4. Optical Sensors for Machine Tool Metrology

The development of smart machine tools will be the trend toward the worldwide need of intelligent manufacturing technology nowadays, which is the goal of industry 4.0 as well as cyber-physical system and China made 2025. Current techniques for machine tool metrology are implemented by measuring instruments mainly suggested by the ISO 230 series of international standard. Although these instruments are used to measure geometric errors of each axis of machine tool, they cannot be used as sensors for real-time detection since they are expensive and are in bulky sizes. In order to understand the functions of the optical sensors for machine tool metrology, this chapter firstly addresses the importance of geometric errors to the accuracy of machine tools. Abbe principle and Bryan principle are two important guidelines in machine design and measurement technology. The volumetric errors of machine tools are largely affected by these two principles. This is the second topic highlighted in this chapter. Some small and low-cost optical sensors for geometric error measurements are presented. These sensors can be portably mounted onto the machine frame for online measurement. They can also be embedded in the machine structure as feedback sensors for respective geometric errors. The integration of individual sensors into a multi-degree-of-freedom measuring (MDFM) module for volumetric error measurement and compensation is also introduced. Some applications of developed optical sensors to measure machine tool errors are described in the last part of this chapter. Experimental validation shows the feasibility of developed optical sensors for machine tool metrology and error compensation. This chapter neither includes the measuring instruments for ISO 230 series as these are the subject of other chapter nor those MDFM systems reported by many other researchers because those are mainly at the laboratory level and not ready for practice on machine tools.