RESEARCH OF TEMPERATURE PROCESSES DURING DRILLING OF HOLES

Abstract

The paper addresses an axisymmetric thermophysical problem occurring during deep-hole drilling, based on a proposed mathematical model for temperature calculation using the heat source method and the principles of spatial-temporal correspondence and local influence. The dependencies of the thermal process were determined, taking into account the mutual positioning of the cutting tool and the part, the material of the workpiece, the presence of cooling with cutting fluid, cutting conditions, chip removal, and the duration of the drilling operation itself. This is particularly important for deep drilling, where the heat source is continuously displaced.

It was established that the calculation of the temperature field in the workpiece depends on the action of a ring-shaped heat source with a uniform heat release intensity distribution. Theoretical analysis showed that the maximum temperature should not exceed 300 °C (without lubricating and cooling fluid) and 180 °C (with lubricating and cooling fluid), respectively. Standard chromel-alumel thermocouples (temperature range −100 °C to +1000 °C) were used for temperature measurement.

Deep-hole drilling experiments were performed on parts made of Steel 45 (analogous to C45E and Ck45 according to the EU standard EN 10083-2) with diameters of 10 mm and 20 mm, using special deep-drilling tools. The machining was carried out on a universal lathe model 16K20, modified for deep drilling. The temperature in the tool-workpiece contact zone and the temperature distribution within the workpiece (temperature gradient) were calculated. The adequacy of the proposed mathematical model was confirmed, as the calculated temperature values corresponded well with the experimental data.

Keywords: heat source, deep drilling, thermal conductivity, heat source method, principle of spatial-temporal correspondence.