Experimental Study on Laser Structuring of Circumferential Surfaces on Cemented Carbide for Slip Force Enhancement

Due to a combination of high surface quality, rigidity, and low tool change times, shrink fit tool holders are a popular choice for machining tool clamping. However, tool slippage and runout can be observed at high-performance machining, especially with low tool diameters. This study provides a possible solution to prevent slippage in shrink fit tool holders. For this, honeycomb-like laser structures were applied to circumferential surfaces of fine-grained 4-mm carbide tool rods with different material compositions. Laser structuring was carried out with a Yb:YAG infrared laser with a pulse duration of 900 fs. In preliminary tests, the ablation behavior of the laser was studied for all materials. Using this data, laser structures with different structure depths and spot-to-spot spacings were generated by varying the laser parameters. Laser-structured tool rods were then clamped in a specifically designed test bench that used a radial clamping element. They were loaded until slippage occurred. Laser-structured tool rods achieved a slip load up to 2.4 times higher than their unstructured counterparts. Slippage almost exclusively occurred due to the wear of the radial clamping element used in the test bench. Lower spot-to-spot spacings as well as higher structure depths generally resulted in higher slip loads. However, at structure depths of 15 µm or greater, tool rods fractured, which was likely attributed to the notch effect. An effect of the material composition of the tool rods on the slip loads could not be observed.