Due to the deterministic nature of manufacturing processes, measuring important process parameters and performing timely adjustment is an effective way to improve manufacturing efficiency and quality. In-process measurement is such a method. It is capable of monitoring manufacturing processes in real time. However, the current information flow between different manufacturing processes is segmented due to the lack of a consolidated data model to represent sufficient information of a product. This directly results in segmented process planning for in-process measurement. The establishment of STEP (STandard for Exchange of Product data) offers manufacturers a new method to exchange product data through the entire product lifecycle. As an extension to STEP, STEP-NC provides the potential to finally close the gap between design and manufacturing in the drive for a complete and integrated product development environment. The STEP/STEP-NC data model is a long overdue improvement in the domain of process planning for Computer Numerical Controlled (CNC) machining in the industry where G-codes have been in use for more than half a century. STEP/STEP-NC brings richer information to the CNC machining industry presenting an opportunity for the development of more intelligent, interoperable and informative machining processes. The research work documented in this thesis introduces a consolidated STEP/STEP-NC data model and system for an automatic and integrated process planning system for machining, in-process measurement, and feedback. This research first developed the current STEP/STEP-NC data model with new definitions covering tolerance requirement information, and measurement operation information. A mechanism to link tolerance requirements and machining feature information was also developed to provide the crucial connection between machining and measurement. With sufficient information provided by the proposed STEP data model, the concept of an integrated process planning system was conceived to carry out automated process planning for machining and in-process measurement. The system is able to analyse and select critical tolerance(s) from an input data file, generate measuring operation(s) for each critical tolerance in-between machining operations. Measurement of each critical tolerance is also planned by the developed system including generating, allocating, and sequencing measurement points for each measuring operation. After the measurement results of each measuring operation are collected, the system analyses the results and provides proper adjustments to the immediate subsequent machining operation(s). A software prototype was developed to test the proposed data model and the integrated process planning and feedback concept. The ultimate goal of performing measurement in a manufacturing system is to gain close control of the machining process based on tolerance requirements and to adjust process errors as they occur. The key issue is to connect machining and tolerance requirements. What to measure and when to measure is another critical issue. This research has made an attempt to address these issues in order to realize a long-awaited paradigm of automatic placement of measurement procedures in-between machining operations and provide automated process-intermittent feedback to the machining process.
| Identifer | oai:union.ndltd.org:CCSD/oai:tel.archives-ouvertes.fr:tel-00726013 |
| Date | 01 December 2009 |
| Creators | Zhao, Yaoyao |
| Source Sets | CCSD theses-EN-ligne, France |
| Language | English |
| Detected Language | English |
| Type | PhD thesis |
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