In-process monitoring strategies and methods in metal forming: A selective review

Abstract

Metal forming is an important method for manufacturing of lightweight components that offer enhanced functionality, energy efficiency and sustainability. The digital transformation in manufacturing, characterized by Industry 4.0, has heightened the need for stringent standards regarding dimensional accuracy, product quality and productivity. This has placed increased focus on flexible and adaptive control strategies, alongside the integration of smart production lines. Consequently, there is an increasing demand for advanced in-process monitoring technologies to meet these evolving needs. This paper reviews in-process measurement methods used in forming processes for metal components. It examines aspects such as force, geometry, temperature and acoustic characteristics through a recent review of current literature. We emphasize the integration of these measurement techniques into metal forming operations with a primary focus on their role in optimizing manufacturing processes for meeting high product-quality standards. The study also highlights recent sensor technologies deployed in selected metal forming processes, including rolling, bending, stamping, and deep drawing to address the evolution of sensor technology in these applications. Key findings include the widespread adoption of optical sensors for high-precision geometric measurements, the use of thermocouples and FBG sensors for temperature monitoring, as well as the integration of acoustic emission sensors for, among other, real-time detection of defects. Despite considerable technology advancements, several challenges still prevail. This applies particularly to integration complexity, accuracy requirements and environmental conditions, emphasizing the continued need for ongoing research and further development efforts in the field. Future work should thus focus on improving sensor integration, measurement accuracy and developing robust solutions for various environmental manufacturing conditions to support implementation of Industry 4.0 strategies to meet digital manufacturing goals.