_Article_  
In-Line Dimensional Inspection of Warm-Die  
Forged Revolution Workpieces Using 3D  
Mesh Reconstruction  
[PERSON] 1,2,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16  
matrix orientation in the forging process is crucial since a severe misalignment between the punch press and the forming matrix axes disables the posterior machining process, resulting in a scrapped part. The circular runout [4] of the forged revolution workpiece indicates the deviation between the punch orientation and the forming matrix axis.  
Standard tools for dimensional assessment of these workpieces rely on contact between the probe and the measured workpiece. Such is the case of Coordinate Measurement Machines (CMMs), which provide highly accurate measurements [5]. However, dimensional assessment with standard CMMs (and contact methods in general) is not convenient due to (1) the high temperatures directly affect (or even damage) the probe and, (2) long measurement times for the cooled-down workpieces. Consequently, a delay of nearly 20 min between the production of a single part and its dimensional assessment (including its cooling down, transportation to the metrology office and measuring times) arises. Such time delay translates into an uncertainty in the quality control process of approximately 400 potential defective workpieces (worst case scenario) for each measurement.  
This manuscript presents an optical (i.e., contact-avoiding) system for in-line dimensional assessment of warm forming of revolution workpieces. Our system can continuously measure the circular runout of the parts at around 600 \({}^{\circ}\)C in less than 60 s per part. Results from experiments conducted in this manuscript show no temperature vs. runout correlation for the system uncertainty level (0.1 mm). The system is integrated and deployed in a warm-die forge industry, in the supply chain of world-class auto makers. Such a system allows continuous monitoring for quality and process control of the production line, providing an early detection mechanism of manufacturing failures which reduces the number of potential defective parts from 400 to 20 (95%) between consecutive measurements. This dimensional assessment for warm workpieces fills a gap in warm-die manufacturing processes in which the advantage of early detection of process bias compensates for the disadvantage of precision loss regarding higher-precision mechanisms (such as contact-based CMM).  
The deployed system improves on the classic approaches for dimensional assessment in warm-die industry. Using technologies from Visual Computing and Industry 4.0 [6], the system allows in-line visual assessment of warm workpieces, either by metrologists, engineers, or operators. Furthermore, the increased cadence of the measurements (from 1 measurement every 20 min to 1 measurement per minute) improves the efficiency in product quality and process control, and leaves open future lines of dimensional assessment focused on data analytics.  
The remainder of this manuscript is organized as follows: Section 2 reviews the relevant literature. Section 3 describes the developed system. Section 4 presents and discusses the results. Section 5 concludes the manuscript and introduces what remains for future work.