Abstract:
One trend in manufacturing industry is that products nowadays become more customized and are manufactured in small batches. This trend requires manufacturing systems to reduce lead time from design to manufacturing, diminish human interventions during the process and be tolerant to machining failures and stoppages. Another trend is servicelization in the entire manufacturing process from the CAD, CAPP, CAM to CNC. Current control system of machine tool is facing difficulties in meeting the requirements of the users and the machine tool vendors. The proposed cloud-base smart machine control system provides control of a machine as a cloud-based service. Low-level machine control data is generated in the cloud and executed in the local. However, the inabilities of the Internet introduce new challenges to the proposed system. Proper Internet protocols were analysed and chosen, and the mechanism dealing with long delay and/or interruption of data transmission was developed. The highlighted smart feature of this research is auto-recovery from machining stoppages. Because of the use of G/M code as the format for part programmes, currently recovering from machining stoppage highly relies on operator’s experience and is time-consuming. The proposed auto-recovery of machining stoppage utilizes STEP-NC as the format of part programmes. As a new generation of the ISO standard for part programmes, it defines the machining job by features and operations rather than toolpaths. Therefore, the proposed system is able to disengage the cutter from the workpiece, generate new toolpaths according to the available cutters, and adjust the sequence of the workingsteps to minimise the overall machining time. The information about the interrupted workpiece can also be stored into the STEP-NC part programme, which can be loaded by another machine tool to continue the interrupted machining. A prototype of the proposed system was developed. The mechanism of transmitting setpoints over the Internet was validated by simulation and experiments. Two case studies were conducted. In one case study, the process of saving information of the interrupted machining into the original STEP-NC part programme was demonstrated. In the other case study, a complete process of a pocket milling controlled by the cloudbased control system was presented.