Build an espresso machine

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julianmp97

#1: Post by julianmp97 »

Hey! I am new on this site. I would love if anybody can help me. I am soon to be called a Mechanical Engineer in my country, Guatemala. For my graduation project I have decided to make an Espresso Machine. It must be a double boiler machine PID controlled. The core of the project is that I will be the one to make the boiler from scratch, other things such as the valves and the pump will be bought via Internet.

I came here to ask if there is anybody that can give me advice for building the boilers. At what pressure should both be? I assume the pressure of the brewing boiler is given by the pump, 9 bar, is that right? And for steaming and hot water?
I was thinking the material could be Stainless-Steel 316. Should they be covered by other material?

Hope someone can help me. Thanks!

Neto

#2: Post by Neto »

If I where you, I would design a machine that would require some kind of mechanical device to build pressure to a coffee puck instead of an electrical pump driven since that would be more inclined as an electrical engineering type project. Look at lever machines such as the olympia cremina and take a look at some videos to see how it works, its a true piece of art and engineering that its design has not change for long years.. Maybe you can design something like that? Maybe use a manual lever press and put a device there that will have water, coffee puck and basket inside where after you compress it it will produce your shot? To heat the water, you would need to get a heating element and to control that, you would need a pressure stat, its purpose is to monitor the pressure inside the boiler (its connected usually with a copper piping to the top of the boiler) and turn on/off the heating element.

julianmp97

#3: Post by julianmp97 »

Thank you very much Neto! I did not consider a lever machine what so ever. I will look into that because, as you say, it would be more like a mechanical engineering type project. Could it also be a double boiler machine? One boiler for hot water and steam and the other one to pull out the espresso?

cdo

#4: Post by cdo » replying to julianmp97 »

Sure you could do that, would just mean that you need some kind of reservoir and a pump to fill the boilers. The Cremina and Pavoni keep it simple by having direct fill boilers so no pumps are required at all.

thirdcrackfourthwave

#5: Post by thirdcrackfourthwave »

julianmp97 wrote:Thank you very much Neto! I did not consider a lever machine what so ever. I will look into that because, as you say, it would be more like a mechanical engineering type project. Could it also be a double boiler machine? One boiler for hot water and steam and the other one to pull out the espresso?
I don't know that you would need two boilers with a manual lever since you would not be pulling a shot and steaming milk at the same time. For instance the Cremina . . .https://www.olympia-express.ch/resource ... b_2015.pdf
I am not an engineer or extremely familiar with all the engineering aspects of all the machines out there but. . . .there is plenty of information out there on a lot of the issues you will deal with/want to incorporate.

Buena suerte

ira
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#6: Post by ira »

As an alternate suggestion because it's probably got a lot more marketing potential, you might consider a very simple open boiler lever machine with a separate stand alone milk steamer, possibly one that's smart enough to steam the mile unattended. The open boiler will sell if it works well and looks beautiful, the steamer seems like a market looking for the product to fill it. It's also a somewhat more challenging project as there is a lot less to build on. In theory, I can drive over to the espresso parts store and buy everything I need to make what you're suggesting and then it's only a packaging problem, but a steamer, not so much to work from.

Ira

Jeff

#7: Post by Jeff »

Typical brew-boiler operating pressures are 6-12 bar.

Typical steam-boiler operating pressures are 1-2 bar.

You will need to determine appropriate materials, fabrication approaches, as well as control and safety mechanisms

but that is what engineering is all about.

Issues to be dealt with in boilers other than pressure and temperature include (among many others) loss of heat out of the boiler, uniformity of temperature within the boiler and group, formation of scale, resistance to chemical cleaning, leaching of material into what needs to be potable water, and serviceability.

There have been multiple ways to fabricate these boilers over the years. Each has advantages and disadvantages. You might want to take a look through the Repairs section to see all the ways one can do it wrong and various types of failures, right up to explosive rupture of a metal vessel containing liters of boiling-hot water at over 10 bar of pressure. Not a pretty sight. Failed mechanicals are common, with all kinds of in-field welding and other craziness being done to repair them.

robbyn

#8: Post by robbyn »

julianmp97 wrote:Hey! I am new on this site. I would love if anybody can help me. I am soon to be called a Mechanical Engineer in my country, Guatemala. For my graduation project I have decided to make an Espresso Machine. It must be a double boiler machine PID controlled. The core of the project is that I will be the one to make the boiler from scratch, other things such as the valves and the pump will be bought via Internet.

I came here to ask if there is anybody that can give me advice for building the boilers. At what pressure should both be? I assume the pressure of the brewing boiler is given by the pump, 9 bar, is that right? And for steaming and hot water?
I was thinking the material could be Stainless-Steel 316. Should they be covered by other material?

Hope someone can help me. Thanks!
stainless 304 is enough I guess :D
I set my espresso machine setting for brew pressure 9 bar, and steam 1.1 bar.

Nunas
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#9: Post by Nunas »

Correct, the pump creates the brewing pressure in a DB. Thus, there is no appreciable pressure generated in the brew boiler. The design of the steam boiler depends on you. 1-bar steam was considered the norm, but lately, many DB machines have been using 2-bar steam. Your PID will set the pressure indirectly by choosing the temperature. For safety, each boiler needs to have a safety release valve. If I recall correctly, the newer 2-bar boilers have them set for 2.25 bar. That sounds like an interesting project!

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Bluecold
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#10: Post by Bluecold »

Unless it's a lever machine, the brew boiler is pressurized up to brewing pressure in a double boiler.
Double boiler lever machines are few and far between...
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