San Francisco

TESLA Inc chief executive Elon Musk took many risks with the technology in his company's cars on the way to surpassing Ford Motor Co's market value. Now he is pushing boundaries in the factory that makes them.

Most carmakers test a new model's production line by building vehicles with relatively cheap, prototype tools designed to be scrapped once they deliver doors that fit, body panels with the right shape and dashboards that don't have gaps or seams.