# Reduce retention on Gaggia MDF?



## FlatWhitey (Apr 15, 2020)

Morning all,

I dismantled my Gaggia MDF on Saturday to give it a thorough clean-out. Removed both burrs and returned them to looking brand spankers again.

After grinding my first coffee, I noticed that the ground output was 4g lower than the beans input. Hefty retention!

This is what the lovely and clean innards look like *after just three 19g bean inputs:*









Any suggestions on how to improve this?

Sugru or the like to form a more angled slope down into the grind chamber perhaps?


----------



## FlatWhitey (Apr 15, 2020)

Any tips?


----------



## BlackCatCoffee (Apr 11, 2017)

I am not sure you will be able to do too much to help I am afraid. A lot of it will be on the burrs, around the grinding chamber.

These grinders were designed in quite a while ago when things like grind retention were not perhaps at the forefront of peoples minds.

Perhaps look at how people reduce grind retention on other doser grinders such as the SJ and see if you can adapt.


----------



## ashcroc (Oct 28, 2016)

Hi, use an MDF myself for syphon. There's a lovely shelf just behind the finger guard in the doser that'll be holding most of it. Some have cut the finger guard off so they can brush the grinds out but I find tipping the grinder forward while it's running & tapping it on the counter gets most of it.
Considering it was designed to grind a fair amount before dosing into the portafilter (with a loaded doser, 1 thwak should be about 7g), retention was definitely not in the designers minds. They pretty much just downsized a commercial doser grinder which has the turnover where it's not a problem.


----------



## FlatWhitey (Apr 15, 2020)

BlackCatCoffee said:


> I am not sure you will be able to do too much to help I am afraid. A lot of it will be on the burrs, around the grinding chamber.
> 
> These grinders were designed in quite a while ago when things like grind retention were not perhaps at the forefront of peoples minds.
> 
> Perhaps look at how people reduce grind retention on other doser grinders such as the SJ and see if you can adapt.


 I like this - just seen some ideas! I shall report back


----------



## FlatWhitey (Apr 15, 2020)

ashcroc said:


> Hi, use an MDF myself for syphon. There's a lovely shelf just behind the finger guard in the doser that'll be holding most of it. Some have cut the finger guard off so they can brush the grinds out but I find tipping the grinder forward while it's running & tapping it on the counter gets most of it.
> Considering it was designed to grind a fair amount before dosing into the portafilter (with a loaded doser, 1 thwak should be about 7g), retention was definitely not in the designers minds. They pretty much just downsized a commercial doser grinder which has the turnover where it's not a problem.


 Very good point. I've not put the doser assembly back yet, so I shall keep it off whilst I try out the direct feed thing I've seen after looking around after what @BlackCatCoffee said.

Tilting will definitely help too judging by the grind chamber to doser chute which appears to have virtually no slope whatsoever!


----------



## BlackCatCoffee (Apr 11, 2017)

Do you have a 3d printer or know anyone that does? Perhaps you could design a spout to go on the front of the grinder instead of the doser.


----------



## FlatWhitey (Apr 15, 2020)

BlackCatCoffee said:


> Do you have a 3d printer or know anyone that does? Perhaps you could design a spout to go on the front of the grinder instead of the doser.


 I don't, unfortunately. But this gets as close to doserless as I can get without hacksawing off the chute (which has virtually no gradient to it!).









- The funnel feeds beans direct into the chamber

- The spare tamper keeps downwards pressure on the beans and stops them jumping out of the hopper

- The chute feeds straight into my weighing scoop and I can access the chute to scrape out the stuck grinds (which happens constantly)

I still need to find a way to create a raised cone to fill the bottom of the grind chamber where beans just sit and thus never make it into the burrs.


----------



## ashcroc (Oct 28, 2016)

BlackCatCoffee said:


> Do you have a 3d printer or know anyone that does? Perhaps you could design a spout to go on the front of the grinder instead of the doser.


I've considered a cone/ramp kinda thing that fits in the doser instead of the teacher to feed the grounds to the exit port.


----------



## FlatWhitey (Apr 15, 2020)

ashcroc said:


> BlackCatCoffee said:
> 
> 
> > Do you have a 3d printer or know anyone that does? Perhaps you could design a spout to go on the front of the grinder instead of the doser.
> ...


 The challenge would seem to be getting the grinds to actually move from the chute into any subsequent assembly, even a steep ramp. The chute itself needs to be bypassed or altered to provide a steeper gradient to encourage the grinds to actually leave the chute's exit.


----------



## bowerfield (Apr 14, 2020)

I got fed up with mine and attempted something similar at the weekend.

Unsurprisingly, it doesn't work at all and just gets stuck in the chute 😆. It's frustrating how it has some decent burrs but any method of getting the grinds from the burrs to the portafilter is awful. I've admitted defeat with the MDF and going to get a Mignon to replace it.

Until then I might copy your method of just putting a scoop underneath instead.


----------



## FlatWhitey (Apr 15, 2020)

@bowerfield I find the chute captures a lot of grinds on the top and sides for some reason, so I find complete access to the chute is needed to enable this (hence the scoop). I'd far rather your method for ease of use, if I could actually get the darn grinds out of the chute in the first place without scraping!


----------



## FlatWhitey (Apr 15, 2020)

Just trimmed down a plastic conical washer which slots over the lower burr nut thereby directing the beans in between the burrs and filling the recess in the bottom of the grind chamber, rather than hoping they bounce out of said recess. Shall report back with a retention check.


----------



## ashcroc (Oct 28, 2016)

FlatWhitey said:


> The challenge would seem to be getting the grinds to actually move from the chute into any subsequent assembly, even a steep ramp. The chute itself needs to be bypassed or altered to provide a steeper gradient to encourage the grinds to actually leave the chute's exit.


Yeah. Think tilting the whole grinder may be easiest but replacing the shelf with a ramp would be more aesthetically pleasing if there's enough clearance with the motor. Been quite a while since I had mine in pieces as decided upgrading to a Eureka mignon was the easiest way to go.


----------



## Iisne (May 19, 2020)

I unscrewed the nut (reverse threaded) located in the middle of the hole of the bottom burr. 
I inserted 3 Penny Washers size M8 (8mm centre hole that sits over the screw) x 30mm diameter (fits the inner diameter of the burr perfectly) x 1.5mm thick. £1.49 on eBay. 
I just tried it out and it's clean as a whistle. No beans or grinds left in the recess of the grind chamber.

Has anyone had any luck reducing retention on the outer rims of the burrs?

I also have a plastic container from a takeaway that fits perfectly into the hopper. At the end of the grind, I push down on this to force air through the grind chamber to expel the grinds in the chute.


----------

