hi
i have lots of projects but to start from the start :
i have friedrich ataxia so soldering is too hard for me !
anyway i can think of using a 3d printer to help me in this task
if i'm able to solder i'll make a soldering bot.
is one of you having one ready to use ?
the evolution of it will be an all electronic work bot (usable by child)
if i have this one i'll make a service for people to buy electronic things at cost price + delivery
all will be open-source
what to put in the soldering bot ?
same for the all electronic work one 
... thanks
Seeedstudio has something like this already, from a limited parts supply.
A couple of notes, pick and place machines already exist. They take components and install them onto a board. Then automated soldering stations also exist, either using wave solder or IR.
The biggest issue with this type of thing is that each new component needs to be entered into the pick and place. Many components are easy, since most surface mount caps and resistors are basically identical. However, once you move away from a few of the standard packages, every part is different and requires someone to enter the information (correctly) into the pick and place.
As for 3D printing circuit boards, many researchers are already working on this. I believe the technology is moving towards actually being usable, but there are non-trivial problems with such things.
southeast us do you have some link to buy not very expensive things you talk about ?
i can code instructions
As for equipment, no. I actually have no clue where to buy such things. It is where-ever you buy electronics manufacturing equipment.
As for the service at Seeedstudio, it is their PCBA service:
http://www.seeedstudio.com/service/index.php?r=site/pcbService&type=pcba
thanks mirith
i was missing the fact that they do 4 layer pcb
anyway for soldering simple things what is the best materials for you all ?
i think i have to start with a mechanical tool to make soldering with filaments as in 3d printer
don't forget it will be open-source so you can all here tell me what you want for a soldering bot
Not that I'm trying to discourage you, but what would be the end use of this, exactly?
To me, it sounds like you want to basically duplicate the use of a guy holding a soldering iron and feeding solder in with a robot. While a neat idea (If impractical, at least to me), there are some terrible complexities to this that are simplified by the human doing it without them realizing, but are terrible hard to reproduce with a robot, mainly telling when a solder joint has 1) Enough solder and 2) is connected properly. Appropriate soldering time and amount depends on: How clean the tip is, soldering iron orientation, Temperature, amount of connected copper on both the pin and the connecting traces, and size of the pad.
mirith
i'll use daily this bot as i have so much projects
i'm aware of those problem and some else that come with soldering
i'll test to find the best way to solve them with the pure mechanical arm i'll make as soon as ihave my 3d printer
nothing you want/need mirith ?
Is this is a mechanical arm to hold a soldering iron that then can be moved around in an XYZ stage so you can move it back and forth to solder joints? This is what it sounds like you are suggesting. The act of using a soldering iron by hand has a significant amount of visual and tactile feedback that is really easy for a human to understand, but not one a robot will.
If so, then no, I would not use this. It is not useful, since if I'm assembling a few boards, its faster for me to just assemble it, rather than program and test assembly procedures with a complicated robot iron, not to mention any concerns of parts moving around mid process. If I'm assembling multiple boards, then I have someone with a wave solder machine do it for me, since their machine will do it much faster, and not require programming. This is an already well-established technology.
If you are looking for a faster way to solder parts yourself, look into the hot-plate/stove-top method. While I've never personally used it, I've heard good things about it.