Experimental Investigation of Hard Turning Mechanisms by PCBN Tooling Embedded Micro Thin Film Thermocouples

Abstract

Temperature-distribution measurements in cutting tools during the machining process are extremely difficult and remain an unresolved problem. In this paper, cutting temperature distributions were measured by thin film thermocouples (TFTCs) embedded into polycrystalline cubic boron nitride (PCBN) cutting inserts in the immediate vicinity of the tool-chip interface. The embedded TFTC array provides temperature measurements with a degree of spatial resolution (100 ßm) and dynamic response (150 ns) that is not possible with currently employed methods due to the micro-scale junction size of the TFTCs. Using these measurements during hard turning, steady-state, dynamic, as well as chip morphology and formation process analyses were performed based on the cutting temperature and cutting force variations in the cutting zone. It has been shown that the temperature changes in the cutting zone depend on the shearing band location in the chip and the thermal transfer rate from the heat generation zone to the cutting tool. Furthermore, it became evident that the material flow stress and the shearing bands greatly affect not only the chip formation morphology but also the cutting temperature field distributions in the cutting zone of the cutting insert.

Progress on Research of Machining of Difficult-to-Machine Materials Using CBN Cutting Tools

“…However, there are still certain problems on locating temperature sensors. Base on the experiment in machining hardened AISI O2 tool steel, Li et al [10] utilized the thin film thermocouples (TFTCs) to perform the temperature measurement. Thus, the measurement precision was greatly improved.…”

An Investigation of Workpiece Temperature in Orthogonal Turn-Milling Compound Machining

“…Lefebvre et al [11] put forward a complete method measuring temperature with foil/workpiece thermocouple. Li et al [12] presented a new method for measuring temperature distribution in cutting tools by the thin film thermocouples embedded into Polycrystalline Cubic Boron Nitride (PCBN) cutting inserts during hard turning. Agarwal and Venkateswara [13] raised an analytical model on unde formed chip thickness, predicating cutting force and energy in ceramic grinding.…”