La Cimbali Junior - Burr "Wobble"?

[RAS]

Just received my La Cimbali Junior after sitting on the fence too long and missing the incredible deal offered on two of them by Chris during the recent HB-anniversary sale. Oh well. When I amortize the price I paid over the number of years the Junior will last, I'm fine with what it cost me.

This last weekend was my first chance to play with it, and as others have already written, this is an incredible grinder. Being a tinkerer, I decided to take the hopper off and have a slightly better look at the burr and entry path for beans into the burrs. I came up with a feed-funnel idea that I've already implemented; it guarantees that no beans get hung up on the little ledge right before the burrs (I used a cycling water bottle which I cut down to give me a funnel which fits perfectly inside the throat).

While I had the hopper off, I plugged the grinder in and turned it on, then off, and noticed that, as the lower burr was slowly coming to a stop, it is not perfectly aligned with the upper burr, in a rotational sense. That is, it seems to wobble a bit relative to the upper, stationary, burr. My guess is that the mounting hole for the lower burr is larger than the motor shaft onto which it mounts, and that it was cinched into place while slightly out of alignment. (A bolt is used to secure the lower burr to the shaft.)

The grinder seems to grind very well in spite of the wobble, so I'm wondering if it's worth trying to correct... Though, if it grinds this well with the burrs slightly out of alignment, how good would it do if they were aligned?! Malachi, or anyone else who's gotten familiar with this grinder, as only a true geek can, I'd appreciate some insight.

Thank you!

[Ken Fox]

Just received my La Cimbali Junior after sitting on the fence too long and missing the incredible deal offered on two of them by Chris during the recent HB-anniversary sale. Oh well. When I amortize the price I paid over the number of years the Junior will last, I'm fine with what it cost me.

This last weekend was my first chance to play with it, and as others have already written, this is an incredible grinder. Being a tinkerer, I decided to take the hopper off and have a slightly better look at the burr and entry path for beans into the burrs. I came up with a feed-funnel idea that I've already implemented; it guarantees that no beans get hung up on the little ledge right before the burrs (I used a cycling water bottle which I cut down to give me a funnel which fits perfectly inside the throat).

While I had the hopper off, I plugged the grinder in and turned it on, then off, and noticed that, as the lower burr was slowly coming to a stop, it is not perfectly aligned with the upper burr, in a rotational sense. That is, it seems to wobble a bit relative to the upper, stationary, burr. My guess is that the mounting hole for the lower burr is larger than the motor shaft onto which it mounts, and that it was cinched into place while slightly out of alignment. (A bolt is used to secure the lower burr to the shaft.)

The grinder seems to grind very well in spite of the wobble, so I'm wondering if it's worth trying to correct... Though, if it grinds this well with the burrs slightly out of alignment, how good would it do if they were aligned?! Malachi, or anyone else who's gotten familiar with this grinder, as only a true geek can, I'd appreciate some insight.

Thank you!

I think you need to confirm that it is really out of alignment, and what you are seeing is not an optical illusion. Also, you need to be sure when this condition exists; if it is just as the burrs are coming to a halt, it may have something to do with the design of the grinder, rather than it being a manufacturing fault.

Any company can make a manufacturing mistake, or any product can be damaged in shipping, however Cimbali does have very high standards on everything they put out with their name on it.

Greg Scace called me with a similar problem he had observed on a Junior grinder that he bought a couple of years ago; in the end he had it replaced. How he confirmed that in fact there was a problem and not just an erroneous observation, I'm not sure.

For the record, I have essentially three of these grinders, a ten year old Cadet (bought new) which is more or less the same thing, plus two current vintage Juniors. I've not had any problems with any of them.

With the information you have given us I don't think there would be any way that we could tell you what the difference would be if you got one that ground in a more "aligned" fashion.

For the record, grinding for espresso the burrs are pretty damn close together. If there was a significant problem with the alignment you would either get poorly and irregularly ground beans with inability to make fine adjustments, or you'd be hearing metal on metal grinding as the burrs hit at some point, or both. In the absence of those observations and if the grinds come out well and you have no problems with adjustability, my guess is that you have either an optical illusion or a design situation in how the grinder stops once the power is cut.

ken

[RAS]

Thanks for the reply Ken.

I really don't think what I'm seeing is an illusion of any kind. When the lower burr slows down enough that it's not a blurr, the lower burr appears to be shifted slightly, again, relative to the upper burr. It's shifted by maybe a millimeter, which is not much, but compared to my Tranquilo, in which the burrs are perfectly aligned, it is certainly noticeable. As I said earlier, the grind consistency is very good (there's just that nagging question about if it could be better).

One detail I forgot to pass along earlier is that I found the zero-point, which just so happened to be located right around 0.5 on the numbered scale, and at this point, there was a very slight burr-to-burr contact sound. The sound was very slight, and consistent sounding... though I'm not sure I'd notice what slightly misaligned burrs would sound like at 1600 RPM!

Again, I'm very happy so far, and I'd like to do what I do with any equipment: wring out every last ounce of performance by dialing-in every parameter I can affect.

[HB]

Ken's thought was mine too: It's an illusion, and one that had me going for awhile until I mocked up a poor man's version of Sean's setup shown below:


From Versalab M3 Grinder

Unlike conical burrs, flat burrs don't fit inside each other, so it's not impossible that the bottom burr "wobbles" relative to its rotational axis and yet the grind flaw isn't immediately apparent. If I remember correctly, the Mazzer's burrs have an interior inset on the bottom of the burrs that seat in a mating circular "ledge" of the carrier; presumably it's purpose is to assure the burr is properly centered without relying on the screwholes. Although I'm skeptical that the wobble is real, it couldn't hurt to remove and reseat the bottom burr.

[k7qz]

Bob:

Ken and Dan's answers were both more academic than mine will be, but here goes-

My brother has a Junior grinder and we noticed the same thing, e.g. apparent burr wobble. To see if indeed this was a true problem we opened up the burr gap and fired her up. We then slowly closed the burr gap until a slight contact sound was heard. The soft contact sound was very uniform without any hint of being uneven or "wobbly".

So we chalked it up to something wrong with our perception rather than a fault with the grinder!

[RAS]

Glad to hear that mine is not the only Junior with this "issue"... if it really is an issue.

Dan, my observation, and concern, about the burr alignment is primarily due to what I've seen on other flat-burr grinders I've owned or played with. One of my other grinders is a Tranquilo, and the lower burr spins in perfect alignment relative to the upper burr. The lower burr is a completely smooth blurr at speed, and continues to be so when power is turned off - all the way until the burr comes to a stop.

Something I noticed last night when checking the Cimbali out a bit more is that the body of the grinder shakes slightly, much like a washer during the spin cycle with an unbalanced load, when it's winding down. The shake is subtle, but still noticeable. My theory is that this due to the lower burr's lack of symmetry.

I'm hoping someone with a Junior can give me some insight on how to reseat the lower burr. I'll probably drop a line to Chris and Roger at ChrisCoffee to see if they have some pointers. I'm an engineer, and tinkering is something I enjoy, so I'm ready to dive in... If there is a chance of improving this impressive grinder.

Thanks to all!

[gscace]

Just received my La Cimbali Junior after sitting on the fence too long and missing the incredible deal offered on two of them by Chris during the recent HB-anniversary sale. Oh well. When I amortize the price I paid over the number of years the Junior will last, I'm fine with what it cost me.

This last weekend was my first chance to play with it, and as others have already written, this is an incredible grinder. Being a tinkerer, I decided to take the hopper off and have a slightly better look at the burr and entry path for beans into the burrs. I came up with a feed-funnel idea that I've already implemented; it guarantees that no beans get hung up on the little ledge right before the burrs (I used a cycling water bottle which I cut down to give me a funnel which fits perfectly inside the throat).

While I had the hopper off, I plugged the grinder in and turned it on, then off, and noticed that, as the lower burr was slowly coming to a stop, it is not perfectly aligned with the upper burr, in a rotational sense. That is, it seems to wobble a bit relative to the upper, stationary, burr. My guess is that the mounting hole for the lower burr is larger than the motor shaft onto which it mounts, and that it was cinched into place while slightly out of alignment. (A bolt is used to secure the lower burr to the shaft.)

The grinder seems to grind very well in spite of the wobble, so I'm wondering if it's worth trying to correct... Though, if it grinds this well with the burrs slightly out of alignment, how good would it do if they were aligned?! Malachi, or anyone else who's gotten familiar with this grinder, as only a true geek can, I'd appreciate some insight.

Thank you!

I think you need to confirm that it is really out of alignment, and what you are seeing is not an optical illusion. Also, you need to be sure when this condition exists; if it is just as the burrs are coming to a halt, it may have something to do with the design of the grinder, rather than it being a manufacturing fault.

Any company can make a manufacturing mistake, or any product can be damaged in shipping, however Cimbali does have very high standards on everything they put out with their name on it.

Greg Scace called me with a similar problem he had observed on a Junior grinder that he bought a couple of years ago; in the end he had it replaced. How he confirmed that in fact there was a problem and not just an erroneous observation, I'm not sure.

For the record, I have essentially three of these grinders, a ten year old Cadet (bought new) which is more or less the same thing, plus two current vintage Juniors. I've not had any problems with any of them.

With the information you have given us I don't think there would be any way that we could tell you what the difference would be if you got one that ground in a more "aligned" fashion.

For the record, grinding for espresso the burrs are pretty damn close together. If there was a significant problem with the alignment you would either get poorly and irregularly ground beans with inability to make fine adjustments, or you'd be hearing metal on metal grinding as the burrs hit at some point, or both. In the absence of those observations and if the grinds come out well and you have no problems with adjustability, my guess is that you have either an optical illusion or a design situation in how the grinder stops once the power is cut.

ken

Hi:

I used a dial indicator to measure the runout on the one I returned. Its replacement also showed runout, but less than the first and I kept it, based on others' praise for the grinders. I forget how much runout either grinder exhibited. My Cimbali was an exemplary flat-burr grinder. I don't own it anymore as I have made the jump to conicals.

-Greg

PS - Ken, I just got back from a week in Nebraska. I'll get your thermofilter out this weekend.

[gscace]

Bob:

Ken and Dan's answers were both more academic than mine will be, but here goes-

My brother has a Junior grinder and we noticed the same thing, e.g. apparent burr wobble. To see if indeed this was a true problem we opened up the burr gap and fired her up. We then slowly closed the burr gap until a slight contact sound was heard. The soft contact sound was very uniform without any hint of being uneven or "wobbly".

So we chalked it up to something wrong with our perception rather than a fault with the grinder!

Actually this isn't a good test. The runout I've observed is runout in which the burr doesn't rotate on its centerline, but rather rotates off-center. This type of runout is measureable by removing the adjustable burr and then measuring with a dial indicator positioned on the outer circumference of the lower burr. The test that is described in the quotes text would only work if both the rotating and non-rotating burrs were misaligned so that the burrs had a "high spot" relative to each other. In the case of one burr exhibiting a high spot and the other perfectly aligned, the high spot would touch the perfectly aligned burr at even pressure throught the revolution of the burr, generating a constant note. This would also be the case for burrs which are parallel to each other, with the rotating burr exhibiting radial runout (the usual case with Cimbali grinders).


The radial runout exhibited by the Cimbali grinders doesn't seem to hurt performance when new. However, the runout affects particle size distribution and burr life. A little runout is prolly OK, but my first Cimbali grinder had enough runout that the grinder "walked" across the counter when motor shaft speed reached resonant frequency as it was spooling down. I deemed that unacceptable and returned it for another one.

the radial runout thing is my only bitch with Cimbali grinders. I've never seen a Mazzer grinder with such runout, and such runout speaks of sloppiness on the part of the machinist making the parts (having worked as a machinist in the past, i'm pretty familiar with how the carrier gets made). This type of runout would be a real pain in the yass if the grinder were a pure conical, but is less problematic for a flat-burr grinder.

-Greg

[k7qz]

Actually this isn't a good test. The runout I've observed is runout in which the burr doesn't rotate on its centerline, but rather rotates off-center.

Hi Greg-

Although I'm not the OP here, I appreciate your thoughts. I don't have the ability to verify my Junior observations as the grinder I referred to lives in TN with my brother.

What we observed appeared to be "wobble" or more accurately nutation of the burrs. Hence our simple "high spot" test. If mal-alignment of the center axis of the burrs is in reality the problem as you state, then I would concur with Ken that what my brother and I observed with his Junior was quite likely indeed an optical illusion.

Is it your opinion that one should "test drive" Cimbali grinders before purchase? Perhaps the alignment issue is only a rare problem? You have me curious now because I've been toying with the idea of purchasing a Junior to see how it compares to my Mini E-

Best-

[cannonfodder]

Bob and I have traded a couple of emails about this prior to the posting. I have to say I have been very happy with my Jr. I do not have any machine shimmy as the burrs spin and I have been perfectly happy with the grind quality. I actually like it better than my Mini, it more 'commercial' than the Mini. However, the discussion has gotten me wondering about my machine. I will have to take the covers off this weekend and give it a look.

[cannonfodder]

I pulled the covers off my Cimbali this evening. There is a very small amount of offset on the lower burr but not enough to concern me. The grind is very good and consistent. Just for posterity sake, here are a few photos with the covers off.

[RAS]

Hello All,

Sorry for the delay in getting back to this discussion... Just got back from an extended weekend up in Ashland, Oregon for the Shakespeare Festival. Great break, and now I'm back to the grind - pun intended.

Thanks very much for the very insightful replies. While I was gone, I got a reply from Jason, from ChrisCoffee, who claims (I hope it's OK to quote him), "The wobble at low speeds is normal. The shaft is not balanced until it reaches a higher rpm level. I have checked other grinders from other manufacturers and they all do the same thing." That could be, and I'll look to see if there's any wobble at full speed, but I doubt my eyes would be able to detect lack of eccentricity at 1600 RPM. One thing that I do know is that my Tranquilo is dead-on at low-speed, high-speed, and everywhere in between, so I'm not sure what about the "they all do the same thing" comment. I'd appreciate anyone's input on this.

The alignment issue I've noted is no where near as extreme as what Greg experienced. To my eye, the lower burr seems to be off center, relative to the upper burr, by 1-2 mm. And, as I think I mentioned, the grind is darn good... I just wonder if it could be better. Plus now, based on Greg's comments, I'm a bit concerned about burr longevity. Has anyone priced Cimbali burrs?

[HB]

Has anyone priced Cimbali burrs?

A mere $30 and change at EPNW (link).

[RAS]

Thanks Dan,

Seeing the replacement burrs clarifies a bit of what Greg had been discussing. Namely, while that the issue is not the lower burr itself, rather it's the actual burr carrier which could have been machined a bit more precisely.

To check Jason's claim, I turned on the grinder and checked out the lower burrs rotational alignment, and I'm not sure I'm buying into the theory that at speed everything lines up. The inner edge of the lower burr seems have a slight soft edge (as opposed to a distinct edge as I'm used to seeing with my Tranquilo's lower burr - which is perfectly aligned), which would indicate that the burr is still slightly out of whack. But what I also notice is that the grinder has doesn't budge at full speed, though I'm not sure a slight alignment issue would cause the body to move when the burr is moving along at 1600 RPM... that would only happen if there were a gross alignment issue. So the question still is if a burr that's 1+ millimeters out justifies a return, or at least further discussion with Chris or others at ChrisCoffee (I certainly get the feeling that my grinder is "within spec").

Thank you,

[gscace]

Hi Greg-

Although I'm not the OP here, I appreciate your thoughts. I don't have the ability to verify my Junior observations as the grinder I referred to lives in TN with my brother.

What we observed appeared to be "wobble" or more accurately nutation of the burrs. Hence our simple "high spot" test. If mal-alignment of the center axis of the burrs is in reality the problem as you state, then I would concur with Ken that what my brother and I observed with his Junior was quite likely indeed an optical illusion.

Is it your opinion that one should "test drive" Cimbali grinders before purchase? Perhaps the alignment issue is only a rare problem? You have me curious now because I've been toying with the idea of purchasing a Junior to see how it compares to my Mini E-

Best-

Well I bought one that danced across the bench when spooling down. I was pretty discouraged, but Al Critzer, a Cimbali proponent and very knowledgeable pro coffee guy encouraged me to try again, so I did and i was very happy with my second grinder.

WRT the mini-e, I own a mini-e, the Cimbali, a Mazzer Kony and now a Robur as well. Both the Mazzer conicals are way better than the flat burr grinders, but cost is very high. The mini-e is very clean and has 64mm burrs. It's faster than a regular mini, but much slower than the Cimbali. It is also underpowered if one is interested in grinding for vac pot or drip. The Cimbali is more powerful. It takes 8 secs to grind 20 grams of coffee. The Cimbali doser is extremely clean and sweeps very well, leaving almost no spare grinds. I prefer the bean hopper design of the Mazzer grinders because the upstream flow path to the burrs is cleaner, but the Cimbali doser is the best one I've used.

-Greg

[gscace]

Hello All,

Sorry for the delay in getting back to this discussion... Just got back from an extended weekend up in Ashland, Oregon for the Shakespeare Festival. Great break, and now I'm back to the grind - pun intended.

Thanks very much for the very insightful replies. While I was gone, I got a reply from Jason, from ChrisCoffee, who claims (I hope it's OK to quote him), "The wobble at low speeds is normal. The shaft is not balanced until it reaches a higher rpm level. I have checked other grinders from other manufacturers and they all do the same thing." That could be, and I'll look to see if there's any wobble at full speed, but I doubt my eyes would be able to detect lack of eccentricity at 1600 RPM. One thing that I do know is that my Tranquilo is dead-on at low-speed, high-speed, and everywhere in between, so I'm not sure what about the "they all do the same thing" comment. I'd appreciate anyone's input on this.

The alignment issue I've noted is no where near as extreme as what Greg experienced. To my eye, the lower burr seems to be off center, relative to the upper burr, by 1-2 mm. And, as I think I mentioned, the grind is darn good... I just wonder if it could be better. Plus now, based on Greg's comments, I'm a bit concerned about burr longevity. Has anyone priced Cimbali burrs?

Sounds like a new "feature" to me. Interesting physics.

-Greg (hmmm)

[Wushoes]

I notice the "wobble" on the bottom burr too. It's only off by about 1mm and only noticeable when slowing down at low revs.

Definitely the tolerance at which the burr carrier was machined could have been increased, but doesn't seem to adversely affect the grinder's performance.

[cannonfodder]

I have both the Mini and Jr. I think the Mini is a bit sexier machine, but based on pure down to business grinding. I believe the Cimbali outclasses the Mini. Faster grind, better doser, easier adjustments, and easier to work on, even with a very slightly off burr carrier. It has had no effect on grind quality that I have noticed. Love my machine.

[T.J.]

This is a response from the La Cimbali factory concerning the grind wobble issues on the La Cimbali Junior Grinder.
The response is provided by Mr. Maurizio Azzarello who is the senior global technical engineer for the Cimbali group (which also manufactures the Faema brand).

The response was sent to myself, T.J. Tarateta of Ammirati importing company, which is the master importer for La Cimbali espresso machines in North America.

Dear Home Barista readers,


We reviewed what people had to say about the Junior grinder, and would like to come back to you with our comments here below:



Firstly, I found the interest in our products and level of passion quite fascinating. We too feel very passionate about our products and industry, therefore, it will be my pleasure to provide you with feedback.



1) By removing the hopper and the fixed burr holder, and activating the grinder motor, you will be able to see the revolving burr in movement. This movement may create an optical effect, making the rotating burr appear to be misaligned. In reality, with specific regards to our grinder, it is extremely important to be certain that the seat of the rotating burr is in alignment with the fixed burr holder. Moreover, during assembly, we couple and set the seat of the rotating burr with the fixed burr holder. This enables us to make certain that these two critical components will be aligned and completely parallel to each other.

2) We noticed a customer attempted to verify the rotation of the burr by using part of a plastic water bottle. I feel certain you'll agree that this is not the most accurate of methods. Without having the proper instruments on hand, we suggest that the best way would be through extracting an espresso, verifying its cup quality, and checking the dregs in the filter holder. Adjustments effected on properly aligned burrs will vary the overall taste and cup quality of your espresso. In regards to the dregs, if the espresso has been extracted using properly ground coffee, the dreg will be compact, solid, and almost completely dry. On the other hand, if you are left with a wet and broken dreg, there may be issues with the teeth or with the alignment of the burrs.

3) The final method for evaluating whether your burrs are aligned is by setting them so they are slightly in contact with each other. At the point of contact, they will make a high pitched sound, which should remain uniform and constant during rotation.



Points 2 and 3 are carried out by our service engineers during preventative maintenance visits. Proper maintenance will ensure the production of quality beverages throughout the life of your LaCimbali products. In conclusion, given what we know about this specific case, it is our opinion that the customer's grinder is in perfect working order. Should you have any further questions, please feel free to contact us.



Kind regards.



Maurizio Azzarello

[T.J.]

A mere $30 and change at EPNW (link).

While I don't intend to hurt anyone's business, I am sure that for those of you who have purchased your Junior Grinders because of their quality, then you would also want original parts to be used to replace those that wear out.

I am concerned that, due to the price (which is not the most scientific method for determining quality) the burrs being offered as replacements above are not "original" Cimbali parts.

Should anyone want "original" parts for your grinders or Junior DT/1 machines, I urge that you contact Chris Coffee. Please ask him for "original" Cimbali O.E.M. parts and we will be sure that he is able to obtain them direct.