Nice idea...

I have built one... Sadly most parts were sourced from many places

It's basically a La Pavoni grouphead installed to a 10 liter water dispenser....

The dispenser had a retrofitted heating coil... 1800w and its controlled by a resetable safety thermostat and pid thermostat....

The dispenser has gotten a safety valve to prevent explosion...

The steam assembly isnt installed yet.....

The steam production is not so good...

The startup times arent any good either.....

If you wanna build one...

Remember if every part if built from scratch it will cost less but take a longer time

Using pre-built parts are a faster approach and is a more expensive approach...

fancycoconut wrote:Wow, who knew it would be so hard to find a standard portafilter for an e61 machine? Anyone on here have one lying around that they would want to sell for a few quick $?

I'll get you some measurements tonight.

You are a god, thank you!

BTW, if any of you all want a little more info about the design specifics, head on over to http://forum.arduino.cc/index.php?topic=276476.0, I do almost all of my work on there. You can see a preliminary schematic of my grouphead on there also, it is attached to one of my most recent replies.

Nice project. One thing I didn't see mentioned was materials used for the group assembly and portafilter. Anything that comes in contact with the water or coffee must be food safe. If metal, that pretty much leaves lead free marine brass or SS. Certain alloys of aluminum may also work, depending on their use. It's proven to be rather problematic for boilers(Microcimbali).

Will be interesting to see how this comes together. Are you keeping track of time and monies spent?

Yep, I am making sure I use food safe aluminum for the group. I really wish I could use stainless or ideally brass, but you can't really CNC either of those. The boiler is SS.

I am keeping track of costs. As of now, with all of the main parts, I am at $140. This doesn't include the casing (acrylic sheets and aluminum L braces), Copper tubing (that will bring up the price some bit), and not to mention the CNCing for the grouphead, I'm a bit nervous to see what that will bring me up to . Luckily, my parents have been really supportive, and are helping me out with the costs.

I'm throwing in some photos because I realized the link to the other forum probably wont let you download the files.
This is the bottom of the group without the bayonet ring. The large ring space is for the gasket and screen.

Not quite sure whats going on with this photo^ shouldn't be black background...

Gonna get my initials engraved

This is a cut-away. The steam is piped to the large, uncapped, empty space in the picture, which effectively heats the group.

This is the bottom of the group without the bayonet ring. The large ring space is for the gasket and screen.

Big thanks to twolane for sending me some really important measurements! I now have everything designed (minus some specifics which will have to wait until my screen and gasket comes).

If you're designing a new group head design you'll get better results if you think through the thermodynamic behavior of the components. I've done a lot of experimenting with temperature control on three substantially different espresso machine designs (e61 double boiler, manual lever, and Gaggia Classic).

This has shown that there are three temperature-management challenges in an espresso machine:

1. Bringing incoming water up to boiler temperature (most important for the brew boiler)
2. Maintaining brew boiler output temperature
3. Maintaining consistent temperature drop from the boiler to the coffee grounds

The typical solutions for these are:

1. Preheating incoming water (typically done with some type of passive heat exchange) reduces the temperature drop that the boiler temperature controller needs to handle
2. Using a thermostat, pstat, PID, or computer to control the boiler temperature and managing the input and output water flow to reduce the impact of cooler, incoming water
3. Heating the group head

Problem 3 of controlling the group head temperature drop is the one that's least discussed and it can be the hardest to sort out the thermodynamics to get it just right. Most of the newly designed espresso machines require some design tweaks to get this right. If I were designing a group head I would build in some mechanism to control the amount of heat that can flow into the group head so that this is directly controllable.

If you are going through the trouble of designing and building a machine, you might as well avoid the hassle of SBDU and HX units and just slap in another boiler for steam. Then you can fill your design with water like slayer, la marzocco, etc. PID controlled, it should be accurate to less than 1 degree Fahrenheit. You can bolt two gaggia or silvia boilers together for a killer steam boiler design.

Just a little update...
Unfortunately, my CNCing fell through, the local University which was going to do the machining for free, pulled the plug and I can't afford to pay the huge sum of money it will cost!
So, I am purchasing an E61. I also picked up this sweet pump from Fluid-o-Tech, it is a super accurate and powerful magnetic drive gear pump. The idea now is to take water from my boiler (not pressurized) and route it to the E61 through the pump (which puts out over 9 bar and can handle the heat). With the E61 group, I have 2 options:
+Replace the lever/cam with a small stepper motor, which the chip will control
+Keep the lever/cam, and only utilize the 1st (closed) and 3rd (brew) positions.
I will probably go the second route. For automatic mode, you select 'automatic', then your volume (and whatever else I decide), then you put the lever in brew. Then, my computer uses the 7.5 or so second ramp up preinfusion style.
For manual, I will select 'manual' then push the lever up, then I will use a dial to control the speed and pressure of the system.