We’ve covered the toner transfer method for creating circuit boards before. Instead of using an iron, Rich uses the fuser out of a laser printer to get consistent results. He wired a dimmer to the power supply to regulate the temperature. The fuser has a built in thermistor, so you can read the temp using an ohm meter. For rate control he built a stepper controller that connects to a parallel port. Using a simple program he’s able to control both speed and direction.