I have a plumbed-in LM GS/3 and a Mazzer Mini E type B grinder.

The combination is certainly capable of pulling great espresso shots when using proper barista technique. Unfortunately, I wasn't there. Pulls turned blonde very early and naked portafilter revealed the reason - pulls always channeled towards the back, indicating uneven distribution. Clearly my distribution technique was not good enough. Both David Schomer's and Stockfleth's techniques did not improve the results. Of all the different distribution techniques discussed here, the only one that resulted in even pours was the Weiss method. Odd.

Clearly the ground coffee from the Mazzer was not evenly distributed. Perhaps the cause was static, perhaps humidity, perhaps it is the type of coffee I purchase - I do not know. But fluffing the grinds with a chopstick or shaking them in a mason jar did the trick. I had a solution, but it was not as convenient as using the Mazzer as originally intended.

So I decided I would not give up on the Mazzer and would try to find a way to fluff the grinds automatically. As I see it, there are two main problems with this grinder:
1. Coffee grinds seems to be sorted and sometimes even clumped.
2. Position of the chute is off center of basket (for 58mm portafilters - it might be okay for smaller portafilters).

Tackling Problem 1 - Fluffing the Grind:
Design goals were:
1. Fluffy grinds, style Versalab grinder
2. Automatic
3. Stable and easy to clean

I tried various contraptions: i. A spinning tie wrap proved that a solution was possible, and that this wasn't it. ii. A spinning plastic k beater proved too dangerous after shaking itself loose and flying across the kitchen. iii. grating with a shaker attached proved adapt at collecting grinds but not letting them through. iv. Spinning wiper (like the Versalab) worked but was too finicky and tended to scratch the chute. v. Spinning grating worked - and worked great!

Starting with the results, the following is a picture of the grinds after the spinning grating. The evenness of the grind is felt during tamping:



Distribution still off center and should be improved. "La Maccina Fluffinata" is nearly here.
The motor for the Fluffinator was purchased first. It is a US made Globe 12VDC model 405A391 acquired NOS (new old stock) at surplus electronics store Halted Specialties Electronics in Santa Clara, CA for less than $2. The motor shaft diameter was measured at 5/32" and the rest of the parts were all selected for this diameter.

At the heart of the Fluffinator is a spinning grid of zinc (source: Home Depot - used for vents) cut into a circle 58mm wide. It is held on a 5cm long, 5/32" stainless steel shaft by two collars and two NSF approved silicon O-rings (source: McMaster-Carr, see BOM below). The advantage of using a grid is that unlike a wiper, it is rather balanced at low RPM. This is important since the shaft is supported only at the top by the chute cover - it is rather long and any imbalance will set it swinging.

In the picture below it is clear where the grid edges hit the sliding coffee, sending it swirling around the chute. Coffee grinds start as a donut shape pile in bottom of portafilter and eventually pile up to make an off-center pile.



The shaft is connected to the motor by a flexible coupler (source: McMaster-Carr) which reduces vibration greatly. The motor is centered by the top lid of the chute. The center of the lid was conveniently pre-marked by the plastic injection mold, and then drilling and using a taper/reamer to widen the hole for the motor rest. A center punch and micrometer were used to position the screw holes which were then drilled.
Remember to use a reamer or large drill to remove any plastic burrs, or they will end up in your coffee. (o-ring on motor shaft was intended to prevent coffee from getting into motor, which proved not really necessary)



The flexible coupling is the only delicate component in the contraption. It is indeed flexible, and giving it a tug will send it into plastic deformation. One nice aspect of it, is that it is 19$ at McMaster Carr. It is not a once in a lifetime find in a junk lot so it can be replaced within 24 hours.

A picture of "La Maccina Fluffinata" installed on the Mazzer:


BOM (bill of materials):
McMaster-Carr
1 9861T109 Alum Helical Beam Set-Screw Shaft Coupling 5/32" X 5/32" Bore, 1/2" Length, 3/8" OD $19.95
1 1263K145 Miniature 316 Stainless Steel Drive Shaft 5/32" OD, 5" Length $5.50
2 9946K3 Aluminum Set Screw Shaft Collar 5/32" Bore, 7/16" Outside Diameter, 1/4" Width $5.78
1 Pack 9396K136 Silicone O-Ring AS568A Dash Number 105, Packs of 100 $8.56
Halted Specialties
Motor Globe 405A391 12VDC: 1.95$
Home Depot
Building exhaust - or perhaps a concrete mold (source of the zinc grating): 4$ at home depot.

Total with shipping ~ 60$

Electrical set up:
For safety, use a UL approved wall wart and a switch.

Want more automation? Well, you can indeed electrocute yourself, or grind a finger away, or inhale stuff known or unknown to the state of California or Europe or believed by someone to cause or not cause a disease or a cancer or brain problems. And you can probably grind your warranty away... So you are on your own. (But if you insist here are some hints: I connected the motor to the timer circuitry located in the base of the grinder. I did not connect the motor in parallel to the relay as the transistor used to trigger the grind relay was not adequately spec'ed for the motor draw current. Instead I hooked a miniature 12V transformer *potted! and shrink wrapped!* in parallel to the grind motor. This then operates the DC motor.)

Tackling Problem 2 - Chute Alignment:
The chute seems to have been designed for a Type A grinder (buttons on top of chute). A 58mm portafilter, resting nearly against the body of the grinder is indeed centered under the chute. For a Type B grinder, this doesn't work since the grind activation button is behind the portafilter and pushes the portafilter out about a centimeter.

The button is a spring loaded cam that pushes a lever microswitch located inside the grinder. Adding a few washers (about 5.8mm worth) should do the trick:


If you are wondering, use an 8mm spanner for the internal lock nut, and a 13mm spanner for the button side. To get to it, you'll need to remove the power switch and the entire switch/trimmer assembly (2 screws below).



Installed, it looks like this:


It is important to verify that the electrical switch still functions correctly: if the button is pressed because of the washers, your grinder will run until the motor burns out. Twist, pull and push the button to verify the switch will always return to the 'off' state.

And the results - centered and fluffy. And a very nice pull indeed!


Happy tinkering!

It seems your analysis is spot on judging from the pictures. The problems you describe are pretty much what I observe myself. I have improved my distribution technique but ever so often the dreaded Mini E clumping messes up my shot.

If I should start modding my Mazzer, and I am tempted after your post, I would aim for a more integrated solution. One, power should be drawn from the grinder; two, no wires should be visible; and three, the motor should be mounted on the inside of the chute (a flat one, PC fan?).

... and then you would have a Mazzer Mini E B with fluffiness enhancement

BR SK,

Elektra T1, Mazzer Mini EB

Oooh I know, a ducted fan on the grind chamber spout would get rid of the clumps. And I bet it could evenly disperse the grinds anywhere (more likely everywhere) in the kitchen.

-C

sk wrote:If I should start modding my Mazzer, and I am tempted after your post, I would aim for a more integrated solution. One, power should be drawn from the grinder; two, no wires should be visible; and three, the motor should be mounted on the inside of the chute (a flat one, PC fan?).

The motor is indeed powered by the grinder. The reason for the outboard motor is that I did not want coffee grinds in the motor. I can share the wiring diagram but be extra careful as there is 110V on these wires: I connected an ultra miniature potted trafo, a full wave rectifier and capacitor in a heat shrink package and tied it inside the grinder with tie wraps.

I marked with white arrows where the timed 110V is. I am not sure if it is similar in the 220V or other models, or even between different production runs, so be extra careful, verify the wiring, or consult an engineer.

In yellow, I pointed out the relay. It is a 12V relay so hooking up the motor in parallel to the relay winding will work. But I don't think the transistor will handle it for long. It can however, be replaced with an equivalent (probably just a high beta) power transistor.



In the current iteration the motor is visible but it is rotated 180 degrees so the motor wire is facing the hopper. The wire is somewhat visible as it runs around the grinder to the back. Come to think of it, there might be a way to fit it through the front panel. But I have the grinder up against a wall so it is not an eye sore.

At least some of my attempts did fan coffee out everywhere.

Great idea and great pics - I dreampt of something similar - to simulate the Versalab but laziness set in and the WDT proves very valuable.

Gosh I know I'm partially nuts now as I had the idea of using a spring wound motor driving a Versalab anti-static blade.

The bridge you used should block any field voltage coming back to the host circuit, but to be sure put a diode to ground any back emf from the motor in to secure the protection. You do not want to blow a controller pin with a large voltage. Any power diode with a high enough reverse voltage twice your feed voltage should do the trick.

A reverse kick from a winding can be much higher than you would think. Better to add a 25 cent part.

-Cecil

CRCasey wrote:The bridge you used should block any field voltage coming back to the host circuit, but to be sure put a diode to ground any back emf from the motor in to secure the protection. You do not want to blow a controller pin with a large voltage. Any power diode with a high enough reverse voltage twice your feed voltage should do the trick.

A reverse kick from a winding can be much higher than you would think. Better to add a 25 cent part.

Cecil is absolutely right.

Whomever is unappreciative of back EMF (electromotive force generated as a magnetic field winds down) should look through the vent grating of their drill and see the sparks fly on the commutator. This motor, having rare earth magnets, should be able to generate quite some back voltage.

But in this case, it is not really necessary:
1. If you decide to hook up in parallel to the relay, there is already a protection diode on the circuitboard (in the picture it is to the right of the relay) to short any back EMF. Relays have coils and hence generate a back EMF and addressed by Mazzer.
2. If you hook it up like me (from the 110V side) then there are no control electronics - only the air gap of the relay. At these currents, I think the relay spring will be able to handle any welding of contacts and contact wiping will take care of any residues.

But do take Cecil's advice to heart if you are to connect any motor to any control electronics. Definitely 25c worth spending!

You would think so, but even on Sirai pressure stats just with the resistive load of the heating coil espresso machine users have seen welded contacts. Total boiler blow. And in a lot of these machines the electronic packages are not water proof. I know DUH. But they are not.

One machine I got blew out a basic 6502 with the water spray. The address side logic was toast. I did diag on all the bus decoders before I noticed that the clock was strange. It was strange because something in the cpu was off. New CPU and all was good again. You never know what will take you to the solution of a problem.

-C

I own a Mazzer Mini E Type B and I have to support both of the two points of critique.

I greatly appreciate your solution to problem #2; I will do that hack on my Mini as well.

As for problem #1, it would be interesting to know if anybody has ever tried to convert the doserless Mazzer Mini E into a doser version. This would be a less tinkering solution, and it could turn the Mazzer Mini E from a half-cocked into a very good grinder for home-baristas.

It would combine:
- the small engine of the Mini (which leads to a kitchen-friendly size)
- 64mm grinding burrs (same size but different profile than Mazzer Super Jolly)
- built-in timer for dosing, no fumbling with external photo-timer
- the doser for a homogeneous distribution.

Has this already been done? Does anybody know which parts are needed and where to get them?

Best regards,
Kleefisch