Case study: influences on the availability of machine tools

For more than three years downtimes, data of a press system were observed. Influences on the availability are shown in the data analysis. Mainly in the pre-production, downtimes are caused by changing the tools and by organizational reasons like no crane for changing the tools. General downtimes of press systems are caused by tryouts of actual and new model tools or overhaul. During the production time the machine is not working due to repair, maintenance or organizational reasons. In the case study further effects on the availability are determined. One can see that downtimes of the press systems depend on the production month and on the weekday respectively. The causes of the downtimes cannot be analyzed exactly because only failure categories are given. In order to analyze the repair and maintenance behavior of the machine exact definitions of the downtimes have to be given for the manufacturer and the user of the press system. A simple method for the prediction of the availability in future for the user and manufacturer is given by the simple exponential smoothing. This method also includes seasonal variations caused by vacation employees, company holiday or maintenance of the system during vacations. The example points out that the simple exponential smoothing can be used for forecasting the availability.