I’m looking into coffee makers to use as the basis of my design. It seems like a logical first step since it will help me narrow down what features are viable. I still haven’t decided if I want to use an espresso machine or one that just makes coffee.
The case for using an espresso machine
An espresso machine is needed to make a wide variety of drinks. Espresso is used in lattes, mochas, cappuccinos and Americanos. It is also generally more impressive, a coffee maker just makes coffee and other drinks that use hot water. In either case I’ll probably need to automatically clean the machine somehow. Since it will be heavily modified I'm open to using a used one too, and a quick search shows I could get a decent home quality one for about $400 that way.
The case for just using a coffee maker
Most espresso machines cost nearly the whole budget for the project. I haven’t found any that don’t involve several manual steps that would need to be automated. For example you must grind the coffee into the portafilter (the metal cup with a nozzle) then press it up into the grouphead (the part that pushes the hot water through the coffee), lock it into place and then start the brewing. Besides that it would need a way to clean the portafilter. This could certainly be automated, but it might not be practical in the amount of time I have. Also, there are coffee machines that include a lot of the features I need such as automatically grinding the beans.
Making my own?
Probably the least practical option since time is limited, but I have found examples of people making their own espresso machine.
Robo-Pavoni-minimal, and well designed, this is basically a well controlled brewing head without all the other parts attached. If I were to take the route of making my own this would be a good starting point
Portable espresso plunger - This is basically what I have seen called an Aeropress elsewhere, it would just be a part of the machinery needed, but it could be a starting point. It's basically a pneumatic ram with a filter at the end, you pour in boiling water and force it through the filter with the air plunger.
The main advantage of building my own would be that it would save money on parts I would modify anyway. If I buy a ready made machine I'm going to be pulling out and cutting up a lot of the existing hardware. I'm sure if I need to I can make parts that meet the mechanical requirements to make good espresso, so this option isn't totally off the table.
I'll be getting into more technical specifics and feature specifications as the project develops.