Potentials of an adaptive blank positioning to control material and process fluctuations in deep drawing

Abstract

Series production of sheet metal components in press shops is permanently subjected to an increasing pressure in time, cost and quality. Varying sheet metal properties due to batch fluctuations and changing process conditions lead to an increase of try out time phase and scrap rate, resulting in a demand for adaptive control strategies for deep drawing. Today, these chal-lenges are met by integrating sensors and actuators into tool structure which measure and control part quality, mainly through blank draw-in. However, such tool-based control systems require a complex and cost-intensive modification of the existing die or press technology. Against this background, the active adjustment of blank position prior the deep drawing process realized with an intelligent transfer and positioning system as a promising approach towards economic and technical aspects. This paper deals with blank positioning and its sensitivity to quality-related failures of deep drawn sheet metal components like splits and wrinkles. Therefore, a numerical study was conducted on a deep drawing process of an exemplary structural part geometry, wherein a typical fluctuation of material parameters and variation of local friction conditions was simulated. Subsequently, correlations between process disturbance and blank draw-in were elaborated, thus using local draw-in values as controlled variables for a closed loop system. Sim-ulation results showed that the manipulating parameter, i.e. the blank position prior deep draw-ing, reveals a significant influence on the draw-in and therefore on the component s quality. An essential finding of this study is the numerical proof of concept for this new deep drawing control strategy, demonstrated for different process conditions. Finally, disturbances in the deep drawing process considered could be successfully controlled by adapting the blank position.

Robust control of the draw-in in a deep-drawing process: a measurement-based approach

“…The quality of the deep-drawn component, however, can also be affected by the process variability due, for example, to the lubrication conditions and to the properties of the material which can change depending on the supplier or the coil adopted [3]. Positioning of the blank is another noise parameter that could affect the quality of the final drawn component [5]. In order to optimize the process, press machines with active blank holders have recently been adopted in order to locally regulate the drawin of the blank thanks, for example, to magnetorheological actuators [6].…”

Monitoring of fluctuating material properties for optimizing sheet-metal forming processes: a systematic literature review

“…Hot rolling [8,[21][22][23] Cold rolling [24] Roller levelling [25][26][27] Stamping [28] RQ3 Stamping [29][30][31] Deep drawing [32][33][34][35][36][37][38][39][40] Bending [41][42][43] Table 2. Summary of the publication conducted in the SLR.…”

“…Furthermore, Endelt develop the control strategy based on an inner loop and an outer loop further by adding numerical simulations to reduce the draw-in error [33]. A numerical study for a deep drawing process, where material fluctuations were included through a sensitivity analysis, and a proof of concept for a new control strategy by adapting the blank position was conducted by Briesenick et al [32].…”