The first machines had a flowmeter installed right after the pump for the cold water but it was not that accurate. They managed to come up with a calculation for their pumps based on strokes/pulses. They know how much volume 1 stroke/pulse is and they control the pumps via the pulses. So they are able to tell the volume of water pumped inside and based on your dose and data they accumulated are able to deliver a volumetric dosed shot. This means the liquid in the cup is calculated via the water pumped.
A gravimetric shot is possible only if a bluetooth compatible scale is connected to the machine. The machine communicates with the scale, displays the actual flow rate in the cup and will stop the shot based on the scale. This is gravimetric. Two different things.
Now the problem is that if your scale is not connected, it’s not sitting good in that custom tray/aftermarket and stuff like that the machine will not stop the shot at desired weight and you gonna waste the shot. From time to time the scale will loose connection with the decent.
They also tried to replace the pumps with something better, specially from the noise perspective. They tried a lot of small pumps that can fit inside their small case. The green olab pumps that are inside the maraX deliver a max flow of 6g/s and that was not enough. They also tried some pulsors/silencer membranes but they would fail or leak after a while. The decent espresso machine was build to be used in a busy shop, and has a shot volume number warranty or a time warranty. Whatever comes first, the shot volume warranty was something hilarious: 10.000shots? that would be 26 shots a day, or was it 100.000 shots? you can find all this info on their website.
