samuellaw178 wrote:Thanks Nick for highlighting the point on axial alignment.
I had gone through some of the videos before. However I am not aware if they mention anything about the accepted runout tolerance, or how do you consider a grinder perfectly aligned, and what are the benefits of going from good enough tolerance to 'perfect' alignment. I know alignment is important, but I'm not sure how good is good enough thus the OP. On my Pharos, HG-1 & Lido, aligning them had never achieved me anything significant/noticable as compared to the difference between flat burrs vs conical burrs.
You're welcome, I do what I can. I'm still learning like everyone else (I could be wrong on some things too). It's a fun and deep rabbit hole.
Most companies don't state acceptable alignment/runout. Otherwise we could hold them too it.
I've only seen Mazzer and Frank state anything.
Mazzer says they aim for .02mm, which if they actually did hit, would be pretty good (I haven't seen it, but need to test more).http://sprudge.com/mazzer-factory-tour-44860.html
The whole 0mm tolerance thing isn't true. Everything has tolerance.
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: https://www.instagram.com/p/BBJDNHNLMFJ/
Bench grinding/lapping the outer conics (which the flats sit on): https://www.instagram.com/p/4-anxCrMKx/
Measuring final axial on static burr: https://www.instagram.com/p/4-VMkhrMBD/
Measuring final axial on rotating burr: https://www.instagram.com/p/BBu0Z0jLMK3/
Measuring radial runout: https://www.instagram.com/p/BB5wBLOrMH3/
He had another on grinding the shaft to final spec, which I can't find now.
As for perfectly aligned, or flat, or round, or parallel... there no such thing. Everything is done to some spec and nothing is perfect. The smaller you get, the harder it gets. Even heating something up a few degrees will change things as it expands.
If you want, I can share some tour videos from a few machining companies who rebuild spindles, lapping machines, and other machining tools. Parts can't be better than the tools which made them, so it's particularly neat so how they do things.
samuellaw178 wrote:On the Versalab, do you do WDT on your shots before the alignment?
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.
samuellaw178 wrote:I've read often enough that alignment makes a huge impact on Versalab's operation. My impression/guess was two fold - one is due the design and secondly the shaft runout was too much to begin with. On the design front, my impression was the Versalab has a static wiper underneath. If this is out of alignment, I suppose that will affect the distribution and retention(thus low EY). On a perfectly aligned Versalab, if you remove the wiper, does it have static, do you still need to distribute for high EY without channeling?
The complaint with the Versalab was the two bearings being next to each other, and the runout/clearances in the bearings would allow the shaft to move. Some argue the shaft will center itself within the bearing clearances. I think that's idealistic. Which is why Frank gives the extra lower bearing and uses tighter clearance bearings.
With the wipers, there are two:
- There is the static wiper (named static because it doesn't move). It's a little piece of wire which knocks the fines off the rotating flat burr.
- There is also the moving wiper. This knocks/brushes/blows the fines off the bottom funnel.
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.
Haven't measured EY with a Versalab yet. I got the refractometer after my accident.
IAlso, 'cutting' is just a layman term as I do not know the right jargon.
To my understanding, attrition is an imprecise process. Basically you have beans fracturing and 'exploding' if you will,to all sort of particle sizes. Then you're hoping the size distribution will fall into the right range with the right ratio, and course the burrs gap opening is helping with determining the grind size threshold. None of these seems like a precise process.
You're right, it's not a very precise process. Basically the beans are shattering, and keep doing so until they are small enough to fly out the burr gap. This is why you get a distribution curve and also why it's bi-modal.
Even with in a distribution curve. Wether it's done by laser diffraction or sieves, each has their merits and downfalls. Ground coffee is 3 dimensional, both methods only measure 2 dimensions. Think of a watermelon, and try to measure it. If you measure it from the end, it may be 30x30cm. If you measure it from the side it may be 30x45cm. When graphing the particles they're only using the longest axis, and the same shape/particle would "measure" very differently based on which side you use. So even with distribution curves, we need to take them with a grain of salt.
Beyond that, particles themselves are just a collection of cells. We extract cell by cell, not particle by particle. The whole "fines over extract" thing is a bit of a misleading truth. The outside cells of the boulders are also over extracted.
But I digress...