Abstract
Incremental sheet forming is a sheet forming process for small lot sizes due to its dieless principle. One of its process variants includes local heating of the sheet to counteract some of the process restrictions (formable materials, forming forces, achievable deformations). Although forming at elevated temperatures provides various advantages, the geometric accuracy of the formed part remains low due to shrinking effects caused by local heating and cooling. This publication presents a data-driven approach where process data is gathered and used in regression learning to predict the geometric accuracy resulting from the shrinking effects. To successfully apply regression learning, a big amount of process data is needed covering a wide range of possible process states. Therefore, a specific experimental series, consisting of 54 individual forming experiments, is designed and carried out. Based on the 3D digitization of the formed parts, a process database is built up comprising 408,296 records, each representing a toolpath point. This process database is used to train 19 different regression models. The performance of their ability to predict the geometric deviations is investigated. A compensation approach is presented that improves the geometric accuracy through a prediction-based modification of the toolpath. Validation experiments demonstrate the improvement of the geometric accuracy of the formed part and the generalizability of the approach.
Highlights
Introduction and state of the art1.1 Sheet heating principles in ISFIncremental sheet forming (ISF)Incremental sheet forming (ISF) is a promising process for the production of sheet metal parts in small batch sizes
In 2007, Duflou et al presented laser assisted single point incremental forming (SPIF) which belongs to the local heating variants
While this is possible in double sided ISF (DSIF), the application of a supporting tool on the backside of the sheet enables the use of an electric circuit through both tools and the sheet [5]
Summary
Incremental sheet forming (ISF) is a promising process for the production of sheet metal parts in small batch sizes. In 2007, Duflou et al presented laser assisted single point incremental forming (SPIF) which belongs to the local heating variants In this case the heating is achieved by a laser beam on the backside of the sheet that is moved ahead the forming tool [1]. In SPIF the electric circuit is closed by the clamping frame [4] While this is possible in double sided ISF (DSIF), the application of a supporting tool on the backside of the sheet enables the use of an electric circuit through both tools and the sheet [5]. This results in a smaller heating zone. Other approaches for global heating include the application of warm fluids [11], hot air streams [12], external electric heater bands [13] and induction heating [14]
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