Answer: Two, and they’ll be done in 20 minutes.
The assembly itself only takes about nine minutes — the robots spend the other 11 plotting (how they will proceed with the chair, and not world dominion, for now). They use this planning time to determine which moves they will make and how to avoid colliding with each other. The robots use 3-D cameras to locate and keep track of the chair's parts, and they have pressure sensors to ensure that they don’t break anything during assembly.
The pair was developed by a research team at Nanyang Technological University in Singapore.
“In the future, we envision that robots like this should be helping with tedious or dangerous tasks,” Dr. Francisco Suárez-Ruiz, a researcher on the team, told The Verge. “There are so many industries where these skills would be useful, like logistics, or packing for e-commerce companies.”