hello
i know it's difficult but i need to try
i want to make this machine that paint...
it's gonna be basically similar to a plotter, i need you to help me to choose the motors
they must be not too slow and i don't need too much accuracy
what kind of motors you suggest? stepper i guess... but which one?
i would prefere cheap ones
thanks alot
If you choose motors before the machine is built, and the torque and power requirements are known, you are just wasting your money and time.
well i have to guess
if they re cheap
i will use them for somethingelse 
What are you going to use this machine to paint? Abstract oils paintings? Portraits? Model airplanes? Cars? Real airplanes?
Unless we know the size of the machine, and the weight of the paint sprayer, sizing components like motors, is pointless.
I work for a company that paints airplanes. For us, customers reject the airplane if it has any runs or other defects in the paint. For that, we can not accept "don't need too much accuracy".
if they re cheap
If you need to move any weight, or need decent speed, you can plan on about $100 each, plus similar amounts for stepper drives that can handle the current, plus a 20 Amp power supply. So, don't count on cheap.
ok
sorry for my ignorance
i want to make a machine that paint with oil an abstract canvas which will be around 70/100 cm square.
i also would need a servo for the brush stroke..
any idea?
i want to make a machine that paint with oil an abstract canvas which will be around 70/100 cm square.
i also would need a servo for the brush stroke..
So, how will you get paint onto the brush? How will you know when you need to get more paint? What will happen when you need to change colors?
Have you looked at any of the RepRap machines or any 2D or 3D CNC machines? Mostly, they use stepper motors and stepper motor drivers.
For carrying a brush holder around, you don't need particularly large stepper motors. Something like this, to get you started, perhaps: http://www.ebay.com/itm/USA-Ship-Wantai-Nema-23-Stepper-Motor-185oz-in-2A-3-Axis-Board-3D-CNC-Kit-/181483126588?hash=item2a413cbf3c:g:txIAAOxyVVJR~Kps
PaulS:
So, how will you get paint onto the brush? How will you know when you need to get more paint? What will happen when you need to change colors?Have you looked at any of the RepRap machines or any 2D or 3D CNC machines? Mostly, they use stepper motors and stepper motor drivers.
the brush take the paint from a container (like a real brush)
i will just make one canvas per session
then recharge the colors manually
like an art performance
it's not similar to any cnc machine at all
the brush take the paint from a container (like a real brush)
So, part of the process of painting means that the brush carrier needs to make frequent visits to the paint pot.
it's not similar to any cnc machine at all
Really? You are trying, you said,
i want to make this machine that paint...
it's gonna be basically similar to a plotter
What the f**k do you think a plotter is? Do you really believe that it is not controlled by a Computer? That's what the first C in CNC means. Do you really think it isn't controlled by Numbers? That's what the N in CNC stands for. Do you really think it isn't Controlled? That's what the last C in CNC stands for.
Good luck with your dream, because that is all it is ever going to be.
PaulS:
So, part of the process of painting means that the brush carrier needs to make frequent visits to the paint pot.
Really? You are trying, you said, What the f**k do you think a plotter is? Do you really believe that it is not controlled by a Computer?
yes
i know
dont freak out 
i just wanted to say that it will not look like the typical plotter machine
i want it to use the brush like a gesture... i know it's a cnc like the others... i meant that it won't look like the typical one...
at least i want to try
At least you chose abstract art, so not too much control required: just needs to slosh paint on randomly
manor_royal:
At least you chose abstract art, so not too much control required: just needs to slosh paint on randomly
exactly mate