The Alicorn: Achieving Precision Alignment with the Baratza Forté/Vario - Page 2

Grinders are one of the keys to exceptional espresso. Discuss them here.
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Jake_G
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#11: Post by Jake_G »

baldheadracing wrote:Interesting about the Loctite - I'll have to try that on my Vario-Forte the next time I wash the burrs.
The Loctite is not needed on the ceramic burrs as they have a solid bottom that seats firmly on the burr carriers. The ditting brew burrs have a raised seating surface on the outer perimeter which leaves most of the "mounting" surface (including all the area under the screws) floating above the burr carrier. I fashioned some .060" spacers to fill this void so that the burrs can be firmly secured to the burr carriers without fear of Taco Burr Syndrome.

This is what the burr interference pattern looks like with the bolts tightened enough to induce TBS when the relief area beneath the burrs isn't supported:

Image: Forté Brew Burrs experiencing TBS

And here is what you get after supporting the relief area with a spacer and tightening the screws to secure the burrs flat against the burr carrier:

Image: Forté Brew Burrs cured of TBS

Of course, to fix this issue, you must first align the lower burr carrier, which gets pulled out of alignment with the drive belt so that you get this when you first check your alignment:

Image: Forté Brew Burrs with Belt-Induced Misalignment Interference Pattern

This is corrected by loosening the four screws that secure the grind chamber to the lower motor plate and then using the levers themselves to force the lower burr to square itself against the upper burr. Doing this will create an air gap between the grind chamber and the lower plate (as long as the screws are loose enough) and will force the bearing in the grind chamber into precise alignment with the bearing in the lower motor plate. With the levers held in place, gently tighten the grind chamber mounting screws in a crisscross pattern and you'll end up with an interference pattern that completely wiped the upper burr clean. You may need to loosen the belt a bit if the wear pattern still shows a half and half pattern and repeat the process to get it dialed in. The second photo above was achieved without using any shims for alignment. The burrs are fully seated in the carriers and the bolts are properly tightened.

The spacers and the burr chamber alignment take care of two of the three major challenges to getting the Forté/Vario into a precise state of alignment. The third item turned out to be the most challenging as the drive pulley on the grinder I had the pleasure of getting to know was completely lopsided on the drive shaft. Correcting this required pressing a sleeve onto the motor shaft (it has a twisted star profile for inexplicable reasons...) and chucking the motor into a lathe to true up the motor shaft. You can see how eccentric the sleeve had to be to get the shaft and pulley turning true:

Image: Modified Forté Drive Pulley

After all of this, I was able to fully choke my GS/3 using the brew burrs even with a prolonged 2.5 bar preinfusion. Prior to alignment, even EKspresso was a tall order for this grinder.

If Rao's Forté is a Unicorn, this one is an Alicorn.


**Edit**
Below is a quick video of a teardown to remove the grinding assembly from a Forte. It was early in the morning and the family was sleeping, so there's no narration or voice over. Sorry :wink:
I'll add another video highlighting the alignment process when time allows.
Cheers!

Here is a video of checking the alignment with an ink test immediately before performing the alignment procedure:

Here's another silent video. This time of the alignment process.

And here is the ink test results after the alignment:
Cheers!

- Jake
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baldheadracing
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#12: Post by baldheadracing »

Awesome, thanks! 8)

Perhaps this info needs to be captured in a new properly-titled thread :wink: .
What I'm interested in is my worst espresso being fantastic - James Hoffmann

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Jake_G
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#13: Post by Jake_G »

Got a suggestion for a title?

baldheadracing
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#14: Post by baldheadracing » replying to Jake_G »

How about "Baratza Vario and Forte Brew Burr Alignment Methods"
... starting from post 138 or so ... (I was just about to use the "Report this post" button ... )
What I'm interested in is my worst espresso being fantastic - James Hoffmann

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Jake_G
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#15: Post by Jake_G » replying to baldheadracing »

Since Peter is the author of this new topic, he can edit the first post and give it whichever title he so chooses :wink:

jasonmolinari

#16: Post by jasonmolinari »

I just spent abou 1.5 hours aligning my vario with metal burrs.
Ended up putting 12! Layers of heavy duty foil for a total of about 0.35mm of added thickness under one side of the burr. Now they are aligned within about 15microns. (One they first touch it takes about 5 more micros for it to wipe the burr clean of marker).

We'll see if it actually tastes any different! But what better way to spend a Friday night :lol:

This is sort of the shape I ended up using of foil. Made 4 layer thick shims, and kept adding them. Then I trimmed them back a bit towards the holes.

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Jake_G
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#17: Post by Jake_G »

jasonmolinari wrote:I just spent abou 1.5 hours aligning my vario with metal burrs.
Ended up putting 12! Layers of heavy duty foil for a total of about 0.35mm of added thickness under one side of the burr. Now they are aligned within about 15microns. (One they first touch it takes about 5 more micros for it to wipe the burr clean of marker).

We'll see if it actually tastes any different! But what better way to spend a Friday night :lol:

This is sort of the shape I ended up using of foil. Made 4 layer thick shims, and kept adding them. Then I trimmed them back a bit towards the holes.
<image>
Jason,

Nice work getting the burrs close using shims. I trust the results will be beneficial for a while, at least.

One concern I have with using this many shims is that half of your burr is sitting significantly higher than the other half. Additionally, only the outer ~1.5mm of your burrs are in contact with the shims, since the center of the Ditting burrs is recessed some .060". If you marked the area on the upper burr carrier where the marker was not being removed, I strongly suspect you would find that it is the area at the back of the grinder. This is because the belt pulls the lower burr carrier towards the motor and tips the front edge of the lower burr up into the upper burr. By shimming the back of the upper burr, you attempt to misalign the upper burr to match the misaligned lower burr. It will work for a while, but bear in mind that you are effectively bending the upper burr when you tighten the screws, due to the stepped mounting surface caused by the shims.

I mentioned the method I used because it actually corrects the alignment where it starts, which is to get the lower burr carrier spinning true to the upper burr. The process is very simple once you remove the back of the grinder (3 screws) and then remove the whole grinding assembly from the case with 4 more screws. Furthermore, the alignment can be checked by hand without needing to power the motor up, and near perfect alignment can be achieved without any foil shims, whatsoever. I fashioned .060" spacers out of polyester shim stock to allow for tightening the burrs without getting low spots at the mounting screw locations, but the spacers themselves are not at all necessary for keeping the burrs aligned.

Also, bear in mind that if you ever wish to swap the ceramic burrs into your grinder, they will break if you leave the foil shims in place. Aligning the lower burr carrier by centering the grind chamber on the lower motor plate allows for easy swapping between ceramic and steel burrs with no additional shims needed.

Using shims will certainly result in a better dry erase marker result and I suspect it will give you better results in the cup for quite some time, but I do wonder about the long term effects of having the burrs so unevenly mounted in the upper burr carrier.

Cheers!

- Jake

jasonmolinari

#18: Post by jasonmolinari »

Thanks jake. That makes sense. No need to worry about going back to ceramic. I moved from ceramic to steel as I got a niche.
What you say makes sense. however the "top" of the burr was what touched first (back of the grinder, away from the grinds bin), so I'm not sure if it's exactly what you describe. I'll take another look at it though. Thanks for the tip.

I mya look further into what you suggest as I generally dislike the idea of a shim kludge :D i did not tighten the screws all that much and instead used Loctite. This should avoid deformation of the burr carrier.

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Jake_G
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#19: Post by Jake_G » replying to jasonmolinari »

If the back of the burrs touch first, that means your grind chamber is located too far forwards! I was amazed at the results of just loosening the grind chamber and using the levers to square the lower burr carrier. It sounds to me that simple loosening and tightening the screws that hold your grind chamber to the lower plate would net better results than what you currently have as it sounds like the belt tension would help level the burr carrier!

Cheers!

- Jake

jasonmolinari

#20: Post by jasonmolinari »

Can you clarify what you mean by "use the levers to square the burr carrier" means?
Thnks!