Mahlkonig E65S retention (or how to lower it)

When I opened the grinder and saw the coffee inside the grinding chamber, I decided to measure the dead space (total retention): I cleaned the grinder with vacuum cleaner, the chute (flapper removed), chamber, burrs. Then I threw inside 10.0g of coffee and ground out all the coffee (single dose) - 4.12g output. Total retention is ca. 5.9g for single dosing, not that big for commercial OD grinder (e.g. Fiorenzato F4E w/o modification has total retention ca. 9g). Ca. 2.4g is trapped in the chute above the flapper, the rest is in dead space around upper burr carrier (stupid MK design, IMO) and in the grinding chamber between sweepers, under lower burr, etc. Practical retention should be lower, the dead space fills only once and stale there. On the other hand in case of hopper dosing more grounded coffee remains between sweepers compared to SD.

 

However, it's possible to lower the total retention (dead space) by „simple“ modification and improve what MK engineers did not do - to fill the dead space with properly designed adapter. Adapter is made of aluminium alloy, hand pressed on original upper burr carrier and securely bonded with Loctite 638. I measured total retention after modification in the same way as above - single dosed 10.00g. Output is 6.63g, so total retention is only 3.4g, reduced from original one by 2.5g. Pictures clearly show cleaner burr chamber above sweepers and around upper burr (note: the center space of the burrs was cleaned on assembled grinder prior to taking pictures, so do not compare to previous pictures above with messy remaining coffee beans in the center of lower burr).

From earlier brush cleaning chute itself holds 2.3 - 2.4g of coffee, so I’ll try some modifications to the flapper too, when I receive suitable material (on Fiorenzato F4E I was able to reduce chute retention from 4g to 0.4 – 0.6g and total retention from 9g to les than 1.5g, but it’s a different story ... ).

P.S. I don't know, how to include uploaded pictures to the text, is that possible?