Drilling Chip Reaking Mechanism And It’s Application In Manufacturing Engine Cylinder Head

The material toughness of turbo engines’ cylinder head is much higher than that of the general engines’ cylinder head. Meanwhile, the interior structure of the cylinder head is very complex and the smallest diameter of the hole is only 4mm.So the aluminum chips produced in drilling will easily be entered into the cylinder head and will be difficult to be washed away. If the aluminum chips produced in drilling is kept in the cylinder head product, it will easily cause the engine seriously failure. Thus it is necessary to make clear the chip breaking mechanism in drilling of cylinder head to improve the performance of engine cylinder head. The main contents include:First, the main factors of chip breaking in drilling including the width, the depth, the bottom radius and the edge width of the groove, are identified. Based on the analysis, an orthogonal experiment is designed on the main factors. The experiment ranks the factors that influent the chip breaking as the width of the groove, the depth of the groove, the groove bottom radius and the edge width.Then, the effects of the cutting speed, the feed rate and the depth of cut on the chip breaking are analyzed. The contrast experiments with different cutting speed and feed rates are conducted. The result shows that the chip length can be shortened as 50% by increasing the feed rate of 100% at the same cutting speed.Subsequently, the impact of the coating tool on chip breaking is studied. The contrast experiment with the coated drill and the coated drill shows that the length of the chips created by the coated drill is shorter than that by the uncoated drill by 20%.Finally, the experiment with the PCD coated drill of optimized chip-breaker parameters(the width, the depth, the bottom radius and the edge width of the groove) and drilling parameters(cutting speed and feed per every rotation) according to the practical manufacturing condition is conducted. The length of longest chip produced under these conditions is only 2.82 mm.By applying the optimized drilling into the actual production, the rate containing chips in the cylinder head decreases from 10% to 0.1%.