I am planning to make a device which has a touch screen LCD. I have searched for solutions and i think if this device has android OS could be use for many applications. This device will be used for connecting to some DC and AC motor drivers. It will show numbers, play music and send data to a server. As price is critical, is using android suitable? If yes how to make a device with android os?
Without a lot of time and experience it will be hard to start from scratch. May I suggest buying a kit for this purpose. Something like those available here: http://www.liquidware.com/shop I'm sure there are many other companies that also supply them.
Making your own android device will not be cost competitive with buying one.
Making a custom adapter for an existing one (probably connecting via USB) is; but be sure that all of the safety systems (E-stop, etc) are in the adapter or even power supply, so that they continue working if the android device fails or mis-operates.
It may even make sense to run the real core of the system on the adapter, and just use the android tablet as a web-client user interface.