deal with the static on exit that doesn't involve rendering the chute inaccessible. This could be mounting a static screen on the lid (so it comes off when you take the lid off, for cleaning), or it might mean that I get an aluminum block milled precisely to block off about 80% of the exit chute (pictured above).

by **networkcrasher** on Wed Apr 22, 2009 1:44 pm

shadowfax wrote:This could be mounting a static screen on the lid (so it comes off when you take the lid off, for cleaning), or it might mean that I get an aluminum block milled precisely to block off about 80% of the exit chute (pictured above).

This is what I did, and it works just fine. Basically the arrangement is funnel, grid, sticky foam sheet (stuck to the funnel), then grinder body.

The other cool thing is if one drills a larger hole underneath the holes that the screws go through to attach the funnel to the grinder, you can just a) leave the screws loose, or b) tighten up the screws, then slightly loosen said screws and slide the funnel up and off the screw heads, making the throat easy to clean.

by **dsc** on Wed Apr 22, 2009 1:55 pm

Hi guys,

something I already mentioned to Nicholas, but I might as well say it hear, you will probably have a lot of problems with static when using the removable grid. At least I did when I was still reluctant to use the permanent grid.

Regards,
dsc.

by **shadowfax** on Wed Apr 22, 2009 2:23 pm

Indeed, a lot of my comments stem from a prior discussion with Tom. Tom's suggestion (and it definitely matches my experience) is that the static grid doesn't prevent static unless the chute is totally full. When it's filling up, the static is just as bad as with no screen.

That's led me to consider a door on the chute that keeps it closed until full, and then allows coffee to extrude out the bottom after it fills up (again, the door would have to come off with the lid or something so that you could sweep out per-shot or per-session or per-adjustment), or, as I suggested earlier, shrinking the chute by a great deal.

by **michaelbenis** on Wed Apr 22, 2009 2:47 pm

Ah! Many thanks for those photos, Nicholas. Makes what you were saying much clearer.

Considering the potential static/clumping problems and the clean sweep you're getting with your doser (seen on Flickr) vs. the comparatively massive amount of grinds retained in the chamber and chute, I'm curious why you want to go doserless.....

Cheers

Mike

by **shadowfax** on Wed Apr 22, 2009 3:08 pm

Mike, good observations--the doser has a lot going for it--it lets you dose evenly into the portafilter, and it holds the coffee so that you can do partial dosing/mid-dose grooming, that type of thing. It's also reasonably easy to clean out.

On the other hand, the doser is noisy if you use it right, and it's kind of a pain to sweep out properly (thoroughly) in terms of cleaning off the tops of the vanes and the static grounds that pepper the side walls of the doser.

I'm a dosered advocate because in my mind the doser gives the best results with the least waste and mess; that said, I am very tempted by the prospect of a doserless system that has no static issues with an easy way to minimize waste (i.e. full chute access). In my mind, I'd be really happy if dosing could be as simple and quiet as pushing a button, popping the lid, and sweeping out the chute with one or two strokes. You know, minus the thwack thwack thwack, and then the chute sweep, and then the vane sweep, and more thwack thwack thwack....

In all honesty, Theodore is right--I should have gotten the Nino. :mrgreen:

by **gyro** on Wed Apr 22, 2009 7:51 pm

shadowfax wrote:Michael, the Robur E has a huge grind path due to the addition of the augur atop the burr set.

I don't think this really adds much to the grind path when the grinder is functioning properly. When mine was choking and blocked up lower in the burrs, therefore slowing the grind, it certainly did however.

shadowfax wrote:30-40g is probably a reasonable guess.

This disaster resulted in around 25 grams, including a few whole beans that slipped through as I was removing the upper burrset. This was from when the grinder was largely choked, ie the beans weren't feeding through at all!

shadowfax wrote:In all honesty, Theodore is right--I should have gotten the Nino.

Theodore wrote:It is for having less stale coffee,that I have bought Nino,as they insist,that it has very small amount of remaining coffee.

I seriously considered getting the Nino myself, but speaking to someone in the industry led me to believe that some Sydney users had experienced reliability issues (ultimately its destined for a cafe, hopefully, so this was more of a concern than for home use only). That and the fact that there were no real reviews on the taste profile of the grinder (vs TGP), pushed me to the Mazzer. If I had the same choice again, I would be very tempted by the Nino, but I think it would still be pretty much 50/50 even after my bad start with the ROBUR E. The minimal ground retention claim of the Nino sounds excellent however, and would be a major bonus.

by **shadowfax** on Wed Apr 22, 2009 8:20 pm

gyro wrote:I don't think this really adds much to the grind path when the grinder is functioning properly. When mine was choking and blocked up lower in the burrs, therefore slowing the grind, it certainly did however.
...

This disaster resulted in around 25 grams, including a few whole beans that slipped through as I was removing the upper burrset. This was from when the grinder was largely choked, ie the beans weren't feeding through at all!

Interesting notes; I am basing my comments on my friend Paul's Robur E. He's had it for about a year now and he's been dealing with the issue that the first 3 shots of his sessions are always quite sub-par; he thinks he's finally figured out that it's attributed to stale grinds in the path on the Robur E, but it's difficult to tell for sure. I've been suggesting that he start posting; maybe at some point he'll post some pictures of what his grinder looks like.

As has been discussed recently, it seems likely that in a chute full of stale grinds there's some degree of mixing, i.e. if there are 15 grams of stale grinds in the path, it's not necessarily the case that purging 15 grams of coffee through the system will yield in removing all and only those 15 grams of stale grinds.

Suffice it to say, I am suspicious that the Robur E is a low-waste solution for grinding at home. I'm curious how much better the Nino will be. It sounds like it might be significantly better, and I would really like to find out... So I ordered one, "on the cheap." More to follow. :mrgreen:

by **gyro** on Wed Apr 22, 2009 9:06 pm

shadowfax wrote:it seems likely that in a chute full of stale grinds there's some degree of mixing, i.e. if there are 15 grams of stale grinds in the path, it's not necessarily the case that purging 15 grams of coffee through the system will yield in removing all and only those 15 grams of stale grinds.

I'm reasonably confident on the ROBUR-E that purging fully clears the chute. I run it with the top off and it certainly appears to come out in an even manner, and then get diced up by the static grid. What I am less sure of, is what happens in the burr chamber, ie after the burrs has spat it out, but before it enters the chute. So while I say I'm fairly confident that the chute is purged of the grinds that were in there, I am not implying that they are necessarily replaced with the freshest ones that were just ground. It seems very likely there will be mixing of the grounds that are yet to enter the chute, but were previously ground.

I've been using the first shot of the day as a seasoner, and although I can get an almost all crema shot out of it, it has the telltale visual sign of a thinner blond crema on top of the rest, and of course the taste is off.

Interestingly, I've been out of the country for a few days and just made a few coffees this morning. First double as a seasoner, then next to drink. This is the first time since I've had the new grinder (in a working fashion) whereby it hasn't been used daily. My second and third shots weren't up to the usual standard today, and I wonder if this is the reason... guess I better go and have another in the interest of research

For solely home use, this of course presents a problem which may be eliminated by the Nino.

shadowfax wrote:So I ordered one, "on the cheap." More to follow.

Do tell!

Cheers, Chris

by **gyro** on Wed Apr 22, 2009 10:24 pm

Ok, so I thought that now the burrs have settled in a bit, I would get an accurate idea of how much grind retention there is in the ROBUR-E. So I ran it until the hopper was empty and no more coffee was exiting the chute.

Here is the coffee retention in the chamber before reaching the chute. For one reason or another, while the grinder is running this residual coffee doesn't enter the chute. Perhaps on the 60Hz version there might be a little less since its spinning faster?

And obviously the chute is full as can be seen at the bottom of this photo...

However, there was much less than I thought. Emptying it all and weighing it, resulted in only 14 grams of coffee. Not an insignificant amount, but less than I had thought.

I believe when purging the stale coffee first thing in the morning, all the grounds in the chute are expelled, but who knows regarding the stale grounds in the chamber itself.

Cheers, Chris

by **shadowfax** on Wed Apr 22, 2009 11:43 pm

gyro wrote:I'm reasonably confident on the ROBUR-E that purging fully clears the chute. I run it with the top off and it certainly appears to come out in an even manner, and then get diced up by the static grid. What I am less sure of, is what happens in the burr chamber, ie after the burrs has spat it out, but before it enters the chute. So while I say I'm fairly confident that the chute is purged of the grinds that were in there, I am not implying that they are necessarily replaced with the freshest ones that were just ground. It seems very likely there will be mixing of the grounds that are yet to enter the chute, but were previously ground.

Indeed, Chris, Paul and I were discussing this recently. When his grinder is freshly cleaned and then filled up, the chute seems to clear fully, i.e. all the sections of static grid eke out coffee. However, we noticed that sometimes, this would stop, and the top 2 sections would purge much more slowly than the bottom 4. Paul just noticed this recently and showed me, so I don't know what causes that, how to fix it, or what, but it was present on his properly functioning grinder at 60 Hz with ~3s, 17g shots.

gyro wrote:Interestingly, I've been out of the country for a few days and just made a few coffees this morning. First double as a seasoner, then next to drink. This is the first time since I've had the new grinder (in a working fashion) whereby it hasn't been used daily. My second and third shots weren't up to the usual standard today, and I wonder if this is the reason... guess I better go and have another in the interest of research

This is the problem that Paul has been having for a year or so with his Robur E/ Synesso setup, which he's demoed for me several times that I've visited. The first shot is a "seasoning shot" for him, and he's fine with that... It always pours thin as you mentioned, and is a full-on sink shot. The problem is, the second and third shots are also "off" in the same way. They usually pour much better, visually, but they have a notable bitterness. They aren't sink shots, usually, but they're not up to par. When you make that 4th shot, you realize that the previous two were rubbish by comparison: with the same coffee, and no adjustments, it's always better-balanced and noticeably sweeter.

For what it's worth, Paul's job is such that he is away from home several days a week, so he routinely comes back after a multi-day absence. I am not sure if he leaves coffee in the hopper during that time or not, though, and, also for what it's worth, he's not completely sure that the grinder is the problem, although we both suspect so. Fingers crossed he'll chime in at some point; I know we're finally talking about something close to his heart...

gyro wrote:Ok, so I thought that now the burrs have settled in a bit, I would get an accurate idea of how much grind retention there is in the ROBUR-E. So I ran it until the hopper was empty and no more coffee was exiting the chute.

Here is the coffee retention in the chamber before reaching the chute. For one reason or another, while the grinder is running this residual coffee doesn't enter the chute. Perhaps on the 60Hz version there might be a little less since its spinning faster?
...

However, there was much less than I thought. Emptying it all and weighing it, resulted in only 14 grams of coffee. Not an insignificant amount, but less than I had thought.

I believe when purging the stale coffee first thing in the morning, all the grounds in the chute are expelled, but who knows regarding the stale grounds in the chamber itself.

If I may critique your experiment: I don't think that emptying the hopper by grinding it till empty will give you a good picture of how much is retained; I think you need to fill the hopper, grind until the system is "full" as usual, and then shut the hopper gate, take off the hopper, scoop out the whole beans on top of the burrs (say, with a vacuum cleaner), and then remove the upper burr assembly. I suspect that running it empty will yield less "held up" coffee than there actually is when you keep the hopper full. I bet you're right that it's closer to 20 grams than the 40 I was guessing, but, as I said, the issue is both the amount of stale retained and the rate at which it "bleeds in" to the fresh ground coffee, tempered by the "detectability" threshold, i.e. what ratio of stale coffee to fresh coffee in the cup is detectable to your palate. Paul's taste experience suggests that it's detectable as a defect in the coffee for three shots. I've experienced that 3-4 times; I am sure he's experienced it 50-100+ times...

Anyway, on that note, it's worth throwing in this comment from Jim in One Shot Grind Remnants:

another_jim wrote:Take a coffee, grind a few grams, put it away for a day. Then brew two cups of coffee fresh ground, and one with 20 percent of the day old ground. Pick out the odd cup. For most people, 20% to 25% will be the low limit of being reliable on this exercise.

Anyway, that's my current take on the issue of staleness/waste on the big Mazzer E grinders. It makes me wonder if the Major E might have less retention owing to how fast its burrs and sweepers spin (3-4x the speed of conicals)--I expect there's a reasonable chance that it throws out the stale grinds faster because of that. WAG, of course.

by **gyro** on Thu Apr 23, 2009 12:03 am

shadowfax wrote:When his grinder is freshly cleaned and then filled up, the chute seems to clear fully, i.e. all the sections of static grid eke out coffee. However, we noticed that sometimes, this would stop, and the top 2 sections would purge much more slowly than the bottom 4.

Hmmm, not seen this yet. I've put the machine back together, but I wonder if the height of the sweepers is less than the height of the chute? It did seem to me that the chute flared slightly, having a larger exit than the entrance... should have had a good look at this while it was apart.

shadowfax wrote:If I may critique your experiment: I don't think that emptying the hopper by grinding it till empty will give you a good picture of how much is retained; I think you need to fill the hopper, grind until the system is "full" as usual, and then shut the hopper gate, take off the hopper, scoop out the whole beans on top of the burrs (say, with a vacuum cleaner), and then remove the upper burr assembly. I suspect that running it empty will yield less "held up" coffee than there actually is when you keep the hopper full.

You are correct, that would have been a better way to do it. I did watch it as it run out of beans, and I would agree perhaps an extra 2-4 grams were removed while it was running empty.

by **gyro** on Thu Apr 23, 2009 12:11 am

Perhaps an option when he has been away for a few days is to clean the whole chute and chamber. I have found this easy to do with the finger guard removed (not the static plate). Cut off the supply of beans, or empty the hopper. Run the grinder with a small vacuum cleaner at the chute exit. Sucks out all the chute and burr chamber in a couple of seconds. Loose the 16-18 grams, but then there would be no chance of stale vs new grinds mixing in the chamber. As for the burrs themselves, they seem to stay fairly clean.

Cheers, Chris

by **dsc** on Thu Apr 23, 2009 5:47 am

Hi guys,

there might be an easy way to see how much grinds are retained and how the old stale coffee mixes with the freshly ground. Now I haven't tried this yet, but I did think about it the last time I was cleaning my grinder.

Remove the doser/funnel cap and remove the hopper, grind anything that's left in the burr chamber and let the grinder run empty for a few seconds to make sure there's nothing in it. Vacuum the inner on the burr chamber (with the upper burr carrier in place) and the 'throat' behind the grid (make sure not to damage the grid). Put some rice in the grinder, enough to fill the grinder up to the brim of the adjustment collar. Turn on the grinder and watch how the rice cleans out the inside of the grinder, throwing out a mixture of rice and stale coffee. Keep grinding until only white stuff comes out the outlet (or mostly white stuff), if you run out of rice before that happens, put some more in, if you still have some left, grind all of it until the grinder is empty. Now without cleaning out anything (the 'throat' behind the grid) put some coffee in the grinder and start grinding. Watch how the coffee mixes with the rice and what falls out from the outlet. You can measure how long it takes to get only brown stuff to fall out and whether any rice is left in any parts of the 'throat'. This should give you some idea of what's left and for how long it stays there.

Regards,
dsc.

by **michaelbenis** on Thu Apr 23, 2009 6:25 am

Sounds like a good idea DSC.

Also sounds like Sounds like just dropping in the beans per shot might overcome the auger problems (or does it popcorn)...

Also on the doser model you can presumably clean the final part of the chute with a chopstick/brush, through there is some risk that you just push the grounds back into the vaned chamber....

Last but not least, many thanks to Nicholas for forking out on the Nino to compare with the Robur. You're saving me a fortune

Seriously, though, I really look forward to hearing your findings.

Throwing away a couple of doubles of Squre Mile a day would break my heart....

Cheers

Mike

by **gyro** on Thu Apr 23, 2009 6:53 am

I too am looking forward to the comparisons, it will be great to get some side by side stuff.

michaelbenis wrote:Also sounds like Sounds like just dropping in the beans per shot might overcome the auger problems (or does it popcorn)...

There are no auger problems as far as I am aware... The problems I experienced seem to be the result of a manufacturing error in the actual burrs. The bigger grinders really need a weight of beans in the hopper to be consistent, but if thats what you always do it will probably be close enough. I haven't experienced any popcorning.

By way of information, I believe the auger was actually added as a customer complained a certain large sized bean wasn't feeding into the burrs well. The auger now gives it no choice.

Might try the rice thing before I clean the machine next time. It should give an idea, but since the density of rice and coffee aren't the same, it might be a bit off.


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