Who made Iron Man's arm?

Drawing is the first step in making Iron Man's arm.

Then buy necessary materials, such as pliers, steel, rulers, screws and so on.

Then, after the materials are prepared, because some welding and large machines are needed, it is necessary to find a good workshop and then operate according to the drawings (which requires certain professional knowledge).

Finally, assemble the appearance to make the finished product look like a movie. As for the function of the mechanical arm to take people off, don't think about it.