The main purpose of this study is to develop a chatter monitoring and suppression system while turning slender workpieces. In order to clarify the chatter behaviour, the ratio of the length to diameter of the cylindrical bar (L/D ratio) is considered as an independent parameter. Experimental investigations were carried out over a wide range of the L/D ratio and cutting conditions to identify the cutting stability. It can be observed that the standard deviation value of the main cutting force obviously increases in the chatter developing period, and this phenomenon can be used to define the chatter threshold. From the observation on the variation of the standard deviation value of the cutting process and then by means of a reasonable application of the standard deviation value, a precise on-line chatter threshold based on the double-standard concept has been defined in this paper. For an accurate judgement of the chatter occurrence, an effective monitoring criterion was proposed and developed. This monitoring criterion was applied to the feed rate control system to suppress the chatter vibration by increasing the feed rate. Experimental results show, furthermore, that the control system is effective when the L/D ratio is smaller than 12.

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Steam is an essential medium used in the industrial process. To ensure steam quality, small and middle scale boilers are often adopted. However, because a higher steam pressure (compared to the necessary steam pressure) is generated, the boiler’s steam pressure will be reduced via a pressure regulator before the steam is directed through the process. Unfortunately, pressure is somewhat wasted during the reducing process. Therefore, in order to promote energy efficiency, a pressure regulator is replaced by a steam expander. With this steam expander, the pressure will be transformed into mechanical energy and extracted during the expansion process. A new type of isothermal steam expander for an industrial steam supplying system will be presented in the paper. The isothermal steam expander will improve the energy efficiency of a traditional steam expander by replacing the isentropic process with an isothermal expansion process. With this, steam condensation will decrease, energy will increase, and steam quality will be improved. Moreover, the mathematical model of the isothermal steam expander will be established by using the Schmidt theory, the same principle used to analyze Stirling engines. Consequently, by verifying the correctness of the theoretical model for the isothermal steam expander using experimental data, a prototype of 100 c.c. isothermal steam expander is constructed.

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