Go get em! Just took some videos of the burrs rotating next to a stopwatch. Had to colour one augers black so when its slowed down you can see which is which. Anyhow, confirmed its rotating at pretty much 420RPM, which is what it should be doing at 50Hz. Really, all that leaves then is the burrs or friction in the exit chute??? anything else??

Cheers, Chris

Hi again, I think it may be defective burrs. Look at the inconsistency in the coarse grinding area, at the tips. I am not sure what they are meant to look like, but I would think they should be consistent from tip to tip.



It would appear that there is metal to metal contact (or has been) high up in the coarser area. I wouldn't have thought that this should happen. It would explain (I think) the slower grind, as it would reduce the been grab rate high up.



Any thoughts anyone?

Nicholas, you are into photography? Any chance of a comparison photo or two from your machine?

Thanks, Chris

Can you post a panned out pic of what you are showing up close; the context is missing, at least for me?

Chris, I took these this morning for something else. Not sure how much help they could be:


Link to full size via Flickr.


Link to full size via Flickr.

It's hard to say. You can see my Robur has some strange looking "defects" on the bean crushers (on the top), but they're not against the part that actually smashes the beans during rotation (and I don't have any speed/consistency/clumping issues).

Are you sure that both your burrs are mounted dead-center? It's unlikely, but possible they aren't aligned right. I think the best way to check is to defeat the interlock and run it while you watch it. Wobble is most apparent at the spin-down, for the bottom burr. Don't know how to check the top one.

another_jim wrote:Can you post a panned out pic of what you are showing up close; the context is missing, at least for me?

shadowfax wrote:Are you sure that both your burrs are mounted dead-center? It's unlikely, but possible they aren't aligned right. I think the best way to check is to defeat the interlock and run it while you watch it. Wobble is most apparent at the spin-down, for the bottom burr. Don't know how to check the top one.

No apparent wobble or vibration. I guess I have nothing to lose by taking them out fully though and reinstalling them.

Nicholas, I can't see enough detail on the flickr photos, could you possibly zoom on the original to show the 'teeth' on the upper burrs to see if they have the same inconsistent 'stamping' as on mine. Looks like the stamping should be there, but on the 3 bigger 'teeth' on mine, look at the third/bottom one is very different to the other two... wish I could figure out how to edit a photo other than zoom etc, just switched to a mac...

Cheers, Chris

OK, so I figured out how to get the large photo off Flickr. Below is Nicholas's ROBUR upper burr, with the areas circled that are of interest to me.



and here is mine...



and...



Looks like mine is poked. Not only is there an inconsistent 'stamping' pattern at the end of the larger teeth, but it appears that the burr edge to the right of each larger tooth is rough. I believe that its roughly this area that has been doing most of the grinder on my machine. Manufacturing error?

Anyway, one of these thing is not like the other.

Chris

Hi guys,

I dunno, I got a fresh pack of flat burrs from Owen a few months ago and I was surprised how uneven some of the surfaces were. Remember this is in the coarse area, so it shouldn't matter that much (or at all) in my opinion.

Are you sure that both your burrs are mounted dead-center? It's unlikely, but possible they aren't aligned right. I think the best way to check is to defeat the interlock and run it while you watch it. Wobble is most apparent at the spin-down, for the bottom burr. Don't know how to check the top one.

I wouldn't trust your eyes when it comes to wobble, few people on this forum thought their burrs were wobbling and in the end it turned out to be an optical illusion. Remember all that's needed for the burrs to look like their wobbling is a slightly off-centre lower burr locking nut/washer.

The grinder is still on warranty and I would just simply pack it up and send it back to where you bought it. Considering the price tag it should work well straight from the beginning.

Looking at that photo of the grinds stuck behind the grid it looks like they are being compacted quite hard and when pressed against the grid they fall out in blocks. Have you tried cleaning out the chute and running the grinder then? the first few seconds should show grinds shooting out from the burr chamber quite far away and hitting the wall of the funnel. After a few moments the 'throat' should get stuck with grinds and it won't shoot out anything any more (just stuff sliding down the funnel).

Regards,
dsc.

dsc wrote:Remember this is in the coarse area, so it shouldn't matter that much (or at all) in my opinion.

The trouble is, I think this is being used as the fine area since the corresponding shaved metal on the inner burr is in this area.

dsc wrote:The grinder is still on warranty and I would just simply pack it up and send it back to where you bought it.

Would in a flash, but it is in HK and it was bought from Europe. Got a price for 830USD to Fedex it back, so not really an option. Couldn't buy one locally so picked it up when I was in Europe, hand carried to aeroplane (heavy).

dsc wrote:Have you tried cleaning out the chute and running the grinder then?

About 10 times! Throws the beans out initially, but not continuously. I have had new flat burrs as well, but I really think there is a problem with these ones. I will reseat the burrs though to be sure.

Hi Chris,

Got a price for 830USD to Fedex it back,

Ouch! well that's not good.

I would take off the funnel, cut a cardboard cup in half (vertically) and stick that in front of the chute. Turn on the grinder, time it and weigh how much grinds it produces. If it's still very slow I'd try to re-seat the burrs.

Btw have you actually tested how the grinds behave in a machine? Do they produce good pours? maybe you're worried for nothing? I mean if it gives nice pours I would try using it for a month or so and see how it behaves afterwards.

Regards,
dsc.

Do you know if those two screws on the funnel are just screws, or do they have a washer behind them. Don't want to hear that 'tink' noise as a washer falls internally inside the machine!

It behaves differently. I did notice a reduction in bitterness immediately, but it was also noticeably blonder. I thought this must have been just the way it was. I did also immediately notice though that the crema produced a distinct line where it changed to liquid, instead of the normal sort of 'guiness' effect as it settled.

When feeling the grounds, they are substantially courser than on the Mini for a similar pour time. I know it sounds a bit funny, but it just feels wrong - the grind, the speed, the lack of consistency. I've put through 10 pounds of coffee, so I feel I've given it a reasonable go at settling down - I'm no espresso savant, but I am certain something is not as it should be.

Cheers, Chris

Hi Chris,

I believe there are two threaded holes behind the funnel, so nothing bad should happen if you unscrew the whole thing.

Maybe the crema problems are all because of old coffee? Have you tried something fresh, like 4-5days after roasting? Try to focus on the taste and see if that's good.

On the other hand I understand your frustration, this is not a 300$ grinder and it should work and at least produce a consistent grind without too much clumping.

Hope it all ends well,
dsc.

I roast my own, so freshness is not a problem. Crema colour not temp related as I have a fairly stable machine. There was an obvious reduction in clumping with some super stale stuff I had lying around, but I'd never consider actually drinking that!

It is very frustrating. Unfortunately the vendor is out of the country for the day, so might not get action until Monday which would be a shame.

I will be interested to get the funnel off to also see (and feel) how smooth the chute is, but I don't think thats the issue. Even with the clumping, it should be being 'pushed' out faster and more consistently than it is.

I actually choked the machine yesterday. Tried a finer setting, and it stopped feeding beans into the burrs, and instead just beat the entry level burrs into oblivion with the auger! and it wasn't a super fine setting and no burr touching noises. This is another reason why I wonder if the burrs are very close to touching higher up than they should be, 'grinding' in an area where they should be more 'feeding'...

Thanks for the ideas. Cheers, Chris.

Hi Chris,

still it might not be a bad idea to try a well known blend, like Black Cat for example, just to see how that works and maybe compare grind times to other people Roburs (Nicholas for example).

Strange thing about the choking, the auger is there to crack some of the beans and allow easier feeding into the burr area. I'm surprised the auger worked but still nothing was actually ground by the burrs.

Regards,
dsc.

dsc wrote:still it might not be a bad idea to try a well known blend, like Black Cat for example

No such thing in Hong Kong unfortunately and I don't go to the States like I used to. I've switched back to the Mini-E for the meanwhile and I think I'll take Dan's advice from another thread and R-E-L-A-X for a couple of days. 10 pounds of coffee and under 10 drinks from it, time for a break!

On the good side of things, the retailer in Europe has said he will forward the pics to Mazzer and he has a set of burrs, so hopefully they might be on their way soon, fingers crossed that will have an effect.

The auger was certainly cracking the beans, over and over again!

I did for a while consider the change of hopper may have influenced it, as the stock hopper seats in the throat mating with a 45 angle which it complements. That meeting of the parts is around auger height, so I considered if by plonking the short mini hopper on there it may have allowed room for the beans to escape the auger action. Tried changing to the stock hopper, but no joy.

Kudos to all the people that have managed to get that damn hopper off the interlock, I can't for the life of me. Read the threads on it, just ended up more angry!

Cheers, Chris

Hi Chris,

yeah 'relax' does sound good, simply try using the grinder as if there was nothing wrong with it. Who knows it might fix itself:)

Glad to hear the retailer is willing to help you out, maybe they can post you the burrs and that will take care of the problem?

With the hopper you want to work slow and be patient, it's probably easier to break something than you think.

Good luck!
dsc.

Indeed, relaxing for awhile, waiting on a response from Mazzer (maybe) and certainly a set of replacement burrs to try from your vendor, all sound like good ideas. You know the burrs are spinning at the right rate, you know that there's no wobble. That's a good sign, it means that if there's something wrong, it's either the burrs or the top burr carrier. Much cheaper to ship than a 60+ lbs. grinder...

You mentioned that you thought the grind was noticeably coarser than your Mini-E for similar dose and pour times. This seems a little strange to me; I would have expected it to be pretty close. Could your Robur be producing too many fines because it's pulverizing the beans a bit to violently/unevenly somewhere between the coarse cutters and the fine cutters? I'm doubt we'll ever know for sure, but trying a new burr set sounds like the best option at this point.

Good luck, Chris; I hope this has a happy ending.

shadowfax wrote:You mentioned that you thought the grind was noticeably coarser than your Mini-E for similar dose and pour times. This seems a little strange to me; I would have expected it to be pretty close. Could your Robur be producing too many fines because it's pulverizing the beans a bit to violently/unevenly somewhere between the coarse cutters and the fine cutters? I'm doubt we'll ever know for sure, but trying a new burr set sounds like the best option at this point.

I was pondering this exact idea last night. The pours start out a little quicker than from the Mini, for about 5 secs then the flow rate drastically reduces before picking up again. Maybe excessive fines migrate down and they are slowing the flow, before a bit of soluables extraction speeds it up again. I would have expected it to be a more bitter than the Mini in that case though... who knows. I hope the replacement burrs to the trick.

As you elude to... it might be technically difficult to design and manufacture a good grinder, but conceptually they are fairly simple. Motor spins - thats verifed as ok. Burrs grind (correctly) - perhaps not.

Cheers, Chris

So the new burrs arrived today. Got them installed and churned through 2 pounds of coffee. Visually the burrs were smoother looking, but still quite rough in places. Last go on the original burrs (after 10+ pounds) I was doing a double in 8.5 secs and seemed very inconsistent and the grind felt coarse. It started the same today, but within a couple of pounds it has settled considerably and is doing a 17 gram double in 6.5 secs with reasonable consistency. The grind felt more like I am used to from the Mini E.

There are still little coffee cubes coming out, but they are much less dense than before, and a simple finger sweep makes them disintegrate nicely with no WDT, no channeling.

Still seems slower than it should be, but perhaps as it seasons a bit more it will get a bit quicker. The grind is much better than the last set already.

Cheers, Chris

Hi Chris,

good to hear things are getting better on the burr front. Hope it solves all your problems and you start enjoying your espressi without worrying too much about the grinder:)

All the best,
dsc.

another_jim wrote:I keep wondering who's sillier; the grinder manufacturer's who keep converting grinders designed for dosers to doserless, or the people who keep buying them. Is there any grinder originally designed to operate with a doser that is better without one?

a grinder is designed to grind, a doser is used to consistently deliver precise volumetric portions in a commercial environment, still ground coffee goes stale very quickly and therefore the need for doserless.
Forgetting the argument of purists who insist on need for degassing ground coffee ( no fully automatic would be making good espresso if that was the case, and still some do an excellent job) the grinding process is identical : the doserless grinder just needs a "better" delivery system in order to avoid that statics sends grounds flying around: it is then evident that for busy commercial application a dosed grinder is probably the best option, for home application like slow going commercial application, or commercial applications that offer a variety of blends, dedicated doserless grinder is the way to go