Control of draw-in in the deep-drawing process by regulating the force on the blank holder

Abstract

Sheet metal forming processes are strongly influenced by process parameters, moreover fluctuations during the process and in material properties often lead to robustness problems. Therefore, numerical simulations as a function of design and noise parameters are usually adopted to detect ahead critical regions. To ensure efficiency and quality, the new era of industry 4.0 aims to develop systems that can control critical issues online. The aim of this work is developing a methodology that allows to adjust the force on the blank holder to obtain an optimal draw-in profile. This latter assures a minimization of defects (e.g., compression areas, thickened areas, insufficient stretch areas, splits) on the final component, even when variability of friction coefficient and yield strength occur. This methodology is applied to the deep-drawing process of a component obtained from a DC05 steel sheet with a thickness of 0.75 mm. For this purpose, Finite Element (FE) simulations in AutoForm software have been performed as a function of the design parameter i.e., Blank Holder Force and of noise parameters i.e., friction coefficient and yield strength. The results explored to evaluate the quality of the stamped part are: (i) percentage of compression areas, (ii) thickened areas, (iii) insufficient stretch areas, (iv) excessive thinning areas and (v) areas with splits. The data collected from FE simulations were adopted to perform a multi-objective optimization by means of the desirability function approach. Consequently, the value of process parameters that minimize defects (high value of total desirability) were identified. In correspondence with this optimal solution, the optimal draw-in profile was obtained. Such optimal profile was compared with the draw-in profile which involves defects on the final component (non-optimal draw-in profile). This latter was obtained for a value of the force on the blank holder equal to the optimal one and for non-optimized values noise parameters. In fact, noise parameters are not controlled process parameter. Based on the point-by-point difference between the two draw-in profiles, a numerical control strategy was implemented using AutoForm and MATLAB software. This iterative strategy allows to modify step by step the force on the blank holder so that the non-optimal draw-in profile match with the optimal one. Finally, experimental tests on a 3000 kN hydraulic press were performed to verify FE results.

Development of Porous Material and Hybrid Porous Ti6Al4V Dental Implants using Metal Injection Molding (MIM)

“…Conversely, excessive BHG can lead to the formation of wrinkles in the product. The research conducted by Palmieri et al [18] confirmed the findings of this study, demonstrating that the force applied to the blank holder, represented by the BHG value in this case, significantly affects the achievement of an optimal draw-in profile and the production of a defect-free product. Generally, the blank holder gap should be set to provide sufficient restraint on the blank without causing excessive friction or wrinkling.…”

“…The deep drawing value is within the safe limit range, which is according to Equations ( 9) and (10), and the critical deep drawing force limit is according to Equations ( 11) and ( 12) so that the product can avoid cracks and wrinkles. The experimental results indicate that implementing both the BHF [18] and the BHG yields similar outcomes. However, the BHG system is significantly easier to use while effectively controlling material flow and preventing issues such as cracking and wrinkling defects.…”

“…The proper combination of blank holding forces and draw beads plays a critical role in achieving high-quality deep-drawn products [15]- [16], as it allows the blank holder to control material flow, minimize defects, and produce parts with the desired geometry and dimensional accuracy. Additionally, the implementation of an antilock brake mechanic system for blank holder control is an innovative approach that leverages real-time data and feedback to optimize the deep-drawing process [17]- [18]. This system effectively controls the flow of material drawn into the die, resulting in higher-quality products, reduced defects, and increased process efficiency.…”

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

“…The action of the blank holder can prevent defects on the drawn component such as cracks, wrinkles and thinning [1][2]. Therefore, one of the design parameters affecting the drawing process is the force on the blank holder [3][4]. In fact, it has been shown that an increase in the force on the blank holder can lead to a reduction in wrinkles.…”

Identification of the Optimal Blank Holder Force through In-Line Measurement of Blank Draw-In in a Deep Drawing Process

“…To attain a reproducible and automated adjustment of the process, many authors proposed implementing a feedback-type control systems [21][22][23][24][25][26][27][28][29]. In this type of control, it is crucial to identify a parameter for in-line monitoring, such as the sliding of the blank.…”