Development of a Calorimeter to Determine the Chip Heat in Drilling of C45EN

This study is focused on developing and testing a calorimeter to measure the chip heat in drilling of C45EN. Inside the calorimeter, the cut chips fall into a fluid with known heat capacity. Its temperature is measured continuously with thermocouples. Based on calorimeter designs found in the literature, the principal assembly of the calorimeter was adapted to be used in drilling and to minimize heat losses. A modular design with measuring box, process box and top cover was developed. This allows a smooth handling of the calorimeter during experiments as well as the use of the calorimeter to analyze further processes like milling. A horizontal configuration of workpiece and tool was chosen to optimize the chip fall into the fluid, which is a basic requirement for measuring the exact temperature of the chips. The temperature is measured by three thermocouples at different positions of the calorimeter to quantify the emperature distribution in the fluid. To accelerate the process of thermal balance between chip and fluid, the system was dynamically stimulated by jerky movements of the machine axes. This aims to a uniform distribution of the chips within the calorimeter. First experimental tests validated the functionality of the calorimeter and demonstrated that dynamic axes movements accelerate the heat transfer from chip to the fluid substantially.