bostonbuzz wrote:I think the obvious reason is that with increased pressure from a mass of beans above, the beans themselves are exerting some force on each other. More pieces of beans are in the stages of the grinding burrs and smashing against each other. It's not too hard to visualize how this might have an effect of making the grind finer than with just a solitary bean chunk in there (you have to adjust the grind setting finer with less beans in the hopper). If you look at the gap of burrs, the grinds come out significantly smaller than that gap, so there must be some bean-on-bean (or grind-on-grind) action going on in there in any event

+1

If you put only 2 beans in the burrs and grind, vs 100 beans at a time, the grind size will be very different. Even the Versalab has a slightly different grind output if I decide to feed the beans slowly or dump the beans all at one go. When you single dose, you start with more beans and less beans in the end so some consistency is compromised. Thus generally you need to WDT(or 'shaking for EG1) to create a homogenous particle size mixture.

The build-up/resistance in chute (after exiting burrs) also affects grind size. If you have a Mazzer etc with accessible chute, try partially block the chute so that the grind flows through more slowly. Your grind will be significantly finer presumably due to more grinding action.

Flexing/warping is not the reason for different grind consistency. The tensile strength & creep point of metal is much higher than any bean could exert (even green beans).

Having beans in a hopper whether 4oz for 4 pounds, it keeps the beans from flying around, that control being as simple a just a cap over the throat, can keep the beans from flying out and getting odd grinds. On the other side, the finished product should be pretty consistent as they all need to flow through the grinding plates. The plates remain consistent in separation, beans going in in the center and flowing out on the ends.
as far as a pre-measured dose of beans, say 19gr. in an empty grinder throat will cause a exit shoot to be a bit unsettling, case in point, the E37S, when the throat runs out, the next load tends to spray all over, thus keeping a steady amount of beans prevents this.

Anyway, I did an experiment dialing in with one the beans that I have one my Quamar 80e and Expobar Leva.

Beans = Industry Beans Winter blend
Dose = 20 g
Out = 30 g

When the hopper is filled to the throat:
- Grinder setting = 6.9
- time = 17 s
this is just right balance of acidity and sweetness
any finer and the shot is bitter and any longer the strength drops and bitterness comes in

When I single dose it:
- I put about 22 g and grind until I get 20 g
- Grinder setting = 5.9! This is very near the end of the range of the grinder
- time = 25 s
Yet, the shot was sweet with nice acidity with cherry notes and not bitter.

Single dosing definitely allows me to pull more shots than I could, but I wonder if I will get the grinder into trouble grinding so close to the end of its range.

For now , my Helor 102 is a single doser, it produces very consistent shot flow , the 1st is 31sec, the 2nd is also 31sec and so on. They have a uniform temperature also , 37 degree Celsius.

I have a Eureka Mignon and a Compak K8 before. If I single Dose them, the first 2 shots are still consistent in flow rate , but for the 3rd time the flow rate increase and keep accelerating for 4th 5th 6th shot etc.

So why is the Helor 102 is consistent but the Mignon and K8 are not for single dosing ? Is because of the RPM ?But the Helor 102 is using the Mazzer Conical Burr and they are designed to be feed by hopper instead of single dosing

So single dosing a single dose grinder or hopper feeding a single dose grinder will get a same taste or even same flow rate without changing grind size ?