Estudo da influência do material do porta-ferramenta sobre temperaturas de usinagem no torneamento

Abstract

The main objective of this work is the experimental investigation of the effect that the material of the toolholder has on the temperature at tool-chip interface and on the surface temperatures of the cutting tool and toolholder. The study was conducted in dry turning of gray iron with uncoated cemented carbide inserts, using the same cutting parameters. Five toolholders had been confectioned in materials having different thermal conductivity, these being: copper, brass, aluminum, stainless steel and titanium alloy. The toolholders are identical and have the constructive aspects obtained from a commercial toolholder for turning that material. The temperature at the tool-chip interface was measured using the toolworkpiece thermocouple method and the surface temperatures in the tools and the toolholders, by conventional type T thermocouples. The system was modified in order to develop an experimental procedure for the physical compensating of the secondary and parasites thermoelectric signals (emf). Also, modifications was carried out in a conventional tailstock for use in driving the emf signal between the workpiece and a stationary conductor, but without significantly altering the stiffness of the system. The tailstock was electric insulated and a mercury bearing was mounted inside it and their internal connections were turned in reference junctions at room temperature because on otherwise it could act as secondary junctions. The calibration of the tool-workpiece thermocouple was developed in the same experimental apparatus using the modifications implemented in this system. Besides the results obtained with the investigation of the effects of the toolholder material on the surface temperatures of the tool and the tool holder and on the tool-chip interface temperature, this research also presents contributions to the use and performance of the tool-workpiece thermocouple method.