DIY Espresso Machine: Dual Thermoblock, Dual Piston Pump, Single Group - Page 3

Need help with equipment usage or want to share your latest discovery?

#21: Post by kangkang »

that is so awesome!!!Looking forward to your sharing。Allow me to express my admiration even though my English is not good.
A coffee lover from China.

Pflunz (original poster)

#22: Post by Pflunz (original poster) »

Hi and thank you.
I am not going to place all files somewhere for sharing. Not because I don't want it, more because it is a lot of work to put all files to proper locations (GitHub for software) and make it accessible.
If there would be an overwhelming large group interested in the files it would be less work to properly place them somewhere online, but only a few people contacted me until now. But those who did, got all the files they were interested in.

kangkang wrote:Looking forward to your sharing
After rereading your comment I think I might have misinterpreted your sentence. If you are looking for future updates, they will come for sure :) Then please ignore the first part of my answer :)


#23: Post by kangkang »

This is great, please keep updating

Pflunz (original poster)

#24: Post by Pflunz (original poster) »

@kangkang you asked for details of the group head. Maybe somebody else is interested:

The group head consists of two parts, the bayonet ring and the ring for the gasket.
Since I am not able to CNC mill a bayonet, I made a simple version and used a metal sheet and lasered a long slit, like this:

Then I bent the long part 4mm up and welded it:

On top I designed a cover, so it doesn't look cheap:

The gasket ring is actually just a ring (ok, several rings):

I had to insert additional o-rings, since at only a few bar the silicon e-61 gasket did not stop the water flow above the the gasket. This was due to the fact that there is only a flat surface above the gasket. The portafilter did not leak since the filters do not have a flat surface but are round.
Here is a video of what can go wrong:
The cross section looks like this:

The left "drill hole" ist the water inlet. There is the 3-way valve above. The middle is the outlet, there is a valve above which opens at the end of the shot. The right hole is for the thermocouple. The first plate under the frame is stainless steel, too. The left inlet hole of this plate is bigger than the rest so that the nut which holds the valve fits in, the hole in the middle is larger since I inserted a blind rivet nut, which holds the holow screw which holds the shower. In the frame, above the nut, there is already a thread for a connector for the tube to the flush valve. In the right hole in the frame there is also a thread for the thermocouple compression fitting. The thread of this fitting is longer than the frame is thick, so the hole of the plate is larger so I can screw it deep enough. This view is actually a side view.

The shower is already shown in the first post.

Pflunz (original poster)

#25: Post by Pflunz (original poster) »

I said I want to come back with a video from a bottomless portafilter, but I just got the last parts for the case electro polished. So I had to test if they all fit together:

At first I wanted to use the bottle from the water I am using as "tank" (so I don't have to clean it), but then I decided to add a "backpack" until I can plump the machine in:

This is how the finished machine will look like, except that I do not yet have the rotary knobs (right and left side next to the display) and the two bars crossing the cup tray.


#26: Post by Marco_83 »

Superb machine. You do a really fantastic job :D

Pflunz (original poster)

#27: Post by Pflunz (original poster) »

I am almost done with the hardware. I need to turn two turning knobs for the side of the espresso machine, so that I can control flow and pressure during a shot.
I finished cable management and crimped some connectors, so that now the whole electronic carrier can be removed:

Electronic carrier:

I did not find a good connector for the thermocouples, so right now I have to connect them directly to the electronics without a connector.

I assambled the machine yesterday evening, so that I could take this morning the very first espresso from the machine. I have chosen a recipe with 4ml/s flow for preinfusion and then limited the parameters to 9bar max pressure and 2.5ml/s max flow. I also decided to use a declining temperature profile. I took two videos simultaniously:
As you may see, the grind was a little to coarse (or not enough beans), so I never hit the 9bar limit, but nonetheless the espresso was really nice (actually better than most of the time with my Lelit machine). I originally planned to use it for a cappuccino, but decided to drink it instead :)

edit: I forgot the add the espresso and puck images:

You can see, the puck is quite leveled, but it seems that in the center something happens to the puck. My guess is, that since I am using a hollow shower screen screw to flush the group after the shot (so the "dirty" water does not have to go through the shower), this happens after the shot when the valve opens.


#28: Post by crwper »

Gorgeous! Coincidentally, I dug this post up from my history yesterday to look at your design again, so it was a real pleasure to see it come up this morning.

Pflunz (original poster)

#29: Post by Pflunz (original poster) »

This will be one of my last replies in this thread (except there a questions which I'll answer gladly).
Yesterday my grind was a bit too fine, but the espresso still was nice:
You can see the 3 parts from the recipe: "preinfusion", "saturate" and "flowout". Preinfusion was 4ml/s, after the group reached a pressure of 7 bar the "saturate" began. This holds the pressure at 9 bar for 10 seconds (after this shot I reduced it to 5 seconds, since it reaches quite fast the 9bar) and after that, the machine keeps the last flow for the rest of the shot, which results in a decreasing pressure.

Today I did not record my shot, but it was next to perfect :) I also changed the samplerate and filter for the weight cells and corrected the forgotten rounding for "weight in cup" ( that's why there were so many digits in the display and I first thought there is an error in communication). This morning it worked perfectly and the machine stopped at 40g. Now I am leaving my machine alone for 7 days, since my family and I are in vacation.