A strategy for on-machine springback measurement in rotary draw bending using digital image-based laser tracking

Rotary draw bending is a commonly used metal forming technique for profile bending. Due to the elastic recovery of the material, springback compensation to control the bent product quality is one of the critical manufacturing issues. The realized bend angle has to be measured for springback compensation before removing the profile from the machine, and the bending process can follow an iterative approach until the product quality is satisfied. However, this trial-and-error is costly for batch production in manufacturing. An on-machine measurement technique is therefore developed to measure springback in rotary draw bending with an affordable laser and a webcam. An image processing technology is integrated with the manufacturing process to track the deformation and measure springback angle in real time, eliminating the need for the workpiece to be transferred to a measurement device. In this paper, bending experiments were conducted with AA6082 rectangular hollow profiles bent at 30°, 45°, 60°, and 90° angles, and springback angles from the conventional manual measurement were compared to that from the on-machine measurement. Since the difference in springback measurement between the proposed and the conventional methods was within 0.15° on average, it is demonstrated that the laser tracking, on-machine measurement is a feasible real-time springback measurement technique for Industry 4.0.

Method for Accuracy Assessment of the Length Measurement Unit of Laser Tracking Systems

Laser tracking systems are widely used in large-scale metrology of geometric quantities. Their importance is confirmed by the fact that one of the parts of the ISO 10360 series of standards has been devoted to the issue of assessing their accuracy (ISO 10360-10). A laser tracker is a device whose final measurement result is calculated using indications from various subsystems included in it, such as devices for measuring length and angle. The analysis of these individual impacts can be useful in creating simulation models of accuracy which, in regard to the Industry 4.0 concept, seem to be the most justified in terms of speed of operation and ease of use. For this reason, it may be particularly important to undertake research on the accuracy of this component in isolation from other factors affecting the measurement of the coordinates of the point. The article describes a method that allows separation of the length measurement error from the other components. The method uses a high-accuracy interferometer which is treated as a reference system that allows for the comparison of indications obtained using the tested distance measurement system. Thanks to the proposed method, it is possible to minimize errors from the optical system and other measuring systems. The use of a precise linear guide allows the reduction of errors related to the implementation of linear motion. The article presents the test method and the results obtained from performed experiments, as well as formulates conclusions and the directions of further development.

Impaired neuro-motor control in chronic whiplash and tension-type headache

BackgroundThe purpose of this study is to support the hypothesis that the neuro-motor control of the neck muscles is impaired in the diseases of chronic whiplash and tension-type headache. This hypothesis is based on a previous study, and if confirmed, it indicates that the central nervous system may be part of the pathophysiology of these diseases. For further verification, we designed a laser tracking method for standardized and quantitative measurements of movements of head and hand. The hand was included as a presumed normal reference to the head movements.MethodsA new laser tracking instrument was designed to monitor the ability of a test-person to track a reference point on the wall by a laser fixed to the forehead or held in the hand. The reference point moves in runs of a circle or a square at three different speeds 10, 20 or 30 cm/sec thus providing 6 runs for both head and hand per test-person. We used a 1x1x1 m set-up geometry. The data of each run was processed on-line. Groups of 22 patients diagnosed with chronic whiplash associated disorder, 19 patients diagnosed with chronic tension-type headache and 37 control persons were compared.FindingsA small but highly significant dyscoordination of head movements was observed in both patients groups, and in whiplash also of the hand. InterpretationOur study confirms the hypothesis that the neuro-motor control of the neck muscles is impaired in both chronic whiplash and tension-type headache. In our view this observation implicates that the central nervous system may be involved in the primary pathology of both these diseases. Accordingly, we suggest a provisional term 'cervical dyssynergia' for these diseases, and suggest further studies along this paradigm.