The only way to make smart phones cheap enough for anybody to afford, you have to make hundreds of thousands. You'll spend millions(10's of millions maybe 100's) on equipment and employees to operate them. Then you have to market them, and sell them. When you're finished manufacturing your first line of phones, you'll be lucky to break even. Hopefully by the third round of phones you'll be profitable. Many phone companies contract out the actual manufacturing of their phones - a large portion of these to Foxconn. http/en.wikipedia.org/wiki/Foxconn
i have the design and all the specifications
so what are the machines needed?
Get ready to spend hundreds of thousands(at least) alone on machines to build the damn thing. You need to have the PCB made, design the lanes, its just too much shit to even tr to type out or think about. Software will also be a massive problem. Now, lets say you made the fucking thing, you got... idk, Android on it, yay, only spent probably near $1M, months or years of development and design, and now you cant even use it. No carrier will let a home made phone on their network. So, you cannot make one, nor will you be able to use it. Its not a small fucking thing to do, its no evening soldering job. Its a huge undertaking. Why do you think a single smartphone costs $600+? Each phone may cost $100 to manufacture, but only because they buy astronomical amounts of material and parts in bulk at a greatly reduced price by the companies. So, they need to cut even... so, do like $100*500000, and thats about how much it probably cost for them to develop and make the final product.