Industry 4.0 passes through the concept of smart factory that consists of bringing into the industrial context a new vision of the way production lines can be designed and redesign and the workflow organized in light of human factors and ergonomics. New technologies create collaboration between all the elements present in the production: operator, machines and tools. The key for optimal interaction between these elements depends on proper use of these technologies and proper design of working environment. Virtual simulations help us in reproducing such interactions in a flexible environment in order to foresee possible ways to improve them before actually installing tools and equipment in the line.