The past consensus on the forum regarding Robur E was it's not suited for single dosing operation. Vberch (Vlad) has been using one for single dosing and found it suitable. Based on his recommendation, I have been using one for almost 6 months now and would like to offer some thoughts.
Today I decided to clean the Robur and measure the retention. The last clean up was 3 months ago and I've been using the Robur 3x at the minimum daily since.
How it looks underneath immediately after removing the collar:
Cleaned and collect everything in a wide ceramic cup:
As shown in the photo, the retention is so minimal that the Brewista couldn't register it. I had to measure it separately and it came up to 0.5g. That's including the baked-on coffee on the burrs surface. Almost negligible considering I sometimes lose more than that on other grinders.
Here're a few points:
i) Fast - quite fast for single dosing (even faster using a hopper but let's not go there)
ii) Quiet - it produces a slightly different/lower pitch than K30. Based on my wife's feedback, the Robur is even quieter than K30 - the K30 woke her but the Robur didn't. Compared to other grinders I have used in the past, this is hands down one of the quietest electric grinder (secondary only to Rosco Mini which is a hand grinder).
iii) No retention - with a spray or two (RDT), retention is almost zero and minimal fuss.
iv) Consistent - initially I had problem with consistency/adjustment but found out later that the blind shaking technique was messing up my consistency. The Robur's been performing predictably and consistently after I eliminate the shaking technique.
v) Grind consistency, refractometer measurement, taste etc - I can't tell apart easily from the Pharos so it is good enough for me.
Compared to Compak K10:
i) No doser twacking (so happy to ditch that)
ii) More efficient at clearing the throat - no need to to pulse and brush multiple times (once is enough)
iii) Way quieter and built much better too. Robur is just heck of a super-built tank, even compared to the K10.
Compared to HG-1:
i) Way quieter - yes, since my coffee corner is right outside my bedroom - the HG-1 was a nightmare to my spouse
ii) No hand grinding - hand grinding can be super tough with light roasted beans and the big burrs
iii) Less footprint - Robur is huge by common standard, but requires less footprint than the HG-1. Really.
i) Since there's almost no back-mixing of the grind, WDT is a compulsory for VST baskets and in general to get good even pours. Grinding into a secondary vessel is what I'd recommend.
As a bonus, I did a retention check after the full-clean up (in a sparkling clean state). To summarize, there was only 0.2g max retention even when the grinder is in a 'brand new' state. It is so far the best single dosing grinder I've used. As flat burrs (Malhkonigs, Mythos et al) are becoming the rage now, sometimes you could find one ex-cafe for cheap ('cheap' is relative of course! and the usual caveats apply - spare a new burrs set at the minimum).
Pardon my single-handed operation (the other hand was holding the camera/phone) - just want to show the usual routine (usually much quicker with both hands). Grind size was for 15g VST basket - which is the finest as it needs to be in most cases.