Investigation of the Solubility of Liquid CO2 and Liquid Oil to Realize an Internal Single Channel Supply in Milling of Ti6Al4V

Abstract

A sustainable approach to increase the productivity in milling of difficult-to-cut materials is the use of internal cryogenic cooling combined with minimum quantity lubrication (MQL). There are various systems available on the market to control the flow of the cryogenic and the MQL medium. These systems are usually based on a delivery of the media through two separate channels. Moreover, a single channel system, which uses the solubility of oil in supercritical CO2 is state of the art. Compared to a two-channel system the geometry of the cooling lubrication channels is simplified, the tools are more stable and easier to manufacture. Furthermore, there is no negative interaction between the CO2 and MQL jets. Instead of supercritical CO2 (SCCO2), liquid CO2 (LCO2) is easier to handle and widely available. Therefore, this paper presents fundamental investigations of the solubility of liquid oil in LCO2. In addition, an innovative single channel system was designed, implemented and tested in milling process of Ti6Al4V.