3-D-Printed Bridge

1 The bot extrudes cords of molten steel in a pattern and waits for them to cool before moving ahead–like a train making its own tracks

2 Along the way, software continuously monitors for engineering errors and instructs the bot to correct course if necessary

3 When the 24-ft. (7 m) bridge is done (it’s expected to take two months), it will support foot traffic and feature intricate designs