In-process feed-forward control approach of tubes and wire torsion in bending machines using VCSEL laser optical sensors

Elongated metal components, such as wires and tubes, are integral to numerous industrial applications, prominently including structural engineering, fluid transportation systems, and heat exchangers fabrication. Following their primary manufacturing phase, these components are typically wound into coils to streamline logistics and storage, necessitating a subsequent straightening phase prior to additional processing operations like bending, cutting, or expanding. The standard straightening technique involves passing the workpiece through multiple arrays of intentionally misaligned and skewed rollers. The axial displacement is conventionally measured using a downstream-mounted contact encoder. However, this approach frequently induces unintended torsional deformation, causing combined translation and rotation movements of the cross section. Precisely quantifying this rotational displacement is still challenging, and uncontrolled torsion can adversely impact the precision and quality of subsequent production stages. In response to these issues, this research introduces an innovative integrated in-process control methodology employing a VCSEL (Vertical-Cavity Surface-Emitting Laser) optical sensor. This advanced non-contact sensing technology enables simultaneous real-time monitoring of both axial displacement and rotational torsion, capturing component displacement data across two orthogonal axes at high sampling rates. Nonetheless, measurement accuracy is contingent upon multiple parameters, including the metallurgical characteristics of the component, measurement distance, sensor alignment accuracy, and the component’s transit speed. This study aims at identifying principal sources of measurement inaccuracies and proposes a targeted correction algorithm. Furthermore, alongside methodologies for robust calculation of both axial feed and rotational torsion are elaborated. Experimental validation through a representative case study confirms the system's efficacy, demonstrating reliable detection and control capabilities for torsional deviations below 1 deg over a 300 mm measurement span.