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Hitachi

Corporate InformationResearch & Development

June 8, 2017

Report from Presenter

The 50th CIRP Conference on Manufacturing Systems (CIRP CMS) was held in Taichung City, Taiwan, during May 3-5, 2017. CIRP CMS is an international conference on manufacturing system engineering. The number of attendees was 168 from 25 countries and 130 papers were presented. Research & Development Group, Hitachi, Ltd. Made a presentation titled "Method for Automatically Recognizing Various Operation Statuses of Legacy Machines". This works is about monitoring technique of machines in a factory.


Fig. 1 System architecture
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Monitoring the operation status of machine tools using IoT is widely carried out in order to improve productivity. However, at manufacturing sites, a lot of legacy machines, which are old and lack the capability of sending data on their operation status to networks, account for more than 80% because the average useful life of machine tools is more than 20 years. Therefore, we developed method for recognizing the operation status of machine tools using a spindle motor current acquired by an add-on current sensor. Because this current is in proportion to the spindle torque, a conventional method recognizes the operation status when the current amplitude is above a threshold value. However, in a high-mix low-volume factory, the threshold value must be reset frequently because a drill and the cutting process change per order so the spindle torque varies. In contrast, we propose an automatic recognition method that can learn the variance in spindle motor current by unsupervised learning and with labeling scheme based on prior knowledge (Fig. 1). We applied the proposed method to eight kinds of machine tools in a real factory, and the accuracy rate of the operation status estimation was more than 90% for all the machines. This result shows that all machine tools could be monitored by using this method.

(By MAEDA Masaaki)

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