To face the challenges of today’s competitive industry, this work studies a real-world problem in semi-automated electronics production. It considers a worker assignment problem with a heterogeneous workforce in the multi-shift environment of protective device manufacturing. Simultaneously with multi-skilled workers, requested orders are assigned to workstations and shifts. One of the main particularities is the restriction of possible assignments of workers and orders to workstations according to qualifications. Additionally, this paper considers sequence-independent family setup times, disparate workstations, and a time limit for completing the orders. A mixed-integer linear programming model is introduced that minimizes the makespan calculated by the last shift used for production. The model is tested using real-world data. Additionally, this contribution examines the influence of the workforce with the help of scenario analysis and solves 49 test instances. The solutions serve as input and support for production planners and personnel planning. Furthermore, this work reveals production problems such as a lack of workers and qualifications.