Abstract
Metal working fluids are used in machining processes of many hard-to-cut materials to increase tool life and productivity. Thereby, the metal working fluids act on the thermal and on the mechanical loads of the tool. The changing mechanical loads can mostly be attributed to the changing friction between rake face and chip and changes in the chip formation, e.g., the contact length between rake face and chip. However, analyzing those effects is challenging, since a detailed look at the chip formation process is prevented by the metal working fluid. In this paper, a novel planing test rig is presented, which enables high-speed recordings of the machining process and process force measurements while using metal working fluids. Experiments reveal that process forces are reduced with increasing pressure of the metal working fluid. However, the average friction coefficient only changes slightly, which indicates that the reduced process forces are mainly the result of reduced contact lengths between rake face and chip.
Highlights
The use of metal working fluids (MWF) is an important approach to reduce tool wear and increase productivity in machining processes
For a stationary process with constant undeformed chip thickness h = 0.1 mm, the chip formation of the dry cutting process is characterized by a high contact length cl = 0.56 mm (Fig. 5c)
This can be attributed to reduced temperatures in the chip–rake face contact area, which leads to reduced thermal-induced stresses in the chip
Summary
The use of metal working fluids (MWF) is an important approach to reduce tool wear and increase productivity in machining processes. Temperature reductions in wet machining processes compared to dry processes were presented by various authors and can be attributed to several effects, e.g., reduced friction and heat absorption of the MWF [2, 6]. The influence of MWF on friction is often investigated on tribometers. A large number of publications deal with the advantages of MWF, investigations on the influence of MWF on local loads and chip formation are very limited due to the limited visibility of the cutting process when using MWF. There is a lack of investigations concerning the influence of the MWF on chip formation, e.g., contact lengths and plowing forces resulting from the minimum chip thickness hmin. A detailed analysis of the chip formation process and process forces, could enable quantitative and qualitative statements about mechanical stresses on the cutting wedge [14]. Using a high-speed camera and a three-component dynamometer, statements can be made about the chip formation process and mechanical loads during chip formation
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