Chip formation, mechanical loads and cooling pressure when micro single-lip deep hole drilling.

What is it about?

The micro single-lip deep hole drilling process is subjected to many difficulties. Especially the machining of difficult-to-cut materials like the nickel-based alloy Inconel 718 results in high thermal and mechanical loads. Irregularities in the drilling process, which lead to early tool failures must be avoided. A major challenge for micro single-lip deep hole drilling is to generate favorable chips and guarantee good chip removal. Since the chip flute of single-lip deep hole drilling tools is straight, the only mechanism to transport the chips and remove them from the bore hole is the coolant flow. In this paper the mechanical loads and the resulting chip formation for various cooling lubricant pressures are analyzed using tools with a diameter of d = 2 mm. In the experiments feed force, drilling torque, tool wear, bore hole quality as well as diameter and roundness deviations were evaluated. Individual chips are digitized and prepared as CAD models for the future consideration of the chip removal in flow simulations of the cooling lubricant. Additional FEM computational analyses of the three-dimensional chip formation with a geometric representation of the chip shape were carried out. This way not only provides valuable validated information about the process and the chip formation but also creates a basis for further investigations, which will allow an innovative simulation of the coolant flow and considers the chip formation and the chip shape.

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Photo by beuwy.com Alexander Pütter on Unsplash

Photo by beuwy.com Alexander Pütter on Unsplash

Why is it important?

The presented modeling of the drilling process is a very important basis for the development of the comprehensive simulation model, which will take the chip formation and the chip removal through the chip flute into account during the analysis of the coolant flow. Especially in machining technology it is necessary to understand the interactions between fluid / tool / workpiece / chip formation / chip shape and chip removal to optimize tool geometries and process parameters. Therefore, only with a deeper insight and knowledge of the micro single-lip deep hole drilling process as a whole it will be possible to improve productivity. Simulations of the process moreover help to reduce the development costs by minimizing the number of necessary experiments to evaluate different cutting parameters, tool geometries as well as the cooling lubricant strategies.

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