How important is grinder's alignment? Is good enough good enough? - Page 2

Grinders are one of the keys to exceptional espresso. Discuss them here.
samuellaw178
Team HB

#11: Post by samuellaw178 »

nickw wrote:
Not WDT, but I did a distribution technique (mixed in a bowl, then dumped in).

We'll see what mine is like once it's back from Frank. He says no distribution needed anymore.

The wipers wont affect grind distribution (or do you mean distribution in the basket?), but they will effect retention. You need the wipers or much of the dose (33-50%?) would stay inside the grinder from static electricity. All grinders must deal with static electricity from grinding somehow.
Appreciate the links! Will look into them!

0.005mm, that's super impressive! I'm sure you can't wait to experience the upgrade when it comes back from Frank.

But that's also where my question comes from again, is it that important to get down to 0.005mm or even 0.02mm? What is the minimum tolerance before we start seeing/tasting a noticable deteriorate in quality? I guess no one knows the answer at this stage - maybe Mazzer does but as usual it's a trade secret. :P Frank might be able to find out as well. What I know for sure is those visually obvious alignment, is definitely way more than 0.02mm.

Yup, I refer to grind distribution, not particle distribution. I guess that's another question I have. In a perfectly (let's take that as tolerance = <0.01mm) aligned grinder, with a straight drop grind design and single dosing mode (ie, HG one style or Versalab), will the grind have to be mixed in order to produce acceptable pour? My experience is yes with all the grinders I have access to, however I don't have a grinder that I can confidentally say is within 0.02mm tolerance.

I was suspecting the Versalab didn't need distribution because the wipers are mixing them sufficiently. On my HG-1, I did mod to improve the mixing and that eliminates the need for distribution completely. If a perfectly aligned grinder doesn't need distribution of any sort to get a perfect extraction, then it can be used as a useful alignment indicator for us common folks.

Keep the discussion and info coming! :mrgreen:

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dsc

#12: Post by dsc »

samuellaw178 wrote:Based on my personal experience, to achieve a perfectly aligned grinder, too much effort is needed (hours and hours of alignment) and you're still not guaranteed a perfect alignment (too many things can go wrong). When translated into a manufacturing scenario, that is not feasible without a significant increase in production cost. Also, your rejection rate of less-than-perfect grinder will sky rocket. Are the consumers willing to pay for 2-4 times more for an increased in precision which they will hardly notice a difference?
I would not agree with this statement, if the design allows for it, alignment isn't hard. The main issue with pretty much all grinders on the market today is that they are not designed to be re-aligned or even checked for alignment. If you cannot even test whether a grinder runs true or not, you're going in blind and guessing, you wouldn't even know if your method of alignment is successful or not (FYI I'm not saying people shouldn't try and align burrs themselves, just that there's no way to assess how good the method or alignment really is).

In my opinion if you can get burrs aligned then it certainly won't hurt, it's not going to make your shots worse than if it's misaligned. In my case (and probably not only mine unless you have access to expensive lab equipment on a daily basis) it's far easier to align burrs than to use LPA, blind testing etc. to see at which point further minimising alignment errors doesn't matter.

As for burr manufacturing precision from what I've tested so far (conics) Mazzer is much better than non-branded burrsets, for example the outer burr inner bore and outer edge are concentric within 0.01mm, the center bore in the smaller burr is true to the bottom of the burr within 0.01mm etc.
nickw wrote: Frank says he shoots for .005mm, and everything is below .01mm. I believe him. But look at how much work he goes to:
Heating the bearings to expand, and freezing the shaft (shrinks it) for a press fitting:
This video was fairly old, not sure if that's how it's still assembled, but my comment then and now is the same: heating rubber sealed bearings (at least that's what I see on the video, but then again I might be wrong) with a hand torch isn't the method I'd use, simply machine the shaft with a slight interference fit and press fit the bearing at room temperature. Not sure why such extreme measures were taken, perhaps a bench press wasn't available, but it's certainly not the only / best method which gives good results. Keep in mind that extreme tight fits lead to bearing failures, normally manufacturers provide data for different bearings sizes and if one "side" of the bearing is press fit, the other tends to stay as a transitional fit anyway. Have a read through Timken / SKF / NTN / FAG websites for more detailed information.
Terranova wrote:Christopher Hendon claims that his tested grinders are running parallel within 1 micron. But I think he also believes in fairy tales.
https://twitter.com/chhendon/status/651154278128619521
That's a ballsy statement, would love to see the conditions and equipment used for measurements. Heck considering SS 316 is used for parts, you are dealing with a coefficient of thermal expansion equal 16 um / mK, on a shaft which is 25mm OD you will see roughly 2um increase in dims with a temperature increase from 20degC to 25degC (this is very simplified just to show how much 5degC can affect). Fart next to the measuring equipment and you're out of your 1 micron tolerance.

FYI all the above are my own views, feel free to disagree, I'm certainly no authority on the subject of alignment / machining.

T.

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Terranova

#13: Post by Terranova »

dsc wrote: This video was fairly old, not sure if that's how it's still assembled, but my comment then and now is the same: heating rubber sealed bearings (at least that's what I see on the video, but then again I might be wrong) with a hand torch isn't the method I'd use, simply machine the shaft with a slight interference fit and press fit the bearing at room temperature. Not sure why such extreme measures were taken, perhaps a bench press wasn't available, but it's certainly not the only / best method which gives good results. Keep in mind that extreme tight fits lead to bearing failures, normally manufacturers provide data for different bearings sizes and if one "side" of the bearing is press fit, the other tends to stay as a transitional fit anyway. Have a read through Timken / SKF / NTN / FAG websites for more detailed information.

This video wasn't old, it was made on the day I posted it (some weeks ago) but I can totally understand you, looking at it when having an office job, knowing everything in theory is a bit different than it is in practice. (no offence)
After a while you have a feeling for it not to heat up the seal directly and you even know when you reach ~80 degrees C.
So in theory you are right and I agree you can find it in the mentioned Timken, SKF etc..

samuellaw178
Team HB

#14: Post by samuellaw178 »

dsc wrote:I would not agree with this statement, if the design allows for it, alignment isn't hard. The main issue with pretty much all grinders on the market today is that they are not designed to be re-aligned or even checked for alignment. If you cannot even test whether a grinder runs true or not, you're going in blind and guessing, you wouldn't even know if your method of alignment is successful or not (FYI I'm not saying people shouldn't try and align burrs themselves, just that there's no way to assess how good the method or alignment really is).

In my opinion if you can get burrs aligned then it certainly won't hurt, it's not going to make your shots worse than if it's misaligned. In my case (and probably not only mine unless you have access to expensive lab equipment on a daily basis) it's far easier to align burrs than to use LPA, blind testing etc. to see at which point further minimising alignment errors doesn't matter.
Exactly right, I wasn't sure how good the alignment is except for basing my judgment on visual/tactile inspection and rubbing point of the burrs (which could be wrong?). On both of the grinders (HG-1 & Pharos), the burrs gaps were changing(enlarging and shrinking) noticably by naked eyes as you crank the handle. I did my best to reduce the fluctuating burrs gap until it was no longer observable by eye. That also did improve the burrs rubbing points. I certainly do not have a solid number for the alignment state but it's definitely a big improvement from the alignment point of view. Still, I did not notice any significant difference in grind. Maybe there is, but I can't tell as it wasn't day and night. So that was why I am kinda doubtful and whether it make sense to shoot for such accuracy when it actually might not matter.

I see some claims occasionally on a perfectly aligned grinder. They claim there's no more static and no more distribution needed on such a grinder. Is that possible due to burrs alignment alone? Tom, what's your take on this?
In a perfectly (let's take that as tolerance = <0.01mm) aligned grinder, with a straight drop grind design and single dosing mode (ie, HG one style or Versalab), will the grind have to be mixed in order to produce acceptable pour?

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Bluecold
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#15: Post by Bluecold »

I doubt Mazzers claims of 20um tolerances. Their upper burr carrier is basically a large sliding bearing. This freely floats inside the adjustment screw, and the thread of that screw has its own tolerance as well.
My Faema, which has a much larger thread area than a Mazzer with the upper burr mounted directly to it has at least 10um on the thread alone (testes with a cheap dial gauge). In any case, most current measurements on alignment are done with the grinder unloaded. A more representative measurement would be done when the grinder is in the process of grinding.

I have come up with a test method to test the impact of grinder alignment. You just grind half the dose slightly coarser, and half the dose slightly finer. Then do a taste test comparing to the nominal grind size.
However, for this to work you need to be sure the grinder you're using is properly aligned. I currently am not sure on my grinders' alignment.
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."

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canuckcoffeeguy

#16: Post by canuckcoffeeguy »

nickw wrote:
Sorry, not trying to make you paranoid. If you're enjoying your coffee and you're happy, then all is well for you :)
Terranova wrote: Don't get paranoid and enjoy your espresso.
If you weight the output shot by shot and the flow rate, time, weight and last not least taste stays the same, than it is very unlikely that your grinders suck.
Good to hear. I'm pretty meticulous about my prep. I single dose only. Weigh my dose, weigh my shots, time my shots, monitor Erics thermometer for temp, and do some painstaking basket and distribution prep.

I also sweep and vacuum any stray grinds in the chute and doser, and take detailed notes for all my shot parameters similar to Andy S. in that EK43 video that documents his laboratory like shot prep. The only thing I don't measure and track is EY since I don't dabble in refractometers.

And I'd say I get consistent results in the cup from shot to shot, unless I fool around with temp. So all must be reasonably good in terms of alignment.

Perhaps, though, we're in a pre-dawn period where manufacturers are going to start paying closer attention to alignment. Maybe akin to when people started realizing how important temp management was for espresso, and PIDs went from experimental and groundbreaking, to now when PIDs are standard features.

Maybe grinders will soon be marketed based on their superior alignment specs, in addition to their burr size and other features. Demand for better espresso created the PID dual boiler craze. Maybe the next frontier, as Tom C. alluded to, is a big leap forward for grinders.

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dsc

#17: Post by dsc »

samuellaw178 wrote:Exactly right, I wasn't sure how good the alignment is except for basing my judgment on visual/tactile inspection and rubbing point of the burrs (which could be wrong?). On both of the grinders (HG-1 & Pharos), the burrs gaps were changing(enlarging and shrinking) noticably by naked eyes as you crank the handle. I did my best to reduce the fluctuating burrs gap until it was no longer observable by eye. That also did improve the burrs rubbing points. I certainly do not have a solid number for the alignment state but it's definitely a big improvement from the alignment point of view. Still, I did not notice any significant difference in grind. Maybe there is, but I can't tell as it wasn't day and night. So that was why I am kinda doubtful and whether it make sense to shoot for such accuracy when it actually might not matter.

I see some claims occasionally on a perfectly aligned grinder. They claim there's no more static and no more distribution needed on such a grinder. Is that possible due to burrs alignment alone? Tom, what's your take on this?
Not sure what the limitations are of naked eye gap comparison (even though apparently the naked eye can see objects as small as 0.02mm - 0.05mm), but there's a difference between static burr gap and dynamic burr gap. On the Pharos the bottom of the shaft is supported so theoretically if you get the gap even around the entire burr (you could try using photography to help yourself, assuming you have a macro lens and can somehow position the lens parallel to the bottom of the burr and dead center) you should be good or at least better than if the gap is uneven. On the HG1 this won't work as no support below the bottom burr allows for too much movement / shaft flex etc. (stuff we already discussed).

As for no static and no more distribution - this is not something I've experienced on my 71mm conical Mazzer burrset. I'm not really surprised as static is the product of the grind process and the uneven grinds "layering" is the byproduct of single dosing. Both in my opinion have very little or nothing to do with burr alignment (although I wouldn't go as far as saying that a badly aligned burrset cannot produce a normal looking / perhaps even tasting shot - I simply have no knowledge in this area).
Bluecold wrote:I doubt Mazzers claims of 20um tolerances. Their upper burr carrier is basically a large sliding bearing. This freely floats inside the adjustment screw, and the thread of that screw has its own tolerance as well.
My Faema, which has a much larger thread area than a Mazzer with the upper burr mounted directly to it has at least 10um on the thread alone (testes with a cheap dial gauge). In any case, most current measurements on alignment are done with the grinder unloaded. A more representative measurement would be done when the grinder is in the process of grinding.
There is indeed clearance on the threaded section (otherwise the thread wouldn't work), but this mostly allows for side movements, not sure how badly those affect grind quality (probably less so than any angular misalignment). On the Mazzers the three springs push the burr carrier up to remove any slack, so assuming the burr is mounted perfectly flat, the runout on the shaft is minimum, the rotating burr runs true and the burr center is dead on aligned with the shaft rotation axis, it should all work fairly well. Loads of assumptions I know :D but in theory Mazzers should be capable of running fairly well aligned (I doubt that myself but I haven't got any to test and it's not easy to test them anyway).

T.

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FotonDrv

#18: Post by FotonDrv »

Terranova wrote:Don't get paranoid and enjoy your espresso.
If you weight the output shot by shot and the flow rate, time, weight and last not least taste stays the same, than it is very unlikely that your grinders suck.





They are "punching above their weight" because burr size is often getting overestimated but at the end the grinders with bigger burrs are mostly better assembled, aligned, so the output can be more consistent just because of less run out, but not just because of the burr size.
Mahlkönig is machining the best burrs (imo) and a grinder can only be as good as the weakest part of it, (alignment) same like the performance of your PC.

So the conclusion is: less run out less boulders, less over-extracting, more consistency. I also had some good shots out of misaligned grinders, it seems that just sometimes it is the right mix out of a certain particle size range, but it is difficult to have consistent and reproducable results.

You can do some little things to have the burrs with low radial play but just radial, the rest are many different numbers from many parts i.e tolerances which meet at the burrs.

Christopher Handon claims that his tested grinders are running parallel within 1 micron. But I think he also believes in fairy tales.

https://twitter.com/chhendon/status/651154278128619521
Good analysis Frank!

Tolerances in not only manufacture of the grinder but of the burrs themselves can also effect the outcome of the shot.
That Light at the End of the Tunnel is actually a train

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nickw

#19: Post by nickw »

samuellaw178 wrote:0.005mm, that's super impressive! I'm sure you can't wait to experience the upgrade when it comes back from Frank.
I think the 5-10micrometre is only for the Titus. If mine is .01-.012mm I'd be very happy.
samuellaw178 wrote:But that's also where my question comes from again, is it that important to get down to 0.005mm or even 0.02mm? What is the minimum tolerance before we start seeing/tasting a noticable deteriorate in quality? I guess no one knows the answer at this stage - maybe Mazzer does but as usual it's a trade secret. :P Frank might be able to find out as well. What I know for sure is those visually obvious alignment, is definitely way more than 0.02mm.
For the VL I think it's around around .01mm

The flats on the VL and EK43 (old coffee burrs) reacted different, even though they both started a similar amount out (.06-.07mm). But there are other factors going on, such as burr size/cut, rpm, orientation (and how they load), etc.. The EK seemed to be more forgiving on alignment.
Bluecold wrote:I doubt Mazzers claims of 20um tolerances.
According to Alex Bernson's tour of Mazzer it's .02mm
http://sprudge.com/mazzer-factory-tour-44860.html

But they also claim a 0mm tolerance on parts, which is impossible.

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Bluecold
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#20: Post by Bluecold »

dsc wrote: There is indeed clearance on the threaded section (otherwise the thread wouldn't work), but this mostly allows for side movements, not sure how badly those affect grind quality (probably less so than any angular misalignment).
I don't know if this works with your ZR71, but should work with most 'conventional' electric grinders.
Empty your grinder, and turn it all the way to zero, to where the burrs just don't touch. Then push down on one quarter sector (nsew) of the upper burr carrier. I guarantee you you'll get a chirping sound. In theory, you should get a similar amount of chirping for similar force on each quarter sector.
Only way around this would be a type of clamping mechanism.
LMWDP #232
"Though I Fly Through the Valley of Death I Shall Fear No Evil For I am at 80,000 Feet and Climbing."