Tesla Inc. factory employees spent almost three times as many days off the job because of work-related injuries and illness in 2018 as the year before, an indication of just how much strain they were under as they manufactured electric cars at scale for the first time.

Tesla CEO Elon Musk says he will walk the entire Model 3 production line Nov. 27-28. From battery cells to finished vehicles, all assembly areas need to be able to support making 1,000 cars per day, he said.