Strained shoulder while using an 8 pound hammer while pounding the outside of the bin. This was not EE's normal job and EE was helping a Maintenance Tech. EE hurt it on 2/7/2020. EE reported it on 2/17/2020, EE saw a doctor on 2/18/2020, EE could continue to do normal job of operating equipment. EE's shoulder did not improve and surgery was needed on 4/1/2020.