Mini-Sym 4.0. a Novel Simulation Tool to Calculate Real-time Production Line Productivity

Abstract

AbstractThis article presents Mini-Sym 4.0, a simulation tool capable of calculating, from the real-time measurements of the mini-terms, the productive capacity of a production line and how pathologies and market demand may affect the line performance.A mini-term is a cycle time subdivision and can be selected by the user for several reasons, the replacement of a machine part or simply to analyse the machine more adequately. A micro-term is a mini-term subdivision and can be as small as the user wishes. Therefore, the cycle time of a machine is the sum of mini-terms or the sum of the micro-terms. This paper focuses its attention on a welding line in a Ford Factory located at Almussafes (Valencia) where a welding unit is isolated and tested for some particular pathologies. This unit is divided in three mini-terms, the robot motion, the welding motion and the welding task. The cycle time of each mini-term is measured by changing the deteriorated components for others in the time. The deterioration of a proportional valve, a cylinder, an electrical transformer, the robot speed and the loss of pressure are tested within a range that alarms and maintenance workers cannot detect, which is, the range of normal production. The real welding line is modelled taking into account all the models fabricated in the welding line (68 models) and a novel simulation algorithm is created based on miniterms. The experimental measurements are introduced in the simulation model and the effect of the pathologies in the production rate was computed, based on actual production data for one month. As a result, the pathologies with greater variability have a deeper impact in the production rate mainly due to the bowl phenomenon effect. On the contrary, the pathologies with low variability have a low effect in the production rate. In fact, this paper demonstrates that the maximum rate capacity can be achieved if the machine variability is near to zero. In the present article, and in difference than our previous work, [6], we analyze the welding line for each of the models independently and later, with the models demanded by the market in a specific month, opening a discussion about how relevant the production orders affects productivity.KeywordsMini-termBottleneckProduction lineThroutghtputSimulation