Influence of the direction and flow rate of the cutting fluid on tool life in turning process of AISI 1045 steel

1. Influence of the direction and flow rate of the cutting fluid on tool life in turning process of AISI 1045 steel Anselmo Eduardo Diniz, Ricardo Micaroni April 2006 Presented by: Trenton Bytheway

2. Introduction • Cutting fluid is used to cool and lubricate the tool and workpiece during machining. • This can cause negative effects on product cost, and also raises environmental and health concerns. • Dry cutting cannot be used with a high depth of cut

3. Introduction (cont’d) • High-pressure coolant (HPC) is a relatively new technology that allows cutting fluid to penetrate tool-workpiece and tool-chip interfaces. • This could lead to increased tool life and machine performance, while making the process more environmentally friendly. • Previous studies have shown that HPC leads to a significant increase in tool life. • HPC also allows for a reduction in the amount of fluid used.

4. Introduction (cont’d) • Previous experiments with HPC initially showed increased tool life, however at increased fluid pressures tool life decreased rapidly. • This experiment tests the effect of the direction and flow rate on tool life for AISI 1045 steel

5. Experiment • Material: AISI 1045 steel, 96 HRB • CNC lathe • Fluid: Vegetable oil emulsion, 6% water • Tooling: Triple coated (TiCN, Al2O3, TiN) • Three experiments were done: high pressure, dry cutting, and low pressure/high flow rate • Tool wear measured with an optical microscope, and scanning electron microscope with EDS analysis • When tool wear reached 0.3 mm, the tool was considered at the end of its life

6. Experiment High Pressure testing: • Three directions were tested: - A) towards the rake face - B) towards the flank face - C) both faces • Each direction tested with two flow rates (both at same pressure): - 11 liters/min - 2.5 liters/min

7. Results • Longest tool life achieved when fluid was applied to both faces, with higher flow rate • Second longest was low-flow rate, applied to flank face only • Other tests were equal or less than conventional or dry cutting techniques.

8. Results (cont’d) Rake face only, high flow: • Fluid kept the chip temperature from rising, therefore hardness was maintained. • Chip particles adhered to the tool surface and removed surface coating as chip moved away from workpiece. • Caused scratching, plowing, and crater wear • Fe deposits found on tool surface support this conclusion • Fluid was unable to penatrate chip/tool interface

9. Results (cont’d) Flank face only, high flow: • Chip still adhered to rake face, but high temperature kept it from removing particles from the tool • Workpiece material built up on flank face • Fluid was burned at the flank face, damaging tool further. This may explain why the lower flow rate had better performance.

10. Results (cont’d) Rake and flank faces, high flow • Highest tool life performance • Chip still removed some particles from rake face, but not as many as when fluid was applied to rake face only. • Less reaction (burning) of fluid • The flow was divided between both faces, however, so this would explain a lower amount of burining and the subsequent tool damage. • This result was unexpected by the authors.

11. Results (cont’d) Rake face only, low flow: • About the same performance as the high flow/rake only test • Worse performance than when fluid was applied to flank face • Chemical reactions of fluid still occuring • Tool coating removed from rake face by chip

12. Results (cont’d) Flank face, low flow: • Second longest performance of all tests • Absence of fluid on rake face does not harm tool life • “Burning” was decreased due to a lower flow rate. This accounts for better performance than the high flow rate on flank only.

13. Results (cont’d) Flank and Rake faces, low flow: • Amount of fluid supplied was insufficient to keep the temperature cool enough • Tool substrate was exposed on the rake face. • It is better for the rake to be in contact with a hotter chip (i.e., no fluid applied to rake face) • “Burning” not as significant—failure caused by high temperature.

14. Results (cont’d) Conventional cooling (low pressure, high flow): • Similar results to dry cutting • Not as good as some high pressure methods • Low fluid reaction amounts (burning) • High wear to the flank face

15. Results (cont’d) Dry cutting: • Substrate exposed on flank face (due to workpiece adhesion) • No black stripes to indicate burning • About 15% shorter life time than the longest tool lives observed in experiment

16. Conclusions • Results showed that tool life can be increased over conventional cooling techniques by using a high-pressure, low flow cooling technique. • This allows for a smaller consumption of cutting fluid, making the process more cost-efficient and environmentally safe. • The most effective methods were the application of fluid to both faces at a high flow rate, or to just the flank face at a low flow rate. • This can be useful to all machining processes with high removal rates or on harder materials.

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