How to make a 12 volt plastic welding iron

How can we make a machine that welds plastic easily and effortlessly. And that this tool works with a current of DC 12 volts only, which gives a very large heat as soon as the two ends of the tool are connected with the metal pin that is inserted inside the plastic, which makes the plastic return to a large extent to its first state and all this thanks to the very simple plastic welding machine