Pflunz wrote:


Hi, valve1 and valve2 are there to switch from filling the cylinder (when not energized they connect the tank to the cylinder) to connecting to the rest of the water path. You could also imagine one water pipe per pump to the tank. The connection between those valves is only so that there is one silicon hose to the tank.

Thank you. I think I understand.

Is the following accurate? The software coordinates valve opening and closing depending on actuation of the respective pump. To draw water into the cylinder, the motor retracts the piston. The motor spins the opposite direction to push the water out for water flow or pressurized group head flow or steam production.

Yes, that's accurate.
I thought about an automatism in the microcontroller, where the valve is actuated as long as the piston drives the water to the group and is not actuated otherwise.
But I thought it could maybe be interesting to so something "strange" like pushing water from one pump to the other (through the thermoblocks) to for example preheat the water in the pump, or when implementing a descaling mechanism. So right now there is nothing that prevents the valve from beeing energized while the piston is pulling water and only my GUI (or Simulink program) handles the valves.

This is great. Would love to see what you plan for a GUI (I have a background there).

Hi, for now there are no big plans for the GUI.
I did something in PyQT5 to have something to play with. The main window looks like this:


The espresso windows is already in a video in my first post:


And here is the "Matilda" Tab. This is actually for some hot water for my daughter when we change the diaper (it takes some really long time until the water from the water tap is warm). The "water" Tab is the same, but with other scaling:


What I will do, when most things are fixed and working, is to use another background and use images instead of those ugly buttons. But basically thats it (as I said, I am far from being a designer). I also found it really difficult to find something touch friendly.

Pflunz wrote: Max flow rate per pump should be in the range of 24ml/s. So basically 48ml/s could be feasible somehow. But with a thermoblock machine it does not really make sense. I could press out the ~20ml per thermoblock which are properly heated, but then the water would be quite cold since it would be only very short time in the thermoblock. I think 10ml/s per pump would work well for a limited time (the thermoblocks (which are in fact thermo coils) are probably designed for whole cup of coffee with a decent "coffee-flow" which is ~8ml/s without getting too cold)

This is quite interesting, maybe you can improve on the DE1 in this respect. Sometimes, it is speculated that a significant advantage of a commercial lever over the decent is that the lever can do very high flow rate preinfusion - I think that the LR24 will do something like 20ml/s compared with the DE1 at (for me at least) around 9ml/s. I'd guess that the volume of water required for this stage is only ~50ml (at least with the DE1 group).

Can you show us some video of you pulling a shot?

Nike Corporation started by making rubber soles with a waffle iron. He took it from his kitchen and told his wife later.

Pflunz wrote:If somebody is interested in some files (CAD files, circuit diagram...) I don't mind sharing.

I'd love to see more details! I'm particularly interested in the two pistons--are these off the shelf or custom parts?

Pflunz wrote:
If somebody is interested in some files (CAD files, circuit diagram...) I don't mind sharing.

I'm interested for a share

ShotClock wrote:Sometimes, it is speculated that a significant advantage of a commercial lever over the decent is that the lever can do very high flow rate preinfusion - I think that the LR24 will do something like 20ml/s compared with the DE1 at (for me at least) around 9ml/s. I'd guess that the volume of water required for this stage is only ~50ml (at least with the DE1 group).

For this I will carry out a test with certainty

ShotClock wrote:Can you show us some video of you pulling a shot?

Unfortunately not. I wanted to do this when the build is finished and has its place in the kitchen (which was planned to be this week, but the wrong angle of the frame prevented that ). I only had my "puck simulator filter" for all the tests and wanted to have fresh water in the machine (all the tests were done with the same water in a reservoir) so I can drink the shot. But I will provide a video during January.

crwper wrote:I'd love to see more details! I'm particularly interested in the two pistons--are these off the shelf or custom parts?

Do you mean the pistons or the whole cylinder/pump? The pistons were solid material. They have received a large hole so that the spindle can plunge into it. There are also threads for the spindle nut and a thread on the side for a screw so that the piston does not turn. Additionaly, the grooves for the seals were turned. The cylinders were pipes and I milled a slit into them as a guide for the screw in the piston:


Then I welded the lid with a thread to one side and a flange to the other side:


The bearing of the spindle more or less looks like this:


The hardest part was actually to find fitting raw material. I needed a pipe with a good surface inside (seamless) and a diameter large enough to have enough water volume, a (commercially available standard) seal which fits to this surface and solid material which can be turned into the piston. I found out there is quite a difference between "planning how I want it to look like" and "finding some fitting standard parts so that I don't have to pay thousands of dollars for custom parts". There are some providers for hydraulic cylinders an their raw material, but they are either tinned or have a way too small diameter. I also found a well fitting pipe, but the provider only would have sold it if I would have bought 8 meters of it.

Thank you! That's everything I wanted to know. I love the concept, and your execution is just gorgeous.