Process Monitoring and Control System Design, Evaluation and Implementation of Abrasive Machining Processes

Abstract

Wood processing industries have continuously developed and improved technologies and processes to transform wood to obtain better final product quality and thus increase profits. Abrasive machining is one of the most important of these processes and therefore merits special attention and study.

The objective of this work was to design, develop, evaluate, and demonstrate a process monitoring and control system for use in the abrasive machining of wood and wood based products. The system developed increases the life of the belt by detecting (using process monitoring sensors) and removing (by cleaning) the abrasive loading during the machining process. This study focused on belt abrasive machining processes and included substantial background work, which provided a solid base understanding of the behavior of the abrasive, and the different ways that the abrasive machining process can be monitored. In addition, the background research showed that the abrasive belts can effectively be cleaned by the appropriate cleaning technique.

The process monitoring and control system developed included data acquisition (information from the sensors), signal analysis, and belt cleaning actions as required which were integrated and continuously monitored during the abrasive machining process.

A control system was created on LabView® version 8.2 from National Instruments (www.ni.com) that integrates the monitoring process and the actions required depending on the abrasive machining process conditions. Thus, the system is able to acquire information from the optical sensor to detect loading and activate the cleaning system. The system designed continuously monitors the condition of the abrasive belt by using an acoustic emission sensor and alerts the operator of the status of the belt (green, yellow and red lights indicate optimal, medium and poor belt condition). The system also incorporates an additional safety device, which helps prevent permanent damage to the belt, equipment or workpiece by alerting the operator when an excessive temperature has been reached. As a final step, the system design was adapted to an industrial machine manufactured by a prominent woodworking machinery manufacturer. This adaptation included the design of a mounting and traversing system for the sensors and cleaning apparatus and the integration of the system with the current machine PLC in order to take action based on information from the sensors relating to belt loading, acoustic emission and temperature and take action based on the status of the process.